Fiber bundle for artificial hair and hair accessory product

Abstract

Provided is a fiber bundle for artificial hair that is capable of both having natural color and glossy appearance that have suitable variations similar to human hair and reducing fibers coming loose and stray fibers after hot water treatment.　The present invention provides a fiber bundle for artificial hair that comprises a plurality of fibers for artificial hair, wherein: the plurality of fibers for artificial hair include hollow fibers for artificial hair which are provided with a hollow part that extends in the lengthwise direction of the fibers for artificial hair; and when a hollowness ratio is defined as the ratio of area occupied by the hollow part in a cross-section perpendicular the lengthwise direction of a fiber for artificial hair, the coefficient of variation of the hollowness ratio of the fibers for artificial hair included in the fiber bundle for artificial hair is 0.02-0.30.

Description

Artificial hair fiber bundles and hair accessories

[0001] The present invention relates to a fiber bundle for artificial hair and a hair accessory product.

[0002] Artificial hair is becoming increasingly important as an alternative to human hair in hair accessories such as wigs, hair accessories, hair bands, doll hair, etc. Materials for artificial hair fibers include acrylic resins, vinyl chloride resins, and polyester resins, and artificial hair fibers made from these resins are commercially available.

[0003] Patent Document 1 discloses artificial hair containing hollow fibers having hollow portions with a hollow ratio of 10 to 50%. Patent Document 2 discloses fibers for artificial hair having a void in the center of the fiber cross section, the ratio of the area of ​​the void to the total area of ​​the fiber cross section being 5% to 50%, the cross-sectional shape of the fiber cross section being flattened multi-lobed, and the void having first and second sides inclined at an angle of 70 to 110 degrees with respect to the major axis of the fiber cross section.

[0004] JP 2008-285772 A

[0005] In recent years, there has been a demand for lightweight artificial hair fibers, and for example, Patent Documents 1 and 2 disclose artificial hair fibers having hollow portions. However, with conventional technology, it has been difficult to impart a natural color and luster with appropriate variation like that of human hair to an artificial hair fiber bundle containing such hollow artificial hair fibers. Furthermore, depending on the application, artificial hair fibers may be braided or otherwise subjected to hot water treatment by immersion in hot water. However, after the hot water treatment, uneven shrinkage of the fibers may occur, causing parts of the braid to unravel or fiber ends to protrude from the surface of the fiber bundle.

[0006] The present invention has been made in consideration of the above circumstances, and provides an artificial hair fiber bundle containing such hollow artificial hair fibers, which can simultaneously achieve a natural color and luster with moderate variation like human hair, and reduced unraveling and popping out after hot water treatment.

[0007] According to the present invention, there is provided an artificial hair fiber bundle comprising a plurality of artificial hair fibers, wherein the plurality of artificial hair fibers include hollow artificial hair fibers having hollow portions extending in the longitudinal direction of the artificial hair fiber, and when the hollow ratio is defined as the area ratio occupied by the hollow portions in a cross section perpendicular to the longitudinal direction of the artificial hair fiber, the coefficient of variation of the hollow ratio of the artificial hair fibers contained in the artificial hair fiber bundle is 0.02 to 0.30.

[0008] The present inventors have conducted extensive research and have found that by controlling the variation rate of the hollow ratio, which is the area ratio occupied by hollow portions in a cross section perpendicular to the longitudinal direction of an artificial hair fiber bundle containing hollow artificial hair fibers, within a certain numerical range, it is possible to achieve a natural color and luster with moderate variation like human hair, while simultaneously reducing unraveling and popping-out after hot water treatment, and have completed the present invention.

[0009] Various embodiments of the present invention are exemplified below. The embodiments shown below can be combined with each other. [1] An artificial hair fiber bundle containing a plurality of artificial hair fibers, wherein the plurality of artificial hair fibers include hollow artificial hair fibers having hollow portions extending in the longitudinal direction of the artificial hair fiber, and the hollow ratio is the area ratio occupied by the hollow portions in a cross section perpendicular to the longitudinal direction of the artificial hair fiber, and the coefficient of variation of the hollow ratio of the artificial hair fibers contained in the artificial hair fiber bundle is 0.02 to 0.30. [2] The artificial hair fiber bundle according to [1], wherein the average hollow ratio of the plurality of artificial hair fibers is 10 to 40%. [3] The artificial hair fiber bundle according to [1] or [2], wherein the fineness of the plurality of artificial hair fibers is 30 to 70 denier. [4] The artificial hair fiber bundle according to any of [1] to [3], wherein the artificial hair fiber contains a vinyl chloride resin. [5] A hair accessory product comprising the artificial hair fiber bundle according to any one of [1] to [4]. [6] The hair accessory product according to [5], which includes a braid.

