Abstract: A moisture absorbing hygroscopic fiber having high whiteness, characterized in that (1) acrylic fiber comprising acrylonitrile copolymer where a (meth)acrylate compound as a copolymer component is less than 5% by weight is treated with a hydrazine compound whereby introduction of crosslink and increase in nitrogen content to an extent of 1.0 about 10.0% by weight is carried out, (2) treatment with an aqueous solution of alkaline metal salt is carried out whereby carboxyl group of a metal salt type by which CN group is hydrolyzed is produced in an amount of 4.0 about 10.0 meq/g and (3) a reducing treatment by a reduction treatment agent selected from a group consisting of hydrosulfite, thiosulfate, sulfite, nitrite, thiourea dioxide, and ascorbate compound is carried out.

Abstract: A highly white and highly moisture absorptive and desorptive fibrous structure where a moisture absorptive and desorptive synthetic fiber having a saturated index of moisture absorption of 10% by weight or more at 20° C. and 65% RH is blended, characterised in that, degree of whiteness of said fibrous structure in terms of indication method described in JIS Z 8729 is that L* is 90 or more, a* is within a range of ±2 and b* is within a range of ±10 and durability of whiteness degree against washing after washing for ten times is class 3-4 or higher.

Abstract: A highly white and highly moisture absorptive and desorptive fibrous structure where a moisture absorptive and desorptive synthetic fiber having a saturated index of moisture absorption of 10% by weight or more at 20° C. and 65% RH is blended, characterised in that, degree of whiteness of said fibrous structure in terms of indication method described in JIS Z 8729 is that L* is 90 or more, a* is within a range of ±2 and b* is within a range of ±10 and durability of whiteness degree against washing after washing for ten times is class 3-4 or higher.

Abstract: A method for the manufacture of moisture absorbing fiber having high whiteness, characterized in that an acrylic fiber comprising acrylonitrile polymer where a (meth)acrylate compound as a copolymer component is less than 5% by weight is subjected to crosslink introduction treatment using a hydrazine compound, to hydrolysis and to reducing treatment.