Polyacrylonitrile-based fiber for artificial hair, method for manufacturing said fiber, and head decoration product containing said fiber

Abstract

The present invention relates to a polyacrylonitrile-based fiber for artificial hair, the polyacrylonitrile-based fiber containing an acrylonitrile copolymer, wherein the acrylonitrile copolymer contains a constituent unit derived from acrylonitrile and a constituent unit derived from a vinyl halide, the average circularity of a transverse cross section of the polyacrylonitrile-based fiber for artificial hair is 0.80 or greater, and the calculated average inclination angle RΔa of a line roughness curve element in a direction orthogonal to the length direction of the fiber is 13.0 to 30.0 degrees on the surface of the polyacrylonitrile-based fiber for artificial hair. As a result of this configuration, provided is a polyacrylonitrile-based fiber for artificial hair, said fiber having favorable curl setting properties when using hot water; a method for manufacturing said fiber; and a head decoration product containing said fiber.

Description

Polyacrylonitrile-based fibers for artificial hair, method for producing the same, and headdress products containing the same

[0001] The present invention relates to polyacrylonitrile-based fibers for artificial hair, a method for producing the same, and headdress products containing the same, which can be suitably used as substitutes for human hair.

[0002] In headdress products such as wigs, human hair has been conventionally used. However, in recent years, the demand for artificial hair as a substitute for human hair has been increasing. As artificial hair, for example, fibers using copolymers of acrylonitrile and halogen-containing monomers such as vinyl chloride and vinylidene chloride have been used. For example, Patent Document 1 describes hair fibers composed of a copolymer of 70 to 85% by mass of vinyl chloride, 15 to 30% by mass of acrylonitrile, and 0 to 5% by mass of a vinyl monomer copolymerizable with these, and having a fiber cross-section in the shape of an H (or dumbbell). Further, Patent Document 2 describes artificial hair composed of fibers using an acrylic polymer composed of 35 to 75% by mass of acrylonitrile, 25 to 65% by mass of vinylidene chloride, and 0 to 10% by mass of a vinyl-based monomer copolymerizable with these, having an average circularity of the fiber cross-section of 0.8 or more, and an average fineness of a single fiber of 30 to 100 dtex.

[0003] JP-A-2-53910 JP 2002-227018 A

[0004] However, the hair fibers having an H-shaped fiber cross-section described in Patent Document 1 have a problem of poor convergence and inferior style durability. Although the artificial hair described in Patent Document 2 having an average circularity of the fiber cross-section of 0.8 or more has good convergence, it has a problem of inferior curl setting property with hot water.

[0005] In order to solve the above problems, the present invention provides polyacrylonitrile-based fibers for artificial hair having good curl setting property with hot water, a method for producing the same, and headdress products containing the same.

[0006] One or more embodiments of the present invention relate to a polyacrylonitrile fiber for artificial hair containing an acrylonitrile copolymer, wherein the acrylonitrile copolymer contains constituent units derived from acrylonitrile and constituent units derived from vinyl halogenate, the average circularity of the cross-section of the polyacrylonitrile fiber for artificial hair is 0.80 or higher, and the calculated average inclination angle RΔa of the line roughness curve elements in a direction perpendicular to the length direction of the fiber on the surface of the polyacrylonitrile fiber for artificial hair is 13.0 to 30.0 degrees.

[0007] One or more embodiments of the present invention relate to a method for producing polyacrylonitrile fibers for artificial hair, comprising a wet spinning step of extruding a spinning solution containing an acrylonitrile copolymer into a coagulation bath using a spinning nozzle with a perfectly circular pore shape to form an undrawn yarn, and a wet drawing step of drawing the undrawn yarn in a drawing bath, wherein the acrylonitrile copolymer comprises constituent units derived from acrylonitrile and constituent units derived from vinyl halogenate, the spinning solution, the coagulation bath and the drawing bath all contain an organic solvent, the organic solvent comprises one or more selected from the group consisting of dimethyl sulfoxide, dimethylacetamide and dimethylformamide, the absolute value of the difference between the concentration Con1 of the organic solvent in the coagulation solution and the concentration Con2 of the organic solvent in the drawing bath |Con1-Con2| is 10% by mass or less, and the temperature of the drawing bath is 90°C or less.

[0008] One or more embodiments of the present invention relate to headwear products containing the polyacrylonitrile fiber for artificial hair.

[0009] According to the present invention, it is possible to provide polyacrylonitrile fibers for artificial hair that have good curl-setting properties when heated with hot water, and headwear products containing the same. Furthermore, according to the manufacturing method of the present invention, polyacrylonitrile fibers for artificial hair that have good curl-setting properties when heated with hot water can be obtained by wet spinning.

[0010] This is an image (3000x magnification) of the surface (side) of the polyacrylonitrile fiber for artificial hair of Example 1, observed with a laser microscope. This is an image (3000x magnification) of the surface (side) of the polyacrylonitrile fiber for artificial hair of Comparative Example 1, observed with a laser microscope. This is a diagram illustrating a method for measuring the linear roughness on the surface of the polyacrylonitrile fiber for artificial hair in a direction perpendicular to the length direction of the fiber. This is a graph showing one example of a linear roughness curve. This is a diagram illustrating a method for calculating the average slope angle RΔa of the linear roughness curve elements. This is an explanatory diagram of a method for evaluating the adhesion properties of fibers. This is an explanatory diagram of a method for evaluating the adhesion properties of fibers.

[0011] The inventors of the present invention have found that when polyacrylonitrile fibers are used in artificial hair, the curl-setting properties with hot water are good, by (1) using vinyl halogen as the monomer copolymerized with acrylonitrile in the acrylonitrile copolymer constituting the polyacrylonitrile fibers, (2) setting the average circularity of the cross-section of the polyacrylonitrile fibers to 0.8 or higher, and (3) setting the average inclination angle RΔa of the line roughness curve element in the direction perpendicular to the length direction of the fiber on the surface of the polyacrylonitrile fibers to the range of 13.0 to 30.0 degrees, thus leading to the present invention. In this specification, the cross-section of a fiber means the cross-section in the direction perpendicular to the length direction of the fiber (also referred to as the axial direction). In the following, unless otherwise specified, the cross-section means the cross-section.

