Classifications

• • A—HUMAN NECESSITIES
  • A41—WEARING APPAREL
  • A41G—ARTIFICIAL FLOWERS; WIGS; MASKS; FEATHERS
  • A41G3/00—Wigs
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/08—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polymers of halogenated hydrocarbons
  • D01F6/10—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polymers of halogenated hydrocarbons from polyvinyl chloride or polyvinylidene chloride

Definitions

• the present invention relates to artificial hair fibers, hair decoration products, and nozzles for melt extrusion of artificial hair fibers.
• artificial hair fibers include acrylic resins, vinyl chloride resins, and polyester resins, and artificial hair fibers made from these resins are commercially available.
• Patent Document 1 discloses artificial hair that is characterized by containing hollow fibers having hollow portions with a hollow ratio of 10 to 50%.
• Patent Document 2 discloses a fiber for artificial hair, which has 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 is 5% or more and 50% or less, the cross-sectional shape of the fiber cross section is flattened and multi-lobed, and the void has first and second sides that are inclined at an angle of 70 degrees or more and 110 degrees or less with respect to the major axis of the fiber cross section.
• Patent Documents 1 and 2 disclose artificial hair fibers with hollow spaces.
• parts of the hollow space formed can become detached or crushed, making it impossible to maintain the structure.
• the present invention has been made in consideration of these circumstances, and provides a fiber for artificial hair having a hollow portion, the structure of which is maintained to a high degree.
• the structure having a hollow portion is not destroyed and is maintained with a high degree of certainty even after undergoing processes such as a drawing process and a heat treatment process.
• a hair accessory product including the fiber for artificial hair is provided.
• a nozzle for melt extrusion of the fiber for artificial hair, which can produce the fiber for artificial hair is provided.
• artificial hair fibers with hollow sections can be made to have a high degree of hollow structure maintained by providing a strength-enhancing structure in the cross section to improve the bonding strength, leading to the completion of the present invention.
• a fiber for artificial hair the fiber for artificial hair having a hollow portion extending in the longitudinal direction of the fiber for artificial hair, a cross section perpendicular to the longitudinal direction of the fiber for artificial hair having at least one joint, the joint having a strength enhancing structure for improving the bonding strength.
• the artificial hair fiber described in [1] or [2], wherein the strength enhancing structure has 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.
• [6] The fiber for artificial hair according to any one of [1] to [5], wherein X MAX is the maximum value of the thickness X at the center of the inner protrusion and the outer protrusion, and Y is the thickness of the thinnest part other than the inner protrusion and the outer protrusion, and X MAX /Y is 0.90 to 2.50.
• X MAX is the maximum value of the thickness X at the center of the inner protrusion and the outer protrusion
• Y is the thickness of the thinnest part other than the inner protrusion and the outer protrusion
• X MAX /Y is 0.90 to 2.50.
• the fiber for artificial hair according to any one of [1] to [6] which contains a vinyl chloride resin.
• a hair accessory product comprising the artificial hair fiber according to any one of [1] to [7].
• a nozzle for melt extrusion of the artificial hair fiber according to any one of [1] to [8], the nozzle having one or more C-shaped nozzle holes or two or more rod-shaped nozzle holes.
• B/A is 3 to 20.
• the nozzle described in [9] or [10] wherein, in an opening surface of the nozzle, when the minor axis length of the nozzle hole is A and the distance between the nozzle holes is C, C/A is 0.5 to 1.5.
• the fiber for artificial hair according to the present invention is a fiber for artificial hair having a hollow portion, and the structure having the hollow portion is unlikely to separate or be crushed, and the fiber for artificial hair is provided in which the structure is maintained.
• the structure having the hollow portion is not destroyed even after processes such as a drawing process and a heat treatment process, and is stably maintained with high accuracy.
• a hair accessory product that includes the fiber for artificial hair, which is lightweight, has an increased volume per unit weight compared to other products, and can form a desired voluminous hairstyle with a small amount of wear, can achieve a wide range of hairstyles, causes less damage to one's own hair and scalp, and can reduce waste and environmental load.
• a nozzle for melt extrusion of the fiber for artificial hair is provided, which can manufacture the fiber for artificial hair.
• FIG. 1 is a schematic cross-sectional view of an artificial hair fiber having an inner protrusion and a shape in which two C-shaped members are joined.
• FIG. 1A shows each component
• FIG. 1B shows the major axis 18, the thickness X of the center of the protrusion, and the thickness Y of the thin portion
• FIG. 1C shows the height Z of the protrusion.
• FIG. 2 is a schematic cross-sectional view of an artificial hair fiber having an inner protrusion and an outer protrusion, in which two C-shaped members are joined together.
• FIG. 2A shows each component
• FIG. 2B shows the thickness X of the center of the protrusion, the thickness Y of the thin portion
• FIG. 2C shows the height Z of the protrusion.
• FIG. 3 is a schematic cross-sectional view of an artificial hair fiber having an outer protrusion and a shape in which two C-shaped members are joined.
• FIG. 3A shows each component
• FIG. 3B shows the thickness X of the center of the protrusion
• the thickness Y of the thin portion shows the height Z of the protrusion.
• FIG. 4 is a schematic cross-sectional view of an artificial hair fiber having no protrusions and having a shape in which two C-shaped portions are joined together, and corresponds to a comparative example of the present invention.
• FIG. 5 is a schematic cross-sectional view of an artificial hair fiber having an inner protrusion and a shape in which three C-shaped members are joined.
• FIG. 5A shows each component
• FIG. 5A shows each component
• FIG. 5B shows the thickness X of the center of the protrusion, the thickness Y of the thin portion, and FIG. 5C shows the height Z of the protrusion.
• FIG. 6 is a schematic cross-sectional view of an artificial hair fiber having three C-shaped members joined together, without any protrusions, which corresponds to a comparative example of the present invention.
• FIG. 7 is a schematic cross-sectional view of a circular artificial hair fiber having inner and outer protrusions, in which FIG. 7A shows each component, FIG. 7B shows the thickness X of the center of the protrusion, the thickness Y of the thin portion, and FIG. 7C shows the height Z of the protrusion.
