Patent Application
20230416946
One or more embodiments of the present invention relate to core-sheath conjugate fibers for artificial hair that can be used as an alternative to human hair, hair ornaments including the core-sheath conjugate fibers for artificial hair, and a method for producing the core-sheath conjugate fibers for artificial hair.
Human hair has conventionally been used for hair ornaments such as hairpieces, hair wigs, hair extensions, hair bands, and doll hair. However, in recent years, it has become difficult to obtain human hair. For this reason, there is a growing demand for artificial hair that can replace human hair. Examples of a material of artificial hair include synthetic fibers such as acrylic fibers, vinyl chloride fibers, vinylidene chloride fibers, polyester fibers, polyamide fibers, and polyolefin fibers. Patent Document 1 discloses, as a fiber for artificial hair, a core-sheath conjugate fiber in which a polyester-based resin is a core component and a polyamide-based resin is a sheath component, for example. Patent Document 1 discloses that in a melt spinning method, polyethylene terephthalate with a high degree of polymerization and polyamide with a high degree of polymerization are used, rapidly solidified through liquid cooling, allowed to pass through a fiber surface layer crystallization facilitating device to provide a specific stripe-shaped uneven structure to the fiber surface, and thereby it is possible to obtain a fiber for artificial hair in which the strength of the fiber is ensured, and the gloss of the polyamide of the sheath is suppressed, and that has a feel similar to that of human hair, and has high durability and heat resistance.
Meanwhile, artificial hair is required to also have curl setting properties and curl-holding properties. Attempts have been made to improve these properties by controlling the material and cross-sectional shape of the fiber. Patent Document 2 discloses that it is possible to obtain a core-sheath conjugate fiber for artificial hair that includes a core and a sheath, in which a major axis of a core cross-section is in a direction that substantially coincides with a direction of a major axis of a fiber cross-section, and an eccentricity in the major axis direction is 5% or more, thus the core-sheath conjugate fiber for artificial hair having a texture and an appearance similar to those of human hair, having favorable curability without setting curls, and having greatly improved curl-holding properties, for example.
However, a fiber for artificial hair in which a polyamide-based resin is used in the sheath as described in Patent Document 1 has a good texture and durability but has a problem of poor curl setting properties. Also, a fiber for artificial hair having a structure eccentric in the major axis direction as described in Patent Document 2 has latent crimpability, and a fiber for artificial hair that has improved curl-holding properties can be obtained without setting curls, but there is a problem of poor curl setting properties when providing curls using a hair iron or the like.
In order to solve the conventional problems, one or more embodiments of the present invention provide fibers for artificial hair that have a texture and an appearance similar to those of human hair and favorable curl setting properties.
One or more embodiments of the present invention relate to a core-sheath conjugate fiber for artificial hair that includes a core and a sheath. The core is composed of a polyester-based resin composition containing a polyester-based resin, and the sheath is composed of a polyamide-based resin composition containing a polyamide-based resin. In the conjugate fiber for artificial hair, a core-to-sheath area ratio of the core to the sheath is 2:8 to 7:3. Both a fiber cross-section and a core cross-section have a flat shape. A major axis of the core cross-section is in a direction that substantially coincides with a direction of a major axis of the fiber cross-section, and an eccentricity ratio of the fiber in a minor axis direction is 5% or more.
One or more embodiments of the present invention also relate to a hair ornament including the core-sheath conjugate fiber for artificial hair.
One or more embodiments of the present invention relate to a method for producing the core-sheath conjugate fiber for artificial hair, the method including melt spinning a polyester-based resin composition and a polyamide-based resin composition using a core-sheath conjugate nozzle, in which both a fiber cross-section and a core cross-section of the core-sheath conjugate fiber for artificial hair have a flat shape, a major axis of the core cross-section is in a direction that substantially coincides with a direction of a major axis of the fiber cross-section, and an eccentricity ratio of the fiber in a minor axis direction is 5% or more.
One or more embodiments of the present invention can provide core-sheath conjugate fibers for artificial hair that have a texture and an appearance similar to those of human hair, and favorable curl setting properties, and a hair ornament that includes the core-sheath conjugate fibers for artificial hair.
According to a production method of one or more embodiments of the present invention, it is possible to obtain core-sheath conjugate fibers for artificial hair that have a texture and an appearance similar to those of human hair, and favorable curl setting properties.
The inventor of the present invention conducted intensive studies in order to resolve the above issues and found that core-sheath conjugate fibers for artificial hair (also simply referred to as “core-sheath conjugate fibers” in the following) with which poor curl setting properties which result from use of a polyamide-based resin, can be improved, that has a texture and an appearance that are similar to those of human hair, and has favorable curl setting properties could be obtained as a result of in a core-sheath conjugate fiber for artificial hair that includes a core and a sheath, the core being composed of a polyester-based resin composition containing a polyester-based resin as a main component, the sheath being composed of a polyamide-based resin composition containing a polyamide-based resin as a main component, setting a core-to-sheath area ratio of the core to the sheath to 2:8 to 7:3, forming a fiber cross-sectional shape and a core cross-sectional shape in a flat shape, setting a major axis of the core cross-section is in a direction that substantially coincides with a direction of a major axis of the fiber cross-section, and setting an eccentricity ratio of the fiber in a minor axis direction to 5% or more, thus completing the present invention.
(Fiber Shape)
The core-sheath conjugate fiber for artificial hair according to one or more embodiments of the present invention includes a core and a sheath, and a fiber cross-section and a core cross-section have a flat shape. Examples of the flat shape include an elliptical shape, a flat multilobed shape, and an oval shape. Examples of the flat multilobed shape include a shape in which two or more lobed portions having a shape selected from the group consisting of a circular shape and an elliptical shape are connected via recesses. In a flat multilobed shape, a circular and/and elliptical shape partially overlap each other at the connected portion. The shape of the fiber cross-section is preferably a flat multilobed shape, and more preferably a flat bilobed shape. Note that the shape of the circular or elliptical portions does not absolutely have to be a continuous arc, and may also be a substantially elliptical shape that is partially deformed, as long as no acute angle is formed. Furthermore, no consideration needs to be given to an unevenness with a size of 2 μm or less generated at an outer circumference of the fiber cross-section and an outer circumference of the core due to an additive or the like contained.