[0012] In one or more embodiments of the present invention, (1) an acrylonitrile copolymer containing constituent units derived from acrylonitrile and constituent units derived from vinyl halogenate is used; (2) a spinning solution containing the acrylonitrile copolymer and an organic solvent is extruded into a coagulation solution containing an organic solvent using a spinning nozzle having a perfectly circular pore shape to form an undrawn yarn; (3) the undrawn yarn is wet-drawn in a drawing bath containing an organic solvent; (4) in the spinning solution, coagulation solution, and drawing bath, one or more organic solvents selected from the group consisting of dimethyl sulfoxide, dimethylacetamide, and dimethylformamide are included; (5) the absolute value of the difference between the concentration of the organic solvent in the coagulation solution Con1 and the concentration of the organic solvent in the drawing bath Con2 |Con1-Con2| is set to 10% by mass or less; and (6) the temperature of the drawing bath is set to 90°C or less, thereby making it possible to suitably obtain polyacrylonitrile fibers that satisfy the above-mentioned average circularity and calculated average inclination angle RΔa.

[0013] In this specification, when a numerical range is indicated by "~", the numerical range includes both endpoints (upper and lower limits). For example, the numerical range "X~Y" includes both endpoints, X and Y. Furthermore, when multiple numerical ranges are described in this specification, the range shall include numerical ranges formed by appropriately combining the upper and lower limits of different numerical ranges. Furthermore, when multiple upper and lower limits of a numerical range are described separately in this specification, the range shall include numerical ranges formed by appropriately combining the upper and lower limits.

[0014] The polyacrylonitrile fiber for artificial hair according to one or more embodiments of the present invention (hereinafter also simply referred to as "polyacrylonitrile fiber") contains an acrylonitrile copolymer. When the total mass of the resin component constituting the polyacrylonitrile fiber is 100% by mass, the content of the acrylonitrile copolymer is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, and may consist of 100% by mass of the acrylonitrile copolymer.

[0015] The acrylonitrile copolymer contains constituent units derived from acrylonitrile and constituent units derived from vinyl halogenate. By using vinyl halogenate such as vinyl chloride as the copolymerized component with acrylonitrile, the average slope angle RΔa of the linear roughness curve element in the direction perpendicular to the length direction of the fiber on the surface of the polyacrylonitrile fiber will satisfy the range described later.

[0016] The aforementioned vinyl halogen is not particularly limited and includes, for example, vinyl chloride, vinyl bromide, and vinyl iodide, but vinyl chloride is preferred.

[0017] The acrylonitrile copolymer is not particularly limited and may, for example, contain 5% by mass or more and less than 95% by mass of constituent units derived from acrylonitrile and more than 5% by mass and 95% by mass or less of constituent units derived from vinyl halogenate, or contain 20 to 80% by mass of constituent units derived from acrylonitrile and 20 to 80% by mass of constituent units derived from vinyl halogenate.

[0018] The acrylonitrile copolymer is not particularly limited, but may contain constituent units derived from other monomer components in addition to constituent units derived from acrylonitrile and vinyl halide. Examples of other monomer components include sulfonic acid group-containing vinyl monomers. The sulfonic acid group-containing vinyl monomer is not particularly limited, but examples include 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. The sulfonic acid group-containing vinyl monomer may be used alone or in combination of two or more.

[0019] The acrylonitrile copolymer is not particularly limited, but it is preferably composed of 30 to 80% by mass of constituent units derived from acrylonitrile, 20 to 70% by mass of constituent units derived from vinyl halogenate (preferably vinyl chloride), and 0 to 5% by mass of constituent units derived from sulfonic acid group-containing vinyl monomer; more preferably composed of 35 to 75% by mass of constituent units derived from acrylonitrile, 24.5 to 64.5% by mass of constituent units derived from vinyl halogenate (preferably vinyl chloride), and 0.5 to 5% by mass of constituent units derived from sulfonic acid group-containing vinyl monomer; and even more preferably composed of 40 to 70% by mass of constituent units derived from acrylonitrile, 29.5 to 59.5% by mass of constituent units derived from vinyl halogenate (preferably vinyl chloride), and 0.5 to 5% by mass of constituent units derived from sulfonic acid group-containing vinyl monomer. When the acrylonitrile content in the acrylonitrile copolymer is within the above range, the heat resistance of the polyacrylonitrile fiber is improved. In the acrylonitrile copolymer, if the content of constituent units derived from vinyl halogens is within the above-mentioned range, the flame retardancy of the polyacrylonitrile fiber is improved. In the acrylonitrile copolymer, if the content of constituent units derived from sulfonic acid group-containing vinyl monomers is within the above-mentioned range, the hydrophilicity of the polyacrylonitrile fiber is increased.

[0020] The acrylonitrile copolymer is not particularly limited, but for example, from the viewpoint of spinning process stability, when dimethylformamide is used as the solvent, it is preferable that the specific viscosity at 30°C is 0.05 to 0.60, and more preferably 0.05 to 0.50.

[0021] The polyacrylonitrile fiber has an average circularity of 0.80 or higher in its cross-section, preferably 0.85 or higher. This improves the convergence of the polyacrylonitrile fiber and improves its curl-setting properties with hot water. It is desirable that the cross-sectional shape of the polyacrylonitrile fiber is circular. This makes it easier to achieve an average circularity of 0.80 or higher in the cross-section. There is no particular upper limit to the average circularity of the cross-section of the polyacrylonitrile fiber, but it may be, for example, 0.96 or lower. In this specification, the circularity of the cross-section of the polyacrylonitrile fiber is calculated using the following formula, and the average circularity of the cross-section of the polyacrylonitrile fiber means the arithmetic mean of the circularity of the cross-sections of 100 polyacrylonitrile fibers. Circularity of cross-section = 4π × {Area of ​​cross-section / (Perimeter of cross-section)} 2}

[0022] On the surface of the polyacrylonitrile fiber, the calculated average inclination angle RΔa (hereinafter also simply referred to as "RΔa") of the line roughness curve element in a direction perpendicular to the length direction of the fiber is 13.0 to 30.0 degrees. This improves the style durability of the polyacrylonitrile fiber and improves the curl-set properties by hot water (hereinafter also referred to as HWS properties). RΔa is preferably 28.0 degrees or less, more preferably 25.0 degrees or less, even more preferably 20.0 degrees or less, even more preferably 18.0 degrees or less, even more preferably 17.0 degrees or less, even more preferably 16.0 degrees or less, and even more preferably 15.0 degrees or less.

