ACRYLIC FIBER FOR ARTIFICIAL HAIR, METHOD FOR MANUFACTURING SAID FIBER, AND HEADDRESS PRODUCT CONTAINING SAID FIBER

1 . An acrylic fiber for artificial hair comprising:

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,

wherein the organic solvent is present in an amount of 0.1 to 3% by mass with respect to a total mass of the acrylic fiber, and

wherein the acrylic fiber has an average surface roughness of 5900 μm 2 or less in an area of 40 μm long and 80 μm wide of a side surface of the acrylic fiber.

2 . The acrylic fiber according to claim 1 , wherein the organic solvent is at least one selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfone, ε-caprolactam, ethylene carbonate, and sulfolane.

3 . The acrylic fiber according to claim 1 , wherein the acrylic copolymer comprises 30 to 70% by mass of the acrylonitrile, 25 to 69.5% by mass of the vinyl chloride and/or vinylidene chloride, and 0.5 to 5% by mass of the sulfonic acid group-containing vinyl monomer, with respect to a total mass of the acrylic copolymer.

4 . The acrylic fiber according to claim 1 , wherein the acrylic fiber has a void fraction of 60% or less.

5 . The acrylic fiber according to claim 1 , wherein the acrylic fiber has an apparent glass transition temperature of 90° C. or less,

wherein the apparent glass transition temperature is defined as a peak temperature of dynamic viscoelasticity (tan δ) expressed by the following formula 1:

Dynamic viscoelasticity (tan δ)=Loss modulus ( E ″)/Storage modulus ( E ′)  (1),

wherein the loss modulus (E″) and the storage modulus (E′) are measured in accordance with JIS K 7244.

6 . A method for producing the acrylic fiber according to claim 1 , the method comprising:

preparing a spinning solution by dissolving an acrylic copolymer obtained by copolymerizing acrylonitrile, vinyl chloride and/or vinylidene chloride, and a sulfonic acid group-containing vinyl monomer in an organic solvent; and

wet spinning the spinning solution to form an acrylic fiber,

wherein the spinning solution comprises 8 to 16 parts by mass of water with respect to 100 parts by mass of the acrylic copolymer, and

wherein, in the wet spinning, a content of the organic solvent is adjusted to 0.1 to 3% by mass.

7 . The method according to claim 6 , wherein the wet spinning comprises at least a water washing process and an oil application process,

wherein, in the oil application process, a water-washed acrylic fiber is impregnated with an organic solvent that can dissolve the acrylic copolymer while the oil is applied to the water-washed acrylic fiber.

8 . The method according to claim 6 , wherein the water washing process is performed by spraying water on the acrylic fiber and pressing the acrylic fiber sprayed with water by a nip roll.

9 . The method according to claim 6 , wherein the organic solvent used in preparing the spinning solution is at least one selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, and dimethylacetamide.

10 . The method according to claim 7 , wherein the organic solvent used in preparing the spinning solution is at least one selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, and dimethylacetamide.

11 . The method according to claim 7 , wherein the organic solvent is impregnated into the acrylic fiber in the oil application process is at least one selected from the group consisting of dimethyl sulfone, ε-caprolactam, ethylene carbonate, and sulfolane.

12 . The method according to claim 6 , the method further comprising preparing the acrylic copolymer by an emulsion polymerization method, wherein

the acrylonitrile, the vinyl chloride and/or vinylidene chloride, and the sulfonic acid group-containing vinyl monomer are continuously polymerized in a single reaction vessel,

the sulfonic acid group-containing vinyl monomer is not introduced into the reaction vessel at the beginning of a polymerization reaction, and

the sulfonic acid group-containing vinyl monomer is continuously introduced into the single reaction vessel at a constant rate during a period from when a yield of the acrylic copolymer reaches 8 to 21% by mass of an intended amount of the acrylic copolymer until when the polymerization reaction ends.

13 . The method according to claim 6 , wherein preparing the spinning solution comprises:

forming a slurry of the acrylic copolymer comprising the acrylic copolymer, water, and the organic solvent; and

evaporating the water in the slurry after supplying the slurry to a thin film evaporator.

14 . The method according to claim 6 , wherein the spinning solution further comprises a polyphosphate.

15 . A hair ornament product comprising an acrylic fiber for artificial hair, wherein the acrylic fiber comprises:

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, wherein the organic solvent is present in an amount of 0.1 to 3% by mass with respect to a total mass of the acrylic fiber for artificial hair,

wherein the acrylic fiber has an average surface roughness of 5900 μm 2 or less in an area of 40 μm long and 80 μm wide of a side surface of the fiber.

16 . The hair ornament product according to claim 15 , wherein the organic solvent is at least one selected from the group consisting of dimethyl sulfoxide, N,N-dimethylformamide, dimethylacetamide, dimethyl sulfone, ε-caprolactam, ethylene carbonate, and sulfolane.

17 . The hair ornament product according to claim 15 , wherein the acrylic copolymer comprises 30 to 70% by mass of the acrylonitrile, 25 to 69.5% by mass of the vinyl chloride and/or vinylidene chloride, and 0.5 to 5% by mass of the sulfonic acid group-containing vinyl monomer, with respect to a total mass of the acrylic copolymer.

18 . The hair ornament product according to claim 15 , wherein the acrylic fiber for artificial hair has a void fraction of 60% or less.

19 . The hair ornament product according to claim 15 , wherein the acrylic fiber has an apparent glass transition temperature of 90° C. or less,

wherein the glass transition temperature is defined as a peak temperature of dynamic viscoelasticity (tan δ) expressed by the following formula 1:

Dynamic viscoelasticity (tan δ)=Loss modulus ( E ″)/Storage modulus ( E ′)  (1),

wherein the loss modulus (E″) and the storage modulus (E′) are measured in accordance with JIS K 7244.

20 . The hair ornament product according to claim 15 , wherein the hair ornament product is at least one selected from the group consisting of a fiber bundle for hair, a hair weave, a wig, a braid, toupee, a hair extension, and a hair accessory.