Acrylic fibers for artificial hair, headwear products containing the same, and methods for manufacturing the same.

Abstract

This acrylic fiber for artificial hair is constituted by an acrylic copolymer, said fiber having a fiber cross-section of one or more forms selected from the group consisting of C-shaped, figure-6-shaped, and hollowed fava-bean-shaped. In the C-shaped, figure-6-shaped, and hollowed fava-bean-shaped forms, the two ends are either separated from each other or in contact with each other. In the fiber cross-section, the circumradius is between 70 μm and 100 μm; the inradius is between 15 μm and 50 μm; the thickness is between 13 μm and 40 μm; and the inter-end canal width is between 0 μm and 15 μm.

Description

[Technical Field]

[0001] The present invention relates to acrylic fibers for artificial hair used in headwear products such as wigs, headwear products containing the same, and a method for manufacturing the same. [Background technology]

[0002] Conventionally, efforts have been made to impart softness and bulkiness to fibers used in artificial hair. For example, Patent Document 1 describes a vinyl chloride fiber for artificial hair that possesses both softness and bulkiness, in which the maximum outer dimension passing through the center of the assumed inscribed circle of the hollow part, the diameter of the assumed inscribed circle of the hollow part, and the angle formed by the line segment connecting the assumed inscribed circle of the hollow part and the two ends of the C-shape are within a predetermined range in the C-shaped fiber cross section. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2006 / 135060 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] On the other hand, synthetic hair fibers require curl-setting properties, particularly the ability to set curls with hot water.

[0005] To solve the aforementioned problems, the present invention provides an acrylic fiber for artificial hair that has good bulkiness, tactile feel, and curl-setting properties, a headwear product containing the same, and a method for manufacturing the same. [Means for solving the problem]

[0006] One or more embodiments of the present invention relate to an acrylic fiber for artificial hair, composed of an acrylic copolymer, having a fiber cross-section of one or more shapes selected from the group consisting of C-shaped, six-shaped, and bean-shaped with a hollow portion, wherein in the C-shaped, six-shaped, or bean-shaped fiber, the two ends are either separated from each other or touching each other, and the fiber cross-section has an circumscribed circle diameter of 70 μm or more and 100 μm or less, an inscribed circle diameter of 15 μm or more and 50 μm or less, a thickness of 13 μm or more and 40 μm or less, and a canal width between the ends of 0 μm or more and 15 μm or less.

[0007] One or more embodiments of the present invention relate to a headwear product containing the acrylic fiber for artificial hair.

[0008] One or more embodiments of the present invention relate to a method for producing acrylic fibers for artificial hair, comprising the step of wet spinning a spinning solution containing an acrylic copolymer, wherein the nozzle used for wet spinning has a C-shaped cross-section with two ends separated from each other, and in the C-shape, each of the two ends has a straight portion and an outwardly bulging projection, and the straight portions of the two ends are parallel to each other, or in the C-shape, one end is located closer to the hollow portion than the other end. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide acrylic fibers for artificial hair and headwear products containing the same, which have good bulkiness, tactile feel, and curl-setting properties. Furthermore, according to the manufacturing method of the present invention, acrylic fibers for artificial hair with good bulkiness, feel, and curl-setting properties can be obtained by wet spinning. [Brief explanation of the drawing]

[0010] [Figure 1]It is a schematic cross-sectional view (C-shaped) of an acrylic fiber in one or more embodiments of the present invention. [Figure 2] It is a schematic cross-sectional view (C-shaped) of an acrylic fiber in one or more embodiments of the present invention. [Figure 3] It is a schematic cross-sectional view (6-shaped) of an acrylic fiber in one or more embodiments of the present invention. [Figure 4] It is a schematic cross-sectional view (6-shaped) of an acrylic fiber in one or more embodiments of the present invention. [Figure 5] It is a schematic cross-sectional view (kidney bean shape with a hollow part) of an acrylic fiber in one or more embodiments of the present invention. [Figure 6] It is a schematic cross-sectional view (kidney bean shape with a hollow part) of an acrylic fiber in one or more embodiments of the present invention. [Figure 7] It is a schematic cross-sectional view of a nozzle for wet spinning in one example. [Figure 8] It is a schematic cross-sectional view of a nozzle for wet spinning in one example. [Figure 9] It is a schematic cross-sectional view of a nozzle for wet spinning in one example. [Figure 10] It is a schematic cross-sectional view of a nozzle for wet spinning in one example. [Figure 11] It is a cross-sectional photograph (400 times magnification) of the acrylic fiber of Example 1. [Figure 12] It is a cross-sectional photograph (400 times magnification) of the acrylic fiber of Example 2. [Figure 13] It is a cross-sectional photograph (400 times magnification) of the acrylic fiber of Example 3. [Figure 14] It is a cross-sectional photograph (400 times magnification) of the acrylic fiber of Example 6. [Figure 15] It is a cross-sectional photograph (400 times magnification) of the acrylic fiber of Example 7. [Figure 16] It is a cross-sectional photograph (400 times magnification) of the acrylic fiber of Comparative Example 3.

Embodiments for Carrying Out the Invention

[0011] The inventors of the present invention have found that in an acrylic fiber for artificial hair having a fiber cross-section of one or more shapes selected from the group consisting of C-shaped, six-shaped, and bean-shaped with a hollow portion, the circumscribed circle diameter of the fiber cross-section is 70 μm to 100 μm, the inscribed circle diameter is 15 μm to 50 μm, the thickness is 13 μm to 40 μm, and the canal width between the ends is 0 μm to 15 μm, which improves bulkiness, tactile feel, and curl-setting properties (especially curl-setting properties with hot water).

