JP7738580B2 - Core-sheath composite fiber for artificial hair, head accessories containing the same, and manufacturing method thereof - Google Patents

Description

The present invention relates to core-sheath composite fibers for artificial hair that can be used as a substitute for human hair, head accessories containing the same, and methods for manufacturing the same.

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, with a polyester resin as the core component and a polyamide resin as the sheath component. Patent Document 1 describes the use of high-polymerization polyethylene terephthalate and high-polymerization polyamide in a melt spinning process. The fiber is then rapidly cooled and solidified by liquid cooling, and then passed through a fiber surface crystallization accelerator to impart a specific streaky uneven structure to the fiber surface. This suppresses the sheath polyamide's luster while maintaining fiber strength, resulting in an artificial hair fiber with a texture similar to human hair and excellent durability and heat resistance.

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 being composed of a core and a sheath, with the long axis direction of the fiber cross section roughly coinciding with the long axis direction of the core, and with an eccentricity in the long axis direction of 5% or more, it is possible to obtain core-sheath composite fibers for artificial hair that have a texture and appearance similar to human hair, have good curling ability even without curl setting, and have extremely high curl retention.

Japanese Patent Application Publication No. 3-185103 International Publication No. 2018/179803

However, while artificial hair fibers using a polyamide resin for the sheath, as described in Patent Document 1, have a good feel and durability, they suffer from 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 although they can produce artificial hair fibers with high curl retention even without curl setting, they suffer from poor curl settability when curling with a hair iron or the like.

In order to solve the above-mentioned conventional problems, the present invention provides artificial hair fibers that have a feel and appearance similar to human hair and have good curl setting properties.

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; the core:sheath ratio in area of the composite fiber for artificial hair is 2:8 to 7:3, the fiber cross section and the core cross section both 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.

In one or more embodiments, the present invention also relates to a head accessory product characterized by containing the core-sheath composite fiber for artificial hair.

In one or more embodiments, the present invention also relates to a method for producing the sheath-core composite fiber for artificial hair, which includes a step of melt-spinning a polyester resin composition and a polyamide 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 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 short axis direction of the fiber is 5% or more.

The present invention makes it possible to provide core-sheath composite fibers for artificial hair that have a texture and appearance similar to human hair and good curl setting properties, as well as headwear products containing the same.

The manufacturing method of the present invention makes it 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.

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. FIG. 2 is a laser microscope photograph of the cross section of the fiber of Example 1. FIG. 3 is a laser microscope photograph of the cross section of the fiber of Comparative Example 1.

As a result of extensive research into solving the above-mentioned problems, the present inventors discovered that, in a sheath-core composite fiber for artificial hair containing a core and a sheath, the core is composed of a polyester-based resin composition containing a polyester-based resin as a primary component, the sheath is composed of a polyamide-based resin composition containing a polyamide-based resin as a primary component, the core:sheath ratio is 2:8 to 7:3 by area, 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 also referred to simply as "sheath-core composite fiber") that has a texture and appearance similar to human hair and good curl settability, and thereby completing the present invention.

(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.

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)

Furthermore, in the fiber cross section, it is preferable that 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, 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)

The core-sheath composite fiber for artificial hair has a flattened multi-lobed fiber cross section, resulting in a shape in which two or more circular and elliptical lobes are joined via recesses. 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.

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 major axis of the fiber cross section and the long 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. This prevents separation of the fibers due to peeling of the two components and exposure of the core to the surface while maintaining a good texture and appearance as artificial hair. Furthermore, there is a molding advantage in that the change in the shape of the fiber cross section after extrusion from the nozzle and the shape of the fiber cross section after extrusion are small, making it easier to design nozzles to achieve the above-mentioned cross-sectional shape. Furthermore, since 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 the same for the entire fiber and the core, making it possible to easily adjust the qualities required for artificial hair, such as feel and combability.

The eccentricity in the short 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 long and short axes. However, when curling with a hair iron or pipe winding, the fiber is bent in the short axis direction, where the bending modulus is smaller, and is heated while strain is generated. By keeping the eccentricity in the short axis direction within the above range, the resin in the core is subjected to greater strain than in the case without eccentricity, resulting in a strong curl in the fiber after setting. Furthermore, when the fiber is eccentric in the long 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.

