Provided is a thermal molding method for producing a thermally molded article having excellent abrasion resistance at its melt-fused part. Polyamide 6 and a copolyester are prepared separately. The copolyester contains terephthalic acid, ethylene glycol, and 1,4-butanediol as copolymerization units. The copolyester may further contain ε-caprolactone and/or diethylene glycol as a copolymerization unit. A multifilament yarn in which core-sheath type composite filaments each containing a core component and a sheath component at a ratio of 1 to 4:1 by mass are bundled is produced by a composite melt-spinning method using the polyamide 6 as the core component and the copolyester as the sheath component. Using the multifilament yarn, a product of filaments is produced by weaving, knitting, knitting and braiding, or braiding. The product of filaments is heated to melt the copolyester and fuse the core-sheath type composite filaments to each other while retaining the initial filament form of the polyamide 6, thus thermally molding the product of filaments.

Provided is a thermal molding method for producing a thermally molded article having excellent abrasion resistance at its melt-fused part. Polyamide 6 and a copolyester are prepared separately. The copolyester contains terephthalic acid, ethylene glycol, and 1,4-butanediol as copolymerization units. The copolyester may further contain ε-caprolactone and/or diethylene glycol as a copolymerization unit. A multifilament yarn in which core-sheath type composite filaments each containing a core component and a sheath component at a ratio of 1 to 4:1 by mass are bundled is produced by a composite melt-spinning method using the polyamide 6 as the core component and the copolyester as the sheath component. Using the multifilament yarn, a product of filaments is produced by weaving, knitting, knitting and braiding, or braiding. The product of filaments is heated to melt the copolyester and fuse the core-sheath type composite filaments to each other while retaining the initial filament form of the polyamide 6, thus thermally molding the product of filaments.

Disclosed is an elastic composite fiber, comprising a fiber body, wherein according to weight percentage, the material composition of the fiber body is made by composite spinning 10%-90% low viscosity PET, 10%-90% high viscosity PET, 10-80% PTT and 10-80% PBT. The present invention combines the advantages of the PET, PTT and PBT fibers into one, and not only has the advantages of good spinnability, high strength, good elasticity, softness, comfortableness, easy dyeing, moisture absorption and the like, but also utilizes reasonable cooperation between materials and the difference between physical and chemical properties to make the three-dimensional structure of the composite fiber more remarkable and the thermal stability better.

Disclosed is an elastic composite fiber, comprising a fiber body, wherein according to weight percentage, the material composition of the fiber body is made by composite spinning 10%-90% low viscosity PET, 10%-90% high viscosity PET, 10-80% PTT and 10-80% PBT. The present invention combines the advantages of the PET, PTT and PBT fibers into one, and not only has the advantages of good spinnability, high strength, good elasticity, softness, comfortableness, easy dyeing, moisture absorption and the like, but also utilizes reasonable cooperation between materials and the difference between physical and chemical properties to make the three-dimensional structure of the composite fiber more remarkable and the thermal stability better.

A method is disclosed including causing a preform 1 that is softened to pass from an inner side of a container-shaped member 10 having a shape of a container having a through hole 12 at a bottom thereof through the through hole 12. The preform 1 includes a resin. At least an inner surface 10i of the container-shaped member 10 is formed of a material including glass, a heat-resistant resin, or aluminum as a main component. In one embodiment of the present invention, the preform 1 is heated while the preform 1 and a metallic member 20 in which the container-shaped member 10 is disposed are not in direct contact with each other, and the preform 1 softened thereby is caused to pass through the through hole 12 and then through a tubular portion 26 of the metallic member 20 to shape the preform 1 into a fibrous shape.

A method is disclosed including causing a preform 1 that is softened to pass from an inner side of a container-shaped member 10 having a shape of a container having a through hole 12 at a bottom thereof through the through hole 12. The preform 1 includes a resin. At least an inner surface 10i of the container-shaped member 10 is formed of a material including glass, a heat-resistant resin, or aluminum as a main component. In one embodiment of the present invention, the preform 1 is heated while the preform 1 and a metallic member 20 in which the container-shaped member 10 is disposed are not in direct contact with each other, and the preform 1 softened thereby is caused to pass through the through hole 12 and then through a tubular portion 26 of the metallic member 20 to shape the preform 1 into a fibrous shape.

Provided are a polycarbonate fiber having a specific orientation degree and/or a specific birefringence value, a fiber structure as well as a resin composite body. The polycarbonate fiber may have an orientation degree (ft) of lower than 0.70, the orientation degree (ft) being defined by the following formula: ft=1−(1.0/C).sup.2, C: obtained sonic velocity (km/sec), and may have a birefringence value of 0.04 or lower. The polycarbonate fiber may comprise a polycarbonate resin having a number-average molecular weight (Mn) of from 12000 to 40000 and/or a weight-average molecular weight (Mw) of from 25000 to 80000.

Provided are a polycarbonate fiber having a specific orientation degree and/or a specific birefringence value, a fiber structure as well as a resin composite body. The polycarbonate fiber may have an orientation degree (ft) of lower than 0.70, the orientation degree (ft) being defined by the following formula: ft=1−(1.0/C).sup.2, C: obtained sonic velocity (km/sec), and may have a birefringence value of 0.04 or lower. The polycarbonate fiber may comprise a polycarbonate resin having a number-average molecular weight (Mn) of from 12000 to 40000 and/or a weight-average molecular weight (Mw) of from 25000 to 80000.

An artificial hair fiber suppressed in formation of nodes is provided. An artificial hair fiber is structured with a fiber of drawn resin composition; wherein: when an initial tensile stress of undrawn fiber at 100° C. is taken as F0, and a tensile stress when drawn by 2.5 times is taken as F1, F1/F0 of an undrawn fiber obtained by spinning the resin composition is 1.2 or more.

An artificial hair fiber suppressed in formation of nodes is provided. An artificial hair fiber is structured with a fiber of drawn resin composition; wherein: when an initial tensile stress of undrawn fiber at 100° C. is taken as F0, and a tensile stress when drawn by 2.5 times is taken as F1, F1/F0 of an undrawn fiber obtained by spinning the resin composition is 1.2 or more.