• FIG. 7A shows each component
• FIG. 7B shows the thickness X of the center of the protrusion
• FIG. 7C shows the height Z of the protrusion.
• FIG. 8 is a schematic cross-sectional view of a circular artificial hair fiber having no protrusions, which corresponds to a comparative example of the present invention.
• FIG. 9 is a schematic cross-sectional view of an approximately triangular artificial hair fiber having an inner protrusion, where FIG. 9A shows each component, and FIG. 9B shows the thickness X of the center of the protrusion, the thickness Y of the thin portion, and the height Z of the protrusion.
• FIG. 10 is a schematic cross-sectional view of a fiber for artificial hair having a substantially triangular shape without any protrusions, which corresponds to a comparative example of the present invention.
• FIG. 11 is a schematic cross-sectional view of a substantially rectangular artificial hair fiber having an inner protrusion, where FIG.
• FIG. 11A shows each component
• FIG. 11B shows the thickness X of the center of the protrusion, the thickness Y of the thin portion, and the height Z of the protrusion.
• FIG. 12 is a schematic cross-sectional view of a fiber for artificial hair having a substantially rectangular shape without any protrusions, and corresponds to a comparative example of the present invention.
• Fig. 13 is a schematic diagram of an opening surface of a nozzle having two C-shaped nozzle holes.
• Fig. 13A is a schematic diagram of an opening surface of a nozzle having two C-shaped nozzle holes and no nozzle hole inner protrusion and no nozzle hole outer protrusion.
• FIG. 13B is a schematic diagram of an opening surface of a nozzle having two C-shaped nozzle holes and a nozzle hole outer protrusion.
• Fig. 13C is a schematic diagram of an opening surface of a nozzle having two C-shaped nozzle holes and a nozzle hole inner protrusion.
• Fig. 13D is a schematic diagram of an opening surface of a nozzle having two C-shaped nozzle holes and a nozzle hole outer protrusion and a nozzle hole inner protrusion.
• Fig. 14 is a schematic diagram of the opening surface of a nozzle having three C-shaped nozzle holes.
• FIG. 14A is a schematic diagram of the opening surface of a nozzle having three C-shaped nozzle holes and no nozzle hole inner protrusion or nozzle hole outer protrusion.
• Fig. 14B is a schematic diagram of the opening surface of a nozzle having three C-shaped nozzle holes and a nozzle hole inner protrusion.
• FIG. 15 is a schematic diagram of an opening surface of a nozzle having four C-shaped nozzle holes.
• Fig. 16 is a schematic diagram of the opening surface of a nozzle having three rod-shaped nozzle holes.
• Fig. 16A is a schematic diagram of the opening surface of a nozzle having three rod-shaped nozzle holes and no nozzle hole inner protrusion or nozzle hole outer protrusion.
• FIG. 14B is a schematic diagram of the opening surface of a nozzle having three rod-shaped nozzle holes and a nozzle hole inner protrusion.
• FIG. 17 is a schematic diagram of an opening surface of a nozzle having four rod-shaped nozzle holes.
• FIG. 18 is a photograph of a cross section of the artificial hair fiber according to Example 2 observed by a laser microscope.
• FIG. 19 is a photograph of a cross section of the artificial hair fiber according to Example 5 observed by a laser microscope.
• FIG. 20 is a photograph of a cross section of the artificial hair fiber according to Example 12 observed by a laser microscope.
• FIG. 21a is a laser microscope photograph of the cross section of the artificial hair fiber according to Comparative Example 1
• FIG. 21b is a laser microscope photograph of the cross section of the artificial hair fiber according to Comparative Example 2.
• the fiber for artificial hair according to one embodiment of the present invention has a hollow portion extending in the longitudinal direction of the fiber for artificial hair, and a cross section perpendicular to the longitudinal direction of the fiber for artificial hair has at least one joint, and the joint has a strength-enhancing structure for improving the bonding strength.
• the artificial hair fiber according to the present invention has a hollow portion extending in the longitudinal direction of the artificial hair fiber.
• the hollow portion can be continuous for 10 cm or more in the longitudinal direction of the artificial hair fiber.
• the artificial hair fiber according to the present invention is lightweight because it has a hollow portion, and offers many advantages, such as being able to create the desired voluminous hairstyle with a small amount of wear, being able to achieve a wide range of hairstyles including heavy long styles, being able to reduce damage to one's own hair and scalp, and being able to reduce waste and environmental impact.
• the cross section perpendicular to the longitudinal direction of the artificial hair fiber can be circular (Figs. 7A-7C) or elliptical, bilobal with two C-shaped members joined together (Figs. 1A-1C, 2A-2C, 3A-3C), trilobal with three C-shaped members joined together (Figs. 5A-5C), quadrilobal with four or more C-shaped members joined together, approximately triangular (Figs. 9A-9B), approximately rectangular (Figs. 11A-11C), or approximately polygonal.
• the artificial hair fiber can have a major axis 18 of 30 to 300 ⁇ m in a cross section perpendicular to the longitudinal direction of the artificial hair fiber.
• the major axis can be, 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 ⁇ m, or it can be within a range between any two of the numerical values exemplified here.
• the hollow spaces 15 can occupy an area of 5 to 50%.
• the area ratio of the hollow spaces 15 is, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50%, and may be within a range between any two of the numerical values exemplified here.
• the area ratio of the hollow parts can be determined by cutting the artificial hair fiber perpendicular to the longitudinal direction, observing the cut surface with a laser microscope or a scanning electron microscope, and performing image analysis, specifically by the method described in the Examples.
• the advantages of having hollow parts can be obtained more reliably.
• a hollow ratio of more than 50% is not preferable because it leads to increased rigidity and poor tactile sensation due to an increase in fiber diameter.
• the artificial hair fiber according to one embodiment of the present invention has at least one joint 13, and the joint 13 has a nozzle for improving the joint strength.
• the artificial hair fiber is generally obtained by melt spinning a resin composition for artificial hair fiber.
