Synthetic fiber processing materials and synthetic fiber

Abstract

Treatment agent for synthetic fibers for the treatment of a synthetic fiber, comprising an amine derivative (A) and a smoothing agent (B), wherein the amine derivative (A) is a compound in which an alkylene oxide having at least 2 and at most 4 carbon atoms is added in a ratio of at least 1 mol and at most 30 mol to 1 mol of the total composition of an amine compound (A1) having a hydrocarbon group having at least 8 and at most 20 carbon atoms and an amine compound (A2) having a hydrocarbon group having at least 8 and at most 20 carbon atoms, which differs in the number of carbon atoms from the hydrocarbon group of the amine compound (A1), wherein the smoothing agent (B) comprises an amino-modified silicone, wherein, if the sum of the proportions of the amine derivative (A) and the smoothing agent (B) is taken as 100 wt%, the treatment agent for synthetic fibers contains the amine derivative (A) in a ratio of at least 3 wt% and at most 50 wt% and the smoothing agent (B) in a ratio of at least 50 wt% and at most 97 wt%.

Description

TECHNICAL AREA

[0001] The present invention relates to a treatment agent for synthetic fibers and a synthetic fiber. STATE OF THE ART

[0002] Synthetic fibers are produced, for example, by performing a spinning step when spinning an acrylic resin or the like into fibers.

[0003] A treatment agent for synthetic fibers can be used in the spinning step to improve the bundling property of the fibers that have undergone the spinning step (hereinafter also referred to as spun fiber bundling property).

[0004] Patent document 1 discloses a treatment agent for synthetic fibers containing a nonionic surfactant and a smoothing agent. JP 2019 - 11 391 A describes an antistatic composition for textiles. cited document patent literature Patent document 1: JP 2019 - 99964 A Patent document 2: JP 2019 - 11 391 A OVERVIEW OF THE INVENTIONAL PROBLEM

[0005] Improving the fiber bundling properties of synthetic fibers can, for example, suppress winding around a roller during the production of synthetic fibers, thus enabling more efficient manufacturing. Furthermore, it can also contribute to improving the quality of the synthetic fibers. Therefore, a treatment agent for synthetic fibers is required to further enhance these fiber bundling properties. SOLUTION TO THE TASK

[0006] A treatment agent for synthetic fibers to solve the above problem contains an amine derivative (A) and a smoothing agent (B).

[0007] The amine derivative (A) is a compound in which an alkylene oxide having at least 2 and at most 4 carbon atoms is added in a ratio of at least 1 mol and at most 30 mol to 1 mol of the total composition of an amine compound (A1) having a hydrocarbon group having at least 8 and at most 20 carbon atoms and an amine compound (A2) having a hydrocarbon group having at least 8 and at most 20 carbon atoms, which differs in the number of carbon atoms from the hydrocarbon group of the amine compound (A1).

[0008] In the treatment agent for synthetic fibers, the alkylene oxide preferably contains an ethylene oxide.

[0009] The treatment agent for synthetic fibers contains the smoothing agent (B) an amino-modified silicone.

[0010] If the sum of the proportions of the amine derivative (A) and the smoothing agent (B) is taken as 100 wt%, the treatment agent for synthetic fibers contains the amine derivative (A) in a ratio of at least 3 wt% and at most 50 wt% and the smoothing agent (B) in a ratio of at least 50 wt% and at most 97 wt%.

[0011] The treatment agent for synthetic fibers preferably also contains a (poly)oxyalkylene derivative (C).

[0012] The (poly)oxyalkylene derivative (C) is a compound in which an alkylene oxide having at least 2 and at most 4 carbon atoms is added in a ratio of at least 1 mol and at most 30 mol to 1 mol of a monohydric aliphatic alcohol having a hydroxy group in a β-position of an alkyl chain having at least 4 carbon atoms.

[0013] If the sum of the proportions of the amine derivative (A), the smoothing agent (B) and the (poly)oxyalkylene derivative (C) is taken as 100 wt%, the treatment agent for synthetic fibers preferably contains the amine derivative (A) in a ratio of at least 3 wt% and at most 30 wt%, the smoothing agent (B) in a ratio of at least 40 wt% and at most 94 wt% and the (poly)oxyalkylene derivative (C) in a ratio of at least 3 wt% and at most 50 wt%.