It is preferable that, on a fiber cross-section of the core-sheath conjugate fiber for artificial hair according to one or more embodiments of the present invention, a length of the major axis of the fiber cross-section, where the major axis of the fiber cross-section is a longest straight line among an axisymmetric axis and straight lines connecting any two points on the outer circumference of the fiber cross-section so as to be parallel to the axisymmetric axis, and a length of a first minor axis of the fiber cross-section, where the first minor axis of the fiber cross-section is a longest straight line formed when any two points on the outer circumference of the fiber cross-section are connected perpendicularly to the major axis of the fiber cross-section, satisfy the equation (1) below.
The length of the major axis of the fiber cross-section/the length of the first minor axis of the fiber cross-section=1.1 or more and 2.0 or less (1)
Further, it is preferable that, on a fiber cross-section, a length of the major axis of the core cross-section, where the major axis of the core cross-section is a longest straight line among an axisymmetric axis and straight lines connecting any two points on the outer circumference of the core cross-section so as to be parallel to the axisymmetric axis, and a length of a first minor axis of the core cross-section, where the first minor axis of the core cross-section is a longest straight line formed when any two points on the outer circumference of the core cross-section are connected perpendicularly to the major axis of the core cross-section, satisfy the equation (2) below.
The length of the major axis of the core cross-section/the length of the first minor axis of the core cross-section=1.3 or more and 2.0 or less (2)
The core-sheath conjugate fiber for artificial hair has a flat multilobed fiber cross-section, which is a shape in which two or more lobed portions of circular and elliptical are connected via recesses. Thus, because the fiber surface has smooth unevenness, the contact area of fibers and the contact area with a hair comb when running the hair comb are reduced, and thus a texture similar to that of human hair and a favorable combing property can be realized with ease.
Also, in the core-sheath conjugate fiber for artificial hair, the major axis of the core cross-section is in a direction that substantially coincides with a direction of the major axis of the fiber cross-section. In one or more embodiments of the present invention, the wording “the major axis of the core cross-section is in a direction that substantially coincides with a direction of the major axis of the fiber cross-section” indicates that an angle formed between the major axis of the fiber cross-section and the major axis of the core cross-section is less than 15 degrees. When the major axis of the core cross-section is in a direction that substantially coincides with the direction of the major axis of the fiber cross-section and a ratio between 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, on a fiber cross-section, the outer circumferential shape of the fiber cross-section and the outer circumferential shape of the core cross-section are similar to each other, and thus a good texture and a favorable appearance of the fiber for artificial hair are maintained and it is possible to prevent fiber separation due to coming off of the two components from each other and prevent the core from being exposed from the fiber surface. Further, there is also an advantage in molding that a nozzle for realizing the above-described cross-sectional shape can be easily designed because a change from the shape of a fiber extruded from the nozzle to the cross-sectional shape of the molded fiber is reduced. Since the major axis of the core cross-section is in a direction that substantially coincides with a direction of the major axis of the fiber cross-section, the entire fiber and the core have the same anisotropy of the modulus of elasticity in bending resulting from the moment of inertia of area, and thus it is easy to adjust the quality required for artificial hair, such as a texture and combability.
An eccentricity ratio of the core-sheath conjugate fiber for artificial hair in the minor axis direction is 5% or more, preferably 5% or more and 50% or less more preferably 6% or more and 40% or less, even more preferably 10% or more and 30% or less, and further preferably 12% or more and 25% or less. When a fiber cross-section is flat, the bending elastic modulus of the fiber is anisotropic in the major and minor axis directions. When curls are to be set using a hair iron or curling iron, fibers are bent in the minor axis direction in which the fibers have a small bending elastic modulus, and are heated while being strained. As a result of setting the eccentricity ratio in the minor axis direction within the above range, a larger strain is applied to the resin in the core compared to a case where fibers have no eccentricity, and the set fibers have strong curls. Also, in the case of fibers that are eccentric in the major axis direction, a torsional moment occurring in a fiber cross-section tends to act, and the fibers crimp in an undesired direction, resulting in an unnatural appearance. On the other hand, in the case of fibers that are eccentric in the minor axis direction, a torsional moment occurring in a fiber cross-section is reduced and latent crimpability caused by eccentricity is reduced, compared to a case where fibers are eccentric in the major axis direction. Therefore, it is possible to suppress undesired crimping and realize a natural appearance.
An eccentricity ratio of the core-sheath conjugate fiber for artificial hair in the minor axis direction can be calculated using the equation (3) below, based on the length of the first minor axis of the fiber cross-section and a two-point 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, on a fiber cross-section. The two-point distance between the center point of the first minor axis of the fiber cross-section and the center point of first the minor axis of the core cross-section refers to the distance between a straight line that passes through the center point of the first minor axis of the fiber cross-section and intersects perpendicularly to the first minor axis of the fiber cross-section and a straight line that passes through the center point of the first minor axis of the core cross-section and intersects perpendicularly to the first minor axis of the core cross-section.
The eccentricity ratio (%) in the minor axial direction=the two-point 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/(length of the first minor axis of the fiber cross-section/2)×100 (3)
In the core-sheath conjugate fiber 1 for artificial hair according to this embodiment, a length L of a major axis 11 of the fiber cross-section and a length S1 of a first minor axis 12 of the fiber cross-section preferably satisfy the equation (1), i.e., L/S1 is preferably 1.1 or more and 2.0 or less.
Further, in the core-sheath conjugate fiber 1 for artificial hair according to this embodiment, a length Lc of a major axis 21 of the core cross-section and a length Sc1 of a first minor axis 22 of the core cross-section preferably satisfy the equation (2), i.e., Lc/Sc1 is preferably 1.3 or more and 2.0 or less.
