Polyacrylonitrile-based artificial hair, head ornament product comprising same, and method for producing same

Abstract

One or more embodiments of the present invention relate to a polyacrylonitrile-based artificial hair having a bean-shaped transverse cross-section having an outer peripheral shape comprising an upper peripheral edge portion with a curved recess at the center and a lower peripheral edge portion curved in an arc shape, in which: in the transverse cross section, the ratio Lf / Sf of a longer diameter Lf to a shorter diameter Sf is 1.20 or more, and the ratio a / b of a cross-sectional minimum thickness a of the recess to a cross-sectional maximum thickness b of protrusions on both sides of the recess is 0.51 to 0.91; the longer axis of the transverse cross-section is positioned above the bottom of the recess, the longer axis being the longest segment among segments connecting arbitrary two points on the outer periphery of the transverse cross-section; the longer diameter Lf represents the length of the longer axis; the shorter diameter Sf represents the linear distance between two parallel lines parallel to the longer axis and sandwiching the transverse cross section; the cross-sectional minimum thickness a of the recess represents the minimum thickness of the transverse cross-section immediately below the bottom of the recess; and the cross-sectional maximum thickness b of the protrusions represents the maximum thickness of the transverse cross-section in the protrusions positioned above the bottom of the recess.

Description

Polyacrylonitrile artificial hair, head accessories containing the same, and manufacturing method thereof

[0001] The present invention relates to polyacrylonitrile artificial hair used in head accessories such as wigs, head accessories containing the same, and a method for producing the same.

[0002] Traditionally, human hair or artificial hair has been used in head accessories such as wigs. However, as human hair has become difficult to obtain, the demand for artificial hair has increased. Synthetic fibers made of polymers containing acrylonitrile or vinyl chloride have been suitably used as artificial hair due to their excellent feel. For example, Patent Document 1 describes a hair fiber made of a copolymer containing vinyl chloride, acrylonitrile, and a vinyl monomer copolymerizable with these.

[0003] Japanese Patent Application Publication No. 2-53910

[0004] In recent years, there has been a trend toward preference for decorative head accessories with a luster that appeals to the consumer's visual sense, and there is a demand for improved luster in the hair fiber described in Patent Document 1. Furthermore, artificial hair fibers are usually opened using a hackling device, and it is desirable for the fibers to have fewer voids inside in order to improve hackling properties.

[0005] In order to solve the above problems, the present invention provides polyacrylonitrile-based artificial hair that has high processing stability, a sparkling luster in which light reflection locally increases or decreases depending on the viewing angle, and a low void ratio, a head accessory product containing the same, and a method for manufacturing the same.

[0006] One or more embodiments of the present invention are polyacrylonitrile-based artificial hair, the outer peripheral shape of which has a broad bean-shaped cross section consisting of an upper peripheral edge portion having a curved recess in the center and a lower peripheral edge portion curved in an arc, in which the ratio Lf / Sf of the major axis Lf to the minor axis Sf in the cross section is 1.20 or more, the ratio a / b of the minimum cross-sectional thickness a of the recess to the maximum cross-sectional thickness b of the protrusions on both sides of the recess in the cross section is 0.51 to 0.91, and the major axis of the cross section is located above the bottom of the recess. , the long axis is the longest line segment among the line segments connecting any two points on the periphery of the cross section, the long diameter Lf indicates the length of the long axis, the short diameter Sf indicates the linear distance between two parallel lines parallel to the long axis and sandwiching the cross section, the minimum cross-sectional thickness a of the recess indicates the minimum thickness of the cross section directly below the bottom of the recess, and the maximum cross-sectional thickness b of the protrusion indicates the maximum thickness of the cross section of the protrusion located above the bottom of the recess.

[0007] One or more embodiments of the present invention relate to a head accessory product comprising the polyacrylonitrile-based artificial hair.

[0008] One or more embodiments of the present invention are a method for producing polyacrylonitrile-based artificial hair, the method comprising: wet-spinning a spinning solution containing an acrylonitrile copolymer; a nozzle used in the wet spinning has a bean-shaped cross section consisting of an upper peripheral edge portion having a curved recess in the center and a lower peripheral edge portion curved in an arc; the ratio Ln / Sn of the major axis Ln to the minor axis Sn of the cross section of the nozzle is 1.60 or more; and the ratio Sr / Sn of the depth Sr of the recess to the minor axis Sn of the cross section of the nozzle is 0.40 to 0.65; The method for producing polyacrylonitrile-based artificial hair relates to the following: a major axis of the cross section of the nozzle is located above the bottom of the recess, the major axis is the longest line segment among line segments connecting any two points on the periphery of the cross section of the nozzle, the major diameter Ln indicates the length of the major axis, the minor diameter Sn indicates the linear distance between two parallel lines that are parallel to the major axis and sandwich the cross section of the nozzle, and the depth Sr of the recess indicates the linear distance from one of the two parallel lines that is located above the bottom of the recess to the bottom of the recess.

[0009] According to the present invention, it is possible to provide polyacrylonitrile-based artificial hair having high processing stability, a sparkling luster in which light reflection locally increases or decreases depending on the viewing angle, and a low void ratio, and a head ornament product containing the same. Furthermore, according to the manufacturing method of the present invention, it is possible to obtain polyacrylonitrile-based artificial hair having a sparkling luster in which light reflection locally increases or decreases depending on the viewing angle, and a low void ratio, with high productivity by wet spinning.

[0010] 1 is a schematic cross-sectional view of polyacrylonitrile-based artificial hair according to one example of the present invention. FIG. 2 is a schematic cross-sectional view of polyacrylonitrile-based artificial hair according to another example of the present invention. FIG. 3 is a schematic cross-sectional view of polyacrylonitrile-based artificial hair according to another example of the present invention. FIG. 4 is a schematic cross-sectional view of a wet spinning nozzle according to one example used in the examples. FIG. 5 is a schematic cross-sectional view of a wet spinning nozzle according to Comparative Example 2. FIG. 6 is a schematic cross-sectional view of a wet spinning nozzle according to Comparative Example 3. FIG. 7 is a schematic cross-sectional view of a wet spinning nozzle according to Comparative Example 4. FIG. 8 is a photograph (400x) of a cross section of polyacrylonitrile-based artificial hair according to Example 1. FIG. 9 is a photograph (400x) of a cross section of polyacrylonitrile-based artificial hair according to Comparative Example 1. FIG. 10 is a photograph (400x) of a cross section of polyacrylonitrile-based artificial hair according to Comparative Example 2. FIG. 11 is a photograph (400x) of a cross section of polyacrylonitrile-based artificial hair according to Comparative Example 3. 1 is a photograph (400x magnification) of the cross section of the polyacrylonitrile-based artificial hair of Comparative Example 4.

[0011] The inventors of the present invention have discovered that, in polyacrylonitrile-based artificial hair, by making the cross section broad bean-shaped and by setting the position of the major axis in the cross section, the ratio Lf / Sf of the major axis Lf to the minor axis Sf, and the ratio a / b of the minimum cross-sectional thickness a of the recesses to the maximum cross-sectional thickness b of the protrusions within predetermined ranges, it is possible to achieve high processing stability, a sparkling luster in which light reflection locally becomes stronger or weaker depending on the viewing angle (hereinafter also referred to simply as "sparkling luster"), and a reduced void fraction. Furthermore, they have discovered that by using a nozzle (also referred to as a spinning nozzle) having an approximately broad bean-shaped cross section and a position of the major axis, a ratio Ln / Sn of the major axis Ln to the minor axis Sn of the cross section, and a ratio Sr / Sn of the depth Sr to the minor axis Sn of the recesses within predetermined ranges, polyacrylonitrile-based artificial hair with a sparkling luster and a reduced void fraction can be obtained with high productivity by wet spinning.

[0012] In this specification, when a numerical range is indicated with "to", the numerical range includes both end values ​​(upper and lower limits). For example, a numerical range of "X to Y" includes both end values ​​X and Y, and is the same range as "X or more and Y or less". Any number within that range and any range included within that range are specifically disclosed. In addition, when multiple numerical ranges are described in this specification, they are intended to include numerical ranges that combine the upper and lower limits of different numerical ranges as appropriate.