• the artificial hair fiber having a hollow portion is formed by melt extrusion from a nozzle having one C-shaped nozzle hole or a nozzle having multiple holes, as shown in FIG. 1 of Patent Document 1, for example.
• the resin composition is at least partially divided while passing through the nozzle, but after being discharged from the nozzle hole, the resin compositions come into contact with each other and fuse to form a hollow portion.
• the part including the joint surface 14 shown by dashed lines in FIG. 1A, FIG. 2A, FIG. 3A, FIG. 5A, FIG. 7A, FIG. 9A, FIG. 11A, etc.
• the joint 13 where the resin compositions are fused to each other during the melt extrusion process
• the artificial hair fiber according to one embodiment of the present invention has at least one joint 13 in a cross section perpendicular to the longitudinal direction of the artificial hair fiber.
• the number of joints 13 can be one or more, preferably two or more, and can be three or more.
• the number of joints 13 can be, for example, 1, 2, 3, 4, or 5, and may be within a range between any two of the numerical values exemplified here.
• the joint 13 is provided with a joint strength enhancing structure 19 for improving the joint strength.
• the joint strength enhancing structure can improve the joint strength by making the joint 13 thicker than other parts. That is, by making the joint thicker and increasing the area of the joint surface 14 where the resin compositions are fused together, the joint strength can be improved.
• the joint is the part where the resin compositions that were separated while passing through the nozzle are fused together.
• the joint is the part that may have the weakest strength, and may be the starting point for causing part of the structure to separate or collapse during, for example, the drawing process, heat treatment process, processing process of undrawn artificial hair fibers, and the post-process of clamping the fibers after the heat treatment process between heated gears to impart a corrugated shape.
• the artificial hair fiber according to one embodiment of the present invention can reduce the probability of separation and destruction of the joint starting point by improving the strength of the points that can be the starting points of structural destruction, and can stably maintain the hollow structure of the artificial hair fiber with a high degree of certainty.
• the artificial hair fiber according to one embodiment of the present invention has at least one joint 13 equipped with a joint strength enhancing structure 19 for improving the joint strength.
• the strength-enhancing structure may have at least one of an inner protrusion 16 protruding toward the hollow portion 15 and an outer protrusion 17 protruding toward the outside of the artificial hair fiber.
• the bonding strength-enhancing structure 19 may have an inner protrusion 16 and an outer protrusion 17 as shown in Figures 2A and 7A, or may have an inner protrusion 16 or an outer protrusion 17, or may have only an outer protrusion 17 as shown in Figure 3A, and preferably has at least an inner protrusion 16, or may have only an inner protrusion 16 as shown in Figures 1A, 5A, 9A, and 11A.
• the size and frequency of the outer protrusions are small, and it is preferable that the outer protrusions 17 are smaller or less frequent than the inner protrusions 16, and it is more preferable to have only the inner protrusions 16.
• the maximum value of the thickness X at the center of the inner protrusion 16 and the outer protrusion 17 is X MAX
• the thickness of the thinnest part other than the inner protrusion and the outer protrusion is Y.
• X MAX /Y can be 0.90 to 2.50, preferably 1.00 to 2.50, and more preferably 1.05 to 2.50.
• X MAX /Y is, for example, 0.90, 0.95, 1.00, 1.05, 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, 1.70, 1.80, 1.90, 2.00, 2.10, 2.20, 2.30, 2.40, or 2.50, and may be within a range between any two of the numerical values exemplified here.
• the thickness X of the center of the inner protrusion 16 and the outer protrusion 17 can be the thickness when crossing the center of the protrusion in the direction of protrusion. If the cross section perpendicular to the longitudinal direction of the artificial hair fiber has multiple protrusions, X MAX can be the maximum value of the multiple X. A thicker thickness at the center means that the area of the bonding surface 14 is larger.
• the thickness Y of the thin-walled portion that is the thinnest at a location other than the inner protrusion 16 and the outer protrusion 17 can be the shortest distance between the outer surface 11 and the inner surface 12 at a location other than the inner protrusion 16 and the outer protrusion 17.
• the thickness Y of the thin-walled portion can be the thickness at a location farthest from any of the joints. When there is one joint 13, the thickness Y of the thin-walled portion can be the thickness at a location facing the joint. When there are two or more joints 13, the thickness Y of the thin-walled portion can be the thickness at a midpoint between adjacent joints.
• X MAX /Y is equal to or greater than the above lower limit, sufficient strength can be imparted to the joint 13.
• X/Y calculated from the thickness X of the center of each protrusion, is within the above-mentioned numerical range.
• X can be 5 to 70 ⁇ m.
• X can be, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70 ⁇ m, or can be within a range between any two of the values exemplified here.
• Y can be 5 to 40 ⁇ m.
• Y can be, for example, 5, 10, 15, 20, 25, 30, 35, or 40 ⁇ m, and may be within a range between any two of the numerical values exemplified here.
• the fiber for artificial hair according to one embodiment of the present invention can have a thickness of 5 ⁇ m or more at the thinnest part.
• the thickness of the thinnest part can be, for example, 5, 10, 15, 20, 25, 30, 35, or 40 ⁇ m, and may be within a range between any two of the numerical values exemplified here.
• separation and crushing of the structure may occur starting from a thin part, but according to the fiber for artificial hair according to one embodiment of the present invention, the thicknesses X and Y are within the above numerical ranges, and/or the thickness of the thinnest part is equal to or greater than the above lower limit, so that separation and crushing of the structure can be further suppressed.
• protrusions will be described based on a representative embodiment.
• Figures 7A to 7C show cross sections having inner protrusions 16 and outer protrusions 17 when the cross section perpendicular to the longitudinal direction of the artificial hair fiber is circular
• Figure 8 shows a cross section of a comparative example having no protrusions.
• having a protrusion can mean a case where the protrusion height Z is 1 ⁇ m or more.
• the protrusion height Z can be, for example, 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, or 50 ⁇ m, and can be within a range between any two of the numerical values exemplified here.