[0023] In this specification, RΔa refers to the absolute value of the slope (angle) of the line segment connecting the start and end points of the line roughness curve within a horizontally divided section of a line roughness curve at regular intervals ΔX, and the average of these values. It is used as a parameter indicating the surface roughness of polyacrylonitrile fibers. Figure 5 shows how to determine RΔa of a line roughness curve. There are n divisions for measurement in a reference length L [there are (n-1) measurement points], and as shown in Figure 5, the vertical height of the line roughness curve in the i-th measurement section ΔX is ΔYi, and the slope angle in each measurement section ΔX is tan -1(ΔYi / ΔX) is obtained, and RΔa is calculated by the following formula 1. The higher the RΔa on the surface of the polyacrylonitrile fiber, the greater the surface roughness of the polyacrylonitrile fiber and the stronger the interfiber friction. In this specification, RΔa can be measured by a non-contact method using a laser microscope, and specifically can be measured and calculated as described in the examples.

[0024]

[0025] The average length RSm (hereinafter also simply referred to as RSm) of the line roughness curve elements in the direction perpendicular to the length direction of the polyacrylonitrile fiber surface is preferably 0.5 to 20.0 μm, more preferably 1.0 to 18.0 μm, even more preferably 1.5 to 15.0 μm, even more preferably 2.0 to 10.0 μm, even more preferably 2.5 to 8.0 μm, and even more preferably 2.75 to 7.5 μm. RSm corresponds to the spacing of irregularities on the surface of the polyacrylonitrile fiber, and when RSm satisfies the above range, the style durability of the polyacrylonitrile fiber is improved and the curl-set properties with hot water are improved. In this specification, RSm can be measured by a non-contact method using a laser microscope, and specifically can be measured and calculated as described in the examples.

[0026] The average height Rc (hereinafter also simply referred to as Rc) of the line roughness curve elements in the direction perpendicular to the length direction of the polyacrylonitrile fiber surface is preferably 0.25 to 5.00 μm, more preferably 0.25 to 4.00 μm, even more preferably 0.25 to 2.00 μm, even more preferably 0.25 to 1.00 μm, and even more preferably 0.25 to 0.70 μm. This improves the style durability of the polyacrylonitrile fiber and improves its curl-setting properties with hot water. In this specification, Rc can be measured by a non-contact method using a laser microscope, and specifically can be measured and calculated as described in the examples.

[0027] The fineness of the single fiber of the polyacrylonitrile fiber is not particularly limited, but from the viewpoint of suitability for use in artificial hair, for example, it is preferably 5 to 100 dtex, more preferably 10 to 95 dtex, even more preferably 15 to 90 dtex, even more preferably 20 to 85 dtex, even more preferably 25 to 75 dtex, and particularly preferably 30 to 60 dtex. This further improves the curl-setting properties, especially the HWS properties, of the polyacrylonitrile fiber.

[0028] The polyacrylonitrile fiber for artificial hair preferably contains chitosan. This makes it easier to suppress fiber adhesion that occurs when heated to temperatures of 100°C or higher. In the polyacrylonitrile fiber for artificial hair, from the viewpoint of effectively suppressing fiber adhesion, it is preferable that the content of chitosan extracted with dilute acetic acid is 0.005 to 0.4% by mass, or the content of chitosan extracted with concentrated hydrochloric acid is 0.014 to 1.2% by mass. From the viewpoint of more effectively suppressing fiber adhesion during heating, it is more preferable that the content of chitosan extracted with dilute acetic acid in the polyacrylonitrile fiber for artificial hair be 0.02% by mass or more, even more preferable that be 0.05% by mass or more, and even more preferable that be 0.10% by mass or more. The upper limit of the content of chitosan extracted with dilute acetic acid may be 0.35% by mass or less, or 0.30% by mass or less, for example, from the viewpoint of preventing a decrease in gloss. Alternatively, from the viewpoint of more effectively suppressing fiber adhesion during heating, the content of chitosan extracted with concentrated hydrochloric acid in the polyacrylonitrile fiber for artificial hair is preferably 0.10% by mass or more, more preferably 0.20% by mass or more, even more preferably 0.30% by mass or more, and particularly preferably 0.40% by mass or more. The upper limit of the content of chitosan extracted with concentrated hydrochloric acid may be 1.00% by mass or less, or 0.80% by mass or less, for example, from the viewpoint of preventing a decrease in gloss. In this specification, the content of chitosan extracted with dilute acetic acid or the content of chitosan extracted with concentrated hydrochloric acid can be measured as described in the examples.

[0029] From the viewpoint of excellent suppression of fiber adhesion during heating, the polyacrylonitrile fiber preferably has a sag angle of 15 degrees or more, and more preferably greater than 30 degrees, when dry-heat-treated at 140°C. In this specification, the sag angle of the polyacrylonitrile fiber (fiber bundle) when dry-heat-treated at 140°C can be measured as described in the examples.

[0030] The polyacrylonitrile fiber may, if necessary, contain additives to improve its fiber properties, as long as they do not hinder the effects of the present invention. Examples of such additives include fatty acid ester oils such as sorbitan fatty acid esters, polyoxyethylene surfactants such as polyoxyethylene castor oil (also called POE castor oil), and amide oils (referred to as fiber treatment agents); gloss modifiers such as titanium dioxide, silicon dioxide, and esters and ethers of cellulose derivatives such as cellulose acetate; 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 fragrances to impart citrus or other scents to the artificial hair fibers. The amount of the additive may be 20 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 3 parts by mass or less per 100 parts by mass of acrylonitrile copolymer.

[0031] The polyacrylonitrile fiber can be produced by a wet spinning method using a spinning solution containing an acrylonitrile copolymer. First, in the wet spinning process (also called the coagulation process), a spinning solution containing an acrylonitrile copolymer and an organic solvent is extruded into a coagulation bath using a spinning nozzle to form an undrawn yarn. As the acrylonitrile copolymer, one containing the constituent units derived from acrylonitrile and the constituent units derived from vinyl halides can be used as appropriate. This makes it possible to obtain a polyacrylonitrile fiber in which RΔa, and preferably RSm and / or Rc, satisfy the above-mentioned ranges.