[0013] (Polyacrylonitrile-Based Artificial Hair) In one or more embodiments of the present invention, the polyacrylonitrile-based artificial hair has a broad bean-shaped cross section. In this specification, the broad bean shape refers to an outer periphery consisting of an upper periphery with a curved recess in the center and a lower periphery curved in an arc, and includes an approximately broad bean shape with a linear portion in part of the outer periphery. In the cross section, with the bottom of the recess as the reference point, anything above the bottom of the recess is considered to be upper or upper, and anything below the bottom of the recess is considered to be lower or lower. Figures 1 to 3 show schematic cross-sectional views of polyacrylonitrile-based artificial hair according to one or more embodiments of the present invention, but are not limited to these.

[0014] 1 is a schematic cross-sectional view of an example of polyacrylonitrile-based artificial hair. In this embodiment, the polyacrylonitrile-based artificial hair 1 has a roughly bean-shaped cross-section, consisting of an upper peripheral edge 3 having a curved recess 2 at approximately the center, and a lower peripheral edge 4 that is curved in an arc. On both sides of the recess 2, protrusions 5 and 6 are formed. The recess 2 gradually becomes wider from the bottom to the top, and can also be said to have a roughly inverted trapezoidal shape.

[0015] 2 is a schematic cross-sectional view of another example of polyacrylonitrile artificial hair. In this embodiment, the polyacrylonitrile artificial hair 11 has a roughly bean-shaped cross section, consisting of an upper peripheral edge 13 having a curved recess 12 at approximately the center and a lower peripheral edge 14 that is curved in an arc. On both sides of the recess 12, a protrusion 15 and a protrusion 16 are formed. The recess 12 has a roughly constricted shape.

[0016] 3 is a schematic cross-sectional view of another example of polyacrylonitrile-based artificial hair (hereinafter, also simply referred to as artificial hair). In this embodiment, polyacrylonitrile-based artificial hair 21 has a roughly bean-shaped cross section, with an upper peripheral edge 23 having a curved recess 22 at approximately the center and a lower peripheral edge 24 curved in an arc. On both sides of recess 22, protrusions 25 and 26 are formed. Recess 22 has a roughly divided, constricted shape, with the central end of protrusion 25 and the central end of protrusion 26 partially in contact with each other.

[0017] In the cross section of the artificial hair, the ratio Lf / Sf (hereinafter also referred to as the aspect ratio) of the major axis Lf to the minor axis Sf is 1.20 or more. This makes it easy for the polyacrylonitrile-based artificial hair to exhibit a sparkling luster in which light reflection locally becomes stronger or weaker depending on the viewing angle. The aspect ratio of the cross section of the artificial hair is preferably 1.25 or more, more preferably 1.30 or more, and particularly preferably 1.40 or more. There is no particular upper limit to the aspect ratio of the cross section of the artificial hair, but for example, it may be 2.00 or less from the viewpoint of easily exhibiting a dark hue. In this specification, the major axis Lf and minor axis Sf of the cross section of the polyacrylonitrile-based artificial hair can be measured as described in the examples.

[0018] The major axis Lf of the cross section of the artificial hair is the length of the major axis, which is the longest line segment among the line segments connecting any two points on the periphery of the cross section, and the minor axis Sf of the cross section is the linear distance between two parallel lines that are parallel to the major axis and sandwich the cross section. For example, in Figures 1 to 3, the major axis Lf of the cross section of the artificial hair is the length of the major axis 30, which is the longest line segment among the line segments connecting any two points on the periphery of the cross section, and the minor axis Sf of the cross section is the linear distance between two parallel lines 40 and 50 that are parallel to the major axis 30 and sandwich the cross section.

[0019] The major diameter Lf of the cross section of the artificial hair is not particularly limited, but is preferably 80.0 μm or more, more preferably 80.5 μm or more, and even more preferably 81.0 μm or more, from the viewpoint of easily exhibiting a sparkling luster. The major diameter Lf of the cross section of the artificial hair is preferably 90.5 μm or less, from the viewpoint of easily reducing the void fraction.

[0020] The minor diameter Sf of the cross section of the artificial hair is not particularly limited, but is preferably 40 μm or more, more preferably 45 μm or more, and even more preferably 50 μm or more, from the viewpoint of more easily developing a sparkling luster. The minor diameter Sf of the cross section of the artificial hair is preferably 75 μm or less, more preferably 65 μm or less, and even more preferably 60.0 μm or less, from the viewpoint of more easily developing a dark hue.

[0021] In the cross section of the artificial hair, the ratio a / b (hereinafter also referred to simply as the cross section thickness ratio) of the minimum cross section thickness a of the recessed portion to the maximum cross section thickness b of the protruding portion is 0.51 to 0.91. This suppresses the generation of voids inside the artificial hair, and reduces the void fraction. The cross section thickness ratio of the cross section of the artificial hair is preferably 0.55 or more, more preferably 0.60 or more, even more preferably 0.65 or more, even more preferably 0.70 or more, and particularly preferably 0.730 or more.

[0022] In this specification, the cross-sectional thickness a of the recesses in the cross section of the artificial hair refers to the minimum thickness of the cross section directly below the bottom of the recess at the top center, and the maximum cross-sectional thickness b of the protrusions in the cross section of the artificial hair refers to the maximum thickness of the cross section located above the bottom of the recesses on both sides of the recesses. For example, in Figures 1 to 3, the cross-sectional thickness a of the recesses in the cross section of the artificial hair refers to the minimum thickness of the fiber cross section directly below the recess 2 (12, 22) at the top center, and the maximum cross-sectional thickness b of the protrusions in the cross section of the artificial hair refers to the maximum thickness of the cross section of the protrusions 5, 6 (15, 16; 25, 26) on both sides above the bottom of the recess 2 (12, 22). The maximum cross-sectional thickness b of the protrusions in the cross section of the artificial hair can also be expressed as the length of the line segment through which the major axis 30 passes through the protrusions. In this specification, the minimum cross-sectional thickness a of the recesses in the cross section of the polyacrylonitrile-based artificial hair and the maximum cross-sectional thickness b of the protrusions in the cross section can be measured as described in the Examples.

[0023] In the cross section of the artificial hair, the major axis is located above the bottom of the recess, which improves productivity and makes it easier for the cross-sectional thickness ratio to fall within the above range.

[0024] The minimum cross-sectional thickness a of the recesses in the cross section of the artificial hair is not particularly limited, but for example, from the viewpoint of further reducing the void ratio, it is preferably 26.5 μm or more, more preferably 27.0 μm or more, and even more preferably 27.5 μm or more. The minimum cross-sectional thickness a of the recesses in the cross section of the artificial hair is not particularly limited, but for example, from the viewpoint of easily maintaining high process stability, it is preferably 40.0 μm or less, more preferably 35.0 μm or less, and even more preferably 33.0 μm or less.

[0025] The maximum cross-sectional thickness b of the convex portions of the cross section of the artificial hair is not particularly limited, but for example, from the viewpoint of productivity, it is preferably 30.0 μm or more, more preferably 33.0 μm or more, and even more preferably 36.0 μm or more. The maximum cross-sectional thickness b of the convex portions of the cross section of the artificial hair is not particularly limited, but for example, from the viewpoint of further reducing the void ratio, it is preferably 42.0 μm or less, more preferably 41.0 μm or less, and even more preferably 40.5 μm or less.

[0026] In the cross section of the artificial hair, the ratio b / Lf (hereinafter simply referred to as b / Lf) of the maximum cross-sectional thickness b of the convex portion to the major axis Lf is not particularly limited, but is preferably 0.450 or more from the viewpoint of further reducing the void ratio. In the cross section of the artificial hair, the ratio b / Lf is not particularly limited, but is preferably 0.7 or less from the viewpoint of easily expressing a deep hue.