[0010] The artificial hair fiber bundle of the present invention is an artificial hair fiber bundle containing hollow artificial hair fibers, which can simultaneously achieve a natural color and luster with moderate variation like human hair, and reduced unraveling and fly-out after hot water treatment.Furthermore, the hair accessory product of the present invention has a natural color and luster with moderate variation like human hair, and is less likely to unravel and fly-out after hot water treatment.

[0011] Figure 1 is a cross-sectional schematic diagram of an artificial hair fiber according to one embodiment of the present invention: Figure 1A shows a circular cross-section, Figure 1B shows a circular cross-section having inner and outer protrusions, Figure 1C shows a bilobal cross-section formed by joining two C-shaped portions, Figure 1D shows a trilobal cross-section formed by joining three C-shaped portions, Figure 1E shows a substantially triangular cross-section, and Figure 1F shows a substantially rectangular cross-section.

[0012] The present invention will be described in detail below by illustrating embodiments of the present invention. The present invention is not limited by these descriptions. The features of the embodiments of the present invention described below can be combined with each other. Furthermore, each feature can be an invention independently.

[0013] 1. Artificial Hair Fiber Bundle The artificial hair fiber bundle according to the present invention is an artificial hair fiber bundle comprising a plurality of artificial hair fibers, the plurality of artificial hair fibers including hollow artificial hair fibers having hollow portions extending in the longitudinal direction of the artificial hair fiber. When the hollow portion is defined as the area ratio occupied by the hollow portions in a cross section perpendicular to the longitudinal direction of the artificial hair fiber, the coefficient of variation of the hollow portion of the artificial hair fibers contained in the artificial hair fiber bundle is 0.02 to 0.30.

[0014] 1.1 Artificial Hair Fiber 1.1.1 Shape of Artificial Hair Fiber In the present invention, the multiple artificial hair fibers include hollow artificial hair fibers having a hollow portion extending in the longitudinal direction of the artificial hair fiber. In the hollow artificial hair fiber according to the present invention, the hollow portion can be continuous for 10 cm or more in the longitudinal direction of the artificial hair fiber. The artificial hair fiber bundle according to the present invention is lightweight because it comprises hollow artificial hair fibers having a hollow portion, and offers many advantages, such as the ability to create the desired voluminous hairstyle with a small amount of wear, the ability to achieve a wide range of hairstyles including heavy long styles, the ability to reduce damage to one's own hair and scalp, and the ability to reduce waste and environmental impact.

[0015] An example of a cross section perpendicular to the longitudinal direction of a hollow artificial hair fiber according to one embodiment of the present invention is shown in Figure 1. The cross section perpendicular to the longitudinal direction of the hollow artificial hair fiber according to one embodiment of the present invention can have any one shape selected from a circular shape (Figures 1A and 1B), an elliptical shape, a bilobal shape formed by joining two C-shaped shapes (Figure 1C), a trilobal shape formed by joining three C-shaped shapes (Figure 1D), a quadrilobal shape formed by joining four or more C-shaped shapes, a substantially triangular shape (Figure 1E), a substantially square shape (Figure 1F), and a substantially polygonal shape.

[0016] While the method for producing the artificial hair fiber according to the present invention is not particularly limited, artificial hair fibers are generally obtained by melt-spinning a resin composition for artificial hair fibers. Furthermore, artificial hair fibers having a hollow portion are formed by melt-extrusion from a nozzle with a single C-shaped nozzle hole or a nozzle with multiple holes, as shown in FIG. 1 of Patent Document 1. Here, the resin composition is at least partially fragmented while passing through the nozzle, but after being discharged from the nozzle hole, the resin composition particles come into contact and fuse together, forming a hollow portion. The hollow artificial hair fiber according to one embodiment of the present invention can have a bonding surface 14 (shown by a dashed line in FIG. 1) where the resin composition particles fuse together during the melt-extrusion process. Furthermore, the bonding surface 13, which is the region including the bonding surface 14, may have at least one of an inner protrusion 16 protruding toward the hollow portion and an outer protrusion 17 protruding toward the outside of the artificial hair fiber (FIG. 1B). 1B shows a case where the fiber cross section is circular, but even when the hollow portion has another shape, the joint can be provided with at least one of an inner protrusion protruding toward the hollow portion and an outer protrusion protruding toward the outside of the artificial hair fiber. In this way, by providing a protrusion to thicken the joint 13 and increasing the area of ​​the joint surface 14 where the resin compositions are fused together, the joint strength can be improved. The manufacturing method will be described in detail later.

[0017] The hollow artificial hair fiber according to one embodiment of the present invention may have a major diameter of 30 to 300 μm in a cross section perpendicular to the longitudinal direction of the artificial hair fiber, for example, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, or 300 μm, or may be within a range between any two of the values ​​exemplified here.