[0032] The organic solvent comprises one or more selected from the group consisting of dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), and dimethylformamide (DMF). This makes it possible to obtain polyacrylonitrile fibers in which RΔa and RSm and / or Rc satisfy the above-mentioned ranges. Dimethyl sulfoxide is preferred from the viewpoint of high safety and ease of obtaining polyacrylonitrile fibers in which RΔa, and preferably RSm and / or Rc, satisfy the above-mentioned ranges. In the spinning solution, the concentration (solid content concentration) of the acrylonitrile copolymer is not particularly limited, but may be, for example, 22 to 28% by mass. The spinning solution may also contain a small amount of water, for example, 1.5 to 4.8% by mass of water. This makes it possible to suppress the formation of voids.

[0033] The spinning solution is not particularly limited, but for example, it may contain 0.1 parts by mass or more, 0.2 parts by mass or more, or 0.3 parts by mass or more of an epoxy group-containing compound per 100 parts by mass of acrylonitrile copolymer. Including an epoxy group-containing compound in the spinning solution is preferable because it can suppress odor, discoloration of fibers due to heat, and devitrification of fibers due to hot water. Including an epoxy group-containing compound in the spinning solution is particularly effective in suppressing the generation of malodorous components due to the decomposition of dimethyl sulfoxide when polyacrylonitrile fibers are heated, especially when dimethyl sulfoxide is used as the organic solvent. Furthermore, from the viewpoint of spinnability, fiber quality, and cost, the spinning solution may contain 5 parts by mass or less, 3 parts by mass or less, or 1 part by mass or less of an epoxy group-containing compound per 100 parts by mass of acrylonitrile copolymer.

[0034] 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.

[0035] The epoxy group-containing compound is preferably one or more selected from the group consisting of glycidyl methacrylate-containing polymers and glycidyl acrylate-containing polymers, and more preferably polyglycidyl methacrylate, from the viewpoint of epoxy equivalent (mass of resin containing one equivalent of epoxy groups), suppression of fiber discoloration, solubility in organic solvents such as dimethyl sulfoxide, and reduction of elution into the spinning bath.

[0036] The mass-average molecular weight (Mw) of the epoxy group-containing compound is not particularly limited and may be appropriately determined considering, for example, its solubility in organic solvents such as 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 mass-average molecular weight is 3,000 or more, and from the viewpoint of solubility in organic solvents such as dimethyl sulfoxide, it is preferable that the mass-average molecular weight is 100,000 or less. In this specification, the mass-average molecular weight (Mw) of the epoxy group-containing compound can be measured using gel permeation chromatography.

[0037] 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, esters and ethers of cellulose derivatives such as cellulose acetate; colorants such as organic pigments, inorganic pigments and dyes; and stabilizers to improve light resistance and heat resistance.

[0038] As the spinning nozzle, a spinning nozzle with a perfectly circular pore shape can be used as appropriate. This makes it possible to obtain polyacrylonitrile fibers in which the average circularity, RΔa, and preferably RSm and / or Rc satisfy the above-mentioned ranges.

[0039] The coagulation bath contains one or more organic solvents selected from the group consisting of dimethyl sulfoxide, dimethylacetamide, and dimethylformamide. This makes it possible to obtain polyacrylonitrile fibers in which RΔa, and preferably RSm and / or Rc, satisfy the above-mentioned ranges. Specifically, as the coagulation bath, an aqueous solution of the organic solvent with a concentration of 20 to 70% by mass can be used. From the viewpoint of easily obtaining polyacrylonitrile fibers in which RΔa, and preferably RSm and / or Rc, satisfy the above-mentioned ranges, the concentration of the organic solvent in the coagulation bath (aqueous solution of organic solvent) is preferably 30 to 60% by mass, more preferably 35 to 55% by mass, and even more preferably 40 to 50% by mass. The temperature of the coagulation bath may be, for example, 5 to 40°C, but from the viewpoint of easily obtaining polyacrylonitrile fibers in which RΔa, and preferably RSm and / or Rc, satisfy the above-mentioned ranges, it is preferably 25°C or higher.

[0040] The spinning speed is not particularly limited, but from the viewpoint of industrial productivity, for example, it is preferably 2 to 17 m / min.

[0041] Next, in the wet drawing process, the undrawn yarn is drawn in a drawing bath to obtain a drawn yarn (polyacrylonitrile-based fiber). The drawing bath contains one or more organic solvents selected from the group consisting of dimethyl sulfoxide, dimethylacetamide, and dimethylformamide. Further, the absolute value |Con1 - Con2| of the difference between the concentration Con1 of the organic solvent in the coagulating liquid and the concentration Con2 of the organic solvent in the drawing bath needs to be 10% by mass or less. Thereby, polyacrylonitrile-based fibers in which RΔa and RS m and / or Rc satisfy the above-described ranges can be obtained. The |Con1 - Con2| is preferably 9% by mass or less, more preferably 8% by mass or less, and even more preferably 7% by mass or less. The drawing bath only needs to satisfy the above-described range of |Con1 - Con2|. For example, an aqueous solution having an organic solvent concentration of 20 to 70% by mass can be used. From the viewpoint of easily obtaining polyacrylonitrile-based fibers in which RΔa and RS m and / or Rc satisfy the above-described ranges, in the drawing bath (aqueous solution of an organic solvent), the concentration of the organic solvent is preferably 30 to 60% by mass, more preferably 35 to 55% by mass, and even more preferably 40 to 50% by mass.

[0042] The temperature of the drawing bath is 90°C or lower. Thereby, polyacrylonitrile-based fibers in which RΔa and preferably RS m and / or Rc satisfy the above-described ranges can be obtained. The lower limit of the temperature of the drawing bath is not particularly limited. For example, it is preferably 30°C or higher, more preferably 40°C or higher, even more preferably 50°C or higher, and even more preferably 60°C or higher. The draw ratio in the wet drawing is not particularly limited. For example, it may be more than 1 time and 8 times or less, or 1.5 to 6 times.

[0043] After the wet drawing process, a water washing process and a drying process may be performed. Further, an oiling process may be performed before the drying process. Further, after the drying process, a dry drawing process and a heat relaxation treatment process may be performed.

[0044] In the washing step, the organic solvent can be removed by washing the drawn yarn with water at 30°C or higher. The temperature of the water used in the washing step may be 30 to 90°C, or 40 to 80°C.