[0027] In the cross section of the artificial hair, the ratio a / Sf (hereinafter simply referred to as a / Sf) of the minimum cross-sectional thickness a of the recess to the minor axis Sf is not particularly limited, but for example, from the viewpoint of further reducing the void ratio, it is preferably 0.400 or more, more preferably 0.450 or more, and even more preferably 0.470 or more. In the cross section of the artificial hair, the upper limit of a / Sf is not particularly limited, but for example, from the viewpoint of maintaining high process stability, it is preferably 0.75 or less.

[0028] From the viewpoint of suitable use as artificial hair, the single fiber fineness of the polyacrylonitrile-based artificial hair is preferably 20 to 90 dtex, more preferably 25 to 80 dtex, even more preferably 35 to 70 dtex, and particularly preferably 30 to 60 dtex. In this specification, the single fiber fineness means the average value of the finenesses of 100 random single fibers.

[0029] Polyacrylonitrile-based artificial hair does not necessarily have to have the same fineness and cross-sectional size for each artificial hair, and artificial hairs having different fineness and cross-sectional sizes may be mixed together.

[0030] From the viewpoint of enhancing hackling resistance, the polyacrylonitrile artificial hair preferably has a void ratio of 30% or less, more preferably 25% or less, even more preferably 15% or less, even more preferably 10% or less, and particularly preferably 5% or less. In this specification, the void ratio of polyacrylonitrile artificial hair can be measured as described in the examples.

[0031] In order to easily develop a sparkling luster, the polyacrylonitrile-based artificial hair preferably has an average reflectance of 1.75% or less, more preferably 1.70% or less, and even more preferably 1.68% or less in the wavelength range (visible light) of 440 to 660 nm (10 nm intervals).Furthermore, in order to easily develop a sparkling luster, the polyacrylonitrile-based artificial hair preferably has an average reflectance of 1.20% or more in the wavelength range of 440 to 660 nm.

[0032] The acrylonitrile copolymer constituting the polyacrylonitrile-based artificial hair is not particularly limited as long as it contains 25% by mass or more of structural units derived from acrylonitrile, and for example, an acrylonitrile copolymer containing 25 to 100% by mass of structural units derived from acrylonitrile and 0 to 75% by mass of structural units derived from other monomers can be used. The acrylonitrile copolymer may contain 95% by mass or less of structural units derived from acrylonitrile and 5% by mass or more of structural units derived from other monomers, or may contain 90% by mass or less of structural units derived from acrylonitrile and 10% by mass or more of structural units derived from other monomers, and preferably contains 25% by mass or more but less than 80% by mass of structural units derived from acrylonitrile and more than 20% by mass but less than 75% by mass of structural units derived from other monomers.

[0033] The other monomer is not particularly limited as long as it is copolymerizable with acrylonitrile, and examples thereof include halogen-containing monomers such as vinyl chloride and vinylidene chloride; unsaturated carboxylic acids such as acrylic acid and methacrylic acid and salts thereof; (meth)acrylic acid esters such as methyl (meth)acrylate; esters of unsaturated carboxylic acids such as glycidyl methacrylate; vinyl esters such as vinyl acetate and vinyl butyrate; and sulfonic acid group-containing vinyl monomers. One type of other monomer may be used alone, or two or more types may be used in combination.

[0034] Examples of the sulfonic acid group-containing vinyl monomer that can be used include allylsulfonic acid, methallyl sulfonic acid, styrenesulfonic acid, isoprene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and metal salts thereof such as sodium salts and amine salts thereof. One type of sulfonic acid group-containing vinyl monomer may be used alone, or two or more types may be used in combination.

[0035] Specifically, the acrylonitrile copolymer preferably contains 29.5 to 79.5 mass% of structural units derived from acrylonitrile, 20 to 70 mass% of structural units derived from vinyl chloride and / or vinylidene chloride, and 0.5 to 5 mass% of structural units derived from a sulfonic acid group-containing vinyl monomer. When the content of structural units derived from acrylonitrile in the acrylonitrile copolymer is within the above-mentioned range, the heat resistance of the polyacrylonitrile-based artificial hair is good. When the content of structural units derived from vinyl chloride and / or vinylidene chloride in the acrylonitrile copolymer is within the above-mentioned range, the flame retardancy of the polyacrylonitrile-based artificial hair is good. When the content of structural units derived from sulfonic acid group-containing vinyl monomer in the acrylonitrile copolymer is within the above-mentioned range, the hydrophilicity of the polyacrylonitrile-based artificial hair is good.

[0036] The acrylonitrile copolymer more preferably contains 34.5 to 74.5 mass% of structural units derived from acrylonitrile, 25 to 65 mass% of structural units derived from vinyl chloride and / or vinylidene chloride, and 0.5 to 5 mass% of structural units derived from a sulfonic acid group-containing vinyl monomer. The acrylonitrile copolymer preferably contains structural units derived from vinyl chloride, from the viewpoint of providing a more excellent feel to the polyacrylonitrile-based artificial hair.

[0037] The polyacrylonitrile-based artificial hair may contain additives to improve the properties of the artificial hair, as needed, as long as the effects of the present invention are not impaired. Examples of such additives include functional agents such as colorants, gloss regulators, stabilizers, fiber-converging agents, deodorizers, and fragrances. The additives may be used alone or in combination of two or more. The polyacrylonitrile-based artificial hair may contain, for example, 10 parts by mass or less of additives per 100 parts by mass of acrylonitrile copolymer. In other words, the polyacrylonitrile-based artificial hair is artificial hair whose main component is an acrylonitrile copolymer, and may contain 91 to 100% by mass of acrylonitrile copolymer and 9% by mass or less of additives.

[0038] The polyacrylonitrile-based artificial hair may contain a colorant to adjust the hue. The colorant may be either a pigment or a dye. The pigment may be either an inorganic pigment or an organic pigment. Two or more pigments may be used in combination, or a pigment and a dye may be used in combination. As the pigment, carbon black is preferred because it can color the polyacrylonitrile-based artificial hair in a desired black hue and is easily available.

[0039] In order to color the polyacrylonitrile-based artificial hair to a desired degree while suppressing thread breakage during combing, the polyacrylonitrile-based artificial hair preferably contains 0.01 to 2.00 parts by mass, more preferably 0.02 to 0.60 parts by mass, of a colorant relative to 100 parts by mass of the acrylonitrile copolymer.

[0040] An oil (also called a fiber treatment agent) may be attached to the polyacrylonitrile-based artificial hair. The oil may be any oil used for preventing static electricity during the production of the polyacrylonitrile-based artificial hair, preventing sticking of the artificial hair, and improving the texture, and is not particularly limited. Examples of oils that can be used include known oils such as anionic surfactants such as phosphate ester salts and sulfate ester salts; cationic surfactants such as quaternary ammonium salts and imidazolium salts; nonionic surfactants such as ethylene oxide and / or propylene oxide adducts of fats and oils, and partial esters of polyhydric alcohols; animal and vegetable oils and fats, mineral oils, fatty acid esters; and silicone surfactants such as amino-modified silicones. One type of oil may be used alone, or two or more types may be used in combination.

[0041] The amount of oil attached is not particularly limited, but from the viewpoints of preventing static electricity, preventing the artificial hair from sticking, and improving the texture, it is preferably 0.06 to 1.0 parts by mass, more preferably 0.1 to 0.6 parts by mass, and even more preferably 0.15 to 0.35 parts by mass, per 100 parts by mass of polyacrylonitrile-based artificial hair. In this specification, the amount of oil attached to polyacrylonitrile-based artificial hair can be measured and calculated as described in the Examples.

[0042] (Method for producing polyacrylonitrile-based artificial hair) Polyacrylonitrile-based artificial hair can be produced by wet-spinning a spinning solution containing the above-mentioned acrylonitrile copolymer. Wet spinning includes at least a step of extruding the spinning solution into a coagulation bath to coagulate it (hereinafter also referred to as the "coagulation step"), and a step of drawing the fiber obtained in the coagulation step in a drawing bath (hereinafter also referred to as the "drawing step").

[0043] The spinning solution contains, for example, an acrylonitrile copolymer and an organic solvent. The spinning solution may be a liquid in which the acrylonitrile copolymer and the organic solvent are mixed in a spinnable state. As long as the acrylonitrile copolymer is spinnable, it is not necessary for the acrylonitrile copolymer to be completely dissolved in the organic solvent. However, it is preferable that the acrylonitrile copolymer is completely dissolved in the organic solvent in the spinning solution.