• the protrusion height Z can be the distance from the tangent at the intersection of a virtual inner surface (outer surface) (dashed line in Figure 7C) that is an extension of the inner surface 12 (or outer surface 11) other than the protrusions assuming that there are no protrusions, and a straight line that extends in the direction of the protrusion through the center of the protrusion, to the apex of the protrusion.
• cross sections having inner protrusions 16 and outer protrusions 17 are shown in Figures 2A to 2C
• cross sections having only inner protrusions 16 are shown in Figures 1A to 1C and Figures 5A to 5C
• cross sections having only outer protrusions 17 are shown in Figures 3A to 3C
• a cross section equivalent to a comparative example having no protrusions is shown in Figure 4.
• having a protrusion can refer to a case in which the protrusion height Z is 1 ⁇ m or more.
• the protrusion height Z can be, for example, 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, or 50 ⁇ m, or it can be within a range between any two of the numerical values exemplified here.
• Z can be the distance from a tangent line passing through two points on the inner (or outer) surfaces of two adjacent C-shaped portions via a protrusion to the apex of the protrusion ( Figures 1C, 2C, 3C, and 5C).
• Figures 1, 2, 3, and 5 show cases where the cross section perpendicular to the longitudinal direction of the artificial hair fiber is a bilobal cross section with two or three C-shaped portions joined together, but the protrusions and protrusion heights can be similarly specified even when the cross section is a quadrilobular cross section or more.
• FIGS. 9A-9B and 11A-11B show cross sections having only inner protrusions 16 when the cross section perpendicular to the longitudinal direction of the artificial hair fiber is a polygonal shape such as a substantially triangular or substantially rectangular shape, while Figs. 10 and 12 show cross sections of a comparative example having no protrusions.
• having a protrusion can refer to a case where the protrusion height Z is 1 ⁇ m or more.
• the protrusion height Z can be, for example, 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, or 50 ⁇ m, and can be within a range between any two of the numerical values exemplified here.
• Z is a line perpendicular to the bisector of the angle of the vertex of the polygon on the imaginary inner surface (outer surface) (dashed lines in Figs. 9B and 11B) that is extended from the inner surface 12 (or outer surface 11) other than the protrusions assuming that there are no protrusions, and can be the distance from the straight line including the vertex to the vertex of the protrusion.
• Figures 9 and 11 show cases where the cross section perpendicular to the longitudinal direction of the artificial hair fiber is substantially triangular or substantially rectangular, but the protrusions and their heights can be similarly specified even when the cross section is pentagonal or larger.
• the cross-sectional shape of the artificial hair fiber can be controlled by the composition of the resin composition for artificial hair fiber that constitutes the artificial hair fiber, the melt extrusion conditions, and the shape of the nozzle used for melt extrusion.
• the resin composition constituting the fiber for artificial hair is not particularly limited, and may contain at least one of polyamide-based resin, polyester-based resin, vinyl chloride-based resin, AS-based resin (acrylonitrile styrene-based resin), PP resin, PET resin, PE resin, PAN-based resin, and PLA-based resin (polylactic acid-based resin).
• the fiber for artificial hair according to one embodiment of the present invention contains a vinyl chloride-based resin.
• the fiber for artificial hair according to one embodiment of the present invention contains a vinyl chloride-based resin and an AS-based resin (acrylonitrile styrene-based resin).
• the polyvinyl chloride resin according to one embodiment of the present invention may contain a vinyl chloride polymer containing a monomer unit (vinyl chloride monomer unit) derived from a vinyl chloride monomer.
• the polyvinyl chloride resin according to the present invention may contain a homopolymer obtained by homopolymerizing a vinyl chloride monomer, and/or a copolymer containing a monomer unit derived from a vinyl chloride monomer and another monomer copolymerizable with the vinyl chloride monomer.
• copolymer examples 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.
• the polyvinyl chloride resin according to the present invention may be made of one type of vinyl chloride polymer, or may contain two or more types of vinyl chloride polymers.
• the resin composition constituting the artificial hair fiber according to one embodiment of the present invention contains 50 to 99% by mass of vinyl chloride resin in 100% by mass of the resin composition, preferably 65 to 95% by mass, and more preferably 65 to 90% by mass. Specifically, for example, it may be 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 99% by mass, and may be within a range between any two of the numerical values exemplified here.
• AS-based resin (acrylonitrile styrene-based resin) is a copolymer having styrene-based monomer units and acrylonitrile-based monomer units, and may contain other monomer units copolymerizable with these as necessary.
• AS-based resin 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 AS resin, and may be within a range between any two of the numerical values exemplified here.
• AS-based resin 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 AS resin, and may be within a range between any two of the numerical values exemplified here.
• the artificial hair fiber according to one embodiment of the present invention may contain other ingredients as necessary. These include antistatic agents, heat stabilizers, lubricants, colorants, processing aids, plasticizers, strengthening agents, UV absorbers, antioxidants, fillers, flame retardants, pigments, initial coloring improvers, conductivity imparting agents, fragrances, etc.
• the fiber bundle for artificial hair according to one embodiment of the present invention contains the above-mentioned fiber for artificial hair.
• the fiber bundle for artificial hair according to one embodiment of the present invention is preferably made of the above-mentioned fiber for artificial hair.
• the structural retention rate of the cross section of the fiber for artificial hair is preferably 90% or more.
• the structural 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 numerical values exemplified here.
• the structural retention rate indicates the proportion of fibers for artificial hair having a cross section in which the joints are not separated and the hollow portion is not crushed, and specifically, it can be calculated based on the following formula using the method described in the examples.
• Structure retention rate (300-i-j)/300 i: The number of fibers having one or more separate junctions j: The number of fibers whose hollow portions have collapsed and whose inner surfaces have come into contact with each other
• the fiber bundle for artificial hair according to one embodiment of the present invention has a high structural retention rate, and even when it undergoes processes such as a stretching process and a heat treatment process, the structure having a hollow portion is not destroyed and is maintained with a high degree of certainty, so that the advantages of having a hollow portion can be obtained with full certainty.