[0045] In the oil application step, the oil is used in a state where it is dissolved or dispersed in water (also referred to as an oil solution). As the oil, those described above can be appropriately used. Specifically, it is preferable to introduce the oil solution into an oil bath and apply the oil by immersing the drawn yarn. The adhesion amount of the oil is not particularly limited, and for example, it may be 0.06 to 1.0 parts by mass with respect to 100 parts by mass of the drawn yarn (polyacrylonitrile-based fiber). The temperature of the oil bath is not particularly limited, but for example, it may be 40 to 80°C. The immersion time is not particularly limited, but for example, it may be 1 to 10 seconds.

[0046] In the oil application step, it is preferable to apply chitosan to the drawn yarn (polyacrylonitrile-based fiber) by including chitosan in the oil solution. The oil solution containing chitosan preferably contains acetic acid, hydrochloric acid, etc. in order to dissolve chitosan. The contents of chitosan and acetic acid in the oil solution containing chitosan are not particularly limited, and for example, it may contain 0.05 to 5 parts by mass of chitosan and 0.025 to 10 parts by mass of acetic acid with respect to 100 parts by mass of the oil solution. Thereby, it becomes easy to obtain a polyacrylonitrile-based fiber in which the content of chitosan extracted with dilute acetic acid is 0.005 to 0.4% by mass, or the content of chitosan extracted with concentrated hydrochloric acid is 0.014 to 1.2% by mass.

[0047] In the drying process, the drawn yarn (polyacrylonitrile fiber) is dried. The drying temperature is not particularly limited, but may be, for example, 110 to 190°C. The dried drawn yarn may be further dry-drawn (secondary-drawn) if necessary. The drawing temperature for dry-drawn is not particularly limited, but may be, for example, 110 to 190°C. The drawing ratio in the dry-drawn process is not particularly limited, but may be, for example, greater than 1x and less than or equal to 4x, greater than 1x and less than or equal to 3x, or greater than 1x and less than or equal to 2x. From the viewpoint of easily obtaining polyacrylonitrile fiber in which RΔa and RSm and / or Rc satisfy the above ranges, the drawing ratio Str2 in the dry-drawn process is preferably higher than the drawing ratio Str1 in the wet-drawn process, and Str2 / Str1 is preferably 1.05 or more, more preferably 1.05 to 1.8, and even more preferably 1.10 to 1.5. The total stretching ratio, including wet stretching before drying, is preferably 2 to 10 times, more preferably 2 to 8 times, and even more preferably 2 to 6 times.

[0048] After drying or dry stretching, the resulting polyacrylonitrile fibers 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 10-30%. The heat relaxation treatment can be carried out at a high temperature, for example, in a dry heat atmosphere or superheated steam atmosphere at 140-200°C or lower.

[0049] Headwear products can be constructed using the polyacrylonitrile fibers described above. The headwear products may also contain human hair or other artificial hair fibers in addition to the polyacrylonitrile fibers, as long as they do not impair the effects of the present invention. Other artificial hair fibers are not particularly limited, but examples include polyvinyl chloride fibers, nylon fibers, polyester fibers, and regenerated collagen fibers.

[0050] Examples of the aforementioned headwear products include hair wigs, hairpieces, weaving, hair extensions, braided hair, hair accessories, and doll hair.

[0051] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0052] (Example 1) An acrylonitrile copolymer (specific viscosity 0.174) consisting of 46% by mass of acrylonitrile, 52% by mass of vinyl chloride, and 2% by mass of sodium styrene sulfonate was dissolved in dimethyl sulfoxide (DMSO), and water was added to prepare an acrylonitrile copolymer solution with a concentration of 26.0% by mass of acrylonitrile copolymer and a water concentration of 2.7% by mass. Next, to the obtained acrylonitrile copolymer solution, 0.26 parts by mass of yellow dye (Color Index Basic Yellow 28) per 100 parts by mass of acrylonitrile copolymer, 0.37 parts by mass of red dye (Color Index Basic Red 46) per 100 parts by mass of acrylonitrile copolymer, 0.46 parts by mass of blue dye (Color Index Basic Blue 41) per 100 parts by mass of acrylonitrile copolymer, and 0.8 parts by mass of polyglycidyl methacrylate (weight-average molecular weight 12,000) per 100 parts by mass of acrylonitrile copolymer were added to prepare a spinning solution. The obtained spun yarn was extruded into a coagulation bath of 47% by mass DMSO aqueous solution at 25°C using a spinning nozzle (hole shape: circular, hole diameter: 0.30 mm, number of holes: 112) and wet-spun at a spinning speed of 5 m / min. The resulting undrawn yarn was wet-drawn 2.1 times in a drawing bath of 50% by mass DMSO aqueous solution at 65°C. Next, the yarn was washed with 90°C hot water, and then immersed for 1 to 3 seconds in an oil tank (60°C) containing an aqueous solution of a mixed oil (POE castor oil, sorbitan stearate, and amide-based oil, with a total oil concentration of 2% by mass) to impregnate the yarn with the oil solution. After drying at 140°C, it was dry-stretched 2.7 times at 140°C, and then subjected to a 20% relaxation treatment at 155°C to produce polyacrylonitrile fibers with a single fiber fineness of approximately 46 dtex (0.4 parts by mass of oil adhering to 100 parts by mass of polyacrylonitrile fiber). In this specification, the amount of oil adhering is calculated based on the amount of oil solution adhering to 100 parts by mass of polyacrylonitrile fiber and the total concentration of oil in the oil solution.

[0053] (Example 2) Polyacrylonitrile fibers with a single fiber fineness of approximately 46 dtex were prepared in the same manner as in Example 1, except that the undrawn yarn was wet-drawn 2.1 times in a drawing bath of 50% by mass DMSO aqueous solution at 75°C.

[0054] (Example 3) Polyacrylonitrile fibers with a single fiber fineness of approximately 46 dtex were prepared in the same manner as in Example 1, except that the undrawn yarn was wet-drawn 2.1 times in a drawing bath of 50% by mass DMSO aqueous solution at 85°C.

[0055] (Example 4) Except for using a spinning nozzle with a perfectly circular pore shape, a pore diameter of 0.30 mm, and 8500 pores, and for wet drawing the undrawn yarn to a drawing ratio of 2.3 times in a drawing bath of 40% by mass DMSO aqueous solution at 85°C, and for dry drawing the drawing ratio to 2.6 times, a polyacrylonitrile fiber with a single fiber fineness of approximately 36 dtex was produced in the same manner as in Example 1.