[0044] As the acrylonitrile copolymer, those mentioned above can be used as appropriate. From the viewpoint of ease of solubility in organic solvents, the specific viscosity of the acrylonitrile copolymer is preferably 0.1 to 0.3, more preferably 0.15 to 0.25. In this specification, the specific viscosity of the acrylonitrile copolymer is defined as the specific viscosity of a polymer solution prepared by dissolving 2 g of the acrylonitrile copolymer in 1 L of dimethylformamide, measured at 30°C using an Ostwald viscometer.

[0045] The organic solvent is not particularly limited, and any good solvent for the acrylonitrile copolymer can be used as appropriate. Examples include acetone, dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide. Among these, dimethyl sulfoxide is preferred from the viewpoints of productivity and safety.

[0046] The spinning solution may contain a colorant. As the colorant, a solid powder pigment may be used, or a pigment dispersion containing a pigment dispersed in a dispersion medium may be used. In terms of the dispersibility of the pigment in the spinning solution and polyacrylonitrile-based artificial hair, it is preferable to prepare the spinning solution using a pigment dispersion. As the pigment, the pigments described above may be used as appropriate.

[0047] 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 an epoxy group-containing compound per 100 parts by weight of the acrylonitrile copolymer. The inclusion of an epoxy group-containing compound in the spinning solution is preferred because it can suppress odor, coloration of the artificial hair due to heat, and devitrification of the artificial hair due to hot water. In particular, when dimethyl sulfoxide is used as the organic solvent, it can effectively suppress the generation of malodorous components due to decomposition of dimethyl sulfoxide when polyacrylonitrile-based artificial hair is heated. Furthermore, from the viewpoints of spinnability, artificial hair 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 an epoxy group-containing compound per 100 parts by weight of the acrylonitrile copolymer.

[0048] Examples of epoxy group-containing compounds that can be used include glycidyl (meth)acrylate-containing polymers, epoxidized vegetable oils, glycidyl ether-type epoxy resins, glycidyl amine-type epoxy resins, glycidyl ester-type epoxy resins, and cycloaliphatic epoxy resins. One type of epoxy group-containing compound may be used alone, or two or more types may be used in combination.

[0049] The epoxy group-containing compound is preferably a glycidyl (meth)acrylate-containing polymer, more preferably polyglycidyl methacrylate, from the viewpoints of epoxy equivalent (weight of resin containing 1 equivalent of epoxy groups), suppression of coloring of the artificial hair, solubility in dimethyl sulfoxide, and reduction of elution into the spinning bath.

[0050] The weight-average molecular weight of the epoxy group-containing compound is not particularly limited and may be determined appropriately, for example, taking into consideration the solubility in dimethyl sulfoxide and the elution into the spinning bath. When the epoxy group-containing compound is a glycidyl (meth)acrylate-containing polymer, for example, the weight-average molecular weight is preferably 3,000 or more from the viewpoint of reducing the elution into the spinning bath, and the weight-average molecular weight is preferably 100,000 or less from the viewpoint of the solubility in organic solvents such as dimethyl sulfoxide.

[0051] The spinning solution may contain water, for example, 8 to 16 parts by mass, or 8 to 15 parts by mass, of water per 100 parts by mass of the acrylonitrile copolymer. Furthermore, the spinning solution may contain other additives to improve the properties of the artificial hair, as needed, as long as the effects of the present invention are not impaired. The additives used in the polyacrylonitrile-based artificial hair described above can be used as appropriate.

[0052] The solids concentration of the spinning solution is not particularly limited, but may be, for example, 22 to 28% by mass. This makes it easy to obtain polyacrylonitrile-based artificial hair that has good stretchability of the fibers obtained in the coagulation step, has a suitable luster for artificial hair, and is less likely to break when combed. In the spinning solution, the solids include the acrylonitrile copolymer and solid additives such as pigments and dyes.

[0053] The method for producing the spinning solution is not particularly limited as long as it can uniformly mix the various components contained in the spinning solution. When the spinning solution contains a pigment, it is preferable to use a pigment dispersion. As the pigment dispersion, a dispersion in which a pigment is dispersed in an organic solvent can be used. The organic solvent is not particularly limited, and a good solvent for the above-mentioned acrylonitrile copolymer may be used.

[0054] Specifically, the spinning solution may be produced by mixing a pigment dispersion with an acrylonitrile copolymer and / or a resin solution in which the acrylonitrile copolymer is dissolved in an organic solvent. The mixed solution obtained by mixing the pigment dispersion with the acrylonitrile copolymer and / or a resin solution in which the acrylonitrile copolymer is dissolved in an organic solvent can be used as a spinning solution as is or after the concentration is adjusted to a solids concentration of 22 to 28 mass%. The method for adjusting the concentration is not particularly limited, and examples include a method of adding an organic solvent to the mixed solution, a method of adding solid components such as the acrylonitrile copolymer or the pigment to the mixed solution, and a method of concentrating the mixed solution by distilling off the organic solvent from the mixed solution.

[0055] Preferred methods for preparing the spinning dope include a method in which the raw materials for the spinning dope are mixed to prepare a spinning dope so that the solid content concentration is 28% by mass or less, and a method in which the raw materials for the spinning dope are mixed to prepare a mixed solution so that the solid content concentration is more than 28% by mass, and the resulting mixture is diluted with an organic solvent.

[0056] When preparing the spinning solution, it is preferable to add an organic solvent to one or more liquids selected from a pigment dispersion, a resin solution, and a colored resin solution containing an acrylonitrile copolymer, a pigment, and an organic solvent.

[0057] In the coagulation step, the spinning solution is discharged through a spinning nozzle into a coagulation bath and coagulated to form fibers. A mixture of water and an organic solvent is preferably used as the coagulation bath, as it is easier to control the coagulation state. Specifically, an aqueous solution of an organic solvent containing 20 to 75% by mass of an organic solvent and 25 to 80% by mass of water may be used as the coagulation bath. The temperature of the coagulation bath may be, for example, 5 to 50°C.

[0058] The organic solvent used in the coagulation bath is not particularly limited as long as it is a good solvent for the acrylonitrile copolymer. From the viewpoint of productivity of polyacrylonitrile-based artificial hair, one or more solvents selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfone, ε-caprolactam, ethylene carbonate, and sulfolane are preferred, and from the viewpoint of safety, dimethyl sulfoxide is more preferred. From the viewpoints of quality of polyacrylonitrile-based artificial hair and ease of process control, it is preferable that the organic solvent in the spinning solution and the organic solvent in the coagulation bath are the same.

[0059] The temperature of the spinning solution extruded into the coagulation bath is not particularly limited, but may be, for example, 20 to 80°C from the viewpoint of keeping the spinning solution stable in the solution tank without change over time.

[0060] For example, a nozzle having a broad bean-shaped cross section can be used as a nozzle for wet spinning. In the cross section of the nozzle, the broad bean shape has an outer periphery consisting of an upper periphery with a curved recess in the center and a lower periphery that is curved in an arc, and includes a roughly broad bean shape with a linear portion in part of the outer periphery. In the cross section of the nozzle, with the bottom of the recess as the reference point, anything above the bottom of the recess is referred to as the upper or upper part, and anything below the bottom of the recess is referred to as the lower or lower part.

[0061] 4 is a schematic cross-sectional view of an example of a wet spinning nozzle. In this example, nozzle 101 has a roughly bean-shaped cross section, consisting of upper peripheral edge 103 having a curved recess 102 at approximately the center and lower peripheral edge 104 curved in an arc. Convex portions 105 and 106 are formed on both sides of concave portion 102. Convex portion 102 gradually widens from the bottom to the top, and can be said to have a roughly inverted trapezoidal shape.