[0014] In the treatment agent for synthetic fibers, the synthetic fiber is preferably a carbon fiber precursor.

[0015] To solve the above problem, a synthetic fiber adhered to the treatment agent for synthetic fibers. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0016] The present invention succeeds in improving the spun fiber bundling property of synthetic fibers. DESCRIPTION OF THE EXAMPLES OF EXECUTION (first example of execution)

[0017] A first embodiment in which a treatment agent for synthetic fibers according to the present invention (hereinafter also simply referred to as the treatment agent) is embodied is now described.

[0018] The treatment product contains an amine derivative (A) and a smoothing agent (B).

[0019] The amine derivative (A) is a compound in which an alkylene oxide having at least 2 and at most 4 carbon atoms is added in a ratio of at least 1 mol and at most 30 mol to 1 mol of the total composition of an amine compound (A1) having a hydrocarbon group having at least 8 and at most 20 carbon atoms and an amine compound (A2) having a hydrocarbon group having at least 8 and at most 20 carbon atoms, which differs in the number of carbon atoms from the hydrocarbon group of the amine compound (A1).

[0020] The treatment agent, which contains the amine derivative (A) and the smoothing agent (B), can improve the spun fiber bundling properties of synthetic fibers.

[0021] The hydrocarbon group with at least 8 and at most 20 carbon atoms in the above amine compound (A1) is not specifically restricted and can be a straight-chain hydrocarbon group or a hydrocarbon group with a branched chain. It can also be a saturated hydrocarbon group or an unsaturated hydrocarbon group.

[0022] Specific examples of the straight-chain hydrocarbon group include an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, and an eicosyl group.

[0023] Specific examples of saturated hydrocarbon groups with a branched chain include an isooctyl group, an isononyl group, an isodecyl group, an isosoundecyl group, an isododecyl group, an isotridecyl group, an isotetradecyl group, an isopentadecyl group, an isohexadecyl group, an isoheptadecyl group, an isooctadecyl group, and an isoeicosyl group.

[0024] The unsaturated hydrocarbon group can be an alkenyl group with a double bond as the unsaturated carbon bond, or it can be an alkadienyl group or an alkatrienyl group with two or more double bonds. It can also be an alkynyl group with a triple bond as the unsaturated carbon bond, or it can be an alkadiynyl group with two or more triple bonds. Specific examples of unsaturated straight-chain hydrocarbon groups with a double bond include an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, a pentadecenyl group, a hexadecenyl group, a heptadecenyl group, an octadecenyl group, and an eicosenyl group.

[0025] Specific examples of the unsaturated hydrocarbon group with a branched chain and a double bond in the hydrocarbon group include an isooctenyl group, an isononenyl group, an isodecenyl group, an isosoundecenyl group, an isododecenyl group, an isotridecenyl group, an isotetradecenyl group, an isopentadecenyl group, an isohexadecenyl group, an isoheptadecenyl group, an isooctadecenyl group, and an isoeicosenyl group.

[0026] The amine compound (A1) can be any primary, secondary, or tertiary amine. Preferably, it is a primary amine.

[0027] The amine compound (A2) has a hydrocarbon group with at least 8 and at most 20 carbon atoms, which differs in the number of carbon atoms from the hydrocarbon group of amine compound (A1). Apart from the difference in the number of carbon atoms in the hydrocarbon group, the same compounds can be used as those given as examples for amine compound (A1).

[0028] The amine compound (A2) is not limited to one type, and several types of amine compounds (A2) can be used. That is, several types of amine compounds (A2), each having a hydrocarbon group with at least 8 and at most 20 carbon atoms, differing in the number of carbon atoms from the hydrocarbon group of amine compound (A1), can be used. The several types of amine compounds (A2) preferably differ from each other in the number of carbon atoms in the hydrocarbon group. The several types of amine compounds (A2) can also be those that have the same number of carbon atoms in the hydrocarbon group but differ in their chemical formula.

[0029] Preferably two or more types, particularly preferably three or more types and most preferably five or more types of the amine compound (A2) are used.

[0030] The mixing ratios of amine compound (A1) and amine compound (A2) are not particularly restricted. For example, the mass ratio of amine compound (A1) / amine compound (A2) is preferably at least 1 / 99 and at most 99 / 1, and particularly preferably at least 5 / 95 and at most 95 / 5.

