PURPOSE: To obtain the subject fiber having both quick shrinkability and high dry heat shrinkage factor and useful as boas, seals, etc., without any hardening and embrittling of fiber even at a high shrinkage factor by spinning and drawing an acrylic polymer, shrinking the resultant fiber, drying and densifying the fiber and subsequently drawing the densified fiber under dry heat conditions.

CONSTITUTION: Acrylic fiber composed of a polymer of ≥80wt.% acrylonitrile, 0.5-5wt.% sulfonic acid group-containing monomer (e.g. sodium allylsulfonate) and 5-15wt.% vinylic monomer (preferably methacrylamide, 2-hydroxyethyl methacrylate, etc.) is wet spun and drawn at 4-10 times draw ratio, shrunk at ≥30% ratio, dried, densified and then drawn at 1.2-2.0 times draw ratio under dry heat conditions to afford the objective fiber having ≥30% dry heat shrinkage factor.