Core-sheath composite fiber for artificial hair, head accessories containing the same, and manufacturing method thereof

Abstract

One or more embodiments of the present invention relate to a core-sheath composite fiber for artificial hair, said core-sheath composite fiber comprising a core part and a sheath part, wherein: the core part is configured from a polyester resin composition that contains a polyester resin as a main component; the sheath part is configured from a polyamide resin composition that contains a polyamide resin as a main component; the core-sheath ratio in the composite fiber for artificial hair, namely the (core part):(sheath part) area ratio is from 2:8 to 7:3; both the fiber cross-section and the core part cross-section have a flattened cross-sectional shape; the major axis direction of the fiber cross-section and the major axis direction of the core part cross-section generally coincide with each other; and the eccentricity ratio of the fiber in the minor axis direction is 5% or more. Consequently, the present invention provides a fiber for artificial hair, said fiber having a texture and appearance close to those of human hair, while exhibiting good curl setting properties.

Description

[Technical Field]

[0001] The present invention relates to a core-sheath composite fiber for artificial hair that can be used as a substitute for human hair, a head accessory containing the same, and a method for producing the same. [Background technology]

[0002] Traditionally, human hair has been used in head accessories such as wigs, hairpieces, false hair, hair bands, and doll hair. However, in recent years, the availability of human hair has become more difficult, leading to an increasing demand for artificial hair as an alternative to human hair. Examples of artificial hair materials include synthetic fibers such as acrylic fibers, vinyl chloride fibers, vinylidene chloride fibers, polyester fibers, polyamide fibers, and polyolefin fibers. For example, Patent Document 1 describes a core-sheath composite fiber for artificial hair, which has a polyester resin as the core component and a polyamide resin as the sheath component. Patent Document 1 describes a method for melt-spinning a high-polymerization polyethylene terephthalate and a high-polymerization polyamide, rapidly solidifying the fiber by liquid cooling, and then passing the fiber through a fiber surface crystallization accelerator to impart a specific streaky uneven structure to the fiber surface. This method ensures the strength of the fiber while suppressing the gloss of the sheath polyamide, resulting in an artificial hair fiber with a texture similar to human hair and excellent durability and heat resistance.

[0003] On the other hand, curl setting ability and curl retention are also properties required for artificial hair. Attempts have been made to improve these properties by controlling the fiber material and cross-sectional shape. For example, Patent Document 2 describes that by comprising a core and a sheath, the longitudinal axis direction of the fiber cross section is approximately the same as the longitudinal axis direction of the core, and the eccentricity in the longitudinal direction is 5% or more, a core-sheath composite fiber for artificial hair can be obtained that has a texture and appearance similar to human hair, has good curling ability even without curl setting, and has extremely high curl retention. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 3-185103 [Patent Document 2] International Publication No. 2018 / 179803 Summary of the Invention [Problem to be solved by the invention]

[0005] However, although artificial hair fibers using a polyamide resin for the sheath as described in Patent Document 1 have a good feel and durability, they have the problem of poor curl settability.Furthermore, artificial hair fibers with an eccentric structure in the longitudinal direction as described in Patent Document 2 have latent crimping properties and can produce artificial hair fibers with high curl retention even without curl setting, but they have the problem of poor curl settability when curls are imparted with a hair iron or the like.

[0006] In order to solve the above-mentioned problems of the prior art, the present invention provides a fiber for artificial hair that has a feel and appearance similar to human hair and has good curl setting properties. [Means for solving the problem]

[0007] In one or more embodiments, the present invention relates to a sheath-core composite fiber for artificial hair, comprising a core and a sheath, wherein the core is made of a polyester-based resin composition containing a polyester-based resin, and the sheath is made of a polyamide-based resin composition containing a polyamide-based resin, and the composite fiber for artificial hair has a core-sheath ratio of 2:8 to 7:3 in terms of area ratio of core:sheath, both the fiber cross section and the core cross section have flat cross-sectional shapes, the direction of the major axis of the fiber cross section and the major axis of the core cross section are approximately the same, and the eccentricity in the minor axis direction of the fiber is 5% or more.

[0008] In one or more embodiments, the present invention also relates to a head accessory comprising the core-sheath composite fiber for artificial hair.

[0009] In one or more embodiments, the present invention also relates to a method for producing the sheath-core composite fiber for artificial hair, comprising a step of melt-spinning a polyester-based resin composition and a polyamide-based resin composition using a sheath-core composite nozzle, wherein the cross-sectional shape of the sheath-core composite fiber for artificial hair and the core are flat, the direction of the long axis of the fiber cross section is approximately the same as the long axis of the core cross section, and the eccentricity in the short axis direction of the fiber is 5% or more. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a core-sheath composite fiber for artificial hair that has a texture and appearance similar to human hair and has good curl setting properties, and a head accessory product containing the same.

[0011] According to the production method of the present invention, it is possible to obtain core-sheath composite fibers for artificial hair that have a texture and appearance similar to human hair and good curl setting properties. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing the cross section of a core-sheath composite fiber for artificial hair according to one or more embodiments of the present invention. [Figure 2] FIG. 2 is a laser microscope photograph of the cross section of the fiber of Example 1. [Figure 3] FIG. 3 is a laser microscope photograph of the cross section of the fiber of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0013] As a result of extensive research into solving the above-mentioned problems, the present inventors have found that, in a sheath-core composite fiber for artificial hair comprising a core and a sheath, the core is made of a polyester-based resin composition containing a polyester-based resin as a main component, the sheath is made of a polyamide-based resin composition containing a polyamide-based resin as a main component, the core:sheath ratio is 2:8 to 7:3 in terms of area ratio, the fiber cross section and core cross section are flat, the long axis direction of the fiber cross section and the long axis direction of the core cross section are approximately aligned, and the eccentricity in the fiber's short axis direction is 5% or more, thereby improving the poor curl settability that is often caused by using polyamide-based resins, and producing a sheath-core composite fiber for artificial hair (hereinafter simply referred to as "sheath-core composite fiber") that has a feel and appearance similar to human hair and good curl settability, and have arrived at the present invention.

[0014] (Fiber shape) The core-sheath composite fiber for artificial hair according to one or more embodiments of the present invention comprises a core and a sheath, and both the fiber cross section and the core cross section have a flat cross-sectional shape. Examples of flat shapes include elliptical, flattened multilobal, and oval. Examples of flattened multilobal shapes include a shape in which two or more lobes selected from the group consisting of circles and ellipses are joined via a recess. In the flattened multilobal shape, the circles and / or ellipses partially overlap at the joining points. The cross-sectional shape of the fiber cross section is preferably flattened multilobal, and more preferably flattened bilobal. Note that the circular or elliptical shape does not necessarily have to be a continuous arc, and includes a roughly elliptical shape with a partially deformed portion as long as it does not have an acute angle. Furthermore, irregularities of 2 μm or less that occur on the fiber cross section and the outer periphery of the core due to the inclusion of additives, etc., do not need to be taken into consideration.