[0062] In the cross section of the nozzle, the ratio Ln / Sn (hereinafter also referred to as the aspect ratio) of the major axis Ln to the minor axis Sn is 1.60 or more. This makes it easier to obtain polyacrylonitrile-based artificial hair with a sparkling luster and an aspect ratio of 1.20 or more by wet spinning. The aspect ratio of the cross section of the nozzle is more preferably 1.70 or more, even more preferably 1.80 or more, and particularly preferably 1.90 or more. There is no particular upper limit to the aspect ratio of the cross section of the nozzle, but it may be 2.10 or less, for example, from the viewpoint of making it easier to obtain polyacrylonitrile-based artificial hair with a dark hue.

[0063] The major axis Ln of the cross section of the nozzle is the length of the major axis, which is the longest line segment among the line segments connecting any two points on the periphery of the cross section of the nozzle, and the minor axis Sn of the cross section of the nozzle is the linear distance between two parallel lines that are parallel to the major axis and sandwich the cross section of the nozzle. For example, in Figure 4, the major axis Ln of the cross section of the nozzle is the length of the major axis 130, which is the longest line segment among the line segments connecting any two points on the periphery of the cross section, and the minor axis Sn of the cross section of the nozzle is the linear distance between two parallel lines 140 and 150 that are parallel to the major axis 130 and sandwich the cross section of the nozzle.

[0064] In the cross section of the nozzle, the ratio Sr / Sn of the depth Sr of the recess to the minor axis Sn (hereinafter also referred to simply as the depth ratio) is preferably 0.40 to 0.65. In this specification, the depth Sr of the recess refers to the linear distance from a parallel line parallel to the major axis and positioned above the bottom of the recess among two parallel lines sandwiching the cross section of the nozzle to the bottom of the recess. This ensures high process stability in wet spinning, making it easier to obtain polyacrylonitrile-based artificial hair with a sparkling luster and a low void fraction. The depth ratio of the cross section of the nozzle is more preferably 0.42 to 0.60, even more preferably 0.44 to 0.58, and particularly preferably 0.45 to 0.57. For example, in Figure 4, the depth Sr of the recess is represented by the linear distance from a parallel line 140 positioned above the bottom of the recess to the bottom of the recess.

[0065] In the cross section of the nozzle, the major axis is located above the bottom of the recess, which improves the processing stability of the wet spinning process and enables polyacrylonitrile-based artificial hair with a sparkling luster and a low void ratio to be obtained with high productivity.

[0066] In order to more easily reduce the void ratio of polyacrylonitrile-based artificial hair in the cross section of the nozzle, the ratio Lr / Ln (hereinafter also referred to as width ratio) of the width Lr of the recess to the major axis Ln is preferably 0.125 or more, more preferably 0.130 or more, and even more preferably 0.135 or more. In order to easily obtain polyacrylonitrile-based artificial hair that exhibits a sparkling luster, the width ratio of the cross section of the nozzle may be 0.16 or less. In this specification, the width of the recess in the cross section of the nozzle means the width on the major axis of the recess. For example, in Figure 4, the width of the recess is indicated by Lr.

[0067] The spinning speed is not particularly limited, but may be, for example, 2 to 17 m / min from the viewpoint of industrial productivity.

[0068] The fiber produced by coagulating the spinning dope in the coagulation bath is then drawn in a drawing bath. The method for transferring the fiber from the coagulation bath to the drawing bath is not particularly limited. Typically, the fiber is stretched between a roll in the coagulation bath and one or more fiber transfer rolls outside the coagulation bath, and the fiber is transferred into the drawing bath by rotating the rolls.

[0069] The stretching bath is not particularly limited as long as it can perform good stretching. For example, water or an aqueous solution of an organic solvent having a lower organic solvent concentration than the coagulation bath can be used as the stretching bath. For example, an aqueous solution of an organic solvent containing 10 to 90% by mass of an organic solvent and 10 to 90% by mass of water is preferred as the stretching bath. When stretching is performed using a water bath, the stretching step may be performed after the water-washing step described below, or stretching and water-washing may be performed simultaneously.

[0070] The fibers transferred into the stretching bath are stretched between an upstream stretching roll located upstream in the direction of fiber movement and a downstream stretching roll located downstream in the direction of fiber movement, and are stretched by the rotation of the upstream stretching roll (sometimes referred to as the first stretching roll) and the downstream stretching roll (sometimes referred to as the second stretching roll).

[0071] In the drawing step, the draw ratio is expressed as the length of the fiber after drawing / the length of the fiber before drawing, and from the viewpoint of improving the strength of the fiber and productivity, it is preferably more than 1 and not more than 8. The draw ratio is adjusted by adjusting the tension applied to the fiber being drawn by the first drawing roll and the second drawing roll and the rotation speeds of the first drawing roll and the second drawing roll.

[0072] The length in the direction of fiber movement in the stretching bath refers to the distance between the first stretching roll and the second stretching roll, and is sometimes referred to as the inter-roll distance. The inter-roll distance is preferably 90 cm or more. Multiple stretching baths may be used, and in such cases, the length in the direction of fiber movement in the stretching bath is the sum of the inter-roll distances in each stretching bath. The stretched fiber is passed over a roll such as a clover roll provided outside the stretching bath and appropriately recovered from the stretching bath.

[0073] Stretching in the stretching bath may be performed in multiple steps. Preferably, the average stretching speeds are different for at least two of the multiple stretching steps. When stretching in the stretching bath is performed in multiple steps, it is easy to control the stretching conditions for each stage of the stretching process, such as the initial, middle, and final stages. The multiple stretching steps may be performed in the same stretching bath, or may be performed using multiple different stretching baths. Using multiple different stretching baths is preferred because the temperature and composition of the stretching bath can be changed for each stretching bath.

[0074] The temperature of the stretching bath is preferably 30 to 110° C. from the viewpoint of suppressing thread breakage and easily developing a sparkling luster. When multiple stretching baths are used, the temperature of the first stretching bath is preferably 50 to 110° C., more preferably 75 to 95° C., from the viewpoint of maintaining a high luster.

[0075] In addition, in order to easily obtain polyacrylonitrile-based artificial hair with a sparkling luster, when drawing in a drawing bath is carried out using a plurality of drawing baths, it is preferable that the temperature of the drawing bath on the most upstream side in the fiber movement direction is 75 to 95°C.

[0076] The fibers (polyacrylonitrile-based artificial hair) obtained by drawing are usually washed with water in a water-washing step. In the water-washing step, the polyacrylonitrile-based artificial hair drawn in the drawing bath is washed with water to remove the organic solvent from the polyacrylonitrile-based artificial hair. In the water-washing step, water or an aqueous solution of an organic solvent with a lower organic solvent concentration than the coagulation bath is preferably used as the washing liquid, and water is more preferably used. The temperature of the washing liquid is preferably 20 to 95°C. The water-washing can be carried out by immersing the drawn polyacrylonitrile-based artificial hair in a bath containing such a washing liquid.

[0077] In the water washing step, although not particularly limited, it is preferable that the ratio of the total fineness to the width of the polyacrylonitrile artificial hair is 300,000 dtex / cm or less in order to enhance the effect of removing the organic solvent.

[0078] The washed polyacrylonitrile-based artificial hair may be dehydrated in a dehydration step, in which the washed polyacrylonitrile-based artificial hair may be dehydrated by pressing with nip rolls.

[0079] The nip rolls are not particularly limited as long as they are normally used when producing fibers by a wet spinning method. Pressing with nip rolls means applying pressure to the polyacrylonitrile-based artificial hair while passing it between a pair of upper and lower nip rolls. The method of applying pressure is not particularly limited as long as pressure can be applied to the polyacrylonitrile-based artificial hair by the nip rolls, and examples include applying pressure to the upper nip roll with a cylinder, placing a weight on the upper nip roll, and pulling the upper nip roll downward.

[0080] Examples of nip rolls that can be used include rubber nip rolls and metal nip rolls. A rubber nip roll (also referred to as a rubber roll) is preferably used as the upper nip roll, and a metal nip roll (also referred to as a metal roll) is preferably used as the lower nip roll. Examples of materials for the rubber nip roll include natural rubber, styrene butadiene rubber, nitrile rubber, chloroprene rubber, and silicone rubber. The rubber nip roll may also be a metal roll wrapped with rubber. From the viewpoint of maintaining the cross-sectional shape of the artificial hair, the thickness of the rubber is preferably 3 mm or more. Examples of materials for the metal nip roll include stainless steel. The hardness of the nip roll is preferably 40 to 100. The hardness of the nip roll refers to a value measured using a Type A durometer in accordance with JIS K 6253.