The eccentricity in the minor axis direction of the sheath-core composite fiber for artificial hair can be calculated 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 using the following formula (3): 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)

Figure 1 is a schematic diagram showing the fiber 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 includes 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-sectional shape in which two ellipses are joined via two recesses, and the core portion 20 has an elliptical cross-sectional shape. In the flattened bilobal shape, the two ellipses partially overlap at the joining point.

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.

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.

Furthermore, in the sheath-core 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

The cross-sectional shape of the above-mentioned fibers and core can be controlled by using a nozzle (hole) with a shape close to the desired cross-sectional shape.

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 oval and flattened multi-lobed shapes including flattened bilobed shapes are more preferably used.

The core-sheath ratio of the sheath-core composite fiber for artificial hair is in the range of 2:8 to 7:3 (core:sheath area ratio). This range of core-sheath ratio results in a bending rigidity value, a physical property related to touch and texture, that is close to that of human hair, resulting in a sheath-core composite fiber for artificial hair with the same properties as human hair. If the core is less than this range, the bending rigidity value will be lower than that of human hair, making it impossible to obtain a sheath-core composite fiber for artificial hair with the same properties as human hair. Conversely, if the core is more than this range, the bending rigidity will be too high, making it less similar to human hair. Furthermore, 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 achieving 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 the range of 3:7 to 7:3 (core:sheath area ratio), and more preferably in the 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.

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.

In one or more embodiments of the core-sheath composite fiber for artificial hair 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, core-sheath ratio, or cross-sectional shape; fibers with different finenesses, core-sheath ratios, and cross-sectional shapes may be mixed.

In the core-sheath composite fiber for artificial hair, the core is made of a polyester-based resin composition primarily composed of polyester-based resin, and the sheath is made of a polyamide-based resin composition primarily composed of polyamide-based resin.

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. Preferably, the polyester-based resin contains 60% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, even more preferably 90% by weight or more, and even more preferably 95% by weight or more.

The polyester resin is preferably one or more selected from the group consisting of polyalkylene terephthalate and copolymer polyesters primarily composed of polyalkylene terephthalate. In one embodiment of the present invention, "copolyesters primarily composed of polyalkylene terephthalate" refers to copolymer polyesters containing 80 mol% or more of polyalkylene terephthalate.

The polyalkylene terephthalate is not particularly limited, but examples include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polycyclohexanedimethylene terephthalate, etc.

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

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.

From the standpoint 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 components. The polyalkylene terephthalate can be a polymer of terephthalic acid and/or its derivatives (e.g., methyl terephthalate) and alkylene glycol. The copolymer polyester may also be produced by polymerizing a mixture of terephthalic acid and/or its derivatives (e.g., methyl terephthalate) and alkylene glycol used in the polymerization of the main polyalkylene terephthalate, with a small amount of other copolymerization components, such as monomers or oligomers.

The copolymer polyester may be formed by polycondensation of the above-mentioned other copolymer components with the main chain and/or side chain of the main polyalkylene terephthalate, and there are no particular limitations on the copolymerization method, etc.

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

The polyalkylene terephthalates and copolymer polyesters primarily composed of polyalkylene terephthalates may be used alone or in combination of two or more. Among these, the following are preferred, either alone or in combination: polyethylene terephthalate; polypropylene terephthalate; polybutylene terephthalate; polyesters primarily composed of polyethylene terephthalate copolymerized with ethylene glycol ether of bisphenol A; polyesters primarily composed of polyethylene terephthalate copolymerized with 1,4-cyclohexanedimethanol; polyesters primarily composed of polyethylene terephthalate copolymerized with isophthalic acid; and polyesters primarily composed of polyethylene terephthalate copolymerized with 5-dihydroxyethyl sodium sulfoisophthalate.

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. If the intrinsic viscosity is 0.3 dL/g or more, the mechanical strength of the resulting fiber will not decrease, and there will be no risk of dripping during a combustion test. Furthermore, if the intrinsic viscosity is 1.2 dL/g or less, the molecular weight will not increase too much, the melt viscosity will not become too high, melt spinning will be easy, and the fineness will tend to be uniform.