[0015] In the fiber cross section of the sheath-core composite fiber for artificial hair according to one or more embodiments of the present invention, it is preferable that the length of the major axis of the fiber cross section, which is the longest line among the line symmetry axis and lines connecting any two points on the periphery of the fiber cross section parallel to the line symmetry axis, and the length of the first minor axis of the fiber cross section, which is the longest line connecting any two points on the periphery of the fiber cross section perpendicular to the major axis of the fiber cross section, satisfy the following formula (1): Length of the major axis of the fiber cross section / Length of the first minor axis of the fiber cross section = 1.1 or more and 2.0 or less (1)

[0016] In addition, in the fiber cross section, the length of the major axis of the core cross section, which is the longest line among the line symmetry axis and lines connecting any two points on the periphery of the core cross section parallel to the line symmetry axis, and the length of the first minor axis of the core cross section, which is the longest line connecting any two points on the periphery of the core cross section perpendicular to the major axis of the core cross section, preferably satisfy the following formula (2): Length of the major axis of the core cross section / Length of the first minor axis of the core cross section = 1.3 to 2.0 (2)

[0017] The core-sheath composite fiber for artificial hair has a flattened multi-lobed fiber cross section, in which two or more circular and elliptical lobes are joined via recesses, and the fiber surface has smooth irregularities, which reduces the contact area between the fibers and when combed, making it easier to achieve a feel similar to human hair and good combability.

[0018] Furthermore, in the sheath-core composite fiber for artificial hair, the longitudinal axis directions of the fiber cross section and the core cross section are approximately aligned. In one or more embodiments of the present invention, "the longitudinal axis directions of the fiber cross section and the core cross section are approximately aligned" means that the angle between the longitudinal axis of the fiber cross section and the longitudinal axis of the core is less than 15 degrees. When the longitudinal axis directions of the fiber cross section and the core cross section are approximately aligned and the ratio of the length of the major axis of the core cross section to the length of the first minor axis of the core cross section is within the above range, the outer circumferential shape of the fiber cross section and the outer circumferential shape of the core cross section are similar in the fiber cross section. This prevents separation of the fibers due to peeling of the two components and exposure of the core at the surface while maintaining a good texture and appearance as artificial hair. Furthermore, there is a small change in the shape of the fiber cross section after extrusion from the nozzle and after extrusion, which is advantageous in terms of processing, as it facilitates nozzle design to achieve the above-mentioned cross-sectional shape. Furthermore, because the longitudinal directions of the fiber cross section and the core cross section are approximately the same, the anisotropy of the bending modulus resulting from the second moment of area is also consistent between the entire fiber and the core, making it easy to adjust the qualities required for artificial hair, such as feel and combability.

[0019] The eccentricity in the minor axis direction of the core-sheath composite fiber for artificial hair is 5% or more, preferably 5% to 50%, more preferably 6% to 40%, even more preferably 10% to 30%, and even more preferably 12% to 25%. When the fiber cross section is flat, the bending modulus of the fiber is anisotropic in the major and minor axis directions. However, when curling with a hair iron or by winding through a pipe, the fiber is bent in the minor axis direction, where the bending modulus is smaller, and is heated while being strained. By keeping the eccentricity in the minor axis direction within the above range, a larger strain is imparted to the resin in the core compared to when there is no eccentricity, resulting in a strong curl in the fiber after setting. Furthermore, when the fiber is eccentric in the major axis direction, a torsional moment is more likely to occur in the fiber cross section, causing the fiber to crimp in an unintended direction, resulting in an unnatural appearance. On the other hand, when the fiber is eccentric in the minor axis direction, the torsional moment generated in the fiber cross section is smaller than when the fiber is eccentric in the major axis direction, and the potential crimp caused by the eccentricity is reduced, so that the occurrence of unintended crimp can be suppressed and a natural appearance can be achieved.

[0020] The eccentricity in the minor axis direction of the sheath-core composite fiber for artificial hair can be calculated using the following formula (3) based on the length of the first minor axis of the fiber cross section and the distance between the center point of the first minor axis of the fiber cross section and the center point of the first minor axis of the core cross section. The distance between the center point of the first minor axis of the fiber cross section and the center point of the first minor axis of the core cross section means the distance between a line that passes through the center point of the first minor axis of the fiber cross section and intersects perpendicularly with the first minor axis of the fiber cross section, and a line that passes through the center point of the first minor axis of the core cross section and intersects perpendicularly with the first minor axis of the core cross section. Eccentricity in the minor axis direction (%) = Distance between the center point of the first minor axis of the fiber cross section and the center point of the first minor axis of the core / (Length of the first minor axis of the fiber cross section / 2) × 100 (3)

[0021] Figure 1 is a schematic diagram showing the cross section of a sheath-core composite fiber for artificial hair according to one or more embodiments of the present invention. The sheath-core composite fiber for artificial hair 1 of this embodiment comprises a sheath portion 10 and a core portion 20. The sheath-core composite fiber for artificial hair 1 of this embodiment has a flattened bilobal cross section in which two ellipses are joined via two recesses, and the core portion 20 has an elliptical cross section. In the flattened bilobal cross section, the two ellipses partially overlap at the joint.

[0022] In the core-sheath composite fiber 1 for artificial hair of this embodiment, it is preferable that the length L of the fiber cross-sectional major axis 11 and the length S1 of the first minor axis 12 of the fiber cross-section satisfy the above formula (1), i.e., L / S1 is 1.1 or more and 2.0 or less.

[0023] Furthermore, in the core-sheath composite fiber 1 for artificial hair of this embodiment, it is preferable that the length Lc of the major axis 21 of the cross section of the core and the length Sc1 of the first minor axis 22 of the cross section of the core satisfy the above formula (2), i.e., Lc / Sc1 is 1.3 or more and 2.0 or less.

[0024] Furthermore, in the core-sheath composite fiber 1 for artificial hair of this embodiment, the eccentricity (%) in the minor axis direction can be calculated as follows based on the length S1 of the first minor axis of the fiber cross section, and the distance d between the center point 13 of the first minor axis 12 of the fiber cross section and the center point 23 of the first minor axis 22 of the core (i.e., the distance between the major axis 11 of the fiber cross section and the major axis 21 of the core cross section). Eccentricity in the minor axis direction (%) = d / (S1 / 2) x 100

[0025] The cross-sectional shapes of the fibers and core can be controlled by using a nozzle (hole) having a shape close to the desired cross-sectional shape.

[0026] The cross-sectional shape of the core is flat and is not particularly limited as long as the long axis direction of the fiber cross section and the long axis direction of the core cross section are approximately the same. However, it is preferable that the ratio of the length of the long axis of the core cross section to the length of the first short axis is within the above range, and shapes such as an ellipse or a flattened multi-lobed shape including a flattened bilobed shape are more preferably used.

[0027] The core-sheath ratio of the sheath-core composite fiber for artificial hair is, in terms of area ratio, a core:sheath ratio in the range of 2:8 to 7:3. By having the core-sheath ratio in this range, the bending rigidity, which is a physical property related to touch and texture, becomes close to that of human hair, thereby obtaining a sheath-core composite fiber for artificial hair of the same quality as human hair. If the core is less than this range, the bending rigidity will be lower than that of human hair, and a sheath-core composite fiber for artificial hair of the same quality as human hair will not be obtained. Conversely, if the core is more than this range, the bending rigidity will be too high and the fiber will not resemble human hair. In addition, the sheath will be extremely thin, making the core more likely to be exposed and prone to peeling between the core and sheath. From the perspective of obtaining a touch and texture similar to that of human hair, the core-sheath ratio of the sheath-core composite fiber for artificial hair is preferably, in terms of area ratio, a core:sheath ratio in the range of 3:7 to 7:3, and more preferably a range of 3:7 to 6:4. In order to prevent separation of the core and sheath in the cross section of the core-sheath composite fiber for artificial hair, it is preferable that the core is not exposed on the fiber surface but is completely covered by the sheath.