Also, in the core-sheath conjugate fiber 1 for artificial hair according to this embodiment, the eccentricity ratio (%) 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 a two-point distance d between a center point 13 of the first minor axis 12 of the fiber cross-section and a center point 23 of the first minor axis 22 of the core cross-section (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 ratio in minor axis direction (%)=d/(S1/2)×100
The above-described cross-sectional shapes of the fiber and the core can be controlled by using a nozzle (pores) with a shape close to the target cross-sectional shape.
There is no particular limitation on the core cross-sectional shape as long as the core cross-sectional shape is flat, and the major axis of the core cross-section is in a direction that substantially coincides with the direction of the major axis of the fiber cross-section. However, the ratio of the length of the major axis of the core cross-section and the length of the first minor axis of the core cross-section is preferably within the above range, and the core having an elliptical cross-sectional shape, a flat multilobed cross-sectional shape such as a flat bilobed shape, or the like is more preferably used.
The core-to-sheath area ratio of the core to the sheath of the core-sheath conjugate fiber for artificial hair is 2:8 to 7:3. When the core-to-sheath area ratio is in this range, a flexural rigidity value, which is a physical property related to a texture, a feel, and the like, is similar to that of human hair, and thus core-sheath conjugate fibers for artificial hair with a quality similar to that of human hair can be obtained. If the area of the core is smaller than this range, the flexural rigidity value is lower than that in human hair, and thus core-sheath conjugate fibers for artificial hair with a quality similar to that of human hair cannot be obtained. On the other hand, if the area of the core is larger than this range, the flexural rigidity value is excessively large and thus is not similar to that of human hair, and, moreover, the sheath is so thin that the core is likely to be exposed, and the core and the sheath are likely to separate from each other. From the viewpoint of obtaining a texture and a feel that are similar to those of human hair, the core-to-sheath area ratio of the core to the sheath of the core-sheath conjugate fiber for artificial hair is preferably 3:7 to 7:3, and more preferably 3:7 to 6:4. In order to prevent separation of the sheath from the core on a fiber cross-section of the core-sheath conjugate fiber for artificial hair, it is preferable that the core is not exposed from the fiber surface and is completely covered by the sheath.
From the viewpoint of suitability for artificial hair, the core-sheath conjugate fiber for artificial hair has a single fiber fineness of preferably 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 even more preferably 50 dtex or more and 90 dtex or less.
When the core-sheath conjugate fibers for artificial hair according to one or more embodiments of the present invention are in the form of an aggregate of fibers, e.g., a fiber bundle, all the fibers do not necessarily have the same fineness, the same core-to-sheath area ratio, and the same cross-sectional shape, but some of them may have different finenesses, different ore-to-sheath area ratios, and cross-sectional shapes.
In the core-sheath conjugate fiber for artificial hair, the core is composed of a polyester-based resin composition containing a polyester-based resin as a main component, and the sheath is composed of a polyamide-based resin composition containing a polyamide-based resin as a main component.
In one or more embodiments of the present invention, the polyester-based resin composition containing a polyester-based resin as a main component indicates that the polyester-based resin composition contains the polyester-based resin in an amount of more than 50% by weight with respect to 100% by weight of the total weight of the polyester-based resin composition, and the content of the polyester-based resin is preferably 60% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, further preferably 90% by weight or more, and still more preferably 95% by weight or more.
It is preferable to use, as the polyester-based resin, at least one selected from the group consisting of polyalkylene terephthalate and a copolyester mainly containing polyalkylene terephthalate. In an embodiment of the present invention, the wording “copolyester mainly containing the polyalkylene terephthalate” refers to the copolyester containing 80 mol % or more of polyalkylene terephthalate.
Examples of the polyalkylene terephthalate include, but are not particularly limited to, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polycyclohexane dimethylene terephthalate.
Examples of the copolyester mainly containing the polyalkylene terephthalate include, but are not particularly limited to, copolyesters mainly containing polyalkylene terephthalate such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, or polycyclohexane dimethylene terephthalate and other copolymerizable components.
Examples of the other copolymerizable components include: polycarboxylic acids 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, and their derivatives; dicarboxylic acids and their derivatives containing sulfonates such as 5-sodiumsulfoisophthalic acid and dihydroxyethyl 5-sodiumsulfoisophthalate; 1,2-propanediol; 1,3-propanediol; 1,4-butanediol; 1,6-hexanediol; neopentyl glycol; 1,4-cyclohexanedimethanol; diethylene glyco; polyethylene glycol; trimethylolpropane; pentaerythritol; 4-hydroxybenzoic acid; ε-caprolactone: and an ethylene glycol ether of bisphenol A.
The copolyester is preferably produced by adding a small amount of other copolymerizable components to polyalkylene terephthalate serving as a main component, and allowing them to react with each other, from the viewpoint of stability and ease of operation. Examples of the polyalkylene terephthalate include a polymer of terephthalic acid and/or its derivatives (e.g., methyl terephthalate) and alkylene glycol. The copolyester may be produced by adding a small amount of monomer or oligomer component serving as other copolymerizable components, to a mixture of terephthalic acid and/or its derivatives (e.g., methyl terephthalate) and alkylene glycol, used for polymerization of polyalkylene terephthalate serving as a main component, and subjecting them to polymerization.
It is sufficient that the copolyester has a structure in which the other copolymerizable components are polycondensed on the main chain and/or side chain of polyalkylene terephthalate serving as a main component, and the copolymerization method and the like are not particularly limited.
Specific examples of the copolyester mainly containing polyalkylene terephthalate include a polyester obtained through copolymerization of polyethylene terephthalate serving as a main component with one compound selected from the group consisting of an ethylene glycol ether of bisphenol A, 1,4-cyclohexanedimethanol, isophthalic acid, and dihydroxyethyl 5-sodiumsulfoisophthalate.