• the structural retention rate can be increased by adjusting the cross-sectional structure of the fiber for artificial hair.
• the artificial hair fiber bundle according to one embodiment of the present invention preferably has a volume of 5 cc/g.
• the volume may be, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 cc/g, or may be within a range between any two of the values exemplified here.
• the manufacturing method of artificial hair fiber according to one embodiment of the present invention can include a step of preparing a resin composition for artificial hair fiber and a spinning step.
• the artificial hair fiber is melt-extruded using a nozzle described below to obtain the artificial hair fiber having the above-mentioned structure.
• resin composition for artificial hair fiber In the preparation of resin composition for artificial hair fiber, raw materials including resins are mixed to obtain a resin composition for artificial hair fiber.
• the raw materials include a base resin and may contain other components as necessary.
• the mixing method is not particularly limited, and a conventionally known method can be used.
• a powdered resin composition can be obtained using a known mixing device such as a Henschel mixer, a super mixer, or a ribbon blender, and the powder compound can be melt-mixed to obtain a pellet-shaped resin composition (pellet compound).
• the powder compound can be produced by hot blending or cold blending.
• hot blending can be performed with a cutting temperature of 105 to 155°C during mixing.
• the pellet compound can be produced by the same method as the pellet compound of a general polyvinyl chloride resin.
• a pellet compound can be produced by using a kneader such as a single-screw extruder, a counter-rotating twin-screw extruder, a conical 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 pieces from the screw and fibers from protective gloves that may be mixed into the pellet compound.
• a cold cut method can be used to produce pellets. A means for removing chips (fine powder generated during pellet production) that may be mixed in during cold cutting may also be used. In addition, the cutter may chip when used for a long time, making it easier for chips to be generated, so it is preferable to replace it as needed.
• the resin composition for artificial hair fibers is melt-spun to obtain artificial hair fibers.
• the resin composition e.g., pellet compound
• the extruder a conventionally known extruder can be used, such as a single screw extruder, a counter-rotating twin screw extruder, a conical twin screw extruder, etc.
• the nozzle for melt extrusion will be described later.
• the melt spinning conditions can be set appropriately depending on the type of resin composition so that the resin melts and a bonded structure is formed at the joint.
• the cylinder temperature can be set to 150-190°C
• the nozzle temperature can be set to 180 ⁇ 15°C.
• the undrawn yarn melt-spun from the nozzle is introduced into a heating cylinder (for example, heating cylinder temperature 250°C) where it is instantly heat-treated, and can then be wound up by a take-up machine installed directly below the nozzle (for example, about 4.5 m away).
• a heating cylinder for example, heating cylinder temperature 250°C
• a take-up machine installed directly below the nozzle (for example, about 4.5 m away).
• the nozzle for melt extrusion of artificial hair fibers may have one or more C-shaped nozzle holes or two or more rod-shaped nozzle holes.
• Figures 13A and 13D show two C-shaped nozzle holes
• Figures 14A and 14B show three C-shaped nozzle holes
• Figure 15 shows four C-shaped nozzle holes
• Figures 16A and 16B show three rod-shaped nozzle holes
• Figure 17 shows four rod-shaped nozzle holes.
• a nozzle having two C-shaped nozzle holes as shown in FIG. 13 can be used.
• a nozzle having three C-shaped nozzle holes as shown in FIG. 14 can be used.
• a nozzle having four C-shaped nozzle holes as shown in FIG. 15 can be used.
• a substantially triangular cross section as shown in FIG. 9 a nozzle having three rod-shaped nozzle holes as shown in FIG. 16 can be used.
• a nozzle having four rod-shaped nozzle holes as shown in FIG. 17 can be used.
• the nozzle can have a separation portion, and can have a separation portion 23 on the opening surface.
• a separation portion 23 on the opening surface.
• the resin composition comes into contact with itself and fuses to form a hollow portion.
• the resin composition discharged from the nozzle hole expands due to the die swell effect, making it possible to form the above-mentioned joint.
• B/A is 3 to 20.
• B/A is, for example, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, and may be within a range between any two of the numerical values exemplified here.
• the minor axis length A can be the shortest distance between the nozzle hole outer surface 21 and the nozzle hole inner surface 22, and can be the distance between the nozzle hole outer surface 21 and the nozzle hole inner surface 22 at the point farthest from the separation portion 23.
• the minor axis length A can be the distance between the nozzle hole outer surface 21 and the nozzle hole inner surface 22 at the point facing the separation portion.
• the minor axis length A can be the distance between the nozzle hole outer surface 21 and the nozzle hole inner surface 22 at the midpoint between adjacent separation portions.
• B is the length of the line connecting the points at the opening surface of the nozzle hole that are equidistant from the nozzle hole inner surface 22 and the nozzle hole outer surface 21, and the points that make up B are at least A/2 away from the outer periphery of each nozzle hole.
• B starts at a point A/2 away from one end and ends at a point A/2 away from the other end.
• B/A of each nozzle hole is within the above-mentioned numerical range. It is also preferable that Bt/At calculated from the sum At of A1, A2, ..., An of the multiple nozzle holes in the nozzle opening surface and the sum Bt of B1, B2, ..., Bn of the multiple nozzle holes is within the above-mentioned numerical range.
• C/A is 0.5 to 1.5 in the opening surface of the nozzle.
• C/A may be, for example, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, or 1.5, and may be within a range between any two of the numerical values exemplified here.
• Coverage/Aaverage calculated from the average value Coverage of the multiple separation distances C and the average value Aaverage of A of the multiple nozzle holes satisfies the above numerical range.
• the nozzle has at least one of the nozzle hole inner protrusion 26 and the nozzle hole outer protrusion 27 on the nozzle opening surface.
• the bonding surface of the artificial hair fiber can be further increased.
• the nozzle hole inner protrusion 26 and the nozzle hole outer protrusion 27 are not essential for the formation of the protrusions on the cross section of the artificial hair fiber.