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

In one or more embodiments of the present invention, a polyamide-based resin composition primarily composed of a polyamide-based resin means that, when the total weight of the polyamide-based resin composition is taken as 100% by weight, it contains more than 50% by weight of polyamide. Preferably, it contains 60% by weight or more of polyamide-based resin, more preferably 70% by weight or more, even more preferably 80% by weight or more, even more preferably 90% by weight or more, and even more preferably 95% by weight or more.

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.

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

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 a mixture of two or more.

Specific examples of dicarboxylic acids used in the mixture of dicarboxylic acid and diamine, mixture of dicarboxylic acid derivative and diamine, or 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, 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. Among these, adipic acid, sebacic acid, dodecanedioic acid, 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.

Specific examples of diamines used in the mixture of dicarboxylic acids and diamines, the mixture of dicarboxylic acid derivatives and diamines, or the salts of dicarboxylic acids and diamines 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-diamino 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.

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.

The polyamide resin can be produced, for example, by a polyamide resin polymerization method in which polyamide resin raw materials are heated with or without 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 desired degree of polymerization, reaction yield, and reaction time of the polymerized product, but a lower temperature is preferable considering the quality of the final polyamide resin. The reaction rate can also be set arbitrarily. There are no pressure restrictions, but it is preferable to reduce the pressure inside the system to efficiently remove volatile components from the system.

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 concentration ratio of terminal amino groups to terminal carboxyl groups does change.

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.

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.

Although there are no particular limitations on the terminal group concentration of the polyamide resin, a higher 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 lower 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 formation, mold deposits during continuous injection molding, and die marks during continuous film extrusion, both the terminal carboxyl group concentration and the terminal amino group concentration are preferably low. The terminal group concentration can be adjusted depending on the application, and both the terminal amino group concentration and the terminal carboxyl group concentration are preferably 1.0 × 10 ⁻⁵ to 15.0 × 10 ⁻⁵ eq/g, more preferably 2.0 × 10 ⁻⁵ to 12.0 × 10 ⁻⁵ eq/g, and particularly preferably 3.0 × 10 ⁻⁵ to 11.0 × 10 ⁻⁵ eq/g. In this specification, a range of values indicated by "to" includes both end values, similar to a range of values indicated by "not less than or equal to."

The end-capping agent can be added by simultaneously charging it with raw materials such as caprolactam at the beginning of polymerization, by adding it midway through polymerization, or by adding it as the nylon resin passes through a vertical agitator-type thin-film evaporator in a molten state. The end-capping agent may be added as is, or dissolved in a small amount of solvent.

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

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

In one or more embodiments of the present invention, a pigment may be included in the resin composition of the core or sheath to obtain core-sheath composite fibers for artificial hair having the 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. Dispersing the pigment in the resin composition in advance makes it easier to handle and reduces color unevenness in the resulting fibers.

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

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; and 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, from the viewpoints of heat resistance and flame retardancy, it is preferable to use a brominated epoxy flame retardant.

The brominated epoxy flame retardant may be a brominated epoxy flame retardant having an epoxy group or tribromophenol at the molecular end as a raw material. However, the structure of the brominated epoxy flame retardant after melt-kneading is not particularly limited. Preferably, when the total number of structural units shown in chemical formula (1) below and structural units obtained by modifying at least a portion of chemical formula (1) below is taken as 100 mol %, 80 mol % or more of the structural units shown in chemical formula (1) below are the structural units shown in chemical formula (1). The structure of the brominated epoxy flame retardant may change at the molecular end after melt-kneading. For example, the molecular end 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 phosphonate group, or the molecular end may be bonded to a polyester component via an ester group.

In addition, the structure of the brominated epoxy flame retardant may change in parts other than the molecular terminals. For example, the secondary hydroxyl group and epoxy group of the brominated epoxy flame retardant may bond to form a branched structure, and some of the bromine in chemical formula (1) may be eliminated or added, as long as the bromine content in the brominated epoxy flame retardant molecule does not change significantly.

As the brominated epoxy flame retardant, for example, a polymeric brominated epoxy flame retardant such as that 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 such as that shown in the following general formula (2), commercially available products such as the brominated epoxy flame retardant manufactured by Sakamoto Yakuhin Kogyo Co., Ltd. (product name "SR-T2MP") may be used.