The polyalkylene terephthalate and the copolyester mainly containing polyalkylene terephthalate may be used individually or in a combination of two or more. In particular, polyethylene terephthalate; polypropylene terephthalate; polybutylene terephthalate; a polyester obtained through copolymerization of polyethylene terephthalate serving as a main component with an ethylene glycol ether of bisphenol A; a polyester obtained through copolymerization of polyethylene terephthalate serving as a main component with 1,4-cyclohexanedimethanol; a polyester obtained through copolymerization of polyethylene terephthalate serving as a main component with isophthalic acid; a polyester obtained through copolymerization of polyethylene terephthalate serving as a main component with dihydroxyethyl 5-sodiumsulfoisophthalate, and the like are preferably used individually or in a combination of two or more.
The intrinsic viscosity (also be referred to as an “IV value”) of the polyester resin is not particularly limited, and 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, it is possible to prevent a decrease in the mechanical strength of the resulting fibers, and also to eliminate the risk of dripping during a flammability test. When the intrinsic viscosity is 1.2 dL/g or less, the molecular weight does not become too large and the melt viscosity does not become too high, thereby facilitating melt spinning and making the fineness of the fibers more likely to be uniform.
The polyester-based resin composition may contain other resins in addition to the polyester-based resin. Examples of the other resins include a polyamide-based resin, a vinyl chloride-based resin, a modacrylic-based resin, a polycarbonate-based resin, a polyolefin-based resin, and a polyphenylene sulfide-based resin. Other resins may be used individually or in combinations of two or more.
In one or more embodiments of the present invention, a polyamide-based resin composition containing a polyamide-based resin as a main component indicates that the polyamide-based resin composition contains the polyamide-based resin in an amount of more than 50% by weight with respect to 100% by weight of the total weight of the polyamide-based resin composition, and the content of the polyamide-based resin is preferably 60% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, further preferably 90% by weight or more, and still more preferably 95% by weight or more.
The polyamide-based resin refers to a nylon resin obtained by polymerizing at least one selected from the group consisting of lactam, an aminocarboxylic acid, a mixture of a dicarboxylic acid and diamine, a mixture of a dicarboxylic acid derivative and diamine, and a salt of a dicarboxylic acid and diamine.
Specific examples of the lactam include, but are not particularly limited to, 2-azetidinone, 2-pyrrolidinone, δ-valerolactam, ε-caprolactam, enantholactam, capryllactam, undecalactam, and laurolactam. Among them, ε-caprolactam, undecalactam, and laurolactam are preferred, and ε-caprolactam is particularly preferred. These lactams may be used individually or in combinations of two or more.
Specific examples of the aminocarboxylic acid include, but are not particularly limited to, 6-aminocaproic acid, 7-aminoheptanoic acid, 8-aminooctanoic acid, 9-aminononanoic acid, 10-aminodecanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. Among them, 6-aminocaproic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid are preferred, and 6-aminocaproic acid is particularly preferred. These aminocarboxylic acids may be used individually or in combinations of two or more.
Specific examples of the dicarboxylic acid, which is used in the mixture of a dicarboxylic acid and diamine, the mixture of a dicarboxylic acid derivative and diamine, or the salt of a dicarboxylic acid and diamine, include, but are not particularly limited to, the following: 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, brassylic 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 them, adipic acid, sebacic acid, dodecanedioic acid, terephthalicacid, and isophthalic acid are preferred, and adipic acid, terephthalic acid, and isophthalic acid are particularly preferred. These dicarboxylic acids may be used individually or in combinations of two or more.
Specific examples of the diamine, which is used in the mixture of a dicarboxylic acid and diamine, the mixture of a dicarboxylic acid derivative and diamine, or the salt of a dicarboxylic acid and diamine, include, but are not particularly limited to, the following: aliphatic diamines such as 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-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 m-xylylenediamine and p-xylylenediamine. Among them, aliphatic diamines are preferred, and hexamethylenediamine (1,6-diaminohexane) is particularly preferred. These diamines may be used individually or in combinations of two or more.
Examples of the polyamide-based resin (also referred to as nylon resin) include, but are not particularly limited to, nylon 6, nylon 66, nylon 11, nylon 12, nylon 6/10, nylon 6/12, semi-aromatic nylons including units of nylon 6T and/or nylon 6I, and copolymers of these nylon resins. In particular, nylon 6, nylon 66, and a copolymer of nylon 6 and nylon 66 are more preferred.
The polyamide-based resin can be produced by, e.g., a polyamide-based resin polymerization method that includes heating raw materials for the polyamide-based resin in the presence or absence of a catalyst. The method may or may not include a stirring process during the polymerization, but it is preferable that the raw materials are stirred to obtain a homogeneous product. The polymerization temperature may be set as appropriate in accordance with the degree of polymerization of the target polymer, the reaction yield, and the reaction time, and may be set to be lower in view of the quality of the polyamide-based resin to be obtained. The reaction rate may also be set as appropriate. The pressure is not particularly limited, and it is preferable that the polymerization system is placed under reduced pressure to efficiently extract volatile components out of the polymerization system.
The ends of the polyamide-based resin used in the present invention may be capped with an end-capping agent such as a carboxylic acid compound or an amine compound, if necessary. When a monocarboxylic acid or monoamine is used as an end-capping agent, the terminal amino group concentration or the terminal carboxyl group concentration of the resulting nylon resin is reduced compared to the case where such an end-capping agent is not used. On the other hand, when a dicarboxylic acid or diamine is used as an end-capping agent, the sum of the terminal amino group concentration and the terminal carboxyl group concentration is unchanged, but the ratio of the terminal amino group concentration to the terminal carboxyl group concentration is changed.