[0018] The hollow artificial hair fiber according to one embodiment of the present invention preferably has a hollow ratio of 10 to 40%, where the hollow ratio is the area ratio occupied by the hollow portions 15 in a cross section perpendicular to the longitudinal direction of the artificial hair fiber. The hollow ratio may be, for example, 10, 15, 20, 25, 30, 35, or 40%, and may be within a range between any two of the values ​​exemplified here. The artificial hair fiber bundle according to the present invention may have a coefficient of variation of the hollow ratio of the multiple artificial hair fibers contained in the artificial hair fiber within a specific numerical range. Therefore, the bundle may contain hollow artificial hair fibers with a hollow ratio of less than 10% or more than 40%, as long as the coefficient of variation is within the specific numerical range.

[0019] The hollow ratio can be calculated using the following formula: Hollow ratio = (area surrounded by the inner surface 12) / (area surrounded by the outer surface 11) x 100 The area surrounded by the outer surface 11 means the cross-sectional area when it is assumed that the artificial hair fiber has no hollow portions. The hollow ratio can be calculated by cutting the artificial hair fiber perpendicular to the longitudinal direction, observing the cut surface with a laser microscope or scanning electron microscope, and performing image analysis, and specifically by the method described in the Examples. By setting the hollow ratio at or above the lower limit, the advantages of having hollow portions can be more reliably obtained. A hollow ratio exceeding the upper limit is not preferred because it leads to a decrease in structure retention, increased rigidity due to an increase in fiber diameter, and a deterioration in tactile feel.

[0020] In addition, the artificial hair fiber bundle according to the present invention may contain solid artificial hair fibers that do not have a hollow portion extending in the longitudinal direction of the artificial hair fiber, as long as the coefficient of variation of the hollow ratio of the plurality of artificial hair fibers contained in the artificial hair fiber falls within a specific numerical range. The shape of the solid artificial hair fiber is not particularly limited, but examples include a circular shape, an elliptical shape, a polygonal shape such as a substantially triangular shape or a substantially rectangular shape, a multi-lobed shape such as a bilobal shape or a trilobal shape, and a Y-shape. Furthermore, the major diameter of the artificial hair fiber in a cross section perpendicular to the longitudinal direction can be approximately the same as that of the hollow artificial hair fiber, and can be 30 to 300 μm.

[0021] 1.1.2 Composition of Artificial Hair Fibers The resin composition constituting the artificial hair fiber according to one embodiment of the present invention is not particularly limited and may include at least one of polyamide-based resins, polyester-based resins, vinyl chloride-based resins, AS-based resins (acrylonitrile-styrene-based resins), PP resins, PET resins, PE resins, PAN-based resins, and PLA-based resins (polylactic acid-based resins). The artificial hair fiber according to one embodiment of the present invention preferably contains a vinyl chloride-based resin, because this facilitates the production of a die-swell effect, a structure having protrusions that increase the area of ​​the bonded surfaces where the resin compositions are fused together, and an artificial hair fiber having a structure with improved bond strength. Furthermore, the artificial hair fiber according to one embodiment of the present invention preferably contains a vinyl chloride-based resin and an AS-based resin (acrylonitrile-styrene-based resin).

[0022] A polyvinyl chloride resin according to one embodiment of the present invention may comprise a vinyl chloride polymer containing monomer units (vinyl chloride monomer units) derived from vinyl chloride monomer. The polyvinyl chloride resin according to the present invention may comprise a homopolymer obtained by homopolymerizing vinyl chloride monomer and / or a copolymer containing monomer units derived from vinyl chloride monomer and another monomer copolymerizable with vinyl chloride monomer. Examples of copolymers include copolymers of vinyl chloride and vinyl esters, such as vinyl chloride-vinyl acetate copolymer and vinyl chloride-vinyl propionate copolymer; copolymers of vinyl chloride and olefins, such as vinyl chloride-ethylene copolymer and vinyl chloride-propylene copolymer; and vinyl chloride-acrylonitrile copolymer. Furthermore, the polyvinyl chloride resin according to the present invention may consist of one type of vinyl chloride polymer, or may contain two or more types of vinyl chloride polymers.

[0023] The resin composition for artificial hair fibers constituting the artificial hair fiber according to one embodiment of the present invention contains 50 to 99 mass % of vinyl chloride resin, preferably 65 to 95 mass %, and more preferably 65 to 90 mass %, based on 100 mass % of the resin composition.Specifically, the mass % may be, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 99 mass %, and may be within a range between any two of the values ​​exemplified here.

[0024] AS resins (acrylonitrile-styrene resins) are copolymers containing styrene-based monomer units and acrylonitrile-based monomer units, and may contain other monomer units copolymerizable with these units as needed. The AS resins may contain, for example, 60, 65, 70, 75, 80, 85, or 90% by mass of styrene-based monomer units relative to 100% by mass of the AS resin, or may fall within a range between any two of the values ​​exemplified here. The AS resins may contain, for example, 10, 15, 20, 25, 30, 35, or 40% by mass of acrylonitrile-based monomer units relative to 100% by mass of the AS resin, or may fall within a range between any two of the values ​​exemplified here.