[0031] Examples of alkylene oxides with at least 2 and at most 4 carbon atoms include ethylene oxide, propylene oxide, and butylene oxide. Preferably, ethylene oxide is present.

[0032] The polymerization sequence of the alkylene oxide is not particularly restricted and can consist of a random adduct or a blocking adduct.

[0033] One type of alkylene oxide with at least 2 and at most 4 carbon atoms can be used alone, or two or more types can be used in combination.

[0034] The smoothing agent (B) is not particularly restricted, and a known smoothing agent used in a treatment agent may be used. Examples of known smoothing agents include a silicone oil, a mineral oil, a polyolefin, and an ester compound. One type of smoothing agent may be used alone, or two or more types may be used in combination. Preferably, the smoothing agent (B) contains a silicone oil.

[0035] Specific examples of the silicone oil include dimethyl silicone, phenyl-modified silicone, amino-modified silicone, amide-modified silicone, polyether-modified silicone, aminopolyether-modified silicone, alkyl-modified silicone, alkylaralkyl-modified silicone, alkylpolyether-modified silicone, ester-modified silicone, epoxy-modified silicone, carbinol-modified silicone, and mercapto-modified silicone. Preferably, the silicone oil contains an amino-modified silicone.

[0036] The smoothing agent (B), which contains an amino-modified silicone, can further improve the strength of the carbon fibers when carbon fibers are manufactured by making the synthetic fibers flame-retardant and further carbonizing them.

[0037] Specific examples of the smoothing agent (B) include an amino-modified silicone with a kinematic viscosity at 25 °C of 650 mm. 2 / s and an amino equivalent of 1800 g / mol, an amino-modified silicone with a kinematic viscosity at 25 °C of 90 mm 2 / s and an amino equivalent of 5000 g / mol, an amino-modified silicone with a kinematic viscosity at 25 °C of 4500 mm 2 / s and an amino equivalent of 1200 g / mol, an amino-modified silicone with a kinematic viscosity at 25 °C of 8000 mm 2 / s and an amino equivalent of 1000 g / mol, a dimethyl silicone with a kinematic viscosity at 25 °C of 350 mm 2 / s and a didodecyl ester of a 2-mol ethylene oxide adduct of bisphenol A.

[0038] One type of silicone oil can be used alone, or two or more types can be used in combination.

[0039] The kinematic viscosity at 25 °C of the smoothing agent (B) can be measured by a known method using a Cannon-Fenske viscometer under a condition of 25 °C.

[0040] There is no restriction on the proportions of the amine derivative (A) and the smoothing agent (B) in the treatment agent. If the sum of the proportions of the amine derivative (A) and the smoothing agent (B) is taken as 100 parts by mass, the treatment agent preferably contains the amine derivative (A) in a ratio of at least 3% by mass and at most 50% by mass, and the smoothing agent (B) in a ratio of at least 50% by mass and at most 97% by mass.

[0041] The treatment agent preferably also contains a (poly)oxyalkylene derivative (C).

[0042] The (poly)oxyalkylene derivative (C) is a compound in which an alkylene oxide having at least 2 and at most 4 carbon atoms is added in a ratio of at least 1 mol and at most 30 mol to 1 mol of a monohydric aliphatic alcohol having a hydroxy group at a β-position to an alkyl chain having at least 4 carbon atoms.

[0043] The treatment agent containing the (poly)oxyalkylene derivative (C) can further improve the spun fiber bundling property.

[0044] Monohydric aliphatic alcohols are not specifically restricted and can be straight-chain or branched-chain. They can also be saturated or unsaturated aliphatic alcohols.

[0045] It can also be any primary, secondary, or tertiary alcohol. Preferably, it is a primary alcohol.

[0046] The number of carbon atoms in the alkyl chain of the monohydric aliphatic alcohol is preferably at least 10 and more preferably at least 12. Furthermore, the number of carbon atoms in the alkyl chain of the monohydric aliphatic alcohol is preferably at most 18 and more preferably at most 16.

[0047] Specific examples for the alkyl chain include the same examples as those mentioned for the hydrocarbon group of the amine compound (A1) used in the amine derivative (A).