Specific examples of the carboxylic acid compound include, but are not particularly limited to, the following: 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; aromatic monocarboxylic acids such as benzoic acid, toluic acid, ethylbenzoic 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, brassylic 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 particularly limited to, the following: 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 B-phenylethylamine; aliphatic diamines such as 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 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 the terminal group concentration of the polyamide-based resin is not particularly limited, the terminal amino group concentration may be high so as to improve dyeability for the intended use of the fibers and design materials suitable for alloying for intended use of resin. Also, the terminal amino group concentration may be low so as to reduce coloration or gelation under long-term aging conditions. Moreover, both the terminal carboxyl group concentration and the terminal amino group concentration may be low so as to prevent the regeneration of lactam during remelting, filament breakage during melt spinning due to the formation of oligomers, mold deposit during continuous injection molding, and die mark formation during continuous film extrusion. The terminal group concentration may be adjusted according to the intended use, 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, or particularly preferably 3.0×10−5 to 11.0×10−5 eq/g. In this specification, a numerical range indicated by “ . . . to . . . ” includes two end values in a manner similar to the numerical range indicated by “ . . . or more and . . . or less”.
There are some methods to add the end-capping agent. For example, the end-capping agent may be (i) added simultaneously with raw materials such as caprolactam in the initial stage of polymerization, (ii) added in the process of polymerization, or (iii) added while the molten nylon resin is passing through a vertical stirring-type thin film evaporator. The end-capping agent may be added as it is, or added after having been dissolved in a small amount of solvent.
The polyamide-based resin composition may contain other resins in addition to the polyamide-based resin. Examples of the other resins include a vinyl chloride-based resin, a modacrylic-based resin, a polycarbonate-based resin, a polyolefin-based resin, and a polyphenylene sulfide-based resin. Other resins may be used individually or in combinations of two or more.
From the viewpoint of obtaining a texture and an appearance similar to those of human hair and improving the curl setting properties and curl-holding properties, the core of the core-sheath conjugate fiber for artificial hair is preferably composed of a polyester-based resin composition containing, as a main component, at least one polyester resin selected from the group consisting of polyalkylene terephthalate and a copolyester mainly containing polyalkylene terephthalate, and the sheath thereof is more preferably composed of a polyamide-based resin composition containing, as a main component, a polyamide-based resin mainly containing at least one selected from the group consisting of nylon 6 and nylon 66. In an embodiment of the present invention, the wording “polyamide-based resin mainly containing at least one selected from the group consisting of nylon 6 and nylon 66” refers to the 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 resin composition in the core or the sheath may contain a pigment in order to obtain core-sheath conjugate fibers for artificial hair having a desired color. There is no particular limitation on the pigment, and ordinary pigments such as carbon black or anthraquinone-based pigments can be used, for example. Pigment masterbatch can also be used. A “pigment masterbatch” is obtained by kneading a pigment and a resin composition using a kneading machine such as an extruder and pelletizing (also referred to as compounding) the resulting mixture, and pigments, which are usually considered to be difficult to handle because the pigments are in the fine powder form, can be easily handled by pre-dispersing a pigment in a resin composition, which can suppress uneven coloring of the fibers to be obtained.
The amount of the pigment added to the polyester-based resin composition that constitutes the core is, but is not particularly limited to, preferably 0.005 parts by weight or more and 2 parts by weight or less, and more preferably 0.01 parts by weight or more and 1 part by weight or less, with respect to 100 parts by weight of the polyester-based resin. Further, the amount of the pigment added to the polyamide-based resin composition that constitutes the sheath is, but is not particularly limited to, preferably 0.005 parts by weight or more and 2 parts by weight or less, and more preferably 0.01 parts by weight or more and 1 part by weight or less, with respect to 100 parts by weight of the polyamide-based resin.
In one or more embodiments of the present invention, a flame retardant may be used in combination from the viewpoint of flame resistance. Examples of the flame retardant include bromine-containing flame retardants and phosphorus-containing flame retardants. Examples of the phosphorus-containing flame retardant include phosphoric acid ester amide compounds and organic cyclic phosphorus-based compounds. Examples of the bromine-based flame retardant include, but are not particularly limited to the following: a brominated epoxy-based flame retardant; bromine-containing phosphate esters such as pentabromotoluene, hexabromobenzene, decabromodiphenyl, decabromodiphenyl ether, bis(tribromophenoxy)ethane, tetrabromophthalic anhydride, ethylene bis(tetrabromophthalimide), ethylene bis(pentabromophenyl), octabromotrimethylphenylindan, and tris(tribromoneopentyl)phosphate; brominated polystyrenes; brominated polybenzyl acrylates; brominated phenoxy resins; brominated polycarbonate oligomers; tetrabromobisphenol A and tetrabromobisphenol A derivatives such as 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. In particular, the brominated epoxy-based flame retardant is preferred in terms of heat resistance and flame resistance.
The brominated epoxy-based flame retardant may have an epoxy group or tribromophenol at the end of the molecule as a raw material. The structure of the brominated epoxy-based flame retardant after melt kneading is not particularly limited, and preferably has 80 mol % or more of a constitutional unit represented by the following chemical formula (1), where the total number of the constitutional unit represented by the chemical formula (1) and other constitutional units in which at least a part of the chemical formula (1) has been modified is taken as 100 mol %. The structure at the end of the molecule of the brominated epoxy-based flame retardant may be changed after melt kneading. For example, the end of the molecule of the brominated epoxy-based flame retardant may be replaced by groups other than the epoxy group or tribromophenol, such as a hydroxyl group, a phosphoric acid group, and a phosphonic acid group. Alternatively, the end of the molecule of the brominated epoxy-based flame retardant may be bound to a polyester component through an ester group.
Apart of the structure of the brominated epoxy-based flame retardant, except for the end of the molecule, may also be changed. For example, the secondary hydroxyl group and the epoxy group of the brominated epoxy-based flame retardant may be bound together to form a branched structure. Moreover, a part of the bromine of the chemical formula (1) may be eliminated or added if the bromine content in the molecule of the brominated epoxy-based flame retardant is not significantly changed.
The brominated epoxy-based flame retardant may be, e.g., a polymeric brominated epoxy-based flame retardant as represented by the following general formula (2). In the general formula (2), m is 1 to 1000. The polymeric brominated epoxy-based flame retardant represented by the general formula (2) may be a commercially available product such as a brominated epoxy-based flame retardant (trade name “SR-T2MP”) manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.