[0028] From the viewpoint of suitability for artificial hair, the core-sheath composite fiber for artificial hair preferably has a single fiber fineness of 10 dtex or more and 150 dtex or less, more preferably 30 dtex or more and 120 dtex or less, even more preferably 40 dtex or more and 100 dtex or less, and particularly preferably 50 dtex or more and 90 dtex or less.

[0029] In the case of the sheath-core composite fiber for artificial hair according to one or more embodiments of the present invention, when the fiber is an aggregate of fibers, for example, a fiber bundle, it is not necessary for all fibers to have the same fineness, sheath-core ratio, or cross-sectional shape, and fibers having different finenesses, sheath-core ratios, and cross-sectional shapes may be mixed.

[0030] In the core-sheath composite fiber for artificial hair, the core is made of a polyester resin composition mainly composed of a polyester resin, and the sheath is made of a polyamide resin composition mainly composed of a polyamide resin.

[0031] In one or more embodiments of the present invention, a polyester-based resin composition containing a polyester-based resin as a main component means that, when the total weight of the polyester-based resin composition is 100% by weight, the polyester-based resin composition contains more than 50% by weight of the polyester-based resin, and preferably contains 60% by weight or more of the polyester-based resin, more preferably contains 70% by weight or more, even more preferably contains 80% by weight or more, even more preferably contains 90% by weight or more, and even more preferably contains 95% by weight or more.

[0032] The polyester resin is preferably one or more selected from the group consisting of polyalkylene terephthalate and copolymer polyester mainly composed of polyalkylene terephthalate. In one embodiment of the present invention, "copolyester mainly composed of polyalkylene terephthalate" refers to a copolymer polyester containing 80 mol % or more of polyalkylene terephthalate.

[0033] The polyalkylene terephthalate is not particularly limited, but examples thereof include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polycyclohexanedimethylene terephthalate.

[0034] The copolymer polyester mainly composed of polyalkylene terephthalate is not particularly limited, and examples thereof include copolymer polyesters mainly composed of polyalkylene terephthalate such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polycyclohexanedimethylene terephthalate and containing other copolymerization components.

[0035] Examples of the other copolymerization components include polycarboxylic acids and derivatives thereof, such as isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, paraphenylenedicarboxylic acid, trimellitic acid, pyromellitic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid; dicarboxylic acids and derivatives thereof, including sulfonates such as 5-sodium sulfoisophthalic acid and 5-dihydroxyethyl sodium sulfoisophthalate; 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, diethylene glycol, polyethylene glycol, trimethylolpropane, pentaerythritol, 4-hydroxybenzoic acid, ε-caprolactone, and ethylene glycol ether of bisphenol A.

[0036] From the viewpoints of stability and ease of operation, the copolymer polyester is preferably produced by reacting a main polyalkylene terephthalate with a small amount of other copolymerization component. As the polyalkylene terephthalate, a polymer of terephthalic acid and / or a derivative thereof (e.g., methyl terephthalate) and alkylene glycol can be used. The copolymer polyester may also be produced by polymerizing a mixture of terephthalic acid and / or a derivative thereof (e.g., methyl terephthalate) and alkylene glycol, which is used in the polymerization of the main polyalkylene terephthalate, with a small amount of other copolymerization component, a monomer or oligomer component.

[0037] The copolymer polyester may be any polyester in which the other copolymer component is polycondensed with the main chain and / or side chain of the main polyalkylene terephthalate, and there are no particular limitations on the copolymerization method.

[0038] Specific examples of the copolymer polyester mainly composed of polyalkylene terephthalate include polyesters mainly composed of polyethylene terephthalate copolymerized with one compound selected from the group consisting of ethylene glycol ether of bisphenol A, 1,4-cyclohexadimethanol, isophthalic acid, and 5-dihydroxyethyl sodium sulfoisophthalate.

[0039] The polyalkylene terephthalates and copolymer polyesters mainly composed of polyalkylene terephthalates may be used alone or in combination of two or more thereof. Among them, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyesters mainly composed of polyethylene terephthalate copolymerized with ethylene glycol ether of bisphenol A, polyesters mainly composed of polyethylene terephthalate copolymerized with 1,4-cyclohexanedimethanol, polyesters mainly composed of polyethylene terephthalate copolymerized with isophthalic acid, and polyesters mainly composed of polyethylene terephthalate copolymerized with 5-dihydroxyethyl sodium sulfoisophthalate are preferably used alone or in combination of two or more thereof.

[0040] The intrinsic viscosity (sometimes referred to as IV value) of the polyester resin is not particularly limited, but is preferably 0.3 dL / g or more and 1.2 dL / g or less, and more preferably 0.4 dL / g or more and 1.0 dL / g or less. When the intrinsic viscosity is 0.3 dL / g or more, the mechanical strength of the resulting fiber does not decrease, and there is no risk of dripping during a combustion test. Furthermore, when the intrinsic viscosity is 1.2 dL / g or less, the molecular weight does not increase too much, the melt viscosity does not become too high, melt spinning is easy, and the fineness tends to be uniform.

[0041] The polyester resin composition may contain other resins in addition to the polyester resin. Examples of the other resins include polyamide resins, vinyl chloride resins, modacrylic resins, polycarbonate resins, polyolefin resins, and polyphenylene sulfide resins. The other resins may be used alone or in combination of two or more.

[0042] In one or more embodiments of the present invention, a polyamide-based resin composition containing a polyamide-based resin as a main component means that, when the total weight of the polyamide-based resin composition is 100% by weight, the polyamide-based resin composition contains more than 50% by weight of polyamide, and preferably contains 60% by weight or more of polyamide-based resin, more preferably contains 70% by weight or more, even more preferably contains 80% by weight or more, even more preferably contains 90% by weight or more, and even more preferably contains 95% by weight or more.

[0043] The polyamide resin refers to a nylon resin obtained by polymerizing one or more members selected from the group consisting of lactams, aminocarboxylic acids, mixtures of dicarboxylic acids and diamines, mixtures of dicarboxylic acid derivatives and diamines, and salts of dicarboxylic acids and diamines.

[0044] Specific examples of the lactam include, but are not limited to, 2-azetidinone, 2-pyrrolidinone, δ-valerolactam, ε-caprolactam, enantholactam, capryllactam, undecalactam, and laurolactam. Among these, ε-caprolactam, undecalactam, and laurolactam are preferred, and ε-caprolactam is particularly preferred. These lactams may be used alone or in a mixture of two or more.

[0045] Specific examples of the aminocarboxylic acid include, but are not limited to, 6-aminocaproic acid, 7-aminoheptanoic acid, 8-aminooctanoic acid, 9-aminononanoic acid, 10-aminodecanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. Of these, 6-aminocaproic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid are preferred, with 6-aminocaproic acid being particularly preferred. These aminocarboxylic acids may be used alone or in combination.