[0056] (Example 5) A polyacrylonitrile fiber with a single fiber fineness of approximately 46 dtex was prepared in the same manner as in Example 3, except that a chitosan-containing oil solution was used, consisting of a total concentration of 2% by mass of POE castor oil, sorbitan stearate, and amide-based oil, a concentration of 0.30% by mass of chitosan, a concentration of 0.15% by mass of acetic acid, and the remainder being water, instead of the oil solution.

[0057] (Example 6) Polyacrylonitrile fibers with an average single fiber fineness of approximately 36 dtex were prepared in the same manner as in Example 3, except that a chitosan-containing oil solution was used, consisting of a total concentration of 2% by mass of POE castor oil, sorbitan stearate, and amide-based oil, a concentration of 1.20% by mass of chitosan, a concentration of 0.60% by mass of acetic acid, and the remainder being water, instead of the oil solution.

[0058] (Example 7) Polyacrylonitrile fibers with an average single fiber fineness of approximately 36 dtex were prepared in the same manner as in Example 3, except that the undrawn yarn was wet-drawn to a draw ratio of 2.3 times in an aqueous DMSO solution, and the draw ratio for dry drawing was set to 2.6 times.

[0059] (Comparative Example 1) Polyacrylonitrile fibers with a single fiber fineness of approximately 46 dtex were prepared in the same manner as in Example 1, except that the undrawn yarn was drawn 2.1 times in a drawing bath of 50% by mass DMSO aqueous solution at 95°C.

[0060] (Comparative Example 2) Except for using a spinning nozzle with an elliptical pore shape (major axis-minor axis ratio of 2.5:1), a pore diameter of 0.33 mm, and 100 pores, a polyacrylonitrile fiber with a single fiber fineness of approximately 46 dtex was prepared in the same manner as in Example 1.

[0061] (Comparative Example 3) Modacrylic fiber (manufactured by Kaneka Corporation, product name "AFRELE", single fiber fineness: 46 dtex, fiber cross-sectional shape: H-shape) was used.

[0062] (Comparative Example 4) A polyacrylonitrile fiber with a single fiber fineness of approximately 46 dtex was prepared in the same manner as in Example 1, except that an acrylonitrile copolymer consisting of 52.0% by mass of acrylonitrile, 46.8% by mass of vinylidene chloride, and 1.2% by mass of sodium styrene sulfonate was used as the acrylonitrile copolymer.

[0063] The single fiber fineness of the polyacrylonitrile fibers in the examples and comparative examples was measured as follows. The average circularity, RΔa, RSm, and Rc of the polyacrylonitrile fibers in the examples and comparative examples were measured and calculated as follows. The HWS of the polyacrylonitrile fibers in the examples and comparative examples was evaluated as follows. These results are shown in Table 1 below. Figures 1 and 2 show images (3000x magnification) of the side surfaces of the polyacrylonitrile fibers in Example 1 and Comparative Example 1, respectively, observed with a laser microscope. In addition, in Examples 5 to 7, the chitosan content and fiber adhesion in the polyacrylonitrile fibers were evaluated as follows, and the results are shown in Table 2 below.

[0064] (Single Fiber Fineness) The single fiber fineness of 100 fibers was measured using an autobibro type fineness meter (DENICON DC-21A, manufactured by Search Co., Ltd.), and the average value was calculated.

[0065] (Average Circularity) <Photography of Cross-sectional Images of Fibers> A suitable amount of fiber cut to a length of approximately 15 cm was packed into a heat-shrinkable tube (Junkou Co., Ltd., model number "FEP-040", inner diameter before shrinkage 4.5 mm, inner diameter after shrinkage 3.3 mm, length 1 m) and left in a 105°C oven for 5 minutes. After that, it was removed and allowed to cool, and using a razor, the heat-shrinkable tube that had been packed with fibers and shrunk was cut to a length of approximately 3 mm to prepare a sample for observing the fiber cross-section. The fiber cross-sectional observation sample was observed using a laser microscope (VK-X260, KEYENCE Co., Ltd.), and images for analysis were taken. <Circularity Analysis> The images for analysis were imported into image analysis software (WinROOF, Mitsubishi Corporation), the circularity of the cross-sections of 100 fibers was measured, and the average value was calculated to determine the average circularity.

[0066] (Surface Roughness) <Image Capture of Fiber Side View> A fiber cut to a length of approximately 5 cm was straightened and attached to a slide to prepare a sample for fiber side view observation. The fiber side view observation sample was observed with a laser microscope (VK-X260, manufactured by KEYENCE) and images for analysis were captured. <Analysis of Surface Roughness> Using the analysis application (VK-H1XA) attached to the laser microscope, the linear roughness on the fiber surface in a direction perpendicular to the length direction of the fiber was measured, and the average length RSm, average height Rc, and arithmetic mean slope angle RΔa of the linear roughness curve elements were calculated. Specifically, the following was performed: (1) On the fiber surface, as shown in Figure 3, the linear roughness of a 18 μm straight section in a direction perpendicular to the length direction of the fiber (direction indicated by arrow Y) was measured, and a linear roughness curve as shown in Figure 4 was obtained. (2) Based on the obtained line roughness curve, the average length RSm, average height Rc, and arithmetic mean slope angle RΔa of the line roughness curve elements were calculated. (3) The operations in (1) and (2) were performed at 21 arbitrary locations on the surface of the fiber. (4) The average values ​​of the average length RSm, average height Rc, and arithmetic mean slope angle RΔa of the line roughness curve elements obtained from the 21 measurements were calculated and used as the average length RSm, average height Rc, and arithmetic mean slope angle RΔa of the line roughness curve elements in the direction perpendicular to the length direction of the fiber.