[0012] In one or more embodiments of the present invention, the fiber cross-section of the acrylic fiber for artificial hair has one or more shapes selected from the group consisting of C-shaped, hexagonal, and bean-shaped with a hollow portion (hereinafter also simply referred to as "hollow bean-shaped"). Figures 1 and 2 are schematic cross-sectional views of an acrylic fiber for artificial hair having a C-shaped cross-section, respectively. In the C-shaped fiber cross-section shown in Figure 1, the two ends of the C are separated from each other, forming a hollow section with an opening. In the C-shaped fiber cross-section shown in Figure 2, the two ends of the C are in contact with each other, forming a hollow section without an opening. Figures 3 and 4 are schematic cross-sectional views of an acrylic fiber for artificial hair having a six-shaped cross-section, one example. In one or more embodiments of the present invention, the six-shaped shape can also be described as a modified C-shape, specifically a shape in which one end of the C-shape is located inward (towards the hollow part) than the other end. In the six-shaped fiber cross-section shown in Figure 3, the two ends of the six-shaped shape are separated from each other, forming a hollow part with an opening. In the six-shaped fiber cross-section shown in Figure 4, the two ends of the C-shape are in contact with each other, forming a hollow part without an opening. Figures 5 and 6 are schematic cross-sectional views of an acrylic fiber for artificial hair having a hollow bean-shaped (kidney-shaped) cross-section, respectively. In one or more embodiments of the present invention, the hollow bean shape can also be described as a deformed C-shape, specifically a shape in which both ends of the C-shape are curved toward the hollow portion. In the hollow bean-shaped fiber cross-section shown in Figure 5, the two ends are separated from each other, forming a hollow portion with an opening. In the hollow bean-shaped fiber cross-section shown in Figure 6, the two ends are in contact with each other, forming a hollow portion without an opening.

[0013] In the acrylic fibers for artificial hair according to one or more embodiments of the present invention, the circumscribed circle diameter is preferably 75 μm or more, more preferably 80 μm or more, and even more preferably 85 μm or more, from the viewpoint of further improving bulkiness and tactile feel. In this specification, "circumscribed circle diameter of the fiber cross-section" means the diameter of the assumed circumscribed circle of the fiber cross-section. For example, in Figures 1 to 6, the circumscribed circle diameter is indicated by R1. If there are multiple assumed circumscribed circles of the fiber cross-section, the largest diameter among the diameters of all circumscribed circles shall be taken as the circumscribed circle diameter of the fiber cross-section.

[0014] In the acrylic fibers for artificial hair according to one or more embodiments of the present invention, while not particularly limited, the inscribed circle diameter is preferably 18 μm or more, more preferably 20 μm or more, even more preferably 22 μm or more, and particularly preferably 25 μm or more, from the viewpoint of improving curl-setting ability while maintaining good bulkiness and tactile feel. In this specification, "inscribed circle diameter of fiber cross-section" means the diameter of the assumed inscribed circle of the hollow portion of the fiber cross-section. For example, in Figures 1 to 6, the inscribed circle diameter is indicated by R2. If there are multiple assumed inscribed circles of the hollow portion of the fiber cross-section, the largest diameter among the diameters of all inscribed circles shall be taken as the inscribed circle diameter of the fiber cross-section.

[0015] In the acrylic fibers for artificial hair according to one or more embodiments of the present invention, from the viewpoint of improving curl-setting properties, particularly hot water curl-setting properties (hereinafter also referred to as HWS properties), while maintaining good bulkiness and tactile feel, the thickness of the fiber cross-section is preferably 15 μm to 40 μm, more preferably 16 μm to 38 μm, even more preferably 16 μm to 36 μm, even more preferably 17 μm to 34 μm, and particularly preferably 17 μm to 32 μm. For example, in Figures 1 to 6, the thickness is indicated by t. The thickness of the fiber cross-section may be uniform throughout or may vary. When the thickness of the fiber cross-section is non-uniform, both the maximum thickness t1 and the minimum thickness t2 are preferably 13 μm or more and 40 μm or less, more preferably 15 μm or more and 40 μm or less, more preferably 16 μm or more and 38 μm or less, even more preferably 16 μm or more and 36 μm or less, even more preferably 17 μm or more and 34 μm or less, and particularly preferably 17 μm or more and 32 μm or less.

[0016] In the acrylic fibers for artificial hair according to one or more embodiments of the present invention, from the viewpoint of improving bulkiness while maintaining good tactile feel and curl-setting properties, the canal width between the two ends of the fiber cross-section (hereinafter simply referred to as "canal width") is preferably 10 μm or less, more preferably 8 μm or less, even more preferably 6 μm or less, and particularly preferably 4 μm or less. In Figure 1, the canal width is indicated by W. As shown in Figure 2, when the two ends of a C-shaped fiber cross-section are touching each other, the "canal width" is 0 μm. In this case, although the fiber has a circular cross-section and a cross-sectional shape similar to a hollow fiber having a circular hollow portion, when observed under a microscope, the point where the two ends of the C shape are touching can be confirmed. In one or more embodiments of the present invention, when the fiber cross-section has a six-shape or a hollow broad bean shape, the "canal width" is 0 μm.

[0017] In the acrylic fiber for artificial hair according to one or more embodiments of the present invention, although not particularly limited, from the viewpoint of further enhancing bulkiness, the angle between the ends in the fiber cross-section (hereinafter, simply referred to as "angle between the ends") is preferably 0° or more and 20° or less, more preferably 0° or more and 15° or less, still more preferably 0° or more and 10° or less, even more preferably 0° or more and 8° or less, and particularly preferably 0° or more and 5° or less. In one or more embodiments of the present invention, the "angle between the ends" means the angle between the line segments connecting the center of the assumed inscribed circle and the two ends in the C-shaped fiber cross-section. For example, in FIG. 1, the angle between the ends is indicated by θ. As shown in FIG. 2, in the C-shaped fiber cross-section, when the two ends are in contact with each other, the "angle between the ends" is 0°. In this case, although it has a cross-sectional shape similar to that of a hollow fiber having a circular fiber cross-section and a circular hollow part, when observed with a microscope, the portion where the two C-shaped ends are in contact can be confirmed. In one or more embodiments of the present invention, when the fiber cross-section has a shape of a hexagon or a hollow kidney bean shape, the "angle between the ends" is 0°.

[0018] In the acrylic fiber for artificial hair according to one or more embodiments of the present invention, although not particularly limited, from the viewpoint of further enhancing bulkiness, the bending rigidity is 4.0×10 -3 gf·cm 2 / yarn or more, preferably 5.0×10 -3 gf·cm 2 / yarn or more, more preferably 6.0×10 -3 gf·cm 2 / yarn or more. In the acrylic fiber for artificial hair according to one or more embodiments of the present invention, the upper limit of the bending rigidity is not particularly limited. For example, from the viewpoint of touch, it is preferably 15.0×10 -3 gf·cm 2 / yarn or less, more preferably 14.0×10 -3 gf·cm 2 / yarn or less, still more preferably 13.0×10 -3 gf·cm 2It is even more preferable that it be less than or equal to / yarn. In this specification, "bending stiffness" can be measured as described in the examples.