[0081] The above-mentioned water washing and pressing with nip rolls may be performed alternately once and multiple times, or the above-mentioned water washing may be performed two or more times, and then pressing with nip rolls may be performed one or more times.

[0082] The polyacrylonitrile-based artificial hair obtained after stretching, the polyacrylonitrile-based artificial hair after washing, or the polyacrylonitrile-based artificial hair after dehydration is then dried in a drying step. In the drying step, it is preferable that the moisture contained in the polyacrylonitrile-based artificial hair is almost completely removed. The drying method is not particularly limited as long as it can remove moisture from the polyacrylonitrile-based artificial hair. Examples of drying methods include hot air drying and drying by contact with a heated roll. The drying temperature is not particularly limited, but is preferably, for example, 110 to 190°C.

[0083] An oil may be applied to the polyacrylonitrile artificial hair before drying. The oil may be any oil typically used during the production of polyacrylonitrile artificial hair for the purposes of preventing static electricity, preventing sticking of the polyacrylonitrile artificial hair, and improving the texture. Examples of oils that can be used include known oils such as anionic surfactants such as phosphate ester salts and sulfate ester salts; cationic surfactants such as quaternary ammonium salts and imidazolium salts; nonionic surfactants such as ethylene oxide and / or propylene oxide adducts of fats and oils, and partial esters of polyhydric alcohols; animal and vegetable oils and fats, mineral oils, fatty acid esters; and silicone surfactants such as amino-modified silicones. One type of oil may be used alone, or two or more types may be used in combination.

[0084] The dried polyacrylonitrile-based artificial hair may be further stretched (also referred to as secondary stretching) as necessary. The stretching method is not particularly limited, and examples thereof include dry and wet stretching. The stretching temperature for the secondary stretching is not particularly limited, and may be, for example, 110 to 190°C or lower. The stretching ratio is not particularly limited, and may be, for example, more than 1 and not more than 4. The total stretching ratio, including the stretching before drying, is preferably more than 1 and not more than 10.

[0085] The dried polyacrylonitrile-based artificial hair or the secondarily drawn polyacrylonitrile-based artificial hair is preferably further relaxed in a heat-relaxing treatment step. The relaxation rate is not particularly limited, but is preferably, for example, 5 to 30%. The heat-relaxing treatment can be carried out in a high-temperature, for example, dry heat atmosphere at 130 to 200°C or in a superheated steam atmosphere. Alternatively, it can be carried out in a pressurized steam or heated pressurized steam atmosphere at a pressure of 0.05 to 0.4 MPa.

[0086] (Head Ornament Product) The polyacrylonitrile-based artificial hair of one or more embodiments of the present invention may be used alone as artificial hair, or may be used in combination with other artificial hair fibers. Furthermore, a head ornament product can be constructed using the polyacrylonitrile-based artificial hair of one or more embodiments of the present invention. This makes it possible to provide a head ornament product that has a sparkling luster, a low void ratio, and good hackling resistance. The head ornament product may contain other artificial hair fibers in addition to the polyacrylonitrile-based artificial hair of one or more embodiments of the present invention. Examples of other artificial hair fibers include, but are not limited to, polyvinyl chloride fibers, nylon fibers, polyester fibers, and regenerated collagen fibers.

[0087] Headwear products include weaving, wigs, braids, toupees, hair extensions, and hair accessories.

[0088] The following examples will illustrate one or more embodiments of the present invention, but the present invention is not limited to the following examples.

[0089] The measurement and evaluation methods used in the examples and comparative examples will be explained below.

[0090] (Amount of Oil Adhesion) Approximately 2 g (sample mass: W0) of sample (polyacrylonitrile-based artificial hair) was cut to a length of 12-15 cm and packed into a stainless steel tube (oil extraction tube) with an approximately 1 mm hole at the bottom. Next, 35 mL of a 1:1 (mass ratio) mixture of ethanol and cyclohexane was prepared as the oil extraction solution, and approximately 20 mL of this mixture was placed into the oil extraction tube. The lid of the oil extraction tube was adjusted to allow the extraction solution to drip at a rate of approximately 1 drop per 1-1.5 seconds, and oil extraction began. A tray (empty tray mass: W1) heated to 120°C was used as a receiver for the dripping solution, and the tube was set so that the dripping solution would fall onto it. Once dripping was complete, the lid was removed, and the fiber inside the oil extraction tube was pressed with a stainless steel rod to squeeze out the extract. This procedure was repeated using the remaining extraction solution (approximately 15 mL). After the extraction was completed, the tray was placed in a 90°C oven and removed after 5 minutes. The weight of the oil in the tray where the extract had dried up and only the oil remained (W2) and the total weight of the tray were measured, and the amount of oil attached to 100 parts by weight of polyacrylonitrile-based artificial hair was calculated using the following formula 1. [Formula 1] Amount of oil attached (parts by weight) = 100 x (W2 - W1) / (W0 + W1 - W2)

[0091] (Method for observing the cross section of polyacrylonitrile artificial hair) <Sample preparation> An appropriate amount of polyacrylonitrile artificial hair cut to a length of 15 cm was packed into a heat-shrinkable tube (manufactured by Junkosha, model number "FEP-040", inner diameter before shrinkage φ4.5 mm, inner diameter after shrinkage φ3.3 mm, length 1 m) and left in an oven at 105°C for 5 minutes. After that, it was removed and allowed to cool, and then the heat-shrinkable tube packed with polyacrylonitrile artificial hair and shrunk was cut to a length of approximately 3 mm using a razor to prepare a sample for cross-sectional observation. <Observation and photography> The sample for cross-sectional observation was observed at 400x magnification with a laser microscope (VK-X260, manufactured by KEYENCE), and an image for analysis (observation measurement range: horizontal 675 μm × vertical 506 μm) was photographed.

[0092] (Method of Analyzing Cross-Sectional Images) The analysis images were imported into image analysis software (WinROOF, Mitsubishi Corporation), and the following parameters were defined and measured. <Major and Minor Diameters> In the analysis image of each sample, the major diameters of 10 arbitrarily selected cross sections were measured, and the calculated average value was taken as the major diameter Lf of the sample. In the analysis image of each sample, the minor diameters of 10 arbitrarily selected cross sections were measured, and the calculated average value was taken as the minor diameter Sf of the sample. <Minimum Cross-Sectional Thickness of Recesses and Maximum Cross-Sectional Thickness of Protrusions> In the analysis image of each sample, the minimum cross-sectional thicknesses of the recesses of 10 arbitrarily selected cross sections were measured, and the calculated average value was taken as the minimum cross-sectional thickness a of the recesses of the sample. In the analysis image of each sample, the maximum cross-sectional thicknesses of 10 arbitrarily selected cross sections of the protrusions of the sample were measured, and the calculated average value was taken as the maximum cross-sectional thickness b of the protrusions of the sample.