[0025] The artificial hair fiber according to one embodiment of the present invention may contain other ingredients as needed, such as antistatic agents, heat stabilizers, lubricants, colorants, processing aids, plasticizers, strengthening agents, UV absorbers, antioxidants, fillers, flame retardants, pigments, initial color improvers, conductivity imparting agents, and fragrances.

[0026] 1.2 Characteristics of Artificial Hair Fiber Bundle The artificial hair fiber bundle according to the present invention comprises a plurality of artificial hair fibers, and the plurality of artificial hair fibers includes hollow artificial hair fibers. In one embodiment of the present invention, the plurality of artificial hair fibers may include solid artificial hair fibers. The artificial hair fiber bundle according to the present invention may have a hollow artificial hair fiber content of 50% by mass or more, when the plurality of artificial hair fibers contained in the artificial hair fiber bundle is taken as 100% by mass. The hollow artificial hair fiber content may be, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100% by mass, or may be within a range between any two of the values ​​exemplified here. The artificial hair fiber bundle according to one embodiment of the present invention is composed of a plurality of artificial hair fibers, and it is preferable that the plurality of artificial hair fibers consist solely of hollow artificial hair fibers.

[0027] In the artificial hair fiber bundle according to the present invention, the coefficient of variation of the hollow ratio of the artificial hair fibers contained in the artificial hair fiber bundle is 0.02 to 0.30. Here, the coefficient of variation is expressed by the following formula: Coefficient of variation = Standard deviation / Average hollow ratio Below, the average hollow ratio, standard deviation, and coefficient of variation will be explained in order.

[0028] The hollow ratio of artificial hair fibers is as described above, and the method for determining the hollow ratio of each artificial hair fiber is as described above. The hollow ratio can be determined by cutting the artificial hair fiber perpendicular to the longitudinal direction, observing the cut surface with a laser microscope or scanning electron microscope, and analyzing the image using the following formula: Hollow ratio = (area surrounded by the inner surface 12) / (area surrounded by the outer surface 11) x 100 The average hollow ratio is the average value of the hollow ratios of multiple artificial hair fibers contained in the artificial hair fiber bundle, and can be the average value for an N number of 50, for example.

[0029] The average hollowness is preferably 10 to 40%, for example, 10, 15, 20, 25, 30, 35, or 40%, and may be within a range between any two of the values ​​exemplified here. By setting the average hollowness at or above the lower limit, the advantages of having hollow portions can be more reliably obtained. If the average hollowness exceeds the upper limit, this is undesirable because it leads to a decrease in structural retention, increased rigidity due to an increase in fiber diameter, and a deterioration in tactile feel.

[0030] The standard deviation of the hollow ratio can be calculated by the following formula.

[0031] where S is the standard deviation, N is the number of artificial hair fibers whose hollowness is measured, Xi is the hollowness of each artificial hair fiber, and X ａｖｅｒａｇｅ indicates the average hollow ratio. The standard deviation can be 1 to 7, for example, 1, 2, 3, 4, 5, 6, or 7, and may be within a range between any two of the values ​​exemplified here.

[0032] The coefficient of variation can be calculated using the above-mentioned average hollow ratio and standard deviation according to the following formula: Coefficient of variation = Standard deviation / Average hollow ratio The coefficient of variation is 0.02 to 0.30, and may be, for example, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.20, 0.22, 0.24, 0.26, 0.28, or 0.30, or may be within a range between any two of the numerical values ​​exemplified here.

[0033] According to the present invention, by setting the coefficient of variation to the above lower limit or more, an artificial hair fiber bundle can be obtained that has a natural color and luster with moderate variation like that of human hair. Furthermore, by setting the coefficient of variation to the above upper limit or less, it is possible to appropriately suppress variation in the shrinkage rate of the artificial hair fibers contained in the artificial hair fiber bundle, and it is presumed that unraveling and popping out after hot water treatment can be further reduced.

[0034] The average hollow ratio, standard deviation, and coefficient of variation can be controlled by adjusting the conditions for producing artificial hair fibers, and in particular by changing the nozzle shape used in the melt spinning process. One example is a method using a nozzle having multiple nozzle holes capable of simultaneously ejecting multiple fibers, the multiple nozzle holes having a distribution of shapes and sizes that allows the average hollow ratio, standard deviation, and coefficient of variation of the resulting fibers to be adjusted within the above-mentioned numerical ranges.