[0046] Specific examples of dicarboxylic acids used in the mixture of dicarboxylic acid and diamine, the mixture of dicarboxylic acid derivative and diamine, or the salt of dicarboxylic acid and diamine include, but are not limited to, aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanediol, dodecanediol, brassicic acid, tetradecanediol, pentadecanedioic acid, and octadecanedioic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, and naphthalenedicarboxylic acid. Among these, adipic acid, sebacic acid, dodecanediol, terephthalic acid, and isophthalic acid are preferred, with adipic acid, terephthalic acid, and isophthalic acid being particularly preferred. These dicarboxylic acids may be used alone or in a mixture of two or more.

[0047] Specific examples of the diamine used in the mixture of dicarboxylic acid and diamine, the mixture of dicarboxylic acid derivative and diamine, or the salt of dicarboxylic acid and diamine include, but are not limited to, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 2-methyl-1,5-diaminopentane (MDP), 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminopentane, 1,13-diaminopentane, 1,14-diaminopentane, 1,15-diaminopentane, 1,16-diaminohexane, 1,17-diaminopentane, 1,18-diaminopentane, 1,19-diaminononane, 1,20-diaminodecane, 1,21-diaminoundecane, 1,22-diaminopentane, 1,23-diaminopentane, 1,24-diaminopentane, 1,25-diaminopentane, 1,26-diaminopentane, 1,27-diaminopentane, 1,28-diaminopentane, 1,29-diaminopentane, 1,30-diaminopentane, 1,31-diaminopentane, 1,32-diaminopentane, 1,33-diaminopentane, 1,34-diaminopentane, 1,35-diaminopentane, 1,36-diaminopentane, 1,37-diaminopentane, 1,38-diaminopentane, 1,39-diaminopentane, 1,40-diaminopentane, 1,41-diaminopentane, 1,42-diaminopentane, 1,43-diaminopentane, 1,44-diaminopentane Examples of suitable diamines include aliphatic diamines such as cyclohexanediamine, 1,13-diaminotridecane, 1,14-diaminotetradecane, 1,15-diaminopentadecane, 1,16-diaminohexadecane, 1,17-diaminoheptadecane, 1,18-diaminooctadecane, 1,19-diaminononadecane, and 1,20-diaminoeicosane; alicyclic diamines such as cyclohexanediamine and bis-(4-aminohexyl)methane; and aromatic diamines such as m-xylylenediamine and p-xylylenediamine. Among these, aliphatic diamines are particularly preferred, with hexamethylenediamine being particularly preferred. These diamines may be used alone or in a mixture of two or more.

[0048] The polyamide resin (sometimes referred to as nylon resin) is not particularly limited, but it is preferable to use, for example, nylon 6, nylon 66, nylon 11, nylon 12, nylon 6·10, nylon 6·12, semi-aromatic nylons containing nylon 6T and / or 6I units, and copolymers of these nylon resins. In particular, nylon 6, nylon 66, and copolymers of nylon 6 and nylon 66 are more preferable.

[0049] The polyamide resin can be produced, for example, by a polyamide resin polymerization method in which a polyamide resin raw material is heated in the presence or absence of a catalyst. The polymerization may be performed with or without stirring, but stirring is preferred to obtain a homogeneous product. The polymerization temperature can be set arbitrarily depending on the polymerization degree, reaction yield, and reaction time of the target polymer, but a low temperature is preferred considering the quality of the final polyamide resin. The reaction rate can also be set arbitrarily. There are no restrictions on the pressure, but it is preferable to reduce the pressure in the system in order to efficiently remove volatile components from the system.

[0050] The polyamide resin used in the present invention may be end-cappinged with an end-capping agent such as a carboxylic acid compound or an amine compound, if necessary. When end-capping is performed by adding a monocarboxylic acid and / or a monoamine, the concentration of terminal amino groups or terminal carboxyl groups in the resulting nylon resin is lower than when the end-capping agent is not used. On the other hand, when end-capping is performed with a dicarboxylic acid or a diamine, the sum of the concentrations of terminal amino groups and terminal carboxyl groups does not change, but the ratio of the concentrations of terminal amino groups to terminal carboxyl groups does change.

[0051] Specific examples of the carboxylic acid compound include, but are not limited to, aliphatic monocarboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, myristoleic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, and arachic acid; alicyclic monocarboxylic acids such as cyclohexanecarboxylic acid and methylcyclohexanecarboxylic acid; benzoic acid, toluic acid, and ethylbenzoic acid. aromatic monocarboxylic acids such as benzoic acid and phenylacetic acid; aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassicic acid, tetradecanedioic acid, pentadecanedioic acid, and octadecanedioic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, and naphthalenedicarboxylic acid.

[0052] Specific examples of the amine compound include, but are not limited to, aliphatic monoamines such as butylamine, pentylamine, hexylamine, heptylamine, octylamine, 2-ethylhexylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, octadecylamine, nonadecylamine, and icosylamine; alicyclic monoamines such as cyclohexylamine and methylcyclohexylamine; aromatic monoamines such as benzylamine and β-phenylethylamine; 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminopentane, and 1,6-diaminopentane; aliphatic diamines such as cyclohexanediamine, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,13-diaminotridecane, 1,14-diaminotetradecane, 1,15-diaminopentadecane, 1,16-diaminohexadecane, 1,17-diaminoheptadecane, 1,18-diaminooctadecane, 1,19-diaminononadecane, and 1,20-diaminoeicosane; alicyclic diamines such as cyclohexanediamine and bis-(4-aminohexyl)methane; and aromatic diamines such as xylylenediamine.

[0053] There is no particular limitation on the terminal group concentration of the polyamide resin, but a high terminal amino group concentration is preferable when it is necessary to improve dyeability in fiber applications or when designing a material suitable for alloying in resin applications. Conversely, a low terminal amino group concentration is preferable when it is desired to suppress coloration and gelation under long-term aging conditions. Furthermore, when it is desired to suppress lactam regeneration during remelting, thread breakage during melt spinning due to oligomer generation, mold deposits during continuous injection molding, and die marks during continuous film extrusion, it is preferable that both the terminal carboxyl group concentration and the terminal amino group concentration are low. The terminal group concentration may be adjusted depending on the application, but both the terminal amino group concentration and the terminal carboxyl group concentration are preferably 1.0 × 10 -5 ~15.0×10-5 eq / g, more preferably 2.0 x 10 -5 ~12.0×10 -5 eq / g, particularly preferably 3.0×10 -5 ~11.0×10 -5 In this specification, a range of values ​​indicated by "... to..." includes both end values, just like a range of values ​​indicated by "not less than... and not more than...".

[0054] The end-capping agent may be added by simultaneously charging it with raw materials such as caprolactam at the beginning of polymerization, by adding it during polymerization, or by adding it when the nylon resin is passed through a vertical agitation-type thin-film evaporator in a molten state. The end-capping agent may be added as is, or may be added after dissolving it in a small amount of solvent.