[0048] Examples of the alkylene oxide having at least 2 and at most 4 carbon atoms include the same examples as those given for the alkylene oxide used in the amine derivative (A).

[0049] Specific examples of the (poly)oxyalkylene derivative (C) include a compound in which 5 mol of ethylene oxide are added to 1 mol of 2-dodecanol, and a compound in which 9 mol of ethylene oxide are added to 1 mol of 2-tetradecanol.

[0050] One type of (poly)oxyalkylene derivative (C) can be used alone, or two or more types can be used in combination.

[0051] There are no restrictions on the proportions of the amine derivative (A), the smoothing agent (B), and the (poly)oxyalkylene derivative (C) in the treatment agent. If the sum of the proportions of the amine derivative (A), the smoothing agent (B), and the (poly)oxyalkylene derivative (C) is taken as 100 parts by mass, the treatment agent preferably contains the amine derivative (A) in a ratio of at least 3 wt% and at most 40 wt%, the smoothing agent (B) in a ratio of at least 20 wt% and at most 94 wt%, and the (poly)oxyalkylene derivative (C) in a ratio of at least 3 wt% and at most 50 wt%. (second example)

[0052] A second embodiment, in which a synthetic fiber is configured according to the present invention, is now described. The synthetic fiber of the present embodiment contains the treatment agent of the first embodiment, which adheres to the synthetic fiber. There is no specific restriction on the synthetic fiber, and specific examples include (1) polyethylene terephthalate, polypropylene terephthalate, polylactic acid esters, and other polyester fibers, (2) nylon 6, nylon 66, and other polyamide fibers, (3) polyacrylic, modacrylic, and other polyacrylic fibers, (4) polyethylene, polypropylene, and other polyolefin fibers, (5) a cellulose fiber, and (6) a lignin fiber.

[0053] The synthetic fiber is preferably a synthetic fiber made from resin that becomes a carbon fiber by undergoing a carbonization step described below. In other words, the synthetic fiber is preferably a carbon fiber precursor.

[0054] The resin that forms the synthetic fiber is not particularly limited, and examples include acrylic resin, polyethylene resin, phenolic resin, cellulose resin, lignin resin, and pitch.

[0055] The proportion of the treatment agent of the first embodiment that is to adhere to the synthetic fiber is not particularly limited, and the treatment agent (without solvent) is preferably adhered in such a way that the proportion of the treatment agent is not less than 0.1 wt% and not more than 2 wt%, particularly preferably the treatment agent is adhered in such a way that the proportion of the treatment agent is not less than 0.3 wt% and not more than 1.2 wt% relative to the synthetic fiber.

[0056] The form of the treatment agent in the first embodiment, when the treatment agent is adhered to the synthetic fiber, is, for example, an organic solvent solution or an aqueous solution.

[0057] The method for adhering the treatment agent to the synthetic fiber can be a method in which, for example, an aqueous solution containing the treatment agent of the first embodiment and water is used, or a further diluted aqueous solution is used to achieve the adhesion by a known method, such as an immersion method, a spraying method, a rolling method, or through-oil lubrication using a metering pump.

[0058] The process for producing carbon fibers using the synthetic fibers of the present embodiment is now described.

[0059] The process for producing carbon fibers is preferably subjected to the first to third steps described below.

[0060] First step: a spinning step of synthetic fibers, which are intended to be a carbon fiber precursor, and the adhesion of the treatment agent of the first embodiment.

[0061] Second step: a flame-retardant processing step for converting the carbon fiber precursor obtained in the first step into flame-retardant fibers in an oxidizing atmosphere of at least 200 °C and at most 300 °C, and preferably at least 230 °C and at most 270 °C.

[0062] Third step: a carbonization step of carbonizing the flame-retardant fibers obtained in the second step in an inert atmosphere of at least 300 °C and at most 2000 °C and preferably at least 300 °C and at most 1300 °C.

[0063] It is assumed that a heat treatment step consists of the second and third steps.

[0064] The spinning step preferably further comprises a wet spinning step for dissolving a resin in a solvent and spinning it into fibers, a drying and compacting step for drying and compacting the wet-spun synthetic fibers, and a drawing step for stretching the dry, compacted synthetic fibers. The treatment agent of the first embodiment is preferably applied between the wet spinning step and the drying and compacting step.