[0035] The artificial hair fiber bundle according to one embodiment of the present invention preferably has a fineness of 30 to 70 denier. The fineness may be, for example, 30, 35, 40, 45, 50, 55, 60, 65, or 70 denier, or may be within a range between any two of the values ​​exemplified here. By controlling the fineness within the above range, the resulting artificial hair fiber bundle will have a natural color and luster with moderate variation like human hair, will be less likely to unravel or pop out after hot water treatment, and will have an excellent feel to the touch. The fineness of the artificial hair fiber bundle can be determined by the method described in the Examples. Furthermore, the fineness can be controlled by adjusting the conditions of the spinning process, drawing process, and heat treatment.

[0036] <Structure Retention Rate> In the artificial hair fiber bundle according to one embodiment of the present invention, the structure retention rate of the cross section of the artificial hair fiber is preferably 90% or more. The structure retention rate may be, for example, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100%, and may be within a range between any two of the values ​​exemplified here. The structure retention rate indicates the percentage of artificial hair fibers having cross sections in which the bonded portions are not separated and the hollow portions are not collapsed. Specifically, it can be calculated using the method described in the Examples. For example, it can be calculated using the following formula based on the observation results of 300 fiber cross sections: Structure Retention Rate = (300 - i - j) / 300, where i is the number of fibers having one or more separated portions, and j is the number of fibers whose hollow portions have collapsed and whose inner surfaces are in contact with each other. A fiber having separated portions refers to, for example, when a fiber has a circular cross section, a cross section that is not doughnut-shaped but C-shaped, with some portions separated.

[0037] The artificial hair fiber bundle according to one embodiment of the present invention has a high structural retention rate, and the hollow structure is maintained with high accuracy without being destroyed even after undergoing processes such as drawing and heat treatment, and the advantages of having a hollow portion can be fully and reliably obtained. The structural retention rate can be increased by adjusting the average hollow ratio, standard deviation, coefficient of variation, and cross-sectional structure of the artificial hair fiber bundle.

[0038] The artificial hair fiber bundle according to the present invention is an artificial hair fiber bundle containing hollow artificial hair fibers, which simultaneously achieves a natural color and luster with moderate variation like that of human hair, as well as reduced loosening and fly-out after hot water treatment. Furthermore, the artificial hair fiber bundle according to the present invention has an excellent feel. Furthermore, the artificial hair fiber bundle according to one embodiment of the present invention has many advantages, such as the hollow structure of each fiber being maintained with high accuracy, being lightweight, allowing the desired voluminous hairstyle to be created with a small amount of wear, allowing a wide range of hairstyles to be achieved, including heavy long styles, reducing damage to one's own hair and scalp, and reducing waste and environmental impact. The artificial hair fiber bundle according to one embodiment of the present invention, which has the above-mentioned characteristics, can be used for hair accessory products of various styles, particularly for braids, including braids and twists.

[0039] 1.3 Method for producing fiber bundle for artificial hair The method for producing fiber bundle for artificial hair according to one embodiment of the present invention includes a step of preparing a resin composition for fibers for artificial hair and a spinning step, and may also include a drawing step, a heat treatment step, and a gear processing step.

[0040] 1.3.1 Preparation of Resin Composition for Artificial Hair Fiber In the preparation of a resin composition for artificial hair fiber, raw materials containing resins are mixed to obtain a resin composition for artificial hair fiber. Here, the raw materials include a base resin and may contain other components as necessary.

[0041] The mixing method is not particularly limited, and conventionally known methods can be employed. For example, a powdered resin composition (powder compound) can be obtained using known mixing devices such as a Henschel mixer, super mixer, or ribbon blender, and the powder compound can then be melt-mixed to obtain a pellet-shaped resin composition (pellet compound). The powder compound can be produced by either hot blending or cold blending. For example, to reduce volatiles from the resin composition, hot blending can be performed at a cut temperature of 105 to 155°C during mixing. The pellet compound can be produced by a method similar to that used to produce pellet compounds of general polyvinyl chloride resins. For example, pellet compounds can be produced using kneaders such as a single-screw extruder, a counter-rotating twin-screw extruder, a conical twin-screw extruder, a co-rotating twin-screw extruder, a co-kneader, a planetary gear extruder, or a roll kneader. The conditions for producing the pellet compound are not particularly limited, but it is preferable to set the resin temperature to 185°C or less to prevent thermal degradation of the resin composition. A mesh can also be installed near the tip of the screw to remove small amounts of metal chips from the screw and fibers from protective gloves that may be mixed into the pellet compound. The cold-cut method can be used to produce pellets. A means of removing chips (fine particles generated during pellet production) that may be mixed in during cold cutting can also be used. Since the cutter blades can chip and generate chips easily after prolonged use, it is recommended to replace them as needed.

