Abstract: Obtained is a polypropylene fiber that selectively satisfies any of the following requirements: the degree of amorphous orientation being not lower than 85%; the degree of crystalline orientation being not lower than 90%; the degree of crystallinity being 60-75%; the strength being not lower than 7 cN/dtex; the initial elastic modulus being not lower than 100 cN/dtex; the rupture elongation being 10-30%; and the single fiber fineness being 3-20 dtex. This polypropylene fiber, in which a crystalline chain and an amorphous chain are highly oriented and that has high strength and high initial elastic modulus, is produced through a two-stage drawing method and by controlling the drawing tension of the final stage while maintaining production speed.

Abstract: An object of the present invention is to provide a polyolefin fiber, particularly a core-sheath composite polypropylene fiber which is possible to be easily deformed corresponding to a stress applied from a direction perpendicular to a fiber axis, to be less fibrillated, and to have an excellent knot strength. The problem of the present invention is solved by providing the polyolefin fiber having a compressive strength of 30 to 51 MPa calculated by the following formula 1 when compressed and deformed by 30% with respect to a fiber diameter in a direction perpendicular to the fiber axis in each single fiber.

Abstract: As a fiber for weight reduction, a modified polyester fiber, which is obtained by copolymerizing: ethylene terephthalate as a main constitutional unit; equal to or more than 16 mol % and equal to or less than 25 mol % of an aliphatic dicarboxylic acid having equal to or more than 4 and equal to or less than 8 carbon atoms; and equal to or more than 2 mol % and equal to or less than 5 mol % of a metal sulfonate group-containing aromatic dicarboxylic acid, is used. This modified polyester fiber has a single fiber fineness of equal to or more than 0.6 dtex and equal to or less than 3.5 dtex. A mixed woven or knitted fabric composed of two or more types of fibers, which are the modified polyester fiber, a regular polyester fiber, and optionally, a polyurethane fiber, is capable of exhibiting good etching finish properties by using an etching finish agent that contains an etching finish accelerator, for example, a Mei printer OP-2 (manufactured by Meisei Chemical Works, Ltd.

Abstract: Obtained is a polypropylene fiber that selectively satisfies any of the following requirements: the degree of amorphous orientation being not lower than 85%; the degree of crystalline orientation being not lower than 90%; the degree of crystallinity being 60-75%; the strength being not lower than 7 cN/dtex; the initial elastic modulus being not lower than 100 cN/dtex; the rupture elongation being 10-30%; and the single fiber fineness being 3-20 dtex. This polypropylene fiber, in which a crystalline chain and an amorphous chain are highly oriented and that has high strength and high initial elastic modulus, is produced through a two-stage drawing method and by controlling the drawing tension of the final stage while maintaining production speed.