[0065] The temperature of the drying and compaction step is not specifically limited, and the synthetic fibers that have undergone the wet spinning step are preferably heated, e.g., to at least 70 °C and at most 200 °C. The point in time at which the treatment agent adheres to the synthetic fibers is not specifically limited and preferably lies between the wet spinning step and the drying and compaction step.

[0066] The oxidizing atmosphere in the flame-retardant processing step is not particularly restricted, and, for example, an air atmosphere can be used.

[0067] The inert atmosphere in the carbonization step is not particularly restricted, and, for example, a nitrogen atmosphere, an argon atmosphere, or a vacuum atmosphere can be used.

[0068] The following effects can be obtained through the treatment agent and the synthetic fiber of the exemplary embodiments. (1) The treatment agent of the present embodiment contains the amine derivative (A) and the smoothing agent (B). Therefore, the spun fiber bundling property of synthetic fibers can be improved. In addition, the flame-retardant bundling property of the synthetic fibers and, if carbon fibers are produced by carbonizing the synthetic fibers, the strength of the carbon fibers can be improved. (2) The smoothing agent (B) contains at least one smoothing agent (B) selected from the amino-modified silicone and the polyether-modified silicone. Therefore, at least one property of the flame-retardant bundling property of the synthetic fibers and the strength of the carbon fibers can be further improved when the carbon fibers are produced by carbonizing the synthetic fibers. (3) The smoothing agent (B) contains the amino-modified silicone. Therefore, the strength of the carbon fibers can be further improved. (4) The treatment agent containing the (poly)oxyalkylene derivative (C) can further improve the spun fiber bundling property.

[0069] The embodiments described above can be modified as follows. The embodiments described above and the following modifications can be implemented if they are combined within a technically feasible range.

[0070] Although in the exemplary embodiments the treatment agent adheres to the synthetic fiber between the wet spinning step and the drying and compacting step, this aspect is not restricted. The treatment agent can adhere to the synthetic fiber between the drying and compacting step and the drawing step, or between the drawing step and the flame-retardant processing step.

[0071] In the exemplary embodiments, the synthetic fiber does not necessarily have to undergo the heat treatment step. That is, the synthetic fiber is not limited to a carbon fiber precursor.

[0072] A stabilizer, an antistatic agent, a binder, an antioxidant, an ultraviolet absorber, an antifoaming agent (silicone compound) and other components commonly used in the treatment agent to maintain the quality of the treatment agent may further be mixed into the treatment agent of the exemplary embodiments within a range that does not impair the effects of the present invention. EXAMPLES

[0073] Examples are given below to describe the features and effects of the present invention in more detail; however, the present invention is not limited to these examples. In the following description of embodiments and comparative examples, parts mean mass parts and % means mass percentage. Experimental Part 1 (Production of treatment agents for carbon fiber precursors) (Example 1)

[0074] The respective components shown in Table 1 were used and placed in a beaker to obtain mixing ratios of 15 parts of an amine derivative (A-1), 50 parts of a smoothing agent (B-1), and 35 parts of a (poly)oxyalkylene derivative (C-1). These were thoroughly mixed by stirring. While stirring continuously, ion-exchanged water was gradually added to achieve a solids concentration of 25%, thereby producing a 25% aqueous solution of a treatment agent for synthetic fibers according to Example 1. (Examples 2 to 24 and comparative examples 1 to 3)

[0075] The respective treatment agents for carbon fiber precursors of Examples 2 to 24 and Comparative Examples 1 to 3 were prepared using the respective components shown in Table 1 and by the same procedure as in Example 1.