[0042] 1.3.2 Spinning Process In the spinning process, the resin composition for artificial hair fibers is melt-spun to obtain artificial hair fibers. As an example, the resin composition (e.g., pellet compound) can be extruded from a heated cylinder through a nozzle to melt-spin. Conventional extruders can be used, such as single-screw extruders, counter-rotating twin-screw extruders, and conical twin-screw extruders.

[0043] The melt spinning conditions can be appropriately set depending on the type of resin composition so that the resin melts and a bonded structure can be formed. For example, the cylinder temperature can be set to 150 to 190°C, and the nozzle temperature can be set to 180±15°C.

[0044] The undrawn yarn melt-spun from the nozzle is introduced into a heating cylinder (for example, heating cylinder temperature 250°C) and instantaneously heat-treated, and can be taken up by a take-up machine installed directly below the nozzle (for example, about 4.5 m away).

[0045] The nozzle for melt extrusion of the artificial hair fiber according to one embodiment of the present invention can be appropriately selected depending on the shape and hollowness of the artificial hair fiber to be obtained, as well as the average hollowness, standard deviation, and coefficient of variation. For example, when producing an artificial hair fiber having a circular cross section as shown in Fig. 1A, a nozzle with a C-shaped nozzle hole can be used. When producing an artificial hair fiber having a bilobal cross section with two C-shaped holes joined together as shown in Fig. 1C, a nozzle with two C-shaped nozzle holes can be used. When producing an artificial hair fiber having a trilobal cross section with three C-shaped holes joined together as shown in Fig. 1D, a nozzle with three C-shaped nozzle holes can be used. Furthermore, when producing an artificial hair fiber having a substantially triangular cross section as shown in Fig. 1E, a nozzle with three rod-shaped nozzle holes can be used. When producing an artificial hair fiber having a substantially rectangular cross section as shown in Fig. 1F, a nozzle with four rod-shaped nozzle holes can be used.

[0046] The nozzle preferably has nozzle holes capable of simultaneously ejecting a plurality of fibers, and the plurality of nozzle holes preferably have a distribution of shapes and sizes, and the average hollow ratio, standard deviation, and coefficient of variation of the final artificial hair fibers are preferably adjusted to fall within desired ranges.

[0047] 1.3.4 Drawing Step and Heat Treatment Step The method for producing artificial hair fiber according to one embodiment of the present invention may also include a drawing step and a heat treatment step. In the drawing step, the undrawn artificial hair fiber obtained in the melt spinning step described above is drawn using a drawing machine to obtain drawn artificial hair fiber. As an example, in the drawing step, the undrawn artificial hair fiber can be drawn 2 to 5 times at 90 to 110°C in an air atmosphere. Furthermore, in the heat treatment step, the drawn artificial hair fiber can be heat-treated using a heat treatment machine. As an example, in the heat treatment step, the drawn artificial hair fiber is heat-treated in an air atmosphere at 90 to 110°C to 0.5 to 3.0 times its original size, causing heat shrinkage of the entire fiber length, thereby obtaining heat-treated artificial hair fiber with the desired fineness.

[0048] 1.3.5 Gear Processing Step The method for producing artificial hair fibers according to one embodiment of the present invention can also include a gear processing step. In this gear processing step, crimping can be achieved by passing the fiber bundle between two meshing, high-temperature gears. The material of the gears used in the gear processing step, the shape of the gear waves, and the number of gear fractions are not particularly limited. In the gear processing step, the shape of the resulting artificial hair fibers can be controlled by appropriately adjusting the depth of the gear wave grooves, the gear surface temperature, the processing speed, and the pressure conditions between the gears, taking into account the fiber material and fineness. These processing conditions are not particularly limited, but as an example, the depth of the gear wave grooves can be 0.2 mm to 6 mm, preferably 0.5 mm to 5 mm, the gear surface temperature can be 30°C to 100°C, preferably 40°C to 80°C, and the processing speed can be 0.5 to 10 m / min, preferably 1.0 m / min to 8.0 m / min.

[0049] The method for producing artificial hair fibers according to one embodiment of the present invention may include other steps, such as a surface treatment agent application step. Note that in the present invention, artificial hair fibers include artificial hair fibers after spinning, and encompass artificial hair fibers before the drawing step, after the drawing step, before the heat treatment step, after the heat treatment step, before the gear processing step, and after the gear processing step.

[0050] 3. Hair Accessory Product A hair accessory product according to one embodiment of the present invention comprises the above-described artificial hair fiber. Also, a hair accessory product according to one embodiment of the present invention comprises the above-described artificial hair fiber bundle.