• the resin composition expands due to the die swelling effect after being extruded from the nozzle hole, which is considered to form a joint (protrusion) with an increased area of the joint surface, and the formation of the protrusions is possible even if the nozzle does not have the nozzle hole inner protrusion 26 and the nozzle hole outer protrusion 27 on the nozzle opening surface.
• the nozzle may have the nozzle hole inner protrusion 26 and the nozzle hole outer protrusion 27 on the nozzle opening surface (Fig. 13D), or may have only the nozzle hole inner protrusion 26 (Figs. 13C, 14B, and 16B) or only the nozzle hole outer protrusion 27 (Fig. 13B). It is preferable that the nozzle has at least the nozzle hole inner protrusion 26 on the nozzle opening surface. From the viewpoint of improving the feel of the obtained artificial hair fiber, it is preferable that the nozzle has only the nozzle hole inner protrusion 26 and does not have the nozzle hole outer protrusion 27 on the nozzle opening surface. Note that Fig.
• FIG. 13 shows an embodiment in which the nozzle hole inner protrusion 26 and/or the nozzle hole outer protrusion 27 are provided on a nozzle having two C-shaped nozzle holes, but the nozzle hole inner protrusion 26 and/or the nozzle hole outer protrusion 27 can be similarly provided on one or more other C-shaped nozzle holes or two or more rod-shaped nozzle holes.
• the method for producing an artificial hair fiber according to one embodiment of the present invention may also include a drawing step and a heat treatment step.
• the undrawn artificial hair fiber obtained in the melt spinning process is drawn by a drawing machine to obtain a drawn artificial hair fiber.
• the undrawn artificial hair fiber can be drawn 2 to 5 times in an air atmosphere at 90 to 110°C.
• the stretched artificial hair fiber can be heat-treated using a heat treatment machine.
• the stretched 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, and is heat-shrunk until the total fiber length is 75% of the length before treatment, to obtain a heat-treated artificial hair fiber having a fineness of 30 to 70 denier.
• the method for producing an artificial hair fiber according to one embodiment of the present invention may also include a gear processing step.
• the fiber bundle can be crimped by passing it between two meshing high-temperature gears.
• the material of the gear used in the gear processing step there are no particular limitations on the material of the gear used in the gear processing step, the shape of the gear waves, the number of gears, etc.
• the shape of the obtained artificial hair fiber can be controlled by appropriately adjusting the depth of the gear wave groove, the surface temperature of the gear, the processing speed, the pressure conditions between the gears, etc., taking into consideration the fiber material and fineness.
• the depth of the gear wave groove can be 0.2 mm to 6 mm, preferably 0.5 mm to 5 mm
• the surface temperature of the gear can be 30° C. to 100° C., preferably 40° C. to 80° C.
• the processing speed can be 0.5 to 10 m/min, preferably 1.0 m/min to 8.0 m/min.
• the total fineness of the fiber bundles used in gear processing is not particularly limited, but can be 100,000 to 2,000,000 decitex, preferably 500,000 to 1,500,000 decitex.
• the productivity of the gear processing can be increased, and further, the occurrence of thread breakage during gear processing can be suppressed.
• the total fineness of the fiber bundles is set to the above lower limit or less, a more uniform wave shape can be obtained.
• the term "fiber for artificial hair” includes fiber for artificial hair after spinning, and encompasses fiber for artificial hair before the drawing process, after the drawing process, before the heat treatment process, after the heat treatment process, before the gear processing process, and after the gear processing process.
• a hair accessory product according to one embodiment of the present invention comprises the above-mentioned artificial hair fiber. Also, a hair accessory product according to one embodiment of the present invention comprises the above-mentioned artificial hair fiber bundle.
• the artificial hair fiber of the present invention can be used in hair accessory products.
• hair accessory products include wigs, hair pieces, braids, and hair extensions.
• Hair accessory products obtained from the artificial hair fiber of the present invention maintain their hollow structure with a high degree of certainty even after undergoing processing steps after melt extrusion, and therefore are lightweight and can create the desired voluminous hairstyle with a small amount of wear, can achieve a wide range of hairstyles including heavy long styles, can reduce damage to one's own hair and scalp, and can reduce waste and environmental impact, among other benefits.
• the fiber for artificial hair according to one embodiment of the present invention has a hollow portion extending in the longitudinal direction of the fiber for artificial hair, and a cross section perpendicular to the longitudinal direction of the fiber for artificial hair has at least one of an inner protrusion protruding toward the hollow portion and an outer protrusion protruding toward the outside of the fiber for artificial hair.
• the following description will focus on the differences from the first viewpoint.
• the artificial hair fiber according to the second aspect has a hollow portion.
• the shape of the hollow portion and the advantages of having a hollow portion are the same as those of the first aspect.
• the cross section perpendicular to the longitudinal direction of the artificial hair fiber can be circular (Figs. 7A-7C) or elliptical, as in the first aspect, bilobal with two joined C shapes (Figs. 1A-1C), trilobal with three joined C shapes (Figs. 5A-5C), quadrilobal with four or more joined C shapes, approximately triangular (Figs. 9A-9B), approximately rectangular (Figs. 11A-11C), or approximately polygonal.
• the cross section perpendicular to the longitudinal direction of the artificial hair fiber according to the second aspect has 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.
• the artificial hair fiber may have an inner protrusion 16 and an outer protrusion 17 as shown in Figures 2 and 7, or may have an inner protrusion 16 or an outer protrusion 17, and preferably has at least an inner protrusion 16, or may have only an inner protrusion 16 as shown in Figures 1, 5, 9, and 11.
• the size and frequency of the outer protrusions are small, and it is preferable that the outer protrusions 17 are smaller or less frequent than the inner protrusions 16, and it is more preferable that the artificial hair fiber has only the inner protrusions 16.
• protrusions are as described in the first aspect, but will be described based on a representative embodiment.
• Figures 7A to 7C show cross sections having inner protrusions 16 and outer protrusions 17 when the cross section perpendicular to the longitudinal direction of the artificial hair fiber is circular
• Figure 8 shows a cross section of a comparative example having no protrusions.
• having a protrusion can mean a case where the protrusion height Z is 1 ⁇ m or more.