[0019] In one or more embodiments of the present invention, in the acrylic fibers for artificial hair, although not particularly limited, from the viewpoint of further improving curl-setting properties, especially HWS properties, the torsional rigidity is 1.3 mg·cm. 2 Preferably, the amount is greater than or equal to 1.5 mg / cm³. 2 The above, and more preferably 1.7 mg·cm 2 That concludes the explanation. Furthermore, in the acrylic fibers for artificial hair of one or more embodiments of the present invention, although not particularly limited, from the viewpoint of increasing strength against external forces, the torsional rigidity is 6.0 mg·cm. 2 Preferably, the following, and more preferably, 5.5 mg·cm 2 The following, and more preferably 5.0 mg·cm 2 The following applies. In this specification, "torsional rigidity" can be measured as described in the examples.

[0020] The acrylic fibers for artificial hair of one or more embodiments of the present invention preferably contain 50% or more C-shaped fiber cross-sections, more preferably 60% or more, even more preferably 70% or more, even more preferably 80% or more, and particularly preferably 90% or more, from the viewpoint of having high torsional rigidity and improved curl-setting properties, especially HWS properties. In this specification, the C-shaped fiber cross-section content can be measured as described in the examples.

[0021] In one or more embodiments of the present invention, the acrylic copolymer constituting the acrylic fiber for artificial hair is not particularly limited. For example, an acrylic copolymer containing less than 95% by weight of acrylonitrile and more than 5% by weight of other monomers can be used, and preferably an acrylic copolymer containing less than 80% by weight of acrylonitrile and more than 20% by weight of other monomers can be used. The other monomers can be any monomer copolymerizable with acrylonitrile and are not particularly limited. Specifically, the acrylic copolymer constituting the acrylic fiber for artificial hair more preferably contains 29.5% to 79.5% by weight of acrylonitrile, 20% to 70% by weight of vinyl chloride and / or vinylidene chloride, and 0.5% to 5% by weight of a sulfonic acid group-containing vinyl monomer. In other words, it is more preferable that the acrylic copolymer is obtained by polymerizing a monomer mixture totaling 100% by weight, which includes 29.5% to 79.5% by weight of acrylonitrile, 20% to 70% by weight of vinyl chloride and / or vinylidene chloride, and 0.5% to 5% by weight of a sulfonic acid group-containing vinyl monomer. When the acrylic copolymer has an acrylonitrile content of 29.5% to 79.5% by weight, it exhibits good heat resistance. When the acrylic copolymer has a vinyl chloride and / or vinylidene chloride content of 20% to 70% by weight, it exhibits good flame retardancy. The inclusion of 0.5% to 5% by weight of a sulfonic acid group-containing vinyl monomer in the acrylic copolymer increases its hydrophilicity. More preferably, the acrylic copolymer contains 34.5% to 74.5% by weight of acrylonitrile, 25% to 65% by weight of vinyl chloride and / or vinylidene chloride, and 0.5% to 5% by weight of a sulfonic acid group-containing vinyl monomer, when the total amount of the acrylic copolymer is 100% by weight. Particularly preferably, it contains 39.5% to 74.5% by weight of acrylonitrile, 25% to 60% by weight of vinyl chloride, and 0.5% to 5% by weight of a sulfonic acid group-containing vinyl monomer. From the viewpoint of superior tactile feel, it is preferable that the acrylic copolymer contains vinyl chloride.

[0022] The sulfonic acid group-containing vinyl monomer is not particularly limited, but for example, allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, isoprene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, and metal salts and amine salts of these, such as their sodium salts, can be used. The sulfonic acid group-containing vinyl monomer may be used alone or in combination of two or more types.

[0023] In one or more embodiments of the present invention, from the viewpoint of further enhancing the tactile feel, it is preferable that a fiber treatment agent is attached to the acrylic fibers for artificial hair, and it is more preferable that the fiber treatment agent includes a fatty acid ester-based oil and a polyoxyethylene-based surfactant. Generally, using a fatty acid ester-based oil and a polyoxyethylene-based surfactant, which are used to improve the texture of acrylic fibers, in combination results in a better tactile feel compared to using each individually.

[0024] In one or more embodiments of the present invention, from the viewpoint of further enhancing the tactile feel, the amount of fiber treatment agent attached to 100 parts by weight of acrylic fiber for artificial hair is preferably 0.1 parts by weight or more and 1.0 parts by weight or less, more preferably 0.2 parts by weight or more and 0.6 parts by weight or less, and even more preferably 0.2 parts by weight or more and 0.4 parts by weight or less. In this specification, the amount of fiber treatment agent attached to acrylic fiber for artificial hair is measured and calculated as described in the examples.

[0025] In one or more embodiments of the present invention, the acrylic fiber for artificial hair may contain other additives to improve fiber properties as needed, provided that they do not impede the effects of the present invention. Examples of such additives include gloss modifiers such as titanium dioxide, silicon dioxide, cellulose acetate and other cellulose derivative esters and ethers; colorants such as organic pigments, inorganic pigments and dyes; stabilizers to improve light resistance and heat resistance; fiber consolidators such as urethane polymers and cationic ester polymers to improve processability during braiding and twisting; inorganic or organic deodorants to capture isovaleric acid, an odor component generated from the scalp; and functional agents such as fragrances to impart a citrus scent to the artificial hair fiber.

[0026] The acrylic fibers for artificial hair described above can be produced by wet spinning a spinning solution containing the acrylic copolymer described above. The spinning solution can be obtained, for example, by dissolving the acrylic copolymer in an organic solvent. The organic solvent is not particularly limited, and any good solvent for the acrylic copolymer can be used as appropriate. Examples include methyl sulfoxide (DMSO), dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and acetone. From the viewpoint of versatility, acetone may be used. From the viewpoint of high safety, dimethyl sulfoxide may be used. The spinning solution may also contain a small amount of water, for example, 1.5% to 4.8% by weight of water. This can suppress the formation of voids.

[0027] The spinning solution preferably contains 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, and even more preferably 0.3 parts by weight or more, of the epoxy group-containing compound per 100 parts by weight of the acrylic copolymer. Including the epoxy group-containing compound in the spinning solution is preferable because it can suppress odor, discoloration of the fibers due to heat, and devitrification of the fibers due to hot water. In particular, when dimethyl sulfoxide is used as the organic solvent, it is possible to effectively suppress the generation of malodorous components due to the decomposition of dimethyl sulfoxide when the acrylic fibers for artificial hair are heated. Furthermore, from the viewpoint of spinnability, fiber quality, and cost, the spinning solution preferably contains 5 parts by weight or less, more preferably 3 parts by weight or less, and even more preferably 1 part by weight or less, of the epoxy group-containing compound per 100 parts by weight of the acrylic copolymer.