[0055] The polyamide resin composition may contain other resins in addition to the polyamide resin. Examples of the other resins include vinyl chloride resins, modacrylic resins, polycarbonate resins, polyolefin resins, and polyphenylene sulfide resins. The other resins may be used alone or in combination of two or more.

[0056] From the viewpoint of approximating the feel and appearance of human hair and further improving curl setting and curl retention, the core of the sheath-core composite fiber for artificial hair is preferably composed of a polyester resin composition primarily composed of one or more polyester resins selected from the group consisting of polyalkylene terephthalates and copolymer polyesters mainly composed of polyalkylene terephthalates, and the sheath is more preferably composed of a polyamide resin composition primarily composed of at least one polyamide resin selected from the group consisting of nylon 6 and nylon 66. In one embodiment of the present invention, "a polyamide resin primarily composed of at least one selected from the group consisting of nylon 6 and nylon 66" means a polyamide resin containing at least 80 mol % of nylon 6 and / or nylon 66.

[0057] In one or more embodiments of the present invention, a pigment may be contained in the resin composition of the core or sheath to obtain a core-sheath composite fiber for artificial hair having a desired color. The pigment is not particularly limited, and common pigments such as carbon black and anthraquinone-based pigments can be used. A pigment masterbatch can also be used. A pigment masterbatch is a mixture of a pigment and a resin composition kneaded using a kneader such as an extruder and pelletized (sometimes referred to as compounding). Pigments are generally difficult to handle due to their fine powder form, but dispersing them in the resin composition in advance makes them easier to handle and reduces color unevenness in the resulting fibers.

[0058] The amount of pigment added to the polyester resin composition constituting the core is not particularly limited, but is preferably 0.005 to 2 parts by weight, more preferably 0.01 to 1 part by weight, per 100 parts by weight of polyester resin. The amount of pigment added to the polyamide resin composition constituting the sheath is also not particularly limited, but is preferably 0.005 to 2 parts by weight, more preferably 0.01 to 1 part by weight, per 100 parts by weight of polyamide resin.

[0059] In one or more embodiments of the present invention, a flame retardant may be used in combination from the viewpoint of flame retardancy. Examples of the flame retardant include bromine-containing flame retardants and phosphorus-containing flame retardants. Examples of the phosphorus-containing flame retardant include phosphate ester amide compounds and organic cyclic phosphorus compounds. The bromine-containing flame retardant is not particularly limited, but examples thereof include brominated epoxy flame retardants; bromine-containing phosphate esters such as pentabromotoluene, hexabromobenzene, decabromodiphenyl, decabromodiphenyl ether, bis(tribromophenoxy)ethane, tetrabromophthalic anhydride, ethylene bis(tetrabromophthalimide), ethylene bis(pentabromophenyl), octabromotrimethylphenylindane, and tris(tribromoneopentyl)phosphate; brominated polystyrenes; brominated polybenzyl acrylates; bromine brominated phenoxy resins; brominated polycarbonate oligomers; tetrabromobisphenol A derivatives such as tetrabromobisphenol A, tetrabromobisphenol A-bis(2,3-dibromopropyl ether), tetrabromobisphenol A-bis(allyl ether), and tetrabromobisphenol A-bis(hydroxyethyl ether); bromine-containing triazine compounds such as tris(tribromophenoxy)triazine; and bromine-containing isocyanuric acid compounds such as tris(2,3-dibromopropyl)isocyanurate. Among these, brominated epoxy flame retardants are preferably used from the viewpoints of heat resistance and flame retardancy.

[0060] The brominated epoxy flame retardant may be a brominated epoxy flame retardant having an epoxy group or tribromophenol at the molecular terminal. However, the structure of the brominated epoxy flame retardant after melt-kneading is not particularly limited. When the total number of structural units represented by the following chemical formula (1) and structural units obtained by modifying at least a portion of the following chemical formula (1) is taken as 100 mol %, it is preferable that 80 mol % or more are structural units represented by the chemical formula (1). The structure of the brominated epoxy flame retardant may be changed at the molecular terminal after melt-kneading. For example, the molecular terminal of the brominated epoxy flame retardant may be substituted with a group other than an epoxy group or tribromophenol, such as a hydroxyl group, a phosphate group, or a phosphonic acid group, or the molecular terminal may be bonded to a polyester component via an ester group.

[0061] [ka]

[0062] Furthermore, the structure of the brominated epoxy flame retardant may be partially changed other than at the molecular terminals. For example, the secondary hydroxyl group and the epoxy group of the brominated epoxy flame retardant may be bonded to form a branched structure, and some of the bromine atoms in the chemical formula (1) may be eliminated or added, provided that the bromine content in the brominated epoxy flame retardant molecule does not change significantly.

[0063] As the brominated epoxy flame retardant, for example, a polymeric brominated epoxy flame retardant as shown in the following general formula (2) is preferably used. In the following general formula (2), m is 1 to 1000. As the polymeric brominated epoxy flame retardant as shown in the following general formula (2), for example, a commercially available product such as a brominated epoxy flame retardant manufactured by Sakamoto Yakuhin Kogyo Co., Ltd. (product name "SR-T2MP") may be used.

[0064] [ka]

[0065] The brominated epoxy flame retardant is preferably contained in the core and / or sheath in an amount of, for example, 5 to 40 parts by weight per 100 parts by weight of the main component resin, although not particularly limited thereto. For example, from the viewpoint of heat resistance and flame retardancy, the core is preferably composed of a polyester-based resin composition containing 100 parts by weight of one or more polyester resins selected from the group consisting of polyalkylene terephthalates and copolymer polyesters mainly composed of polyalkylene terephthalates, and 5 to 40 parts by weight of a brominated epoxy flame retardant, and the sheath is preferably composed of a polyamide-based resin composition containing 100 parts by weight of a polyamide-based resin mainly composed of at least one selected from the group consisting of nylon 6 and nylon 66, and 5 to 40 parts by weight of a brominated epoxy flame retardant.

[0066] In one or more embodiments of the present invention, a flame retardant aid may be used in combination. The flame retardant aid is not particularly limited, but from the viewpoint of flame retardancy, it is preferable to use, for example, an antimony-based compound or a composite metal containing antimony. Examples of the antimony-based compound include antimony trioxide, antimony tetraoxide, antimony pentoxide, sodium antimonate, potassium antimonate, and calcium antimonate. In terms of the effect of improving flame retardancy and the influence on the touch, one or more selected from the group consisting of antimony trioxide, antimony pentoxide, and sodium antimonate are more preferable.

[0067] The flame retardant aid is not particularly limited, but is preferably contained in the core and / or sheath in an amount of, for example, 0.1 to 10 parts by weight per 100 parts by weight of the main component resin.

[0068] In particular, by incorporating a flame retardant auxiliary into the polyamide resin composition that constitutes the sheath, appropriate surface irregularities are formed on the fiber surface, making it easier to obtain core-sheath composite fibers for artificial hair that are flame retardant and have a low-gloss appearance similar to that of human hair.

[0069] The core-sheath composite fiber for artificial hair may contain various additives such as heat-resistant agents, stabilizers, fluorescent agents, antioxidants, and antistatic agents, as needed, within the range that does not impair the effects of the present invention.