[0051] The artificial hair fiber according to the present invention can be used in hair accessory products. Examples of hair accessory products include wigs, hairpieces, braids, hair extensions, doll hair, hair wigs, false hair, and hair bands. Hair accessory products obtained from the artificial hair fiber bundle according to the present invention simultaneously achieve a natural color and luster with moderate variation similar to that of human hair, as well as reduced loosening and fly-out after hot water treatment. Furthermore, hair accessory products obtained from the artificial hair fiber bundle according to one embodiment of the present invention have an excellent feel. Furthermore, hair accessory products obtained from the artificial hair fiber bundle according to one embodiment of the present invention maintain the hollow structure of each fiber with high accuracy, resulting in many advantages, such as lightweight, allowing the creation of desired voluminous hairstyles with a small amount of wear, enabling the realization of a wide range of hairstyles, including heavy long styles, reducing damage to natural hair and the scalp, and reducing waste and environmental impact. The hair accessory product according to one embodiment of the present invention, having the above-mentioned characteristics, can be applied to various styles, but is particularly suitable for braids, including braids and twists.

[0052] The present invention will be described in more detail below based on examples, but the present invention should not be construed as being limited to these examples.

[0053] Example 1 Preparation of Resin Composition for Artificial Hair Fibers 70 parts by mass of polyvinyl chloride resin (manufactured by Taiyo Vinyl Corporation, product name: TH1000), 30 parts by mass of vinyl copolymer resin (manufactured by Denka Company, GR-AT-6S) containing 68% by mass of styrene monomer units and 32% by mass of acrylonitrile monomer units, and 5 parts by mass of additives such as plasticizers, stabilizers, and lubricants (specifically, 3 parts by mass of stabilizer composition, 1 part by mass of epoxidized soybean oil, 0.4 parts by mass of phosphorus-based chelating agent, and 0.6 parts by mass of polyethylene wax), and 0.5 parts by mass of carbon black were mixed in a blender. The blended materials were kneaded using a φ40 mm single-screw extruder to obtain Resin Composition 1 for Artificial Hair Fibers in the form of pellets for spinning. The stabilizer composition used to obtain the resin composition had the following components and composition: Hydrotalcite compound (Mg ４ Al ２ (OH)CO ３ ・3H ２ O) 72.6 parts by mass Zinc stearate 13.1 parts by mass Silica ("Carplex (registered trademark) #80" manufactured by DSL Japan Co., Ltd.) 2.2 parts by mass Dibenzoylmethane 2.3 parts by mass Dipentaerythritol 0.9 parts by mass Vinyl chloride resin (product name: TH1000 manufactured by Taiyo PVC Co., Ltd.) 8.9 parts by mass Other additives used to obtain the resin composition are as follows: Epoxidized soybean oil: "ADEKA CIZER (registered trademark) O-130P" manufactured by ADEKA Corporation Phosphorus-based chelating agent: "ADEKA STAB (registered trademark) 1030" manufactured by ADEKA Corporation Polyethylene wax: manufactured by Mitsui Chemicals, Inc.

[0054] <Spinning step> The obtained pellet-shaped resin composition for artificial hair fibers was spun using a φ40 mm single-shaft melt spinning machine. The discharge rate and winding speed were adjusted to produce undrawn yarn from the molten resin discharged from the nozzle. The cylinder temperature and nozzle temperature of the spinning machine were set to 140 to 180°C. For melt spinning, a nozzle capable of simultaneously discharging 100 hollow fibers was used. The nozzle had nozzle holes corresponding to each of the 100 hollow fibers. The 100 nozzle holes had a distribution of shapes and sizes, and were adjusted so that the coefficient of variation of the hollow ratio of the final artificial hair fiber was 0.04.

[0055] <Drawing step and heat treatment step> The obtained undrawn yarn was drawn at 100°C and then annealed at 100 to 200°C to obtain artificial hair fiber 1. The draw ratio was 3 times, and the relaxation rate during annealing was 0.5 to 3%. The relaxation rate during annealing is a value calculated by (rotational speed of the take-up roller during annealing) / (rotational speed of the delivery roller during annealing).

[0056] (Examples 2 to 11, Comparative Example 1) By changing the nozzle used in the spinning process, and the conditions of the spinning process, drawing process and heat treatment, artificial hair fibers with different hollow ratios, their variation coefficients and finenesses were obtained.

[0057]

[0058] (Method for evaluating artificial hair fibers) The obtained artificial hair fibers were evaluated by the following method. For cross-sectional observation, the artificial hair fibers were cut to an appropriate length, the resulting bundle was wrapped in vinyl tape, and the bundle was cut perpendicular to the longitudinal direction with a cutter knife to prepare a cross section.

[0059] <Fineness> The mass of one fiber per 90 cm was measured and the fineness (unit: d, denier) was calculated using an electronic balance (AUW220, manufactured by Shimadzu Corporation) as the measuring instrument.

