Patent ID: 8148475

Claim:
A process for producing melt spun thermoplastic polyurethane fibers comprising: (a) melting in an extruder a TPU polymer made by the one shot process and having a shore hardness of from 65 A to 95 A and formed by the reaction of: (i) a first hydroxyl terminated polyether intermediate having a number average molecular weight of from 1500 to 4000 Daltons; (ii) a second hydroxyl terminated polyether intermediate having a number average molecular weight of from 700 to 1500 Daltons; (iii) at least one aromatic hydroxyl terminated chain extender; and (iv) at least one polyisocyanate; wherein said first hydroxyl terminated polyether intermediate is present in larger amount than said second hydroxyl terminated polyether intermediate, wherein the weight ratio of the first polyether hydroxyl terminated intermediate to the second hydroxyl terminated intermediate is from about 60:40 to about 90:10 and wherein said first hydroxyl terminated polyether intermediate has a higher number average molecular weight than said second hydroxyl terminated polyether intermediate, and wherein the weighted average number average molecular weight of said first and said second hydroxyl terminated intermediate is at least 1200 Daltons; (b) adding to said melted thermoplastic polyurethane polymer at least one crosslinking agent made from reacting (i) a hydroxyl terminated polyol selected from the group consisting of polyether, polyester, polycaprolactone, polycarbonate, and mixtures thereof, and (ii) at least one polyisocyanate, wherein said crosslinking agent is added to said melted thermoplastic polyurethane polymer by the method selected from the group consisting of adding said crosslinking agent in said extruder and adding said crosslinking agent after said polymer exits said extruder; (c) feeding said melted thermoplastic polyurethane polymer mixed with said crosslinking agent to at least one spinneret; (d) passing said melted polymer containing said crosslinking agent through said spinneret to produce melt spun fibers; (e) cooling said fibers; and (f) winding said fibers onto bobbins.