[0028] Examples of epoxy group-containing compounds that can be used include glycidyl methacrylate-containing polymers, glycidyl acrylate-containing polymers, epoxidized vegetable oils, glycidyl ether-type epoxy resins, glycidyl amine-type epoxy resins, glycidyl ester-type epoxy resins, and cyclic aliphatic-type epoxy resins. The epoxy group-containing compound may be used alone or in combination of two or more types.

[0029] The epoxy group-containing compound is preferably a glycidyl methacrylate-containing polymer and / or a glycidyl acrylate-containing polymer, and more preferably a polyglycidyl methacrylate, from the viewpoint of epoxy equivalent (weight of resin containing 1 equivalent of epoxy groups), suppression of fiber discoloration, solubility in dimethyl sulfoxide, and reduction of elution into the spinning bath.

[0030] The weight-average molecular weight of the epoxy group-containing compound is not particularly limited and may be determined appropriately, for example, considering its solubility in dimethyl sulfoxide and its elution into the spinning bath. When the epoxy group-containing compound is a glycidyl methacrylate-containing polymer and / or a glycidyl acrylate-containing polymer, for example, from the viewpoint of reducing elution into the spinning bath, it is preferable that the weight-average molecular weight be 3000 or more, and from the viewpoint of solubility in organic solvents such as dimethyl sulfoxide, it is preferable that the weight-average molecular weight be 100000 or less.

[0031] The spinning solution may, if necessary, contain other additives to improve fiber properties, as long as they do not hinder the effects of the present invention. Examples of such additives include gloss modifiers such as titanium dioxide, silicon dioxide, cellulose esters and ethers of cellulose derivatives including cellulose acetate, colorants such as organic pigments, inorganic pigments and dyes, and stabilizers to improve light resistance and heat resistance.

[0032] The wet spinning process may include at least a coagulation step, a washing step, and a drying step. Preferably, it may also include a bath stretching step performed before the washing step or after the washing step and before the drying step. Preferably, it may also include an oil application step before the drying step. Furthermore, it may include a stretching step and a heat relaxation treatment step performed after the drying step.

[0033] First, in the coagulation process, the spinning solution is discharged through a spinning nozzle into a coagulation bath and coagulated to form a yarn (also referred to as coagulated yarn).

[0034] The nozzle used for wet spinning is not particularly limited, but for example, a nozzle having a C-shaped cross-section can be used. The ends of the C-shape may have a straight section or an arc shape. Also, the two ends of the C-shape may be arranged symmetrically with respect to the central axis of the hollow section or asymmetrically. By adjusting the spinning conditions such as the spinning speed, nozzle draft, and draw ratio according to the nozzle shape, acrylic fibers with a desired cross-sectional shape and dimensions can be obtained.

[0035] As a nozzle used in wet spinning, for example, by using a nozzle having a C-shaped cross-section with two ends separated from each other, where each end of the C-shape has a straight section and an outwardly bulging projection, acrylic fibers having the above-described shape and dimensions in the fiber cross-section can be suitably obtained, and in particular, C-shaped acrylic fibers having the above-described dimensions can be suitably obtained. Furthermore, it is more preferable that the straight sections of the two ends are parallel to each other. That is, by using a nozzle having a C-shaped cross-section with two ends separated from each other, where each end of the C-shape has a straight section and an outwardly bulging projection, where the straight sections of the two ends are parallel to each other (hereinafter also referred to as an I-type spinning nozzle), acrylic fibers having the above-described shape and dimensions in the fiber cross-section, and in particular, C-shaped acrylic fibers having the above-described dimensions can be suitably obtained. Figure 7 shows a schematic cross-sectional view of an example of an I-type spinning nozzle. In the cross-section of the I-type spinning nozzle, the two C-shaped ends each have straight sections 1a and 1b and protruding sections 2a and 2b, respectively, with the straight sections 1a and 1b being parallel to each other. The straight sections and protruding sections can be adjusted as appropriate depending on the desired fiber cross-sectional shape and size. In the I-type spinning nozzle, the circumscribed circle diameter Cd may be between 0.37 mm and 0.60 mm, the canal width Cw may be between 0.06 mm and 0.24 mm, the slit width Aw may be between 0.06 mm and 0.15 mm, and the pore area may be 0.0850 mm². 2 More than 0.1256mm 2 The following is also acceptable.

[0036] As a nozzle used in wet spinning, for example, one having a C-shaped cross-section, where one end of the C-shape is positioned inward from the other end (hereinafter also referred to as a Type II spinning nozzle), acrylic fibers with a fiber cross-section having the shape and dimensions described above and being resistant to external forces during production can be suitably obtained. Figure 8 shows a schematic cross-sectional view of an example of a Type II spinning nozzle. In the Type II spinning nozzle, one end 3a of the C-shape is positioned inward (towards the hollow part) from the other end 3b. The degree of displacement between the two ends can be appropriately adjusted depending on the desired fiber cross-sectional shape and size. In the cross-section of the Type II spinning nozzle, the circumscribed circle diameter Cd may be 0.37 mm or more and 0.60 mm or less, the canal width Cw may be 0.06 mm or more and 0.24 mm or less, the slit width Aw may be 0.06 mm or more and 0.15 mm or less, and the pore area is 0.0850 mm². 2 More than 0.1256mm 2 The following is also acceptable.

[0037] The spinning speed is not particularly limited, but from the viewpoint of industrial productivity, for example, it is preferably 2 m / min to 17 m / min. The nozzle draft is not particularly limited, but from the viewpoint of manufacturing process stability, for example, it is preferably 0.8 to 2.0. By appropriately adjusting the cross-sectional shape and size of the spinning nozzle, spinning conditions such as spinning speed and nozzle draft, and the draw ratio described later, acrylic fibers having a predetermined cross-sectional shape and size can be obtained.

[0038] The coagulation bath can be an aqueous solution of a good solvent, such as dimethyl sulfoxide, with a concentration of 20% to 70% by weight. The temperature of the coagulation bath may be between 5°C and 40°C. If the organic solvent concentration in the coagulation bath is too low, coagulation will proceed too quickly, resulting in a coarse coagulation structure and a tendency to form voids inside the fibers.