[0076] The type and proportion of the amine derivative (A), the type and proportion of the smoothing agent (B), and the type and proportion of the (poly)oxyalkylene derivative (C) in each respective example are as shown in the columns "Amine derivative (A)," "Smoothing agent (B)," and "C," respectively. “(Poly)oxyalkylene derivative (C)” is shown in Table 1. [Table 1] Amine derivative (A) Smoothing agent (B) (Poly)oxyalkylene derivative (C) Evaluation type Mass parts Art Mass parts type Mass parts Spun fiber bundling property Flame-retardant bundling property strength Example 1 A-1 15 B-1 50 C-1 35 ◯ ◯ ◯◯ Example 2 A-1 15 B-2 50 C-2 35 ◯◯ ◯ ◯◯ Example 3 A-1 10 B-2 65 C-1 25 ◯◯ ◯ ◯◯ Example 4 A-1 10 B-3 50 C-1 40 ◯◯ ◯ ◯◯ Example 5 A-1 10 B-4 50 C-1 40 ◯◯ ◯ ◯◯ Example 6 A-1 10 B-1B-6 3030 C-1 30 ◯◯ ◯ ◯◯ Example 7 A-1 10 B-2 80 C-1 10 ◯◯ ◯ ◯◯ Example 8 A-1 10 B-3 B-4 3535 C-1 20 ◯◯ ◯ ◯◯ Example 9 A-1 5 B-4 50 C-1 45 ◯◯ ◯ ◯◯ Example 10 A-2 25 B-1 50 C-1 25 ◯◯ ◯ ◯◯ Example 11 A-3 20 B-1 B-6 2020 C-1 40 ◯◯ ◯ ◯◯ Example 12 A-4 10 B-1 50 C-1 40 ◯◯ ◯ ◯◯ Example 13 A-5 10 B-1 50 C-1 40 ◯◯ ◯ ◯◯ Example 14 A-5A-6 510 B-1 50 C-1 35 ◯◯ ◯ ◯◯ Example 15 A-7 10 B-1 50 C-1 40 ◯ ◯ ◯◯ Example 16 A-8 10 B-1 50 C-1 40 ◯ ◯ ◯◯ Example 17 A-1A-9 105 B-1 50 C-1 35 ◯ ◯ ◯◯ Example 18 A-1 5 B-1 90 C-1 5 ◯◯ ◯ ◯◯ Example 19 A-1 30 B-1 40 C-1 30 ◯ ◯ ◯◯ Example 20 A-1 25 B-1 75 - - ◯ ◯ ◯◯ Example 21 A-1 10 B-1 75 C-1 15 ◯◯ ◯ ◯◯ Example 22 A-9A-10 1010 B-1 80 - - ◯ ◯ ◯◯ Example 23 A-1 10 B-6 50 C-1 40 ◯◯ ◯ ◯ Example 24 A-1 25 B-6 75 - - ◯ ◯ ◯ Comparative example 1 A-9 30 B-2 70 - - × × ◯ Comparative example 2 A-10 50 B-6 50 - - × × × Comparative example 3 a-1a-2 525 B-5 70 - - × × ×

[0077] Details of the amine derivatives (A), smoothing agents (B) and (poly)oxyalkylene derivatives (C) in Table 1 are as follows. (Amine derivatives (A))

[0078] The types and mixing ratios of the amine compound (A1) and the amine compound (A2), as well as the types and numbers of the added moles of the alkylene oxides with at least 2 and at most 4 carbon atoms in each of the respective amine derivatives (A) in Table 1 are given in the column “Types and mixing ratios (parts by mass) of the amine compounds” and the column “Types and numbers of the added moles of the alkylene oxides” of Table 2.

[0079] In Table 2, "C8" means an amine compound in which the number of carbon atoms in the hydrocarbon group is 8. Similarly, "C16:1" means an amine compound in which the number of carbon atoms in the hydrocarbon group is 16 and which has an unsaturated bond, and the same applies to other cases.

[0080] Entries containing “ ∗The letters added to the top right of a number denote amine compounds (A1), and all other entries denote amine compounds (A2). In Example 25, an amine compound of an amine derivative (A-9) is to be an amine compound (A1), and an amine compound of an amine derivative (A-10) is to be an amine compound (A2). EO means ethylene oxide, and PO means propylene oxide.

[0081] The amine derivatives (A-1) and (A-3) to (A-8) were each prepared by adding EO to a liquid mixture of 1 mol of the total amine compound (A1) and the amine compounds (A2).

[0082] An amine derivative (A-2) was prepared by block addition in the order of EO and PO to a liquid mixture of 1 mol of the total amine compound (A1) and the amine compounds (A2). As with all amine derivatives (A-1) to (A-10), primary amines, each with a straight-chain hydrocarbon group, were used.