[0067] (Chitosan content extracted with dilute acetic acid) The following procedure was used to extract chitosan from the fibers with dilute acetic acid and determine the content of chitosan extracted with dilute acetic acid. 1) 1.87 g of glycine [Fujifilm Wako Pure Chemical Industries] and 1.46 g of sodium chloride [Fujifilm Wako Pure Chemical Industries] were dissolved in pure water to make a 250 g solution, and 0.1 M hydrochloric acid [Fujifilm Wako Pure Chemical Industries] was added until the pH reached 3.2 to prepare a buffer solution. 2) 150 mg of Reactive Red 4 [MP Biomedicals, LLC] was dissolved in pure water to make a 100 g solution, and 5 g of this solution was diluted 50 times with the buffer solution from 1) to prepare a dye solution. 3) 3.0 g of fiber and 20 g of 0.1 wt% acetic acid aqueous solution were added to a glass bottle and heated at 90°C for 1 hour to prepare an extract. 4) After the extract had cooled, 5 mL of dye solution and 0.5 mL of the extract were immediately mixed, and the absorbance at 578 nm was measured using a UV-Vis spectrophotometer [Shimadzu Corporation, UV-1800]. At this time, a mixture of 0.5 mL of buffer solution and 5 mL of dye solution was used as a reference. 5) Using the mixture of 0.5 mL of buffer solution and 5 mL of dye solution as a reference, a calibration curve was created from the absorbance at 578 nm using a mixture of 0.5 mL of chitosan aqueous solution prepared to 0.0025% to 0.025% by weight and 5 mL of dye solution. Based on this calibration curve and the absorbance values ​​from 4), the chitosan concentration in the extract was calculated, and the content of chitosan extracted with dilute acetic acid was determined.

[0068] (Chitosan content extracted with concentrated hydrochloric acid) The following procedure was used to extract chitosan from the fibers with concentrated hydrochloric acid and to determine the content of chitosan extracted with concentrated hydrochloric acid. 1) 0.2 g of pulverized fiber sample was heated under reflux with 10 mL of 12N hydrochloric acid to decompose the chitosan, and then diluted to 20 mL with water to obtain a chitosan hydrolysis solution. 2) 2 mL of the chitosan hydrolysis solution and 3.8 g of sodium borate were added to 30 mL of water, then neutralized to pH 7 with 12N hydrochloric acid and diluted to 50 mL. 3) 1 mL of the solution obtained in 2) was mixed with the derivatization reagent 9-fluorenylmethyl chloroformate (20 mg / 20 mL acetonitrile solution), allowed to stand for 24 hours, and then 3 mL of a mixed solvent of acetonitrile:water = 1:1 (containing 0.25% formic acid) was added to prepare the HPLC test solution. 4) The chitosan content extracted with concentrated hydrochloric acid was determined from the peak area obtained by HPLC analysis and the calibration curve created using glucosamine hydrochloride.

[0069] (HWS properties) Polyacrylonitrile fibers (multifilaments) were cut to a length of approximately 20 inches (50.8 cm), and the cut polyacrylonitrile fibers were bundled together to a mass of 2 g. The resulting fiber bundle (approximately 20 cm in length, 2 g in mass) was wrapped around a 3-inch (7.62 cm) section of a 15 mm diameter metal pipe, and both ends were secured with rubber bands to prevent movement. The fiber bundle wrapped around the metal pipe was immersed in 90°C hot water for 15 seconds, then removed, the moisture was lightly removed with a towel, and it was left to dry in a dryer (40°C) for 2 hours. After drying, the fiber bundle was removed from the metal pipe and suspended with the rubber band attached to one end facing upwards. The length of the fiber bundle after HWS (cm) from directly below the rubber band to the tip of the fiber bundle was measured, and the HWS set rate was calculated according to the following formula to evaluate the HWS properties. A lower HWS set rate indicates better HWS properties, and an HWS set rate of 32% or less was considered to indicate good HWS properties. HWS set rate (%) = 100 × {[Length of fiber bundle after HWS (cm) - 7.62 (cm)] / 7.62 (cm)}

[0070] (Adhesion Evaluation) A fiber bundle of polyacrylonitrile fiber with a total fineness of approximately 1.24 million dtex was cut to a length of 28 cm. As shown in Figure 6, the 2 cm portions from both ends of the 28 cm fiber bundle 1 were fixed with cable ties 2a and 2b, respectively. Two 2 kg pillow-shaped weights 3, each 10 cm long and preheated to 140°C, were placed side by side between the cable ties 2a and 2b and placed on the fiber bundle 1. The bundle was then dry-heat treated in a dryer at 140°C for 15 minutes. Next, as shown in Figure 7, the dry-heat treated fiber bundle 1 was placed on a horizontal stand 4. The fiber bundle 1, which was protruding 12 cm (indicated as L in Figure 7) from the end of the horizontal stand 4, was fixed with a weight 5 (1 kg). The angle α between the horizontal stand 4 and the hanging fiber bundle 1 was defined as the hanging angle. Based on the hanging angle, the adhesion of the fibers was evaluated according to the following criteria. A: The hanging angle exceeds 30 degrees, indicating extremely good adhesion suppression. B: The angle of sagging is 15 to 30 degrees, indicating good resistance to stagnation. C: The angle of sagging is less than 15 degrees, indicating poor resistance to stagnation.

[0071]

[0072] As can be seen from Table 1, the polyacrylonitrile fibers of the examples had an average circularity of 0.80 or higher in the cross-section, and a fiber surface RΔa of 13.0 to 30.0 degrees, indicating good HWS properties.

[0073] On the other hand, the polyacrylonitrile fiber of Comparative Example 1, which had an average circularity of 0.80 or higher in its cross-section but a fiber surface RΔa of less than 13.0 degrees, had an HWS set rate exceeding 32%, indicating poor HWS properties. The polyacrylonitrile fibers of Comparative Examples 2 and 3, which had a fiber surface RΔa in the range of 13.0 to 30.0 degrees but an average circularity of 0.80 in its cross-section, also had an HWS set rate exceeding 32%, indicating poor HWS properties. The polyacrylonitrile fiber of Comparative Example 4, which contained an acrylonitrile copolymer obtained by copolymerizing acrylonitrile with vinylidene chloride, also had an HWS set rate exceeding 32%, indicating poor HWS properties.

[0074]

[0075] As can be seen from the data in Table 2, the polyacrylonitrile fibers of Examples 5 and 6 containing chitosan exhibit better adhesion suppression properties during dry heat treatment at 100°C or higher compared to the polyacrylonitrile fibers of Example 7 that do not contain chitosan.

