Abstract: Provided is a polyamide fiber having excellent color developability, as well as a method for producing such a polyamide fiber, and a fiber structure. The polyamide fiber comprises a polyamide resin composition comprising a polyamide resin and an amino group-containing color enhancer, the polyamide fiber having terminal amino groups at a concentration of from 5.0 ?eq/g to 40.0 ?eq/g. Such a fiber can be produced by a production method at least comprising: melt-kneading a polyamide resin composition including a polyamide resin and an amino group-containing color enhancer to give a melt-kneaded product having a predetermined melt viscosity; and spinning the melt-kneaded product to give fibers.

Abstract: A fiber made of a polyester copolymer (B), wherein the polyester copolymer (B) comprises a dicarboxylic acid component and a glycol component, and the dicarboxylic acid component comprises 75 mol % or more of a terephthalic acid component, 1.0 mol % to 3.5 mol % of component (a) derived from a compound represented by formula (I), 2.0 mol % to 10.0 mol % of a cyclohexane dicarboxylic acid component (b), and 2.0 mol % to 8.0 mol % of an aliphatic dicarboxylic acid component (c). This can afford a polyester fiber that exhibits deep color property to cation dyes and disperse dyes under a normal pressure environment and is superior in color fastness to washing and color fastness to light and can secure good spinnability.

Abstract: Disclosed is a polyamide fiber having a degree of orientation equal to or higher than 0.7 and equal to or lower than 0.85. The polyamide fiber is suitably obtained by forming a polyamide component having high moisture absorbency and a specific soluble component into a conjugated fiber under specific fiber formation conditions.

Abstract: To provide a polyester composite fiber having a heat-shielding property due to high reflectance in an infrared wavelength range (800 to 3000 nm) easy to be changed into thermal energy, and having color development property comparable to that of conventional polyester fibers. The composite fiber is a core-sheath type composite fiber including a core component and a sheath component of 10:90 to 30:70 (mass ratio). The core component includes a thermoplastic polymer including a sunlight shielding material having an average particle size of 0.5 ?m or smaller in 8-70 wt %. The sheath component includes a polyester-type polymer including heat-shielding fine particles in 0.5-10 wt %, the heat-shielding fine particles capable of maintaining color development property and having an average particle size of 0.1 ?m or smaller which is smaller than that of the sunlight shielding material.

Abstract: A fiber made of a polyester copolymer (B), wherein the polyester copolymer (B) comprises a dicarboxylic acid component and a glycol component, and the dicarboxylic acid component comprises 75 mol % or more of a terephthalic acid component, 1.0 mol % to 3.5 mol % of component (a) derived from a compound represented by formula (I), 2.0 mol % to 10.0 mol % of a cyclohexane dicarboxylic acid component (b), and 2.0 mol % to 8.0 mol % of an aliphatic dicarboxylic acid component (c). This can afford a polyester fiber that exhibits deep color property to cation dyes and disperse dyes under a normal pressure environment and is superior in color fastness to washing and color fastness to light and can secure good spinnability.