[0070] The core-sheath composite fiber for artificial hair can be produced by melt-kneading the core-sheath resin compositions using various common kneaders and then melt-spinning them using a core-sheath composite nozzle. For example, a polyester-based resin composition obtained by dry-blending components such as the polyester resin and brominated epoxy-based flame retardant is melt-kneaded using various common kneaders to form a core component. Alternatively, a polyamide-based resin composition obtained by dry-blending components such as the polyamide-based resin, pigment, and brominated epoxy-based flame retardant is melt-kneaded using various common kneaders to form a sheath component, which is then melt-spun using a core-sheath composite spinning nozzle. Examples of the kneader include single-screw extruders, twin-screw extruders, rolls, Banbury mixers, and kneaders. Twin-screw extruders are preferred for their ease of adjustment of the degree of kneading and ease of operation.

[0071] The preferred method for producing the fiber of the present invention is melt spinning. For example, in the case of a polyester-based resin composition, the temperature of the extruder, gear pump, nozzle, etc. is set to 250°C or higher and 300°C or lower, and in the case of a polyamide-based resin composition, the temperature of the extruder, gear pump, nozzle, etc. is set to 260°C or higher and 320°C or lower. After melt spinning, the material is cooled to a temperature below the glass transition point of each resin and taken up at a speed of 30 m / min or higher and 5000 m / min or lower to obtain a spun yarn (undrawn yarn).

[0072] Specifically, during melt spinning, the polyester resin composition constituting the core is fed through a core extruder of a melt spinning machine, and the polyamide resin composition constituting the sheath is fed through a sheath extruder of the melt spinning machine. The molten polymer is extruded through a core-sheath multi-component spinning nozzle (hole) having a predetermined shape to obtain a spun yarn (undrawn yarn). The spun yarn (undrawn yarn) is preferably hot-drawn, and the drawing may be performed by either a two-step method in which the spun yarn is once wound up and then drawn, or a direct spin-drawing method in which the spun yarn is continuously drawn without being wound up. Hot drawing is performed by a one-stage drawing method or a multi-stage drawing method of two or more stages.

[0073] As the heating means for the hot stretching, a heating roller, a heat plate, a steam jet device, a hot water bath, etc. can be used, and these can also be used in combination as appropriate.

[0074] The core-sheath composite fiber for artificial hair may be treated with a fiber treatment agent, a softener, or other oil to make the feel and texture closer to that of human hair. Examples of the fiber treatment agent include silicone-based fiber treatment agents and non-silicone-based fiber treatment agents for improving the feel and combability.

[0075] The core-sheath composite fiber for artificial hair may be subjected to gear crimping, which gives the fiber a gentle bend, resulting in a natural appearance and improving combability by reducing adhesion between the fibers. In this gear crimping process, the fiber is generally heated to above its softening temperature and passed between two meshing gears, and the shape of the gears is transferred to the fiber, thereby creating a bent shape. Furthermore, if necessary, different curl shapes can be created by heat-treating the core-sheath composite fiber for artificial hair at different temperatures during the fiber processing stage.

[0076] (headdress products) In one or more embodiments of the present invention, the core-sheath composite fiber for artificial hair may be used alone as artificial hair, or may be used in combination with other fibers for artificial hair or natural fibers such as human hair or animal hair. Examples of other fibers for artificial hair include acrylic fibers.

[0077] In one or more embodiments of the present invention, the core-sheath composite fiber for artificial hair can be used for any head accessory product, including, but not limited to, hair wigs, hairpieces, weaving, hair extensions, braided hair, hair accessories, and doll hair.

[0078] The head ornament product may be composed solely of the sheath-core composite fiber for artificial hair of the present invention, or may be composed of a combination of the sheath-core composite fiber for artificial hair of the present invention with other fibers for artificial hair or natural fibers such as human hair or animal hair. [Example]

[0079] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0080] The measurement and evaluation methods used in the examples and comparative examples are as follows.

[0081] (single fiber fineness) Measurements were made using an auto-blow type fineness measuring instrument "DENIER COMPUTER Type DC-11" (manufactured by Search Co.), and the average value of the measurements for 30 samples was calculated to obtain the single fiber fineness.

[0082] (Evaluation of fiber cross section) At room temperature (23°C), the fibers were cut into 150 mm lengths, 0.7 g of the cut fibers were bundled, and passed through a rubber tube. Heat was applied at 80°C to shrink the tube and fix the fiber bundle so that it would not shift. The tube was then cut into rings with a cutter to prepare 5 mm long fiber bundles for cross-sectional observation. This fiber bundle was photographed at 400x magnification using a laser microscope (Keyence Corporation, "VK-9500") to obtain a fiber cross-sectional photograph. The core-sheath ratio was calculated based on the fiber cross-sectional photograph. Thirty fiber cross sections were randomly selected from the fiber cross-sectional photograph, and the length of the major axis of the fiber cross section, the length of the first minor axis of the fiber cross section, the length of the major axis of the core cross section, the length of the first minor axis of the core cross section, and the distance between the center point of the first minor axis of the fiber cross section and the center point of the first minor axis of the core cross section were measured. In the sheath-core composite fiber for artificial hair according to one embodiment of the present invention, the values ​​of the length of the major axis of the fiber cross section and the length of the first minor axis of the fiber cross section, the length of the major axis of the core cross section and the length of the first minor axis of the core cross section, the distance between the center point of the first minor axis of the fiber cross section and the center point of the first minor axis of the core cross section, the ratio of the major axis of the fiber cross section to the first minor axis of the fiber cross section, and the ratio of the major axis of the core cross section to the first minor axis of the core cross section can be expressed as the average value of the measurements of 30 arbitrarily selected fiber cross sections.

[0083] (Tactile sensation) A sensory evaluation was conducted by a professional hairdresser, and the results were rated on the following four-point scale. A: Very good texture similar to human hair B: Slightly inferior to human hair, but has a good feel C: Inferior to human hair but good texture D: Poor texture, significantly inferior to human hair

[0084] (exterior) A sensory evaluation was conducted by a professional hairdresser, and the results were rated on the following four-point scale. A: Natural appearance equivalent to human hair B: Slightly inferior to human hair, but natural appearance C: Inferior to human hair but natural appearance D: Unnatural appearance, significantly inferior to human hair

[0085] (Curl setting ability) At room temperature (23°C), 2.8 g of filament was wound into a 25 cm long strand, wound around a φ32 mm pipe, and curl-set at 120°C for 60 minutes. After aging at room temperature (23°C) for 60 minutes, one end of the curled filament was fixed and suspended, and the filament length after curl-set was measured. The filament length was used as an index of curl-set property and evaluated according to the following four-level scale. A: The filament length after curl setting is less than 13 cm B: The filament length after curl setting is 13 cm or more but less than 15 cm C: The filament length after curl setting is 15 cm or more but less than 17 cm D: The filament length after curl setting is 17 cm or more