[0093] (Void Ratio) In the analysis image of each sample, the number of all cross sections and the number of cross sections with voids (holes) inside the cross sections were visually counted, and the void ratio was calculated using the following formula 2. [Formula 2] Void ratio (%) = 100 × (number of cross sections with voids inside the cross sections / number of all cross sections)

[0094] (Gloss) Polyacrylonitrile artificial hair measuring 30 cm x 30 g (length x weight) was used as a sample, and the sample was placed on a semi-cylindrical stand with a diameter of 10 cm, and a sensory evaluation was carried out by a professional beauty evaluator. At this time, the sample was observed from the top, bottom, left and right directions, and the gloss of the sample was scored in increments of 0.25 points in a range of 1 to 5 points, with the gloss of comparison level 1 (polyacrylonitrile fiber, "Afrelle" manufactured by Kaneka Corporation) being scored as 3 points. A gloss evaluation score of 4 or more indicates a sparkling gloss. 1: Gloss weaker than that of comparison level 1 2: Gloss slightly weaker than that of comparison level 1 3: Gloss equivalent to that of comparison level 1 4: Glossy gloss slightly stronger than that of comparison level 1 5: Glossy gloss stronger than that of comparison level 1

[0095] (Hue) Polyacrylonitrile artificial hair measuring 30 cm x 30 g (length x weight) was used as a sample, and the sample was placed on a semi-cylindrical stand with a diameter of 10 cm, and a sensory evaluation was carried out by a professional beauty evaluator. At this time, the sample was observed from the top, bottom, left and right directions, and the hue of the sample was scored in increments of 0.25 points in a range of 1 to 5 points, with the hue of comparison level 1 (polyacrylonitrile fiber, black, "Afrelle" manufactured by Kaneka Corporation) being scored as 3 points. The higher the score in the hue evaluation, the darker the color. 1: Lighter hue than the hue of comparison level 1 2: Slightly lighter hue than the hue of comparison level 1 3: Same hue as the hue of comparison level 1 4: Slightly darker hue than the hue of comparison level 1 5: Darker hue than the hue of comparison level 1

[0096] (Reflectance) A 30 cm x 25 g (length x weight) polyacrylonitrile artificial hair sample was set in the groove of a hair bundle measuring jig (manufactured by Konica Minolta, Inc.). After the presser foot for fixing the hair bundle was placed down, the sample was rotated by 90° for each measurement. The reflectance was measured four times at wavelengths in 10 nm intervals in the wavelength range of 440 to 660 nm using a spectrophotometer ("CM-2600d" manufactured by Konica Minolta, Inc.), and the average of the four measured values ​​was taken as the reflectance at the corresponding wavelength. The light source was D65, the viewing angle of the observation field was 2°, and the mask diameter was 8 mm. The specular reflection light treatment was SCI + SCE simultaneous measurement, and the UV setting was UV 100%.

[0097] (Process Stability) In the drawing process, the maximum draw ratio at which stable drawing was possible without single yarn breakage, drawing breakage, or winding around the drawing roll was investigated, and the process stability was evaluated according to the following criteria: High: Maximum draw ratio at 130°C is 3.2 times or more Medium: Maximum draw ratio at 130°C is 2.9 times or more and less than 3.2 times Low: Maximum draw ratio at 130°C is less than 2.9 times

[0098] Example 1 An acrylonitrile copolymer (specific viscosity 0.174) 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 (DMSO) to prepare an acrylonitrile copolymer solution having an acrylonitrile copolymer concentration of 26.0% by weight and a water concentration of 2.7% by weight. Next, 0.26 parts by weight of a yellow dye (Color Index Basic Yellow 28) per 100 parts by weight of the acrylonitrile copolymer, 0.37 parts by weight of a red dye (Color Index Basic Red 46) per 100 parts by weight of the acrylonitrile copolymer, 0.46 parts by weight of a blue dye (Color Index Basic Blue 41) per 100 parts by weight of the acrylonitrile copolymer, and 0.8 parts by weight of polyglycidyl methacrylate (weight average molecular weight 12,000) per 100 parts by weight of the acrylonitrile copolymer were added to the obtained acrylonitrile copolymer solution to prepare a spinning dope. This spinning solution was extruded into a coagulation bath of 47% by mass DMSO aqueous solution at 35°C using a spinning nozzle having an approximately bean-shaped cross section as shown in Figure 4 and the size shown in Table 1, and wet-spun at a spinning speed of 5 m / min, followed by drawing 2.1 times in a drawing bath of 50% by mass DMSO aqueous solution at 75°C. Subsequently, after washing with warm water at 90°C, the yarn was immersed for 1 to 3 seconds in an oil bath (60°C) containing an oil (a mixed oil of POE castor oil, sorbitan stearate, and an amide-based oil) to impregnate the yarn with the oil, dried at 140°C, drawn 3 times, and then subjected to a 27% relaxation treatment at 155°C to produce polyacrylonitrile-based artificial hair with a single fiber fineness of approximately 46 dtex (oil deposition amount: 0.2 parts by mass).

[0099] Examples 2 to 6 Polyacrylonitrile-based artificial hair with a single fiber fineness of approximately 46 dtex (amount of oil applied: 0.2 parts by mass) was produced in the same manner as in Example 1, except that a spinning nozzle having the shape shown in FIG. 4 and the size shown in Table 1 was used.

[0100] Comparative Example 1 Polyacrylonitrile-based artificial hair with a single fiber fineness of approximately 46 dtex (amount of oil applied: 0.2 parts by mass) was produced in the same manner as in Example 1, except that a spinning nozzle having the shape shown in FIG. 4 and the size shown in Table 1 was used.

[0101] Comparative Example 2 Polyacrylonitrile-based artificial hair with a single fiber fineness of approximately 46 dtex (amount of oil applied: 0.2 parts by mass) was produced in the same manner as in Example 1, except that a spinning nozzle having the shape shown in Fig. 5 and the size shown in Table 1 was used. In the nozzle having an approximately broad bean-shaped cross section shown in Fig. 5, the bottom of the recess is located on the major axis, so the recess does not have a width Lr on the major axis.

[0102] (Comparative Example 3) Polyacrylonitrile-based artificial hair with a single fiber fineness of approximately 46 dtex (amount of oil applied: 0.2 parts by mass) was produced in the same manner as in Example 1, except that a spinning nozzle having the shape shown in Fig. 6 and the size shown in Table 1 was used. In the nozzle having an approximately broad bean-shaped cross section shown in Fig. 6, the major axis is located below the bottom of the recess, so the width Lr of the recess on the major axis does not exist.

[0103] (Comparative Example 4) Polyacrylonitrile-based artificial hair with a single fiber fineness of approximately 46 dtex (amount of oil applied: 0.2 parts by mass) was produced in the same manner as in Example 1, except that a spinning nozzle having the shape shown in Figure 7 and the size shown in Table 1 was used. In the nozzle having a dumbbell-shaped cross section shown in Figure 7, Lr means the width of the bottom of the recess.

[0104] The cross sections of the polyacrylonitrile-based artificial hair of the Examples and Comparative Examples were observed and evaluated as described above, and the results are shown in Table 1 below. The properties of the polyacrylonitrile-based artificial hair of the Examples and Comparative Examples were also observed as described above, and the results are shown in Table 1 below. Photographs of the cross sections of the polyacrylonitrile-based artificial hair of Example 1 and Comparative Examples 1 to 4 are shown in Figures 8 to 12, respectively. The reflectance of the polyacrylonitrile-based artificial hair of Examples 1 and 2 and Comparative Example 1 was measured as described above, and the results are shown in Table 2 below.

[0105]

[0106]

[0107] As can be seen from Table 1, the polyacrylonitrile-based artificial hair of the Examples had high processing stability, a sparkling luster, and a low void ratio. On the other hand, the polyacrylonitrile-based artificial hair of Comparative Examples 1 and 2, which had an approximately broad bean-shaped cross section but a cross-sectional thickness ratio a / b outside the range of 0.51 to 0.91, had a high void ratio. Furthermore, the polyacrylonitrile-based artificial hair of Comparative Example 3, which had an approximately broad bean-shaped cross section but the long axis of the cross section was below the bottom of the cross-sectional recess, had low processing stability. The polyacrylonitrile-based artificial hair of Comparative Example 4, which had a dumbbell-shaped cross section, was unable to exhibit a sparkling luster. Furthermore, the polyacrylonitrile-based artificial hair of the Examples, which had an approximately broad bean-shaped cross section, had a better feel to the touch than the polyacrylonitrile-based artificial hair of Comparative Example 4, which had a dumbbell-shaped cross section.

[0108] As can be seen from Table 2, the polyacrylonitrile-based artificial hair of the Examples has a lower average reflectance in the wavelength range of 440 to 660 nm (visible light), in the range of 1.20 to 1.75%, compared to the polyacrylonitrile-based artificial hair of the Comparative Examples, and is excellent in sparkling luster.

[0109] The present invention is not particularly limited, but includes at least the following embodiments.