[0083] The process for the preparation of the amine derivatives (A-1) to (A-8) is not limited to a process in which an alkylene oxide is added to a liquid mixture of amine compounds. The preparation can instead be carried out by adding an alkylene oxide to each amine compound individually and then mixing. a-1: Compound in which 15 mol of ethylene oxide and 10 mol of propylene oxide are added to 1 mol of distyrolated phenol a-2: Compound in which 15 mol of ethylene oxide and 10 mol of propylene oxide are added to 1 mol of distyrolated phenol (Smoothing agent (B)) B-1: amino-modified silicone with a kinematic viscosity at 25 °C of 650 mm 2 / s and an amino equivalent of 1800 g / mol B-2: an amino-modified silicone with a kinematic viscosity at 25 °C of 90 mm 2 / s and an amino equivalent of 5000 g / mol B-3: amino-modified silicone with a kinematic viscosity at 25 °C of 4500 mm 2 / s and an amino equivalent of 1200 g / mol B-4: amino-modified silicone with a kinematic viscosity at 25 °C of 8000 mm 2 / s and an amino equivalent of 1000 g / mol B-5: Dimethyl silicone with a kinematic viscosity at 25 °C of 350 mm 2 / s B-6: Didodecyl ester of a 2-mol ethylene oxide adduct of bisphenol A ((poly)oxyalkylene derivatives (C)) C-1: Compound in which 5 moles of ethylene oxide are added to 1 mole of 2-dodecanol C-2: Compound in which 9 moles of ethylene oxide are added to 1 mole of 2-tetradecanol, Experimental Part 2 (Production of synthetic fibers and carbon fibers)

[0084] Synthetic fibers and carbon fibers were produced using the aqueous solution of the synthetic fiber treatment agents prepared in experimental part 1.

[0085] As a first step, an acrylic resin was wet-spun. Specifically, a copolymer with an intrinsic viscosity of 1.80, consisting of 95 wt% acrylonitrile, 3.5 wt% methyl acrylate, and 1.5 wt% methacrylic acid, was dissolved in dimethylacetamide (DMAC) to prepare a spinning solution with a polymer concentration of 21.0 wt% and a viscosity of 500 poise at 60 °C. The spinning solution was discharged at a draw ratio of 0.8 from a spinneret with 12,000 holes, each with an inner diameter of 0.075 mm, into a coagulation bath containing a 70 wt% aqueous solution of DMAC, which was maintained at a spinning bath temperature of 35 °C.

[0086] The coagulated yarn was stretched fivefold while being desolvated in a rinsing tank to produce acrylic fiber strands (raw material fibers) in a water-swollen state. The synthetic fiber treatments prepared in Experimental Part 1 were then applied to these acrylic fiber strands, each with a solids adhesion of 1 wt% (excluding the solvent). The application of each synthetic fiber treatment was carried out by an immersion process using a 4% ion-exchange aqueous solution of the treatment. The acrylic fiber strands were then dried and compacted by a heating roller set to 130 °C, stretched 1.7 times between heating rollers set to 170 °C, and subsequently wound onto a spool using a winding device.

[0087] Then, in a second step, yarns were unwound from the wound carbon fiber precursor and, after being subjected to flame-retardant processing for 1 hour in an air atmosphere in a flame-retardant processing oven with a temperature gradient of at least 230 °C and at most 270 °C, wound around a spool to obtain flame-retardant yarns (flame-retardant fibers).

[0088] Then, in a third step, yarns were unwound from the wound flame-retardant yarns and, after being converted into carbon fibers by heat treatment in a nitrogen atmosphere in a carbonization furnace with a temperature gradient of at least 300 °C and at most 1300 °C, wound around a spool to obtain the carbon fibers. Experimental Part 3 (Evaluation)

[0089] With regard to each of the treatment agents of Examples 1 to 24 and of the comparative examples 1 to 3, the spun fiber bundling property, the flame-retardant bundling property and the strength of the carbon fibers were each evaluated using the methods described below. (Spun fiber bundling property)

[0090] The bundling state, as the acrylic fiber strands with the applied synthetic fiber treatment passed through the heating roller set to 130 °C in the first step of experimental part 2, was visually inspected and evaluated according to the criteria specified below. The evaluation results are shown in the "Spun Fiber Bundling Property" column of Table 1. • Evaluation criteria for the spun fiber bundling property

[0091] ◯◯ (satisfactory): The fibers are bundled, the yarn width is relatively narrow, there is no wrapping around the heating roller, and there are no problems in functionality.