The brominated epoxy flame retardant is not particularly limited, but 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 resin component. For example, from the standpoint 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 resin selected from the group consisting of nylon 6 and nylon 66, and 5 to 40 parts by weight of a brominated epoxy flame retardant.

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 perspective of flame retardancy, it is preferable to use, for example, an antimony-based compound or a composite metal containing antimony. Examples of antimony-based compounds include antimony trioxide, antimony tetroxide, antimony pentoxide, sodium antimonate, potassium antimonate, and calcium antimonate. In terms of the flame retardancy improvement effect 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.

The flame retardant auxiliary is not particularly limited, but it is preferable to include it 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.

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 not only flame-retardant but also have a low-gloss appearance similar to that of human hair.

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

The core-sheath composite fibers 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 described above can be melt-kneaded using various common kneaders to form the 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 can be melt-kneaded using various common kneaders to form the sheath component, which can then be melt-spun using a core-sheath composite spinning nozzle. Examples of kneaders include single-screw extruders, twin-screw extruders, rolls, Banbury mixers, and kneaders. Twin-screw extruders are preferred for their ease of operation and ability to adjust the degree of kneading.

The preferred method for producing the fibers 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 mixture is cooled to below the glass transition point of each resin and taken up at a speed of 30 m/min or higher and 5,000 m/min or lower to obtain a spun yarn (undrawn yarn).

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

Heating means for hot stretching include heated rollers, heat plates, steam jet devices, hot water baths, etc., and these can also be used in combination as appropriate.

The core-sheath composite fiber for artificial hair may be treated with oils such as fiber treatment agents and softeners to make the feel and texture more similar to that of human hair. Examples of such fiber treatment agents include silicone-based fiber treatment agents and non-silicone-based fiber treatment agents to improve the feel and combability.

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 the gear crimping process, the fiber is generally heated to a temperature above its softening point 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.

(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.

In one or more embodiments of the present invention, the core-sheath composite fiber for artificial hair can be used in any headwear product without any particular limitations. For example, it can be used in hair wigs, hairpieces, weaving, hair extensions, braided hair, hair accessories, and doll hair.

The head ornament product may be composed solely of the sheath-core composite fiber for artificial hair of the present invention. Alternatively, the head ornament product 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.

The present invention will be explained in more detail below based on examples. However, the present invention is not limited to these examples.

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

(Single fiber fineness)
Measurement was carried out using an auto-blow type fineness measuring instrument "DENIER COMPUTER Type DC-11" (manufactured by Search Co.), and the average value of the measured values of 30 samples was calculated to be the single fiber fineness.

(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 portion was then cut into rings with a cutter to prepare 5 mm long fiber bundles for cross-section observation. This fiber bundle was photographed at 400x magnification using a laser microscope (Keyence Corporation, "VK-9500") to obtain a fiber cross-section photograph. The core-sheath ratio was calculated based on the fiber cross-section photograph. Thirty fiber cross sections were randomly selected from the fiber cross-section 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 measured values of 30 arbitrarily selected fiber cross sections.

(Tactile sensation)
A sensory evaluation was carried out by a professional hairdresser and the results were rated according to the following four-level scale.
A: Very good feel, equivalent to human hair B: Slightly inferior to human hair, but good feel C: Poor feel, but inferior to human hair D: Poor feel, significantly inferior to human hair

(exterior)
A sensory evaluation was carried out by a professional hairdresser and the results were rated according to the following four-level scale.
A: Natural appearance equivalent to human hair B: Slightly less natural appearance than human hair C: Less natural appearance than human hair D: Unnatural appearance significantly less natural than human hair

(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 hung down, 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 and less than 15 cm. C: The filament length after curl setting is 15 cm or more and less than 17 cm. D: The filament length after curl setting is 17 cm or more.

Example 1
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) were mixed with 30 parts by weight of a 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 a black pigment masterbatch (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., trade name "PESM22367BLACK(20)", pigment: 20% by weight, base resin: polyester-based resin), 3.0 parts by weight of a yellow pigment masterbatch (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., trade name "PESM22367BLACK(20)", pigment: 20% by weight, base resin: polyester-based resin), and 100 parts by weight of a 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 a black pigment masterbatch (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., trade name "PESM22367BLACK(20)", pigment: 20% by weight, base resin: polyester-based resin). 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., trade name "PESM3005RED(20)" (pigment: 20% by weight, base resin: polyester-based resin) were added, dry-blended, and then fed to a twin-screw extruder, melt-kneaded at a barrel setting temperature of 280°C, and pelletized to obtain a polyester-based resin composition.

