Acrylic fiber and a manufacturing process therefor

An acrylic fiber

• (a) comprising corrugations on its surface,
• (b) having an average tilt angle of 15 to 20° between two adjacent corrugations in a cross section vertical to the fiber axis direction,
• (c) having a maximum level difference of 0.15 to 0.35 μm between the bottom and the top of the corrugations, and
• (d) exhibiting a luster of 10 to 20% in a luster determination method for a 45° mirror surface for a fiber bundle surface.

A process for manufacturing an acrylic fiber comprising the steps of:

• discharging a spinning feed solution comprising an acrylonitrile polymer comprising 80 wt % or more and less than 95 wt % of acrylonitrile unit in an organic solvent, into the first coagulation bath consisting of an aqueous organic solvent solution at 30 to 50° C. containing 20 to 70 wt % of an organic solvent which may be the same as or different from the organic solvent for the spinning feed solution, to form a coagulated filament;
• drawing the filament from the first coagulation bath at a rate of 0.3 to 2.0 times of the discharge linear velocity of the spinning feed solution;
• stretching the filament by 1.1 to 2.0 times in the second coagulation bath consisting of an aqueous organic solvent solution at 30 to 50° C. containing 20 to 70 wt % of an organic solvent which may be the same as or different from any of the two organic solvents;
• and
• subsequently conducting wet heat stretching of the filament by three times or more.