Polyurethane elastic fiber and method for producing polyurethane elastic fiber

A polyurethane elastic fiber, comprising:

• a polyurethane urea polymer (A) represented by general formula (1) described below, which has a number average molecular weight calculated in terms of polystyrene ranging from 11,000 to 50,000, and has tertiary nitrogen groups at the terminal groups;
• a polyurethane urea polymer (B) obtained by reacting a prepolymer obtained by reacting a high-molecular diol and a diisocyanate with an active hydrogen-containing compound;
• and
• a polymer of a compound having an anionic functional group,
• {wherein R1 and R2 are the same or different and represent a linear or branched alkyl group or hydroxyalkyl group having 1 to 5 carbon atoms, or R1 and R2 are bonded to form a heterocyclic group together with the nitrogen atom to which they are bonded, R3 is a linear or branched alkylene group having 1 to 5 carbon atoms, X is a urea bond, R4, R5 and R6 are the same or different diisocyanate residue, P is a diol residue, Q is a diamine residue, UT is a urethane bond, UA is a urea bond, each of k, l, m and n is a positive number, n may be 0, and l is 1}
• wherein a solid content of said polyurethane urea polymer (A) in a ratio of 0.01 to 20 parts by mass with respect to 100 parts by mass of the solid content of said polyurethane urea polymer (B).