An acrylic fiber for artificial hair includes an acrylic copolymer obtained by copolymerizing acrylonitrile, vinyl chloride and/or vinylidene chloride, and a sulfonic acid group-containing vinyl monomer; and an organic solvent that can dissolve the acrylic copolymer, where the organic solvent is present in an amount of 0.1 to 3% by mass with respect to the total mass of the acrylic fiber for artificial hair. The acrylic fiber for artificial hair has an average surface roughness of 5900 μm.sup.2 or less in an area of 40 μm long and 80 μm wide of the side surface of the fiber.

A human hair fiber treatment agent for treating human hair fibers having free ends at both ends, comprising the following components (A) to (C) in the formulation thereof: (A): formaldehyde or hydrate thereof; (B): melamine derivative represented by the formula (1):

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wherein R.sup.1 to R.sup.3 are the same or different and each represent a hydrogen atom, a hydroxymethylamino group, a hydroxy group, a halogen atom, a phenyl group, a linear or branched alkyl group or alkenyl group having 1 or more and 6 or less carbon atoms, or a linear or branched alkoxy group or alkenyloxy group having 1 or more and 6 or less carbon atoms; and (C): water.

Provided is artificial hair including chemical fibers and a fiber treatment composition that is adhered to the surfaces of the chemical fibers. The fiber treatment composition may include an oxazoline group-containing acrylic resin and an organic-modified silicone oil. The oxazoline group-containing acrylic resin may have a main chain that includes a (meth)acrylic acid ester and styrene.

A human hair fiber treatment agent comprised of one or more compositions for treating human hair fibers having free ends at both ends, wherein the human hair fiber treatment agent comprises the following components (A) to (C) in the formulation thereof: (A): at least one formaldehyde derivative selected from the group consisting of formaldehyde, and the like; (B): phenol compound(s) having electron-donating group(s) on at least one of the meta positions and having hydrogen atom(s) on at least one of the ortho positions and the para position, with the proviso that the electron-donating group at the meta position optionally forms, together with a carbon atom attached thereto, a benzene ring optionally substituted with hydroxy group(s); and (C): water.

One or more embodiments of the present invention relate to a core-sheath conjugate fiber for artificial hair including a core and a sheath. 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. A core-to-sheath area ratio of the core to the sheath is 2:8 to 7:3, and 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. As a result, fibers for artificial hair having a texture and an appearance that are similar to those of human hair and having favorable curl setting properties are provided.

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 as a main component, and the sheath is composed of a polyamide-based resin composition containing a polyamide-based resin as a main component. The polyester-based resin composition and the polyamide-based resin composition contain a bromine-based flame retardant. In the core-sheath conjugate fiber for artificial hair, a core-to-sheath area ratio of the core to the sheath is 2:8 to 8:2. A fiber cross-section of the core-sheath conjugate fiber for artificial hair has a flat multilobed shape, and the fiber cross-section includes a hollow portion. A ratio of an area of the hollow portion to a total area of the fiber cross-section is 5% or more and 30% or less. The hollow portion has a polygonal shape. As a result, fibers for artificial hair that have a texture similar to that of human hair, high durability, favorable curl setting properties, and high flame resistance are provided.

A resin composition for flame retardant artificial hair which has favorable transparency and combability similar to those of human hair and exhibits excellent flame retardancy. A resin composition for flame retardant artificial hair is obtained by configuring a resin composition including 100 parts by mass of a polyester (A) and 5-40 parts by mass of a bromine-containing flame retardant (B) including at least one kind selected from poly(pentabromobenzyl acrylate), a brominated phenol resin, and polydibromophenylene oxide, wherein the melt viscosity of the polyester (A) is 80-300 Pa.Math.s.

The present invention pertains to an artificial hair fiber that includes an artificial fibroin fiber containing a modified fibroin and that expands when being in a wet state and shrinks when being dried after the wet state.

Provided is a strand extending in the longitudinal direction, wherein the strand includes filaments of one type having a gradient-length effect through spiral rotational twists and an irregular fine texture through self-thermal shrinking. The filaments of the strand have natural coiling characteristics that are very similar to those of natural hair of black people, and these characteristics are caused by the facts that the filaments have 3-dimensional waveforms occurred due to many fine and irregular windings or projections and that the waveforms exhibit fractal structure features and a fine kinky texture.

The present invention is to provide a fiber for artificial hair which can freely change the hairstyle at home while maintaining the wave shape of the fiber. A fiber for artificial hair having a bending rigidity maintaining ratio defined by formula (1) is 40 to 80% and a heat shrinkage ratio defined by formula (2) is 0.0 to 5.0% is provided.
bending rigidity maintaining ratio (%)=100{(bending rigidity in a state after conditioning for 24 hours at 30 C.90% RH)/(bending rigidity in a state after conditioning for 24 hours at 23 C.50% RH)}(1)
heat shrinkage ratio (%)=100{(length before heat treatment)(length after heat treatment for 5 min at 155 C.)}/(length before heat treatment)(2).