• the protrusion height Z can be, for example, 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, or 50 ⁇ m, and may be within a range between any two of the numerical values exemplified here.
• the protrusion height Z can be the distance from the tangent at the intersection of a virtual inner surface (outer surface) (dashed line in Figure 7C) that is an extension of the inner surface 12 (or outer surface 11) other than the protrusions assuming that there are no protrusions, and a straight line that extends in the direction of the protrusion through the center of the protrusion, to the apex of the protrusion.
• cross sections having inner protrusions 16 and outer protrusions 17 are shown in Figures 2A to 2C
• cross sections having only inner protrusions 16 are shown in Figures 1A to 1C and Figures 5A to 5C
• cross sections having only outer protrusions 17 are shown in Figures 3A to 3C
• a cross section equivalent to a comparative example having no protrusions is shown in Figure 4.
• having a protrusion can refer to a case in which the protrusion height Z is 1 ⁇ m or more.
• the protrusion height Z can be, for example, 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, or 50 ⁇ m, and may be within a range between any two of the numerical values exemplified here.
• Z can be the distance from a tangent line passing through two points on the inner (or outer) surfaces of two adjacent C-shaped portions via a protrusion to the apex of the protrusion ( Figures 1C, 2C, 3C, and 5C).
• Figures 1, 2, 3, and 5 show cases where the cross section perpendicular to the longitudinal direction of the artificial hair fiber is a bilobal cross section with two or three C-shaped portions joined together, but the protrusions and protrusion heights can be similarly specified even when the cross section is a quadrilobular cross section or more.
• FIGS. 9A-9B and 11A-11B show cross sections having only inner protrusions 16 when the cross section perpendicular to the longitudinal direction of the artificial hair fiber is a polygonal shape such as a substantially triangular or substantially rectangular shape, while Figs. 10 and 12 show cross sections of a comparative example having no protrusions.
• having a protrusion can refer to a case where the protrusion height Z is 1 ⁇ m or more.
• the protrusion height Z can be, for example, 1, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, or 50 ⁇ m, and can be within a range between any two of the numerical values exemplified here.
• Z is a line perpendicular to the bisector of the angle of the vertex of the polygon on the imaginary inner surface (outer surface) (dashed lines in Figs. 9B and 11B) that is extended from the inner surface 12 (or outer surface 11) other than the protrusions assuming that there are no protrusions, and can be the distance from the straight line including the vertex to the vertex of the protrusion.
• Figures 9 and 11 show cases where the cross section perpendicular to the longitudinal direction of the artificial hair fiber is substantially triangular or substantially rectangular, but the protrusions and their heights can be similarly specified even when the cross section is pentagonal or larger.
• the protrusions may include a joint surface and a joint portion where the resin compositions come into contact with each other and are fused together.
• the cross section of the fiber for artificial hair may include a protrusion that does not include a joint surface and a joint portion.
• the fiber for artificial hair according to one embodiment of the present invention has a structure having a hollow portion and a protrusion portion, which significantly improves the structural retention rate of the fiber for artificial hair and enables the hollow structure of the fiber for artificial hair to be stably maintained with a high degree of certainty.
• X MAX the maximum value of the thickness X of the center of the inner protrusion 16 and the outer protrusion 17 in a cross section perpendicular to the longitudinal direction of the artificial hair fiber
• X MAX the thickness of the thinnest part other than the inner protrusion and the outer protrusion
• Y the thickness of the thinnest part other than the inner protrusion and the outer protrusion
• X MAX /Y can be 0.90 to 2.50, preferably 1.00 to 2.50, and more preferably 1.05 to 2.50.
• X MAX /Y is, for example, 0.90, 0.95, 1.00, 1.05, 1.10, 1.20, 1.30, 1.40, 1.50, 1.60, 1.70, 1.80, 1.90, 2.00, 2.10, 2.20, 2.30, 2.40, or 2.50, and may be within a range between any two of the numerical values exemplified here.
• the thickness X of the center of the inner protrusion 16 and the outer protrusion 17 can be the thickness when crossing the center of the protrusion in the direction of protrusion. If the cross section perpendicular to the longitudinal direction of the artificial hair fiber has multiple protrusions, X MAX can be the maximum value of the multiple X. A thicker thickness at the center means that the area of the bonding surface 14 is larger.
• the thickness Y of the thin-walled portion that is the thinnest at a location other than the inner protrusion 16 and the outer protrusion 17 can be the shortest distance between the outer surface 11 and the inner surface 12 at a location other than the inner protrusion 16 and the outer protrusion 17.
• the thickness Y of the thin-walled portion can be the thickness at a location farthest from any of the joints. When there is one joint 13, the thickness Y of the thin-walled portion can be the thickness at a location facing the joint. When there are two or more joints 13, the thickness Y of the thin-walled portion can be the thickness at a midpoint between adjacent joints.
• X MAX /Y is equal to or greater than the above lower limit, sufficient strength can be imparted to the joint 13.
• X/Y calculated from the thickness X of the center of each protrusion, is within the above-mentioned numerical range.
• X can be 5 to 70 ⁇ m.
• X can be, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70 ⁇ m, or can be within a range between any two of the values exemplified here.
• Y can be 5 to 40 ⁇ m.
• Y can be, for example, 5, 10, 15, 20, 25, 30, 35, or 40 ⁇ m, and may be within a range between any two of the numerical values exemplified here.
• the fiber for artificial hair according to one embodiment of the present invention can have a thickness of 5 ⁇ m or more at the thinnest part.
• the thickness of the thinnest part can be, for example, 5, 10, 15, 20, 25, 30, 35, or 40 ⁇ m, and may be within a range between any two of the numerical values exemplified here.
• separation and crushing of the structure may occur starting from a thin part, but according to the fiber for artificial hair according to one embodiment of the present invention, the thicknesses X and Y are within the above numerical ranges, and/or the thickness of the thinnest part is equal to or greater than the above lower limit, so that separation and crushing of the structure can be further suppressed.
