PURPOSE: To obtain the subject fiber having excellent whiteness and extremely excellent feeling by wet-spinning a specific spinning dope, washing the fiber with water, applying a specific fluorescent dye and subjecting the fiber to drawing, drying and thermal relaxation treatment.
CONSTITUTION: The spinning dope used in the present fiber is composed of (A) an acrylonitrile polymer having an acrylonitrile content of ≥50 wt.% and 0.05-0.7 wt.% of an organic carboxylic acid and (B) 0.02-1.0 wt.% of a phosphite compound of formula I (R1 to R3 are 8-15C alkyl or phenyl group derivative) dissolved in one or more solvent selected from dimethylformamide, dimethylacetamide and dimethyl sulfoxide. The spinning dope is spun by wet- spinning, washed with water and drawn at a draw ratio of ≤ 5. The obtained gelatinous fiber is added with ≥0.05 wt.% of (C) an aqueous solution of a benzimidazole derivative fluorescent dye of formula II and is subjected to drawing, drying and thermal relaxation treatment to obtain the objective fiber.
OKADA KIMIO
MORIISHI HIDEKI