[0039] Next, in the bath stretching process, it is preferable that the acrylic fibers (coagulated yarn) be stretched in a stretching bath (also referred to as primary stretching). The stretching bath can be an aqueous solution with a lower concentration of a good solvent such as dimethyl sulfoxide than the coagulation bath. The temperature of the stretching bath is preferably 30°C or higher, more preferably 40°C or higher, and even more preferably 50°C or higher. The stretching ratio is not particularly limited, but from the viewpoint of increasing the strength and productivity of the fibers, it is preferably between 2 and 8 times. When primary stretching is performed using a water bath, the bath stretching process may be performed after the water washing process described later, or primary stretching and water washing may be performed simultaneously.

[0040] Next, in the washing process, the acrylic fibers are washed with hot water at 30°C or higher to remove beneficial solvents such as dimethyl sulfoxide from the acrylic fibers. Alternatively, the coagulated yarn may be guided to hot water at 30°C or higher, and primary stretching and washing may be performed simultaneously. In the washing process, for example, using hot water at 70°C or higher makes it easier to remove beneficial solvents such as dimethyl sulfoxide from the acrylic fibers.

[0041] In the oil application process, a fiber treatment agent containing a fatty acid ester-based oil and a polyoxyethylene-based surfactant can be used in a state in which it is dissolved or dispersed in water (also referred to as an oil solution). Specifically, it is preferable to apply the fiber treatment agent to acrylic fibers by introducing a predetermined concentration of the fiber treatment agent into an oil tank and immersing the yarn that has undergone the water washing process. The temperature of the oil tank is not particularly limited, but for example, it may be 40°C or higher, or 40°C to 80°C. The immersion time is not particularly limited, but for example, it may be 1 second to 10 seconds, or 1 second to 5 seconds.

[0042] The aforementioned oily liquid may, if necessary, contain other additives for improving fiber properties, as long as they do not impair the effects of the present invention. Examples of such additives include fiber consolidators such as urethane polymers and cationic ester polymers.

[0043] Next, in the drying process, the acrylic fibers after being treated with the fiber treatment agent can be dried. The drying temperature is not particularly limited, but for example, it is 110°C to 190°C. The dried fibers may be further stretched (secondary stretching) as needed. The stretching temperature for secondary stretching is not particularly limited, but for example, it may be 110°C to 190°C. The stretching ratio is not particularly limited, but for example, it is preferably 1 to 4 times, more preferably 1 to 3 times, and even more preferably 1 to 2 times. The total stretching ratio, including bath stretching before drying, is preferably 2 to 10 times, more preferably 2 to 8 times, even more preferably 2 to 6 times, and particularly preferably 2 to 4 times.

[0044] The fibers obtained by drying or further stretching after drying are preferably further relaxed in a heat relaxation treatment process. The relaxation rate is not particularly limited, but is preferably 5% or more, and more preferably 10% to 30%. The heat relaxation treatment can be carried out at a high temperature, for example, in a dry heat atmosphere or superheated steam atmosphere at 140°C to 200°C.

[0045] From the viewpoint of suitability for use as artificial hair, the single fiber fineness of the acrylic fiber for artificial hair is preferably 10 dtex or more and 100 dtex or less, more preferably 20 dtex or more and 95 dtex or less, even more preferably 25 dtex or more and 85 dtex or less, even more preferably 30 dtex or more and 75 dtex or less, and particularly preferably 35 dtex or more and 65 dtex or less. When the single fiber fineness of the acrylic fiber for artificial hair is 35 dtex or more and 65 dtex or less, the curl-setting properties, especially the HWS properties, are further improved.

[0046] The acrylic fibers for artificial hair do not necessarily need to have the same fineness, cross-sectional shape, and cross-sectional size; fibers with different fineness, cross-sectional shape, and cross-sectional size may be mixed together.

[0047] The aforementioned acrylic fibers for artificial hair may be used alone as artificial hair, or they may be used in combination with other artificial hair fibers to form artificial hair. Furthermore, the aforementioned acrylic fibers for artificial hair can be used to construct headwear products. These headwear products may include other artificial hair fibers in addition to the aforementioned acrylic fibers for artificial hair. Other artificial hair fibers are not particularly limited, but examples include polyvinyl chloride fibers, nylon fibers, polyester fibers, and regenerated collagen fibers.

[0048] Examples of the aforementioned headwear products include hair fiber bundles, weaving, wigs, braids, toupees, hair extensions, and hair accessories. [Examples]

[0049] One or more embodiments of the present invention will be described below with reference to examples, but the present invention is not limited to the following embodiments.

[0050] (Example 1) An acrylic copolymer consisting of 49% by weight acrylonitrile, 50% by weight vinyl chloride, and 1% by weight sodium styrenesulfonate was dissolved in acetone to prepare a resin solution with a resin concentration of 28.0% by weight. Next, carbon black, cationic liquid red, and blue dyes (manufactured by Hodogaya Chemical Co., Ltd.) were added to the resin solution as colorants in amounts of 0.6 parts by weight, 0.25 parts by weight, and 0.4 parts by weight, respectively, per 100 parts by weight of the acrylic copolymer. Furthermore, 1.0 part by weight of polyglycidyl methacrylate (weight-average molecular weight 12000) was added per 100 parts by weight of the acrylic copolymer to prepare a spinning solution. This spinning solution was extruded into a coagulation bath of 35% by weight aqueous acetone at 25°C using a spinning nozzle having the shape shown in Figure 7 and the size shown in Table 1, and wet-spun at a spinning speed of 3 m / min and a nozzle draft of 1.26. After that, desolventing and 2.2x stretching were carried out in 75°C hot water. Next, the primary drawn yarn after washing was immersed for 3-5 seconds in an oil bath (60°C) containing a fiber treatment agent (total concentration of fatty acid ester oil and polyoxyethylene surfactant: 1.8% by weight) to impregnate the yarn with the oil. After drying at 130°C, it was stretched to 1.8 times its original length and subjected to a 10% relaxation treatment at 140-145°C to obtain acrylic fibers with a single fiber fineness of approximately 51 dtex (amount of fiber treatment agent attached: 0.3 parts by weight).

[0051] (Example 2) Except for using a spinning nozzle having the shape shown in Figure 7 and the size shown in Table 1, an acrylic fiber with a single fiber fineness of approximately 51 dtex (amount of fiber treatment agent attached: 0.3 parts by weight) was obtained in the same manner as in Example 1.

[0052] (Example 3) Except for using a spinning nozzle having the shape shown in Figure 8 and the size shown in Table 1, an acrylic fiber with a single fiber fineness of approximately 51 dtex (amount of fiber treatment agent attached: 0.3 parts by weight) was obtained in the same manner as in Example 1.