[0060] <Hollow Ratio, Average Hollow Ratio, Standard Deviation of Hollow Ratio, and Coefficient of Variation> Using a laser microscope, a cross-sectional photograph of the fiber was taken at 400x magnification, and the area ratio of hollow portions in the cross-section (hollow ratio) was measured. Hollow ratio = Area surrounded by inner surface / Area surrounded by outer surface. The hollow ratio was calculated using a controller VK-X150 manufactured by Keyence Corporation. The average hollow ratio was calculated with an N number of 50. The standard deviation of the hollow ratio was calculated using the following formula.

[0061] where S is the standard deviation, N is the number of artificial hair fibers whose hollowness is measured, Xi is the hollowness of each artificial hair fiber, and X ａｖｅｒａｇｅ The coefficient of variation was calculated using the obtained standard deviation and average hollow ratio according to the following formula: Coefficient of variation = standard deviation / average hollow ratio

[0062] <Appearance> The artificial hair fibers of the Examples and Comparative Examples were bundled into a length of 250 mm and a mass of 20 g, and the appearance was evaluated by visual inspection by 10 artificial hair fiber processing technicians (with at least 5 years of work experience) according to the following evaluation criteria. Note that "good appearance" means that the color and luster have natural variations, like human hair. ◎: 9 or more technicians evaluated the appearance as good ○: 6 to 8 technicians evaluated the appearance as good △: 3 to 5 technicians evaluated the appearance as good ×: 2 or less technicians evaluated the appearance as good

[0063] <Tactile Feel> The artificial hair fibers of the Examples and Comparative Examples were bundled to a length of 250 mm and a mass of 20 g, and 10 artificial hair fiber processing technicians (with at least 5 years of work experience) evaluated the feel of the fibers according to the following criteria. The feel was evaluated as either "soft" or "hard" based on the softness felt when the fiber bundle was pressed against the palm of the hand, and then judged according to the following criteria: ◎: 9 or more technicians evaluated it as soft ○: 6 to 8 technicians evaluated it as soft △: 3 to 5 technicians evaluated it as soft ×: 2 or less technicians evaluated it as soft

[0064] <Finish after Hot Water Treatment> The artificial hair fibers of the Examples and Comparative Examples were bundled to a length of 500 mm and a mass of 5 g, braided, and immersed in 90°C hot water for 15 seconds. Next, the braided structure was removed from the water, and the surface of the braided structure was gently rubbed three times to wipe off the water. The braided structure was then left to dry naturally at room temperature (25°C) for 24 hours or more, after which the finish was visually observed. Evaluation was made by visual judgment by 10 artificial hair fiber processing technicians (with at least 5 years of work experience) according to the following criteria. A good finish after hot water treatment means that there was little unraveling (partial unraveling of the braid) or protrusion (short fibers protruding from the surface of the bundled braided fiber bundle) in the fiber bundle after hot water treatment. Unraveling and protrusion are thought to occur when the fibers shrink unevenly. ◎: 9 or more engineers evaluated the finish as good. ○: 6 to 8 engineers evaluated the finish as good. △: 3 to 5 engineers evaluated the finish as good. ×: 2 or less engineers evaluated the finish as good.

[0065] <Structure Retention Rate> A laser microscope was used to photograph the cross section of the fiber at a magnification of 400x. Then, the structure retention rate was calculated based on the following formula with an N number of 300. The structure retention rate was calculated using the following formula: Structure retention rate = (300 - i - j) / 300 i: number of fibers having one or more separated portions j: number of fibers whose hollow portions have collapsed and whose inner surfaces have come into contact with each other A fiber having separated portions refers to a state in which, for example, when a fiber has a circular cross section, the cross section is not doughnut-shaped but C-shaped, with some portions separated.

[0066] 100 Cross section of artificial hair fiber 11 Outer surface 12 Inner surface 13 Joint portion 14 Joint surface 15 Hollow portion 16 Inner protrusion 17 Outer protrusion

Claims

1. An artificial hair fiber bundle comprising a plurality of artificial hair fibers, the plurality of artificial hair fibers including hollow artificial hair fibers having a hollow portion extending in the longitudinal direction of the artificial hair fiber, and when the hollow ratio is the area ratio occupied by the hollow portion in a cross section perpendicular to the longitudinal direction of the artificial hair fiber, the coefficient of variation of the hollow ratio of the artificial hair fibers contained in the artificial hair fiber bundle is 0.02 to 0.

30.

2. The fiber bundle for artificial hair according to claim 1, wherein the average hollow ratio of the plurality of fibers for artificial hair is 10 to 40%.

3. The artificial hair fiber bundle according to claim 1 or 2, wherein the fineness of the plurality of artificial hair fibers is 30 to 70 denier.

4. The fiber bundle for artificial hair according to claim 1 or 2, wherein the fiber for artificial hair contains a vinyl chloride resin.

5. A hair accessory product comprising the artificial hair fiber bundle according to claim 1 or 2.

6. A hair accessory product according to claim 5, comprising a braid.

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