Next, 100 parts by weight of nylon 6 (manufactured by Unitika Ltd., trade name "A1030BRL", also referred to as PA6) were added with 12 parts by weight of a brominated epoxy flame retardant (manufactured by Sakamoto Yakuhin Kogyo, trade name "SR-T2MP"), 2 parts by weight of sodium antimonate (manufactured by Nippon Seiko, trade name "SA-A"), 2.0 parts by weight of a black pigment masterbatch (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., trade name "PAM(F)25005BLACK(20)"), 0.8 parts by weight of a yellow pigment masterbatch (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., trade name "PAM(F)28990YELLOW(20)"), and 0.5 parts by weight of a red pigment masterbatch (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., trade name "PAM(F)28991RED(20)"), dry blended, and then fed into 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.

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

The resulting unstretched yarn was stretched using a heated roll at 85°C while being taken up at a speed of 45 m/min, resulting in a 3x stretched yarn. This was then continuously wound up using a heated roll heated to 200°C at a speed of 45 m/min, subjected to heat treatment, and a polyether-based oil agent (Marubishi Yuka Kogyo Co., Ltd., product name "KWC-Q") was applied to the yarn to a concentration of 0.20% omf (pure oil agent weight percentage relative to the dry fiber weight). The yarn was then 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%.

Example 2
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 repeated except that 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 to obtain a core-sheath composite fiber.

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 terms of area ratio.

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 temperature during pelletization was set to 260°C, the nozzle temperature was set to 260°C, the eccentricity in the minor axis direction was 6.8%, and the core-sheath ratio was 7:3 in terms of area ratio.

(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 repeated except that the eccentricity in the minor axis direction was set to 0% to obtain core-sheath composite fibers.

(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.

(Comparative Example 3)
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 repeated except that 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.

(Comparative Example 4)
A core-sheath composite spinning nozzle having the nozzle shape shown in Table 1 below was used, and the procedure was the same as in Example 1, except that the eccentricity in the minor axis direction was set to 9.3%. Core-sheath composite fibers were obtained.

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. These results are shown in Table 1.

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 this core-sheath composite fiber for artificial hair, the fiber has a flat bilobal shape, 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.

Figure 3 is a laser microscope photograph of the cross section of the fiber of Comparative Example 1. As shown in Figure 3, in this core-sheath composite fiber for artificial hair, both the fiber and the core have a flattened 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.

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.

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 set properties. The fibers of Comparative Example 3, which had a high core ratio, had the core exposed on the fiber surface, resulting in very poor texture and appearance and making it impossible to mold into a good fiber. The fibers of Comparative Example 4 had an unnatural appearance and poor texture due to the round cross-sectional shapes of the fiber and core.

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,
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] 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] The sheath-core composite fiber for artificial hair according to any one of [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 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 or more and 2.0 or less (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 rate in the short axis direction of the fiber is 5% or more.

1. Core-sheath composite fiber for artificial hair (cross section)
10 Sheath 11 Fiber cross-sectional major axis 12 Fiber cross-sectional first minor axis 13 Center point of fiber cross-sectional first minor axis 20 Core 21 Core cross-sectional major axis 22 Core cross-sectional first minor axis 23 Center point of core cross-sectional first minor axis

Claims (10)

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. The core-sheath composite fiber for artificial hair described in claim 1 has a flattened multi-lobed cross-sectional shape. A core-sheath composite fiber for artificial hair as described in claim 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 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. 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) The core-sheath composite fiber for artificial hair described in 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. A core-sheath composite fiber for artificial hair according to any one of claims 1 to 6, wherein the polyamide resin composition contains a polyamide resin primarily composed of at least one selected from the group consisting of nylon 6 and nylon 66. A head accessory comprising the core-sheath composite fiber for artificial hair described in any one of claims 1 to 7. The headwear product described in claim 8, wherein the headwear product is one selected from the group consisting of hair wigs, hairpieces, weaving, hair extensions, braided hair, hair accessories and doll hair. 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.