Process for the manufacture of elastic polyurethane fiber and the elastic polyurethane fiber made thereby

Disclosed is a process for the manufacture of an elastic polyurethane fiber, including mixing one component selected from among polystyrene polymers or polystyrene copolymers having a number average molecular weight of 50,000–500,000 with polyurethane having a number average molecular weight of 15,000–100,000, to prepare a polymer mixture, which is then spun. The polyurethane elastic fiber made by the method is also provided, which is greatly increased in heat set properties, with a very low rate of change of fundamental properties as the results compared with conventional elastic polyurethane fibers. Hence, the elastic polyurethane fiber can be directly applied for preparation of end products requiring superior heat set properties with no change of conventional conditions of the process.