[0053] ( reference Example 4) Except for increasing the discharge rate (amount of spinning solution discharged per hour) by approximately 3.3 times and performing wet spinning at a spinning speed of 10 m / min, and immersing the primary drawn yarn after washing in an oil bath containing 2.2% by weight of fiber treatment agent for 1 to 2 seconds to impregnate the yarn with the oil, an acrylic fiber with a single fiber fineness of approximately 51 dtex (amount of fiber treatment agent attached: 0.3 parts by weight) was obtained in the same manner as in Example 1.

[0054] (Example 5) Aside from using a spinning nozzle having the shape shown in Figure 7 and the size shown in Table 1, and setting the draw ratio after drying to 1.5 times, reference In the same manner as in Example 4, an acrylic fiber with a single fiber fineness of approximately 63 dtex (amount of fiber treatment agent attached: 0.3 parts by weight) was obtained.

[0055] (Example 6) Using a spinning nozzle having the shape shown in Figure 8 and the size shown in Table 1, wet spinning was performed in a solidification bath of 30% by weight aqueous acetone with a nozzle draft of 1.3, then the yarn was immersed for 1-2 seconds in an oil bath containing 2.2% by weight fiber treatment agent to impregnate the yarn with the oil, and after drying, it was stretched to 2.0 times its original size. Except for these steps, an acrylic fiber with a single fiber fineness of approximately 51 dtex (amount of fiber treatment agent attached: 0.3 parts by weight) was obtained in the same manner as in Example 4.

[0056] (Example 7) Except for using a spinning nozzle having the shape shown in Figure 8 and the size shown in Table 1, wet spinning with a nozzle draft of 1.17, then immersing the yarn in an oil bath containing 2.2% by weight of fiber treatment agent for 1-2 seconds to impregnate the yarn with the oil, drying, and then stretching it to 2.3 times its original length, reference In the same manner as in Example 4, an acrylic fiber with a single fiber fineness of approximately 51 dtex (amount of fiber treatment agent attached: 0.3 parts by weight) was obtained.

[0057] (Comparative Example 1) Except for using a spinning nozzle having the shape shown in Figure 9 and the size shown in Table 2, increasing the draw ratio after drying to 2.5 times, and performing a 20% relaxation treatment at 160°C, an acrylic fiber with a single fiber fineness of approximately 51 dtex (amount of fiber treatment agent attached: 0.6 parts by weight) was obtained in the same manner as in Example 1.

[0058] (Comparative Example 2) An acrylic copolymer consisting of 46% by weight of acrylonitrile, 52% by weight of vinyl chloride, and 2% by weight of sodium styrenesulfonate was dissolved in dimethyl sulfoxide to prepare a resin solution with a resin concentration of 28.0% by weight and a water concentration of 3.5% by weight. Next, carbon black, a red dye (CI Basic Red 46), and a blue dye (CI Basic Blue 41) were added to the resin solution as colorants in amounts of 2.1 parts by weight, 0.04 parts by weight, and 0.07 parts by weight, respectively, per 100 parts by weight of the acrylic copolymer. Furthermore, 1.0 part by weight of polyglycidyl methacrylate (weight-average molecular weight 12000) was added per 100 parts by weight of the acrylic copolymer to prepare a spinning solution. The spun yarn was extruded into a coagulation bath of a 52% by weight DMSO aqueous solution at 20°C using a spinning nozzle having the shape shown in Figure 10 and the size shown in Table 2, and wet-spun at a spinning speed of 2 m / min and a nozzle draft of 1.15. The yarn was then stretched 2.4 times in a stretching bath of a 30% by weight DMSO aqueous solution at 90°C. Subsequently, it was washed with hot water at 80°C. Next, the primary stretched yarn after washing was immersed for 3 to 5 seconds in an oil bath (60°C) containing a fiber treatment agent (total concentration of 6% by weight of fatty acid ester oil and polyoxyethylene surfactant) to impregnate the yarn with the fiber treatment agent. After drying at 140°C, it was stretched to twice its original size and subjected to a 20% relaxation treatment at 160°C to obtain acrylic fibers with a single fiber fineness of approximately 46 dtex (amount of fiber treatment agent attached: 0.45 parts by weight).

[0059] (Comparative Example 3) Except for using a spinning nozzle having the shape shown in Figure 8 and the size shown in Table 1, and setting the draw ratio after drying to 2.0 times, an acrylic fiber with a single fiber fineness of approximately 46 dtex (amount of fiber treatment agent attached: 0.3 parts by weight) was obtained in the same manner as in Example 1.

[0060] (Comparative Example 4) Aside from using a spinning nozzle having the shape shown in Figure 7 and the size shown in Table 1, and setting the draw ratio after drying to 2.4 times, reference In the same manner as in Example 4, an acrylic fiber with a single fiber fineness of approximately 40 dtex (amount of fiber treatment agent attached: 0.3 parts by weight) was obtained.

[0061] The amount of fiber treatment agent applied in Examples 1-7 and Comparative Examples 1-4 was measured and calculated as follows.

[0062] (Amount of fiber treatment agent applied) Approximately 2 g of the sample (fiber) (sample weight W0) was cut into 12-15 cm lengths and packed into a stainless steel tube (oil extraction tube) with a hole of approximately 1 mm at the bottom. Next, 35 mL of a mixture of ethanol and cyclohexane (weight ratio) was prepared as the fiber treatment agent extract, and approximately 20 mL was added to the oil extraction tube. The lid of the oil extraction tube was adjusted so that the extraction rate was approximately 1 drop / 1-1.5 seconds, and the extraction of the fiber treatment agent was started. At this time, a tray (empty tray weight W1) heated to 120°C by a heater was used as a receiving tray for the dripping liquid, and the tube was set up so that the dripping liquid fell into it. Once the dripping was complete, the lid was removed, and the fibers inside the oil extraction tube were pressed with a stainless steel rod to squeeze out the extract. This operation was repeated using the remaining extract (approximately 15 mL). After extraction was complete, the tray was placed in a 90°C oven, removed after 5 minutes, and the total tray weight (W2) was measured after the extract had dried and all of the fiber treatment agent remained. The amount of fiber treatment agent adhering to 100 parts by weight of fiber was calculated using the following formula 1. [Formula 1] Amount of oil applied (parts by weight) = (W2 - W1) / (W0 + W1 - W2) × 100

[0063] [Table 1]

[0064] [Table 2]