The content of the brominated epoxy flame retardant in the core and/or the sheath is, but is not particularly limited to, 5 parts by weight or more and 40 parts by weight or less with respect to 100 parts by weight of the main component resin, for example. From the viewpoint of heat resistance and flame resistance, for example, it is preferable that the core is composed of a polyester-based resin composition containing at least one polyester resin selected from the group consisting of polyalkylene terephthalate and a copolyester mainly containing polyalkylene terephthalate in an amount of 100 parts by weight and a brominated epoxy flame retardant in an amount of 5 parts by weight or more and 40 parts by weight or less, and the sheath is composed of a polyamide-based resin composition containing a polyamide-based resin mainly containing at least one selected from the group consisting of nylon 6 and nylon 66 in an amount of 100 parts by weight and a brominated epoxy flame retardant in an amount of 5 parts by weight or more and 40 parts by weight or less.
In one or more embodiments of the present invention, a flame retardant auxiliary may be used in combination. The flame retardant auxiliary is not particularly limited, and from the viewpoint of flame resistance, it is preferable to use an antimony-based compound or a composite metal containing antimony, for example. Examples of the antimony-based compound include antimony trioxide, antimony tetroxide, antimony pentoxide, sodium antimonate, potassium antimonate, and calcium antimonate. In terms of the effects of the flame retardant auxiliary on the flame resistance and the texture, it is more preferable that the flame retardant auxiliary may be at least one selected from the group consisting of antimony trioxide, antimony pentoxide, and sodium antimonate.
The content of the flame retardant auxiliary in the core and/or the sheath is preferably; but is not particularly limited to, 0.1 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the main component resin, for example.
In particular, as a result of adding a flame retardant auxiliary to the polyamide-based resin composition that constitutes the sheath, an appropriate surface unevenness is formed on the fiber surface, thus obtaining core-sheath conjugate fibers for artificial hair having flame resistance, and a low gross and an appearance that are similar to those of human hair.
The core-sheath conjugate fibers for artificial hair may contain various additives as needed, to the extent that they do not interfere with the purpose of one or more embodiments of the present invention. The additives include, e.g., a heat-resistant agent, a stabilizer, a fluorescent agent, an antioxidant, and an antistatic agent.
The core-sheath conjugate fibers for artificial hair can be produced by melt kneading the resin compositions respectively for the core and the sheath using various ordinary kneading machines, and melt spinning the resulting composition using a core-sheath conjugate nozzle. A core component is prepared by melt kneading, using various ordinary kneading machines, a polyester-based resin composition obtained by dry-blending the above-described components such as the polyester resin and the brominated epoxy-based flame retardant, whereas a sheath component is prepared by melt kneading, using various ordinary kneading machines, a polyamide-based resin composition obtained by dry-blending the above-described components such as the polyamide-based resin, the pigment, and the brominated epoxy-based flame retardant, and then the core-sheath conjugate fibers for artificial hair can be produced by melt spinning the core component and the sheath component using a core-sheath conjugate spinning nozzle, for example. Examples of the kneading machine include a single-screw extruder, a twin-screw extruder, a roll, a Banbury mixer, and a kneader. In particular, the twin-screw extruder is preferred in terms of the adjustment of the degree of kneading and ease of operation.
As the method for producing the fiber of the present invention, it is preferable to use a melt spinning method, and, for example, in the case of a polyester-based resin composition, melt spinning is performed while the temperatures of an extruder, a gear pump, a nozzle, and the like are set to 250° C. or more and 300° C. or less, and in the case of a polyamide-based resin composition, melt spinning is performed while the temperatures of an extruder, a gear pump, a nozzle, and the like are set to 260° C. or more and 320° C. or less, after which the extruded yarns are cooled to a temperature of not more than the glass transition point of the corresponding resin, and wound up at a speed of 30 m/min or more and 5000 m/min or less, and thus melt spun yarns (undrawn yarns) are obtained.
Specifically, during the melt spinning, the polyester-based resin composition for constituting the core is supplied from a core extruder of a melt spinning machine, the polyamide-based resin composition for constituting the sheath is supplied from a sheath extruder of the melt spinning machine, and the molten polymer is extruded through a core-sheath type conjugate spinning nozzle (holes) with a predetermined shape, and thus the melt spun yarns (undrawn yarns) are obtained. It is preferable that the melt spun yarns (undrawn yarns) are hot drawn. The drawing may be performed by either a two-step method or a direct spinning-drawing method. In the two-step method, the melt spun yarns are once wound, and then drawn. In the direct spinning-drawing method, the melt spun yarns are drawn continuously without winding. The hot drawing may be performed by a single-stage drawing method or a multi-stage drawing method that includes two or more stages.
The heating means in the hot drawing may be, e.g., a heating roller, a heat plate, a steam jet apparatus, or a hot water bath, and they can be used in combination as appropriate.
Oils such as a fiber treatment agent and a softening agent may be applied to the core-sheath conjugate fibers for artificial hair to make the texture and feel of the fibers more similar to human hair. The fiber treatment agent may be, e.g., a silicone-based fiber treatment agent or a non-silicone-based fiber treatment agent used to improve the texture and combing property of the fibers.
The core-sheath conjugate fibers for artificial hair may be subjected to gear crimping. The gear crimping imparts gentle curves and natural appearance to the fibers, and also reduces the adhesion between the fibers, thereby also improving the combing property.
In the gear crimping, the fibers are generally heated to a temperature higher than the softening temperature and allowed to pass through two engaged gears so that the shape of the gears is transferred to the fibers. This can create curls on the fibers.
Also, in the fiber processing stage, if necessary, curls having different shapes can be created by heating the core-sheath conjugate fibers for artificial hair at different temperatures.
(Hair Ornaments)
In one or more embodiments of the present invention, the core-sheath conjugate fibers for artificial hair can be used as artificial hair either individually or can be used in combination with other artificial hair fibers and natural fibers such as human hair and animal hair. Examples of the other artificial hair fibers include acrylic fibers.