• the cross-sectional shape of the artificial hair fiber can be controlled by the composition of the resin composition for artificial hair fiber that constitutes the artificial hair fiber, the melt extrusion conditions, and the shape of the nozzle used for melt extrusion.
• composition of the artificial hair fiber according to the second aspect may be the same as that of the first aspect.
• composition of the artificial hair fiber bundle according to the second aspect may be the same as that of the first aspect.
• the manufacturing method of the artificial hair fiber according to the second aspect is not particularly limited, and any manufacturing method can be used as long as it can obtain a structure in which an artificial hair fiber having a hollow portion and a cross section perpendicular to the longitudinal direction of the artificial hair fiber has at least one of an inner protrusion and an outer protrusion.
• the artificial hair fiber according to the second aspect can be obtained by the same method as in the first aspect, and a nozzle similar to the nozzle described in the first aspect can be used as a nozzle for melt extrusion.
• the hair accessory product according to the second aspect may be similar to that of the first aspect.
• Example 1 ⁇ Step of Preparing Resin Composition for Artificial Hair Fiber> 70 parts by mass of polyvinyl chloride resin (manufactured by Taiyo PVC Co., Ltd., product name: TH1000), 30 parts by mass of vinyl copolymer resin (manufactured by our company, GR-AT-6S) containing 68% by mass of styrene monomer units and 32% by mass of acrylonitrile monomer units, 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.
• polyvinyl chloride resin manufactured by Taiyo PVC Co., Ltd., product name: TH1000
• GR-AT-6S vinyl copolymer resin
• additives such as
• the blended materials were kneaded using a ⁇ 40 mm single-screw extruder to obtain a 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 ( Mg4Al2 (OH) 12CO3.3H2O ) 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 - Polyvinyl chloride resin (manufactured by Taiyo PVC Co., Ltd., product name: TH1000) 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 P
• nozzle 1 is a nozzle having two identical C-shaped nozzle holes with a nozzle hole inner protrusion.
• B the length of the line connecting the points at the same distance from the inner surface and the outer surface on the nozzle hole opening surface
• C/A was 1.0.
• the molten resin discharged from the nozzle was adjusted in discharge amount and winding speed to produce an undrawn yarn.
• the cylinder temperature and nozzle temperature of the spinning machine were set to 140 to 180°C.
• ⁇ Stretching step and heat treatment step> The obtained undrawn yarn was drawn at 100°C, and then annealed at 100°C 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).
• Examples 2 to 11, Comparative Examples 1 and 2 Fibers 2 to 13 for artificial hair were obtained in the same manner as in Example 1, except that nozzles 2 to 13 were used as the nozzles used in the spinning process.
• nozzles 2, 3, and 6 to 11 have two identical C-shaped nozzle holes having a nozzle hole inner protrusion, and B/A and C/A are as shown in Table 1.
• nozzle 4 has three identical rod-shaped nozzle holes having a nozzle hole inner protrusion, and B/A and C/A are as shown in Table 1.
• FIG. 16B nozzle 4 has three identical rod-shaped nozzle holes having a nozzle hole inner protrusion, and B/A and C/A are as shown in Table 1.
• nozzle 5 has three identical C-shaped nozzle holes having a nozzle hole inner protrusion, and B/A and C/A are as shown in Table 1.
• nozzle 12 has two identical C-shaped nozzle holes having a nozzle hole outer protrusion, and B/A and C/A are as shown in Table 1.
• the nozzle 12 has three identical C-shaped nozzle holes, with B/A and C/A as shown in Table 1.
• the nozzle 13 has four identical C-shaped nozzle holes, with B/A and C/A as shown in Table 1.
• the obtained artificial hair fibers were evaluated by the following methods. For cross-sectional observation, the artificial hair fibers were cut to an appropriate length, wrapped in vinyl tape, and cut perpendicular to the longitudinal direction with a cutter knife to prepare a cross section.
• ⁇ Cross-section observation> A cross-sectional photograph of the fiber was taken at a magnification of 400 times using a laser microscope to confirm the presence or absence of protrusions.
• the thickness X of the thick part at the center of the inner protrusion and the outer protrusion, and the thickness Y of the thinnest part other than the inner protrusion and the outer protrusion were measured, and XMAX /Y was calculated.
• ⁇ Tactile sensation> 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 the texture was evaluated by 10 artificial hair fiber processing technicians (with 5 years or more of work experience) who judged the texture according to the following criteria. 4: Nine or more engineers rated the texture as good. 3: Six to eight engineers rated the texture as good. 2: Three to five engineers rated the texture as good. 1: Two or fewer engineers rated the texture as good.
• a laser microscope photograph of the cross section of the artificial hair fiber according to Example 2 is shown in Figure 18, a laser microscope photograph of the cross section of the artificial hair fiber according to Example 5 is shown in Figure 19, a laser microscope photograph of the cross section of the artificial hair fiber according to Comparative Example 1 is shown in Figure 21A, and a laser microscope photograph of the cross section of the artificial hair fiber according to Comparative Example 2 is shown in Figure 21B.
• the cross section of the artificial hair fiber according to the Examples has a strength enhancing structure (protrusion) for improving the joint strength at the joint, and the protrusion height Z is 1 ⁇ m or more.
• the cross section of the artificial hair fiber according to the Comparative Example is thinner at the joint than the thickness of the other parts, and no protrusions were observed.
• 100 Cross section of artificial hair fiber, 11: Outer surface, 12: Inner surface, 13: Joint, 14: Joint surface, 15: Hollow portion, 16: Inner protrusion, 17: Outer protrusion, 18: Major axis, 19: Joint strength enhancing structure, X: Thickness at the center of the thickest protrusion, Y: Thickness of the thinnest portion, Z: Protrusion height, 200: Nozzle hole, 21: Outer surface of nozzle hole, 22: Inner surface of nozzle hole, 23: Separation portion, 24: Inner protrusion of nozzle hole, 25: Outer protrusion of nozzle hole, A: Minor axis length, B: Length of line connecting points at equal distances from the inner surface and the outer surface, C: Separation distance

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