[0065] Example 1~ 3、5~ 7. Reference example 4 The cross-sections of the acrylic fibers of Comparative Examples 1-4 were observed under a microscope as described below. Using the cross-sectional photographs, image analysis was performed as described below to measure the circumscribed circle diameter, inscribed circle diameter, maximum thickness, minimum thickness, canal width, and angle between ends, and the results are shown in Table 3 below. Also, Examples 1- 3、5~ 7 , Reference example 4 The torsional and bending stiffness of the acrylic fibers of Comparative Examples 1-4 were measured and evaluated as follows, and the results are shown in Table 4 below. 3、5~ 7 , Reference example 4 The bulkiness, tactile feel, and HWS properties of the acrylic fibers of Examples 1-3 and Comparative Examples 1-4 were measured and evaluated as follows, and the results are shown in Table 4 below. Figures 11-16 show cross-sectional photographs of the fibers of Examples 1-3, 6, 7, and Comparative Example 3, respectively. In Example 1, as shown in Figure 11, all fibers had a C-shaped cross-section in the observation field. In Examples 2 and 3, as shown in Figures 12 and 13, most fibers had a C-shaped cross-section in the observation field, but some fibers had a six-shaped cross-section. In Example 6, as shown in Figure 14, C-shaped, six-shaped, and hollow bean-shaped cross-sections were mixed. In Example 7, as shown in Figure 15, C-shaped and six-shaped cross-sections were mixed.

[0066] (Method for observing fiber cross-sections) <Sample preparation> An appropriate amount of acrylic fiber cut to a length of 15 cm was packed into a heat-shrinkable tube (Junkou Co., Ltd., model number "FEP-040", inner diameter before shrinkage φ4.5 mm, inner diameter after shrinkage φ3.3 mm, length 1 m) and left in a 105°C oven for 5 minutes. After removal and cooling, the heat-shrinkable tube filled with acrylic fiber was cut to a length of approximately 3 mm using a razor to prepare a sample for observing the fiber cross-section. <Observation and Photography> Fiber cross-section samples were observed and photographed using a laser microscope (VK-X260, KEYENCE) with an observation and measurement area of ​​675 μm (width) x 506 μm (height). Observation and photography were performed at a total of five locations.

[0067] (Method for analyzing cross-sectional images) Cross-sectional images were imported into image analysis software (WinROOF, Mitsubishi Corporation), and measurements were performed after defining the following parameters. <Circumcircle diameter> The diameters of the circumscribed circles of the three cross-sections were measured, and the average of these values ​​was defined as the circumscribed circle diameter. For example, in Figures 1 to 6, the diameter of the circumscribed circle is indicated by R1. <Diameter of inscribed circle> The inscribed circle diameters of three cross-sections were measured, and the average of these values ​​was used as the inscribed circle diameter. For example, in Figures 1 to 6, the inscribed circle diameter is indicated by R2. <thickness> The maximum thickness (maximum wall thickness) was measured in one cross-section, and the average value of the three cross-sections was defined as the maximum thickness t1. The minimum thickness (minimum wall thickness) was measured in one cross-section, and the average value of the three cross-sections was taken as the minimum thickness t2. For example, in Figures 1 to 6, the thickness is indicated by t. <Canal width> In the C-shaped fiber cross-section, the width between the two ends of the C (distance between two points) was measured, and the average value of the three cross-sections was defined as the canal width. For example, in Figure 1, the canal width is indicated by W. When the fiber cross-section was six-shaped or hollow bean-shaped, the canal width was set to 0 μm. <Angle between ends> In the C-shaped fiber cross-section, the angle between the line segments connecting the center of the inscribed circle and each of the two ends of the C-shape was measured, and the average value of a total of 3 cross-sections was used as the angle between the ends. For example, in Fig. 1, the angle between the ends is indicated by θ. When the fiber cross-section is hexagonal or hollow kidney bean-shaped, the angle between the ends was set to 0°. <Content ratio of C-shaped fiber cross-section> For 5 cross-section photos taken, the number of cross-sections with a C-shape and the total number of all cross-sections were measured, and the content ratio (%) of the C-shaped fiber cross-section was calculated by "number of C-shaped cross-sections ÷ total number of cross-sections × 100". <Content ratio of hexagonal fiber cross-section> For 5 cross-section photos taken, the number of cross-sections with a hexagonal shape and the total number of all cross-sections were measured, and the content ratio (%) of the hexagonal fiber cross-section was calculated by "number of hexagonal cross-sections ÷ total number of cross-sections × 100". <Content ratio of hollow kidney bean-shaped fiber cross-section> For 5 cross-section photos taken, the number of cross-sections with a hollow kidney bean shape and the total number of all cross-sections were measured, and the content ratio (%) of the hollow kidney bean-shaped fiber cross-section was calculated by "number of hollow kidney bean-shaped cross-sections ÷ total number of cross-sections × 100".

[0068] (Method for measuring torsional rigidity) Using a torsion testing machine (KES-YN1, manufactured by Kato Tech Co., Ltd.), the torsional rigidity of a 3-cm-long sample (single fiber) was measured under the conditions of a torsional rotation number of ±3 rotations and a torsional speed of 12° / second, and the average value of 5 measurements was calculated as the value of the torsional rigidity (unit: mg·cm 2 )

[0069] (Method for measuring bending rigidity) Using a KES-FB2 pure bending testing machine (manufactured by Kato Tech Co., Ltd.), the bending rigidity was measured as follows. 49 fibers (single fibers) were pasted on cardboard at an interval of 1 mm, and the upper and lower parts were fixed with cellophane tape so that the pasted fibers would not loosen. The obtained sample was fixed to the jig of the device, and measurements were taken at a deformation speed of 0.5 cm / sec within the range of curvature -2.5 to +2.5 (cm -1 ). The average value of the repulsive force between curvatures of 0.5 to 1.5 (cm -1 ) was measured, and the value per fiber was calculated as the bending rigidity.

[0070] (Method for evaluating bulkiness) <Sample preparation method> Crimped acrylic fibers were processed under the conditions of a pull-up speed of 1.5-2 m / min, a gear temperature of 90-100°C, and a gear pitch of 2.5 mm, so that the crimp angle was 141°±3° (average value of 5 samples measured at one point on each fiber), thereby obtaining crimped fibers. <Volume Determination Method> Using crimped straw measuring 45.7 cm x 4 g (length x weight) per strand, a professional beauty evaluator created two braided hair strands (BRDs). The width and thickness of each BRD were measured at 10 points using calipers, and the width and thickness values ​​were calculated from the average of the two strands. Next, the width x thickness value was calculated as the volume judgment value, and the ratio to the volume judgment value of the comparison level (Comparative Example 2) was calculated to determine the volume increase rate. A volume increase rate of 10% or more was considered a pass (good), and a rate of less than 10% was considered a fail.