In one or more embodiments of the present invention, the core-sheath conjugate fibers for artificial hair may be used without particular limitation as long as they are used for hair ornaments. The core-sheath conjugate fibers for artificial hair may be used for hair wigs, hairpieces, weaving hair hair extensions, braided hair, hair accessories, and doll hair.
The hair ornaments may include only the core-sheath conjugate fibers for artificial hair of one or more embodiments of the present invention. Alternatively, the hair ornaments may include the core-sheath conjugate fibers for artificial hair of the present invention in combination with other artificial hair fibers and natural fibers such as human hair and animal hair.
Hereinafter, one or more embodiments of the present invention will be described in more detail by way of examples. However, one or more embodiments of the present invention are not limited to the following examples.
The measurement methods and the evaluation methods used in Examples and Comparative Examples are as follows.
(Single Fiber Fineness)
Using an auto-vibronic fineness measuring device “DENIER COMPUTER DC-11” (manufactured by Search Co., Ltd), 30 samples were measured to determine their respective single fiber fineness, and the average of the measured values of the samples was calculated and taken as the single fiber fineness of the core-sheath conjugate fibers.
(Evaluation of Fiber Cross-Section)
At room temperature (23° C.), fibers were cut to a length of 150 mm and 0.7 g of the cut fibers were bundled, inserted into a rubber tube, and heated at 80° C. so as to shrink the tube such that the fiber bundle was fixed so as not to be displaced. Thereafter, a portion of the tube was cut using a cutter, and thus a fiber bundle for cross-section observation having a length of 5 mm was prepared. An image of this fiber bundle was captured using a laser microscope (“VK-9500” manufactured by Keyence Corporation) at a magnification of 400 times, and thus a photograph of fiber cross-sections was obtained. A core-to-sheath area ratio was calculated based on the fiber cross-section photograph. Also, fiber cross-sections of thirty fibers were selected at random from this fiber cross-section photograph, and the length of the major axes of the fiber cross-sections, the length of first minor axes of the fiber cross-sections, the length of the major axes of the core cross-sections, the length of the first minor axes of the core cross-sections, and the two-point distance between the center point of the first minor axes of the fiber cross-sections and the center point of the first minor axes of the core cross-sections were measured. Note that, in the core-sheath conjugate fibers for artificial hair according to an embodiment of the present invention, values such as 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, the two-point 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, a ratio between the length of major axis of the fiber cross-section and the length of the first minor axis of the fiber cross-section, and a ratio between the length of the major axis of the core cross-section and the length of the first minor axis of the core cross-section can be indicated using the corresponding average value of the measured values of the fiber cross-sections of the thirty fibers, which were selected at random.
(Texture)
Sensory evaluation was performed by a professional cosmetologist, and the texture was evaluated in the following four stages.
(Appearance)
Sensory evaluation was performed by a professional cosmetologist, and the appearance was evaluated in the following four stages.
(Curl Setting Properties)
2.8 g of filaments were formed into a hair tress with a length of 25 cm and wrapped around a pipe with a diameter of 32 mm at room temperature (23° C.), curled at 120° C. for 60 minutes, and aged at room temperature (23° C.) for 60 minutes. Thereafter, one end of the curled filaments was fixed and suspended, and the length of the curled filaments was measured. The curl setting properties were evaluated using the filament length as an index for curl setting properties in the following four stages.
First, 100 parts by weight of polyethylene terephthalate pellets (EastPET trade name “A-12”, which is referred to as PET, manufactured by East West Chemical Private Limited) were mixed with 30 parts by weigh of a brominated epoxy-based flame retardant (trade name “SR-T2MP” manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.), 3 parts by weight of sodium antimonate (trade name “SA-A” manufactured by Nihon Seiko Co., Ltd.), 3.0 parts by weight of black pigment masterbatch (trade name “PESM 22367 BLACK (20)” manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., pigment: 20% by weight, base resin: polyester-based resin), 0.6 parts by weight of yellow pigment masterbatch (trade name “PESM 1001 YELLOW (20)” manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., pigment: 20% by weight, base resin: polyester-based resin), and 0.2 parts by weight of red pigment masterbatch (trade name “PESM 3005 RED (20%) manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., pigment: 20% by weight, base resin: polyester-based resin). The mixture was dry blended and then fed into a twin-screw extruder, where it was melt-kneaded at a barrel temperature of 280° C. and pelletized. Thus, a polyester-based resin composition was obtained.
Then, 100 parts by weight of nylon 6 (also referred to as PA) (trade name “A1030BRL” manufactured by Unitika Ltd.) were mixed with 12 parts by weight of a brominated epoxy-based flame retardant (trade name “SR-T2MP manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.), 2 parts by weight of sodium antimonate (trade name “SA-A” manufactured by Nihon Seiko Co., Ltd.), 2.0 parts by weight of black pigment masterbatch (trade name “PAM (F) 25005 BLACK (20)” manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), 0.8 parts by weight of yellow pigment masterbatch (trade name “PAM (F) 28990 YELLOW (20)” manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), and 0.5 parts by weight of red pigment masterbatch (trade name “PAM (F) 28991 RED (20)” manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.). The mixture was dry blended and then fed into a twin-screw extruder, where it was melt-kneaded at a barrel temperature of 260° C. and pelletized. Thus, a polyamide-based resin composition was obtained.
Next, the polyester-based resin composition in the form of pellets and the polyamide-based resin composition in the form of pellets were fed into extruders, respectively; and then extruded through a core-sheath type conjugate spinning nozzle having a 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. This resulted in undrawn yarns of core-sheath conjugate fibers containing the polyester-based resin composition as a core and the polyamide-based resin composition as a sheath and having a core-to-sheath area ratio of 5:5.
The undrawn yarns thus obtained were drawn to 3 times and taken up at a speed of 45 m/min by using a heating roller at 85° C. Subsequently, the drawn yarns were further heat-treated and wound up at a speed of 45 m/min by using a heating roller at 200° C. A polyether oil (trade name “KWC-Q” manufactured by Marubishi Oil Chemical Corporation) was applied to the drawn yarns so that the amount of oil applied was 0.20% omf (i.e., the weight percentage of the oil (pure content) with respect to the dry fiber weight). Then, the resulting yarns were dried, and thus core-sheath conjugate fibers with a single fiber fineness shown in Table 1 below and an eccentricity ratio of 15.6% in the minor axis direction were obtained.