[0092] ◯ (appropriate): Although the fibers are only mostly bundled and the yarn width is somewhat wide, there is no wrapping around the heating roller, and there are no problems in functionality.

[0093] × (bad): There is a large proportion of unbundled yarns, the yarn width is wide, yarn breakage occurs frequently due to winding around the heating roller, and functionality is impaired. (Flame-retardant bundling property)

[0094] For the flame-retardant fibers on which the flame-retardant processing was carried out in the second step of experimental part 2, the bundling state was visually inspected before winding around the spool and evaluated according to the criteria specified below. The evaluation results are shown in the column "Flame-retardant bundling property" of Table 1. • Evaluation criteria for flame-retardant bundling properties

[0095] ◯ (appropriate): Although the fibers are bundled, there are no spaces within the fiber bundles.

[0096] × (bad): The fibers are not bundled, there are gaps within the fiber bundles, and the yarn width is wide. (Strength)

[0097] The carbon fibers obtained in the third step of experimental part 2 were used to measure their strength according to JIS R7606 (corresponding international standard: ISO 11566:1996). The evaluation was performed using the criteria specified below. The evaluation results are shown in the "Strength" column of Table 1. • Evaluation criteria for strength

[0098] ◯◯ (satisfactory): The strength is at least 4.0 GPa, but less than 4.5 GPa.

[0099] ◯ (adequate): The strength is at least 3.5 GPa but less than 4.0 GPa.

[0100] × (bad): The strength is less than 3.5 GPa.

[0101] The results in Table 1 show that the present invention succeeds in improving the spun fiber bundling properties of the synthetic fibers. Furthermore, the flame-retardant bundling properties can be improved, and the strength of the carbon fibers can be enhanced.

Claims

[1] Treatment agent for synthetic fibers for the treatment of a synthetic fiber, comprising an amine derivative (A) and a smoothing agent (B), wherein the amine derivative (A) is a compound in which an alkylene oxide having at least 2 and at most 4 carbon atoms is added in a ratio of at least 1 mol and at most 30 mol to 1 mol of the total composition of an amine compound (A1) having a hydrocarbon group having at least 8 and at most 20 carbon atoms and an amine compound (A2) having a hydrocarbon group having at least 8 and at most 20 carbon atoms, which differs in the number of carbon atoms from the hydrocarbon group of the amine compound (A1), wherein the smoothing agent (B) comprises an amino-modified silicone, wherein, if the sum of the proportions of the amine derivative (A) and the smoothing agent (B) is taken as 100 wt%, the treatment agent for synthetic fibers contains the amine derivative (A) in a ratio of at least 3 wt% and at most 50 wt% and the smoothing agent (B) in a ratio of at least 50 wt% and at most 97 wt%. [2] Treatment composition for synthetic fibers according to claim 1, wherein the alkylene oxide comprises an ethylene oxide. [3] Treatment composition for synthetic fibers according to claim 1 or 2, further comprising a (poly)oxyalkylene derivative (C), wherein the (poly)oxyalkylene derivative (C) is a compound in which an alkylene oxide having at least 2 and at most 4 carbon atoms is added in a ratio of at least 1 mol and at most 30 mol to 1 mol of a monohydric aliphatic alcohol having a hydroxy group in a β-position of an alkyl chain having at least 4 carbon atoms. [4] Treatment composition for synthetic fibers according to claim 3, wherein, when the sum of the proportions of the amine derivative (A), the smoothing agent (B) and the (poly)oxyalkylene derivative (C) is taken as 100 wt%, the treatment composition for synthetic fibers contains the amine derivative (A) in a ratio of at least 3 wt% and at most 30 wt%, the smoothing agent (B) in a ratio of at least 40 wt% and at most 94 wt% and the (poly)oxyalkylene derivative (C) in a ratio of at least 3 wt% and at most 50 wt%. [5] Treatment composition for synthetic fibers according to any one of claims 1 to 4, wherein the synthetic fiber is a carbon fiber precursor. [6] Synthetic fiber to which the treatment agent for synthetic fibers according to any one of claims 1 to 5 is adhered.