[0086] Example 1 For 100 parts by weight of polyethylene terephthalate pellets (manufactured by East West Chemical Private Limited, EastPET trade name "A-12", also referred to as PET), 30 parts by weight of brominated epoxy flame retardant (manufactured by Sakamoto Yakuhin Kogyo, trade name "SR-T2MP"), 3 parts by weight of sodium antimonate (manufactured by Nippon Seiko, trade name "SA-A"), 3.0 parts by weight of black pigment masterbatch (manufactured by Dainichi Seika Color & Chemicals Mfg. Co., Ltd., trade name "PESM22367BLACK(20)", pigment: 20% by weight, base resin: polyester-based resin), 3.0 parts by weight of yellow pigment masterbatch (manufactured by Dainichi Seika Color & Chemicals Mfg. Co., Ltd., trade name "PESM22367BLACK(20)", pigment: 20% by weight, base resin: polyester-based resin), 1.0 parts by weight of yellow pigment masterbatch (manufactured by Dainichi Seika Color & Chemicals Mfg. Co., Ltd., 0.6 parts by weight of "PESM1001YELLOW(20)" (pigment: 20% by weight, base resin: polyester-based resin) and 0.2 parts by weight of a red pigment masterbatch (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., product name "PESM3005RED(20)" (pigment: 20% by weight, base resin: polyester-based resin) were added, dry-blended, and then fed into a twin-screw extruder, melt-kneaded at a barrel setting temperature of 280°C, and pelletized to obtain a polyester-based resin composition.

[0087] Next, 100 parts by weight of nylon 6 (manufactured by Unitika Ltd., trade name "A1030BRL", also referred to as PA6) was mixed with 12 parts by weight of a brominated epoxy flame retardant (manufactured by Sakamoto Pharmaceutical Industry Co., Ltd., trade name "SR-T2MP"), 2 parts by weight of sodium antimonate (manufactured by Nippon Seiko Co., Ltd., trade name "SA-A"), 2.0 parts by weight of a black pigment masterbatch (manufactured by Dainichi Seika Chemicals Mfg. Co., Ltd., trade name "PAM (F) 25005 BLACK (20)"), 0.8 parts by weight of a yellow pigment masterbatch (manufactured by Dainichi Seika Chemicals Mfg. Co., Ltd., trade name "PAM (F) 28990 YELLOW (20)"), and 0.5 parts by weight of a red pigment masterbatch (manufactured by Dainichi Seika Chemicals Mfg. Co., Ltd., trade name "PAM (F) 28991 RED (20)"), and the mixture was dry blended and then fed to a twin-screw extruder. The mixture was melt-kneaded at a barrel setting temperature of 260 ° C. and pelletized to obtain a polyamide resin composition.

[0088] Next, the pellet-like polyester-based resin composition and polyamide-based resin composition were each fed into an extruder, extruded through a core-sheath type composite spinning nozzle having a nozzle shape shown in Table 1 below and set at a temperature of 270°C, and wound up at a speed of 40 to 200 m / min to obtain an undrawn yarn of a core-sheath composite fiber having the polyester-based resin composition as the core and the polyamide-based resin composition as the sheath, with a core-sheath ratio of 5:5 in terms of area.

[0089] The resulting undrawn yarn was drawn using a heated roll at 85°C while being taken up at a speed of 45 m / min to obtain a 3x drawn yarn, which was then continuously taken up at a speed of 45 m / min using a heated roll heated to 200°C and subjected to a heat treatment. A polyether-based oil (Marubishi Yuka Kogyo Co., Ltd., product name "KWC-Q") was applied to the yarn to a concentration of 0.20% omf (pure oil weight percentage relative to the dry fiber weight), and the resulting yarn was dried to obtain a core-sheath composite fiber having the single fiber fineness shown in Table 1 below and an eccentricity in the minor axis direction of 15.6%.

[0090] Example 2 A core-sheath composite spinning nozzle having the nozzle shape shown in Table 1 below was used, and the eccentricity in the minor axis direction was set to 12.7%, and the core-sheath ratio was set to 6:4 in terms of area ratio, in the same manner as in Example 1, to obtain a core-sheath composite fiber.

[0091] Example 3 A core-sheath composite fiber was obtained in the same manner as in Example 1, except that the resin used for the sheath was nylon 66 (manufactured by Toray Industries, Inc., trade name "Amilan CM3001", sometimes referred to as PA66), the barrel temperature during pelletization was set to 280°C, the nozzle temperature was set to 280°C, the eccentricity in the minor axis direction was 15.1%, and the core-sheath ratio was 3:7 in area ratio.

[0092] Example 4 A core-sheath composite fiber was obtained in the same manner as in Example 1, except that a core-sheath composite spinning nozzle having the nozzle shape shown in Table 1 below was used, the resin used for the core was polybutylene terephthalate (manufactured by Mitsubishi Chemical Corporation, trade name "Novaduran 5020", sometimes referred to as PBT), the barrel set temperature during pelletization was 260°C, the nozzle set temperature was 260°C, the eccentricity in the minor axis direction was 6.8%, and the core-sheath ratio was 7:3 in area ratio.

[0093] (Comparative Example 1) A core-sheath type composite spinning nozzle having the nozzle shape shown in Table 1 below was used, and the same procedure as in Example 1 was carried out except that the eccentricity in the minor axis direction was set to 0% to obtain a core-sheath composite fiber.

[0094] (Comparative Example 2) A core-sheath composite fiber was obtained in the same manner as in Example 1, except that the eccentricity in the minor axis direction was set to 14.1% and the core-sheath ratio was set to 1:9 in terms of area ratio.

[0095] (Comparative Example 3) A core-sheath composite spinning nozzle having the nozzle shape shown in Table 1 below was used, and the eccentricity in the minor axis direction was set to 2.4%, and the core-sheath ratio was set to 8:2 in terms of area ratio, but the same procedure as in Example 1 was carried out to obtain a core-sheath composite fiber.

[0096] Comparative Example 4 A core-sheath type composite spinning nozzle having the nozzle shape shown in Table 1 below was used, and the same procedure as in Example 1 was carried out except that the eccentricity in the minor axis direction was set to 9.3% to obtain a core-sheath composite fiber.

[0097] The cross-sectional shapes of the fibers of the Examples and Comparative Examples were evaluated and observed as described above. The texture, appearance, and curl settability of the fibers of the Examples and Comparative Examples were also evaluated as described above. The results are shown in Table 1.

[0098] [Table 1]

[0099] Figure 2 is a laser microscope photograph of the cross section of the fiber of Example 1. As can be seen from Figure 2, in the sheath-core composite fiber for artificial hair, the fiber has a flat bilobal cross section, the core has an elliptical cross section, and the long axis direction of the fiber cross section and the long axis direction of the core cross section are approximately the same, and are eccentric to the short axis direction of the fiber.

[0100] Figure 3 is a laser microscope photograph of the cross section of the fiber of Comparative Example 1. As shown in Figure 3, in the sheath-core composite fiber for artificial hair, both the fiber and the core have a flat bilobal cross section, and the long axis direction of the fiber cross section and the long axis direction of the core cross section are approximately the same, but are not eccentric to the short axis direction of the fiber.

[0101] As can be seen from Table 1, the fibers of Examples 1 to 4 had a texture and appearance similar to human hair, and also had good curl setting properties.

[0102] On the other hand, the fibers of Comparative Example 1, which had an eccentricity of 0%, and Comparative Example 2, which had a high sheath ratio, had poor curl settability. The fibers of Comparative Example 3, which had a high core ratio, had the core exposed to the fiber surface, resulting in very poor texture and appearance and making it impossible to mold them into a good fiber. The fibers of Comparative Example 4, which had round cross-sectional shapes of the fiber and core, had an unnatural appearance and a poor texture.