[0110] [1] Polyacrylonitrile-based artificial hair, the outer peripheral shape of which has a broad bean-shaped cross section consisting of an upper peripheral edge portion having a curved recess in the center and a lower peripheral edge portion curved in an arc, wherein in said cross section, the ratio Lf / Sf of the major axis Lf to the minor axis Sf is 1.20 or more, and in said cross section, the ratio a / b of the minimum cross-sectional thickness a of said recess to the maximum cross-sectional thickness b of the convex portions on both sides of said recess is 0.51 to 0.91, the major axis of said cross section is located above the bottom of said recess, and said major axis is the longest line segment among line segments connecting any two points on the periphery of said cross section, said major axis Lf indicates the length of said major axis, and said minor axis Sf indicates the linear distance between two parallel lines parallel to said major axis and sandwiching said cross section,

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[420] [4] The polyacrylonitrile-based artificial hair according to any one of [1] to [3], wherein the polyacrylonitrile-based artificial hair contains an acrylonitrile copolymer, the acrylonitrile copolymer containing 29.5 to 79.5% by mass of structural units derived from acrylonitrile, 20 to 70% by mass of structural units derived from one or more halogen-containing monomers selected from the group consisting of vinyl chloride and vinylidene chloride, and 0.5 to 5% by mass of structural units derived from a vinyl monomer containing a sulfonic acid group. [5] The polyacrylonitrile-based artificial hair according to any one of [1] to [4], wherein the polyacrylonitrile-based artificial hair has an average reflectance of 1.75% or less in the wavelength range of 440 to 660 nm. [6] A head accessory comprising the polyacrylonitrile-based artificial hair according to any one of [1] to [5]. [7] The headwear product according to [6], which includes at least one selected from the group consisting of weaving, wigs, braids, toupees, hair extensions and hair accessories.[8] A method for producing polyacrylonitrile-based artificial hair, comprising a step of wet-spinning a spinning solution containing an acrylonitrile copolymer, wherein a nozzle used for wet spinning has a broad bean-shaped cross section consisting of an upper peripheral edge portion having a curved recess in the center and a lower peripheral edge portion curved in an arc, wherein the ratio Ln / Sn of the major axis Ln to the minor axis Sn of the cross section of the nozzle is 1.60 or more, wherein the ratio Sr / Sn of the depth Sr of the recess to the minor axis Sn of the cross section of the nozzle is 0.40 to 0.65, wherein the major axis of the cross section of the nozzle is located above the bottom of the recess, and wherein the major axis is the longest line segment among line segments connecting any two points on the periphery of the cross section of the nozzle, wherein the major axis Ln indicates the length of the major axis, and the minor axis Sn indicates the linear distance between two parallel lines parallel to the major axis and sandwiching the cross section of the nozzle, The depth Sr of the recess indicates the linear distance from the parallel line located above the bottom of the recess to the bottom of the recess. [9] A method for producing polyacrylonitrile artificial hair according to [8], wherein in a cross section of the nozzle, the ratio Lr / Ln of the width Lr of the recess to the major axis Ln is 0.125 or more, and the width Lr of the recess indicates the width of the recess on the major axis.

[10] A method for producing polyacrylonitrile artificial hair according to [8] or [9], wherein the acrylonitrile copolymer contains 29.5 to 79.5 mass% of structural units derived from acrylonitrile, 20 to 70 mass% of structural units derived from one or more halogen-containing monomers selected from the group consisting of vinyl chloride and vinylidene chloride, and 0.5 to 5 mass% of structural units derived from a sulfonic acid group-containing vinyl monomer.

[0111] 1, 11, 21 Polyacrylonitrile artificial hair (cross section) 2, 12, 22 Concave portion 3, 13, 23 Upper peripheral portion 4, 14, 24 Lower peripheral portion 5, 6, 15, 16, 25, 26 Convex portion 30 Long axis 40, 50 Parallel lines 101 Spinning nozzle (cross section) 102 Concave portion 103 Upper peripheral portion 104 Lower peripheral portion 105, 106 Convex portion 130 Long axis 140, 150 Parallel lines

Claims

1. A polyacrylonitrile-based artificial hair, the outer peripheral shape of which has a broad bean-shaped cross section consisting of an upper peripheral portion having a curved recess in the center and a lower peripheral portion curved in an arc, the ratio Lf / Sf of the major axis Lf to the minor axis Sf of said cross section being 1.20 or more, the ratio a / b of the minimum cross-sectional thickness a of said recess to the maximum cross-sectional thickness b of the protrusions on both sides of said recess being 0.51 to 0.91, the major axis of said cross section being located above the bottom of said recess, said major axis being the longest line segment among the line segments connecting any two points on the outer periphery of said cross section, said major axis Lf indicating the length of said major axis, and said minor axis Sf indicating the straight-line distance between two parallel lines parallel to said major axis and sandwiching said cross section, In the polyacrylonitrile-based artificial hair, the minimum cross-sectional thickness a of the recessed portion indicates the minimum thickness of the cross section directly below the bottom of the recessed portion, and the maximum cross-sectional thickness b of the protruding portion indicates the maximum thickness of the cross section of the protruding portion located above the bottom of the recessed portion.

2. The polyacrylonitrile-based artificial hair according to claim 1, wherein the polyacrylonitrile-based artificial hair has a void ratio of 30% or less.

3. The polyacrylonitrile artificial hair according to claim 1, wherein the polyacrylonitrile artificial hair has a single fiber fineness of 30 to 60 dtex.

4. The polyacrylonitrile-based artificial hair according to claim 1, wherein the polyacrylonitrile-based artificial hair contains an acrylonitrile copolymer, the acrylonitrile copolymer containing 29.5 to 79.5% by mass of structural units derived from acrylonitrile, 20 to 70% by mass of structural units derived from one or more halogen-containing monomers selected from the group consisting of vinyl chloride and vinylidene chloride, and 0.5 to 5% by mass of structural units derived from a vinyl monomer containing a sulfonic acid group.

5. The polyacrylonitrile-based artificial hair according to claim 1, wherein the polyacrylonitrile-based artificial hair has an average reflectance of 1.75% or less in the wavelength range of 440 to 660 nm.

6. A hair accessory comprising the polyacrylonitrile artificial hair according to any one of claims 1 to 5.

7. The head decoration product according to claim 6, which includes at least one selected from the group consisting of weaving, wigs, braids, tupes, hair extensions and hair accessories.

8. A method for producing polyacrylonitrile-based artificial hair, comprising a step of wet-spinning a spinning solution containing an acrylonitrile copolymer, wherein a nozzle used in the wet spinning has a broad bean-shaped cross section consisting of an upper peripheral portion having a curved recess in the center and a lower peripheral portion curved in an arc, wherein the ratio Ln / Sn of the major axis Ln to the minor axis Sn of the cross section of the nozzle is 1.60 or more, wherein the ratio Sr / Sn of the depth Sr of the recess to the minor axis Sn of the cross section of the nozzle is 0.40 to 0.65, wherein the major axis of the cross section of the nozzle is located above the bottom of the recess, wherein the major axis is the longest line segment among line segments connecting any two points on the periphery of the cross section of the nozzle, wherein the major axis Ln indicates the length of the major axis, and the minor axis Sn indicates the straight-line distance between two parallel lines parallel to the major axis and sandwiching the cross section of the nozzle, A method for producing polyacrylonitrile-based artificial hair, wherein the depth Sr of the recess indicates the straight-line distance from the parallel line located above the bottom of the recess among the two parallel lines to the bottom of the recess.

9. A method for producing polyacrylonitrile-based artificial hair according to claim 8, wherein in a cross section of the nozzle, a ratio Lr / Ln of a width Lr of the recess to a major axis Ln is 0.125 or more, and the width Lr of the recess indicates a width of the recess on the major axis.

10. A method for producing polyacrylonitrile-based artificial hair according to claim 8 or 9, wherein the acrylonitrile copolymer contains 29.5 to 79.5 mass% of structural units derived from acrylonitrile, 20 to 70 mass% of structural units derived from one or more halogen-containing monomers selected from the group consisting of vinyl chloride and vinylidene chloride, and 0.5 to 5 mass% of structural units derived from a vinyl monomer containing a sulfonic acid group.

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