Core-sheath conjugate fibers were produced in the same manner as Example 1 except that a core-sheath type conjugate spinning nozzle having the nozzle shape shown in Table 1 below was used, the eccentricity ratio in the minor axis direction was 12.7% and the core-to-sheath area ratio was 6:4.
Core-sheath conjugate fibers were produced in the same manner as Example 1 except that the resin used for the sheath was changed to nylon 66 (also referred to as “PA66”) (trade name “Amilan CM3001” manufactured by Toray Industries, Inc.), the barrel temperature was set to 280° C. during pelletization, the nozzle temperature was set to 280° C., the eccentricity ratio in the minor axis direction was 15.1%, and the core-to-sheath area ratio was 3:7.
Core-sheath conjugate fibers were produced in the same manner as Example 1 except that a core-sheath type conjugate spinning nozzle having the nozzle shape shown in Table 1 below was used, the resin used for the core was changed to polybutylene terephthalate (also referred to as “PBT”) (trade name “Novaduran 5020” manufactured by Mitsubishi Chemical Corporation), the barrel temperature was set to 260° C. during pelletization, the nozzle temperature was set to 260° C., the eccentricity ratio in the minor axis direction was 6.8%, and the core-to-sheath area ratio was 7:3.
Core-sheath conjugate fibers were produced in the same manner as Example 1 except that a core-sheath type conjugate spinning nozzle having the nozzle shape shown in Table 1 below was used, and the eccentricity ratio in the minor axis direction was 0%.
Core-sheath conjugate fibers were produced in the same manner as Example 1 except that the eccentricity ratio in the minor axis direction was 14.1% and the core-to-sheath area ratio was 1:9.
Core-sheath conjugate fibers were produced in the same manner as Example 1 except that a core-sheath type conjugate spinning nozzle having the nozzle shape shown in Table 1 below was used, the eccentricity ratio in the minor axis direction was 2.4% and the core-to-sheath area ratio was 8:2.
Core-sheath conjugate fibers were produced in the same manner as Example 1 except that a core-sheath type conjugate spinning nozzle having the nozzle shape shown in Table 1 below was used, and the eccentricity ratio in the minor axis direction was 9.3%.
The cross-sectional shapes of the fibers of the examples and comparative examples were evaluated and observed as described above. Furthermore, the texture, appearance, and the curl setting properties of the fibers of the examples and comparative examples were evaluated as described above. Table 1 shows the results.
As can be seen from Table 1, the fibers of Examples 1 to 4 had a texture and an appearance that are similar to those of human hair, and favorable curl setting properties.
On the other hand, the fibers of Comparative Example 1 having an eccentricity ratio of 0% and the fibers of Comparative Example 2 having a high sheath ratio had poor curl setting properties. Cores of the fibers of Comparative Example 3 having a high core ratio were exposed from the fiber surface, and the fibers of Comparative Example 3 had very bad texture and appearance, and thus was not formed as good fibers. The fibers of Comparative Example 4 had a circular fiber cross-sectional shape and a circular core cross-sectional shape, resulting in an unnatural appearance and a bad texture.
One or more embodiments of the present invention preferably include at least the following embodiments, but are not limited thereto.
[1] A core-sheath conjugate fiber for artificial hair comprising:
[2] The core-sheath conjugate fiber for artificial hair according to [1], wherein the fiber cross-section has a flat multilobed shape.
[3] The core-sheath conjugate fiber for artificial hair according to [1] or [2], wherein the core cross-section has an elliptical or flat multilobed shape.
[4] The core-sheath conjugate fiber for artificial hair according to any one of [1] to [3], wherein a length of the major axis of the fiber cross-section and a length of a first minor axis of the fiber cross-section satisfy the equation (1) below, where the major axis of the fiber cross-section is a longest straight line among an axisymmetric axis and straight lines connecting any two points on the outer circumference of the fiber cross-section so as to be parallel to the axisymmetric axis, and the first minor axis of the fiber cross-section is a longest straight line formed when any two points on the outer circumference of the fiber cross-section are connected perpendicularly to the major axis of the fiber cross-section,
the length of the major axis of the fiber cross-section/the length of the first minor axis of the fiber cross-section=1.1 or more and 2.0 or less (1).
[5] The core-sheath conjugate fiber for artificial hair according to any one of [1] to [4], wherein a length of the major axis of the core cross-section and a length of a first minor axis of the core cross-section satisfy the equation (2) below, where the major axis of the core cross-section is a longest straight line among an axisymmetric axis and straight lines connecting any two points on the outer circumference of the core cross-section so as to be parallel to the axisymmetric axis, and the first minor axis of the core cross-section is a longest straight line formed when any two points on the outer circumference of the core cross-section are connected perpendicularly to the major axis of the core 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=1.3 or more and 2.0 or less (2).
[6] The core-sheath conjugate fiber for artificial hair according to any one of [1]to [5], wherein the polyester-based resin composition contains at least one polyester-based resin selected from the group consisting of polyalkylene terephthalate and a copolyester mainly containing polyalkylene terephthalate.
[7] The core-sheath conjugate fiber for artificial hair according to any one of [1] to [6], wherein the polyamide-based resin composition contains a polyamide-based resin mainly containing at least one selected from the group consisting of nylon 6 and nylon 66.
[8] A hair ornament comprising the core-sheath conjugate fiber for artificial hair according to any one of [1] to [7].
[9] The hair ornament according to [8], wherein the hair ornament is any one selected from the group consisting of a hair wig, a hairpiece, weaving hair, a hair extension, braided hair, a hair accessory, and doll hair.
[10]A method for producing the core-sheath conjugate fiber for artificial hair according to any one of [1] to [7], comprising:
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-219465 | Dec 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/038781 | 10/20/2021 | WO |