[0103] The present invention is not particularly limited, but preferably includes at least the following embodiments. [1] A core-sheath composite fiber for artificial hair, comprising a core and a sheath, the core is made of a polyester-based resin composition containing a polyester-based resin as a main component, and the sheath is made of a polyamide-based resin composition containing a polyamide-based resin as a main component, In the core-sheath composite fiber for artificial hair, the core:sheath ratio in area ratio is 2:8 to 7:3, the fiber cross section and the core cross section both have flat cross-sectional shapes, the long axis direction of the fiber cross section and the long axis direction of the core cross section are approximately the same, and the eccentricity in the short axis direction of the fiber is 5% or more. [2] The core-sheath composite fiber for artificial hair according to [1], wherein the core-sheath composite fiber for artificial hair has a flattened multi-lobed cross-sectional shape. [3] The core-sheath composite fiber for artificial hair according to [1] or [2], wherein the core has an elliptical or flattened multi-lobed cross-sectional shape. [4] The sheath-core composite fiber for artificial hair according to any one of [1] to [3], wherein the length of the major axis of the fiber cross section, which is the longest line among the line symmetry axis and lines connecting any two points on the periphery of the fiber cross section parallel to the line symmetry axis, and the length of the first minor axis of the fiber cross section, which is the longest line among the line symmetry axis and lines connecting any two points on the periphery of the fiber cross section perpendicular to the major axis of the fiber cross section, satisfy the following formula (1): Length of the major axis of the fiber cross section / Length of the first minor axis of the fiber cross section = 1.1 or more and 2.0 or less (1) [5] In the sheath-core composite fiber for artificial hair, the length of the major axis of the core cross section, which is the longest line among the line symmetry axis and lines connecting any two points on the periphery of the core cross section parallel to the line symmetry axis, and the length of the first minor axis of the core cross section, which is the line connecting any two points on the periphery of the core cross section perpendicular to the major axis of the core cross section, satisfy the following formula (2): Length of the major axis of the core cross section / Length of the first minor axis of the core cross section = 1.3 to 2.0 (2) [6] The core-sheath composite fiber for artificial hair according to any one of [1] to [5], wherein the polyester-based resin composition contains one or more polyester-based resins selected from the group consisting of polyalkylene terephthalates and copolymer polyesters mainly composed of polyalkylene terephthalates. [7] The core-sheath composite fiber for artificial hair according to any one of [1] to [6], wherein the polyamide-based resin composition contains a polyamide-based resin mainly composed of at least one selected from the group consisting of nylon 6 and nylon 66. [8] A head accessory comprising the core-sheath composite fiber for artificial hair according to any one of [1] to [7]. [9] The head accessory product according to [8], which is one selected from the group consisting of hair wigs, hairpieces, weaving, hair extensions, braided hair, hair accessories and doll hair.

[10] A method for producing a core-sheath composite fiber for artificial hair according to any one of [1] to [7], The method includes a step of melt-spinning a polyester-based resin composition and a polyamide-based resin composition using a core-sheath composite nozzle, A method for producing a sheath-core composite fiber for artificial hair, characterized in that the cross-sectional shape of the sheath-core composite fiber for artificial hair and the core are flat, the long axis direction of the fiber cross section is approximately the same as the long axis direction of the core, and the eccentricity in the short axis direction of the fiber is 5% or more. [Explanation of symbols]

[0104] 1. Core-sheath composite fiber for artificial hair (cross section) 10 Sheath 11 Fiber cross section long axis 12 Fiber cross section first minor axis 13 Center point of the first minor axis of the fiber cross section 20 core 21 Core section long axis 22 Core section first short axis 23 Center point of the first minor axis of the core section

Claims

1. A core-sheath composite fiber for artificial hair, comprising a core and a sheath, the core is made of a polyester-based resin composition containing a polyester-based resin, and the sheath is made of a polyamide-based resin composition containing a polyamide-based resin, The core-sheath composite fiber for artificial hair is characterized in that the core:sheath ratio in terms of area ratio is 2:8 to 7:3, the fiber cross section and the core cross section both have flat cross-sectional shapes, the long axis direction of the fiber cross section and the long axis direction of the core cross section are approximately the same, and the eccentricity rate in the short axis direction of the fiber is 5% or more.

2. 2. The sheath-core composite fiber for artificial hair according to claim 1, wherein the sheath-core composite fiber for artificial hair has a flattened multilobal cross section.

3. 3. The core-sheath composite fiber for artificial hair according to claim 1, wherein the core has an elliptical or flattened multilobal cross section.

4. 4. The sheath-core composite fiber for artificial hair according to claim 1, wherein the length of the major axis of the fiber cross section, which is the longest line among the line symmetry axis and lines connecting any two points on the periphery of the fiber cross section parallel to the line symmetry axis, and the length of the first minor axis of the fiber cross section, which is the longest line among the line symmetry axis and lines connecting any two points on the periphery of the fiber cross section perpendicular to the major axis of the fiber cross section, satisfy the following formula (1): Length of the major axis of the fiber cross section / Length of the first minor axis of the fiber cross section = 1.1 or more and 2.0 or less (1)

5. 5. The sheath-core composite fiber for artificial hair according to any one of claims 1 to 4, wherein the length of the major axis of the core cross section, which is the longest line among the line symmetry axis and lines connecting any two points on the periphery of the core cross section parallel to the line symmetry axis, and the length of the first minor axis of the core cross section, which is the longest line among the line symmetry axis and lines connecting any two points on the periphery of the core cross section perpendicular to the major axis of the core cross section, satisfy the following formula (2): Length of the major axis of the core cross section / Length of the first minor axis of the core cross section = 1.3 or more and 2.0 or less (2)

6. The core-sheath composite fiber for artificial hair according to any one of claims 1 to 5, wherein the polyester-based resin composition contains one or more polyester-based resins selected from the group consisting of polyalkylene terephthalates and copolymer polyesters mainly composed of polyalkylene terephthalates.

7. The core-sheath composite fiber for artificial hair according to any one of claims 1 to 6, wherein the polyamide-based resin composition contains a polyamide-based resin mainly composed of at least one selected from the group consisting of nylon 6 and nylon 66.

8. A head accessory comprising the core-sheath composite fiber for artificial hair according to any one of claims 1 to 7.

9. 9. The head accessory product according to claim 8, wherein the head accessory product is one selected from the group consisting of a hair wig, a hairpiece, a weaving, a hair extension, a braided hair, a hair accessory, and a doll hair.

10. A method for producing the core-sheath composite fiber for artificial hair according to any one of claims 1 to 7, comprising: The method includes a step of melt-spinning a polyester-based resin composition and a polyamide-based resin composition using a core-sheath composite nozzle, A method for producing a sheath-core composite fiber for artificial hair, characterized in that the cross-sectional shape of the sheath-core composite fiber for artificial hair and the core are flat, the long axis direction of the fiber cross section is approximately the same as the long axis direction of the core cross section, and the eccentricity rate in the short axis direction of the fiber is 5% or more.

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