Polyurethane urea elastic fiber and production method therefor

A method for producing a polyurethane urea elastic fiber, the method comprising:

• dry spinning a spinning solution containing polyurethane urea polymer A having a molecular chain using a polymer diol, a diisocyanate, and an organic amine as starting materials, and polyurethane urea polymer B having a molecular chain using a polymer diol, a diisocyanate, and an organic amine, and having a sulfonic acid amine salt on at least one end of the molecular chain, wherein:
• (a) spinning stock solution a containing polyurethane urea polymer A having a molecular chain using a polymer diol, a diisocyanate, and an organic amine as starting materials, and having an amino group at both ends of the molecular chain is prepared, and a sulfonic acid compound with a molecular weight of 96 or more and 300 or less is added to spinning stock solution a and reacted to turn some of polyurethane urea polymer A in spinning stock solution a into polyurethane urea polymer B and obtain a spinning solution;
• or
• (b) spinning stock solution a containing polyurethane urea polymer A having a molecular chain using a polymer diol, a diisocyanate, and an organic amine as starting materials, and having an amino group at both ends of the molecular chain is prepared, some of spinning stock solution a is divided, a sulfonic acid compound with a molecular weight of 96 or more and 300 is added to and reacted with one of the divided portions to prepare spinning stock solution b in which polyurethane urea polymer B has been produced, and
• a spinning solution obtained by mixing together spinning stock solution a and spinning stock solution b is dry spun.