[0071] (Method for evaluating tactile sensation) A 30cm x 30g (length x weight) hair bundle was used, and a sensory evaluation was conducted by three professional beauty evaluators. A comparative level (Comparative Example 2, with a texture extremely similar to human hair) was given a score of 5 points. The three professional beauty evaluators assigned scores of 5, 4, 3, 2, and 1 based on the degree of texture, and then calculated the average. Based on the average, the texture was evaluated on a three-level scale as described below. A: Over 4.0 points and under 5.0 points B: Over 2.0 points and under 4.0 points C: 2.0 points or less

[0072] (Method for evaluating HWS properties) A bundle of hair measuring 20 inches (50.8 cm) in length and weighing 2 g was used, wrapped around a 7 mm diameter pipe (metal tube) and secured, immersed in 90°C hot water for 15 seconds, and then left to dry in a dryer (40°C) for 2 hours. After drying, the bundle was removed from the pipe, and immediately after removal, the bundle was loosened by pinching it. Subsequently, the length of the bundle immediately after hanging was measured, and the length immediately after hanging in Comparative Example 2 was used as the control level. The length immediately after hanging was evaluated according to the following three-level criteria. A: The length immediately after hanging is less than or equal to the control level +1cm. B: The length immediately after hanging is greater than the control level +1.1cm and less than or equal to 2.0cm. C: The length immediately after hanging exceeds the control level +2.0cm.

[0073] [Table 3]

[0074] [Table 4]

[0075] As can be seen from Tables 3 and 4, the acrylic fibers of the examples exhibit good bulkiness, tactile feel, and HWS properties. On the other hand, the acrylic fiber of Comparative Example 1, which had a Y-shaped cross-section, had poor tactile properties. Also, the acrylic fiber of Comparative Example 2, which had an H-shaped cross-section, had poor bulkiness. The acrylic fiber of Comparative Example 3, which had a six-shaped cross-section but a thin fiber cross-section, had poor HWS properties. The acrylic fiber of Comparative Example 4, which had a C-shaped cross-section but a thin fiber cross-section, also had poor HWS properties. [Explanation of Symbols]

[0076] 1a, 1b Straight section at the end of the spinning nozzle 2a, 2b Protrusions at the end of the spinning nozzle 3a, 3b Ends of the spinning nozzle

Claims

1. Acrylic fiber for artificial hair, composed of an acrylic copolymer, The fiber cross-section has one or more shapes selected from the group consisting of C-shaped, six-shaped, and bean-shaped with a hollow section. In the aforementioned C-shape, six-shape, or bean-shaped form having a hollow section, the two ends are either separated from each other or touching each other. In the fiber cross-section, the circumscribed circle diameter is 70 μm or more and 100 μm or less, the inscribed circle diameter is 15 μm or more and 50 μm or less, the thickness is 13 μm or more and 40 μm or less, and the canal width between the ends is 0 μm or more and 15 μm or less. The aforementioned acrylic fiber for artificial hair has a torsional rigidity of 1.3 mg / cm². 2 That's all. The acrylic fiber for artificial hair has a bending rigidity of 7.30 × 10⁻³ gf·cm² / yarn or more and 15.0 × 10⁻³ gf·cm² / yarn or less.

2. The acrylic fiber for artificial hair according to claim 1, wherein the single fiber fineness is 35 dtex or more and 65 dtex or less.

3. The acrylic fiber for artificial hair according to claim 1, comprising a fiber having a C-shaped fiber cross-section.

4. The acrylic fiber for artificial hair according to claim 1, wherein a fiber treatment agent is attached to the acrylic fiber for artificial hair, and the fiber treatment agent comprises a fatty acid ester-based oil and a polyoxyethylene-based surfactant.

5. The acrylic copolymer comprises 29.5% to 79.5% by weight of acrylonitrile, 20% to 70% by weight of one or more monomers selected from the group consisting of vinyl chloride and vinylidene chloride, and 0.5% to 5% by weight of a sulfonic acid group-containing vinyl monomer, as described in claim 1.

6. A head accessory product comprising acrylic fibers for artificial hair according to any one of claims 1 to 5.

7. The head ornament product according to claim 6, wherein the head ornament product is at least one selected from the group consisting of hair fiber bundles, weaving, wigs, braids, toupees, hair extensions, and hair accessories.

8. A method for producing acrylic fibers for artificial hair composed of an acrylic copolymer, The process includes wet spinning of a spinning solution containing an acrylic copolymer, The nozzle used in wet spinning has a C-shaped cross-section with two ends that are separated from each other. In the aforementioned C-shape, each of the two ends has a straight section and an outwardly bulging projection, and the straight sections of the two ends are parallel to each other, or In the aforementioned C-shape, one end is located closer to the hollow portion than the other end. The acrylic fiber for artificial hair has a fiber cross-section of one or more shapes selected from the group consisting of C-shape, six-shape, and bean-shaped with a hollow portion, and in the C-shape, six-shape, or bean-shaped with a hollow portion, the two ends are either separated from each other or touching each other, and in the fiber cross-section, the circumscribed circle diameter is 70 μm or more and 100 μm or less, the inscribed circle diameter is 15 μm or more and 50 μm or less, the thickness is 13 μm or more and 40 μm or less, and the canal width between the ends is 0 μm or more and 15 μm or less. The acrylic fiber for artificial hair has a torsional rigidity of 1.3 mg / cm² or more, and the method for producing an acrylic fiber for artificial hair.

9. The method for producing an acrylic fiber for artificial hair according to claim 8, wherein the acrylic fiber for artificial hair has a single fiber fineness of 35 dtex or more and 65 dtex or less.

10. The method for producing acrylic fibers for artificial hair according to claim 8, wherein the acrylic fibers for artificial hair include fibers having a C-shaped fiber cross-section.

11. The method for producing acrylic fibers for artificial hair according to claim 8, wherein the acrylic fibers for artificial hair are coated with a fiber treatment agent, and the fiber treatment agent comprises a fatty acid ester-based oil and a polyoxyethylene-based surfactant.

12. The method for producing acrylic fibers for artificial hair according to Claim 8, wherein the acrylic copolymer comprises 29.5% by weight or more and 79.5% by weight or less of acrylonitrile, 20% by weight or more and 70% by weight or less of one or more monomers selected from the group consisting of vinyl chloride and vinylidene chloride, and 0.5% by weight or more and 5% by weight or less of a sulfonic acid group-containing vinyl monomer.

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