[0076] The present invention is not particularly limited, but preferably includes the following embodiments: [1] A polyacrylonitrile fiber for artificial hair comprising an acrylonitrile copolymer, wherein the acrylonitrile copolymer comprises constituent units derived from acrylonitrile and constituent units derived from vinyl halogenate, the average circularity of the cross-section of the polyacrylonitrile fiber for artificial hair is 0.80 or more, and the calculated average inclination angle RΔa of the line roughness curve elements in a direction perpendicular to the length direction of the fiber on the surface of the polyacrylonitrile fiber for artificial hair is 13.0 to 30.0 degrees. [2] The polyacrylonitrile fiber for artificial hair according to [1], wherein the average height Rc of the line roughness curve elements in a direction perpendicular to the length direction of the fiber on the surface of the polyacrylonitrile fiber for artificial hair is 0.25 to 5.00 μm. [3] The polyacrylonitrile fiber for artificial hair according to [1] or [2], wherein the average length RSm of the line roughness curve elements in a direction perpendicular to the length direction of the fiber on the surface of the polyacrylonitrile fiber for artificial hair is 0.5 to 20.00 μm. [4] The polyacrylonitrile fiber for artificial hair according to any one of [1] to [3], wherein the vinyl halogenate comprises vinyl chloride. [5] The polyacrylonitrile fiber for artificial hair according to any one of [1] to [4], wherein the acrylonitrile copolymer comprises 30 to 80% by mass of constituent units derived from acrylonitrile, 20 to 70% by mass of constituent units derived from vinyl halogenate, and 0 to 5% by mass of constituent units derived from sulfonic acid group-containing vinyl monomer. [6] The polyacrylonitrile fiber for artificial hair according to any one of [1] to [5], wherein the single fiber fineness is 30 to 60 dtex. [7] The polyacrylonitrile fiber for artificial hair according to any one of [1] to [6], wherein the polyacrylonitrile fiber for artificial hair contains chitosan, and the content of chitosan extracted with dilute acetic acid is 0.005 to 0.4% by mass, or the content of chitosan extracted with concentrated hydrochloric acid is 0.014 to 1.2% by mass.[8] A method for producing polyacrylonitrile fibers for artificial hair according to any one of [1] to [7], comprising: a wet spinning step of extruding a spinning solution containing an acrylonitrile copolymer into a coagulation bath using a spinning nozzle with a perfectly circular pore shape to form an undrawn yarn; and a wet drawing step of drawing the undrawn yarn in a drawing bath, wherein the acrylonitrile copolymer comprises constituent units derived from acrylonitrile and constituent units derived from vinyl halogenate; the spinning solution, the coagulation bath and the drawing bath all contain an organic solvent, the organic solvent contains one or more selected from the group consisting of dimethyl sulfoxide, dimethylacetamide, and dimethylformamide; the absolute value of the difference between the concentration Con1 of the organic solvent in the coagulation solution and the concentration Con2 of the organic solvent in the drawing bath |Con1-Con2| is 10% by mass or less; and the temperature of the drawing bath is 90°C or less. [9] A headwear product comprising a polyacrylonitrile fiber for artificial hair as described in any of [1] to [7].

[10] The headwear product according to [9], wherein the headwear product comprises at least one selected from the group consisting of hair wigs, hairpieces, weaving, hair extensions, braided hair, hair accessories, and doll hair.

[0077] 1. Fiber bundle 2a, 2b Cable ties 3. Pillow-shaped weight 4. Horizontal stand 5. Weight

Claims

1. A polyacrylonitrile fiber for artificial hair comprising an acrylonitrile copolymer, wherein the acrylonitrile copolymer comprises constituent units derived from acrylonitrile and constituent units derived from vinyl halogenate, the average circularity of the cross-section of the polyacrylonitrile fiber for artificial hair is 0.80 or higher, and the average slope angle RΔa calculated for the line roughness curve elements in a direction perpendicular to the length direction of the fiber on the surface of the polyacrylonitrile fiber for artificial hair is 13.0 to 30.0 degrees.

2. The polyacrylonitrile fiber for artificial hair according to claim 1, wherein the average height Rc of the linear roughness curve elements in a direction perpendicular to the length direction of the fiber on the surface of the polyacrylonitrile fiber for artificial hair is 0.25 to 5.00 μm.

3. The polyacrylonitrile fiber for artificial hair according to claim 1, wherein the average length RSm of the linear roughness curve elements in a direction perpendicular to the length direction of the fiber on the surface of the polyacrylonitrile fiber for artificial hair is 0.5 to 20.00 μm.

4. The polyacrylonitrile fiber for artificial hair according to claim 1, wherein the vinyl halogen includes vinyl chloride.

5. The polyacrylonitrile fiber for artificial hair according to claim 1, wherein the acrylonitrile copolymer contains 30 to 80% by mass of structural units derived from acrylonitrile, 20 to 70% by mass of structural units derived from vinyl halogenate, and 0 to 5% by mass of structural units derived from sulfonic acid group-containing vinyl monomer.

6. The polyacrylonitrile fiber for artificial hair according to claim 1, wherein the single fiber fineness is 30 to 60 dtex.

7. The polyacrylonitrile fiber for artificial hair according to claim 1, wherein the polyacrylonitrile fiber for artificial hair contains chitosan, and the content of chitosan extracted with dilute acetic acid is 0.005 to 0.4% by mass, or the content of chitosan extracted with concentrated hydrochloric acid is 0.014 to 1.2% by mass.

8. A method for producing polyacrylonitrile fibers for artificial hair according to any one of claims 1 to 7, comprising: a wet spinning step of extruding a spinning solution containing an acrylonitrile copolymer into a coagulation bath using a spinning nozzle with a perfectly circular pore shape to form an undrawn yarn; and a wet drawing step of drawing the undrawn yarn in a drawing bath, wherein the acrylonitrile copolymer comprises constituent units derived from acrylonitrile and constituent units derived from vinyl halogenate; the spinning solution, the coagulation bath and the drawing bath all contain an organic solvent, the organic solvent contains one or more selected from the group consisting of dimethyl sulfoxide, dimethylacetamide, and dimethylformamide; the absolute value of the difference between the concentration Con1 of the organic solvent in the coagulation solution and the concentration Con2 of the organic solvent in the drawing bath |Con1-Con2| is 10% by mass or less; and the temperature of the drawing bath is 90°C or less.

9. A head accessory product comprising a polyacrylonitrile fiber for artificial hair according to any one of claims 1 to 7.

10. The headwear product according to claim 9, wherein the headwear product includes at least one selected from the group consisting of hair wigs, hairpieces, weaving, hair extensions, braided hair, hair accessories, and doll hair.

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