Method for making over-indexed thermoplastic polyurethane elastomer precursor and thermoplastic polyurethane elastomer made from the precursor

1. A method for making a dried over-indexed thermoplastic polyurethane elastomer precursor having unreacted isocyanate moieties, the method comprising:

combining reactants and reacting them to form an over-indexed thermoplastic polyurethane elastomer precursor,

cooling the over-indexed thermoplastic polyurethane elastomer precursor in water to form cooled precursor,

pelletizing the cooled precursor to form cooled precursor pellets,

drying the cooled precursor pellets to a moisture concentration less than about 800 ppm to form dried over-indexed thermoplastic polyurethane elastomer precursor, and

packaging the dried over-indexed thermoplastic polyurethane elastomer precursor in moisture-resistant packaging under conditions that essentially maintain the moisture content of the dried over-indexed thermoplastic polyurethane elastomer precursor at or below about 800 ppm.

2. The method of claim 1 , wherein the drying further comprises

partially drying the cooled precursor pellets to a moisture concentration less than about 3,000 ppm by heating to form partially dried precursor pellets and

further drying the partially dried precursor pellets to a moisture concentration less than about 800 ppm in an inert gas flow to form dried over-indexed thermoplastic polyurethane elastomer precursor.

3. The method of claim 1 , wherein the cooled precursor pellets are partially dried to a moisture concentration less than about 1,000 ppm.

4. The method of claim 2 , wherein the cooled precursor pellets are partially dried to a moisture concentration less than about 1,000 ppm.

5. The method of claim 1 , wherein the dried over-indexed thermoplastic polyurethane elastomer precursor has a moisture content of 500 ppm.

6. The method of claim 5 , wherein the dried over-indexed thermoplastic polyurethane elastomer precursor has a moisture content of 300 ppm.

7. The method of claim 2 , wherein the dried over-indexed thermoplastic polyurethane elastomer precursor has a moisture content of 300 ppm.

8. The method of claim 2 , wherein the partially dried precursor pellets are further dried at a temperature between about 70° C. and about 90° C. with inert gas flow.

9. The method of claim 5 , wherein the partially dried precursor pellets are further dried at a temperature between about 70° C. and about 90° C. with inert gas flow.

10. The method of claim 1 , wherein the over-indexed thermoplastic polyurethane elastomer precursor comprises a cross-linking agent.

11. The method of claim 1 , wherein the dried over-indexed thermoplastic polyurethane elastomer precursor has an NCO index of between about 1.05 and about 1.35.

12. The method of claim 11 , wherein the dried over-indexed thermoplastic polyurethane elastomer precursor has an NCO index of between about 1.06 and about 1.18.

13. A method for making over-indexed thermoplastic polyurethane elastomer, said method comprising:

making an over-indexed thermoplastic polyurethane elastomer precursor having unreacted isocyanate moieties by combining reactants and reacting them to form an over-indexed thermoplastic polyurethane elastomer precursor,

cooling the over-indexed thermoplastic polyurethane elastomer precursor in water to form cooled precursor,

pelletizing the cooled precursor to form cooled precursor pellets,

drying the cooled precursor pellets to a moisture concentration less than about 800 ppm to form dried over-indexed thermoplastic polyurethane elastomer precursor,

packaging the dried over-indexed thermoplastic polyurethane elastomer precursor in moisture-resistant packaging under conditions that essentially maintain the moisture content of the dried over-indexed thermoplastic polyurethane elastomer precursor at or below about 800 ppm; and

removing the dried over-indexed thermoplastic polyurethane elastomer precursor from the package and curing the dried over-indexed thermoplastic polyurethane elastomer precursor by contact with water.

14. The method of claim 13 , wherein the drying further comprises

partially drying the cooled precursor pellets to a moisture concentration less than about 3,000 ppm by heating to form partially dried precursor pellets and

further drying the partially dried precursor pellets to a moisture concentration less than about 800 ppm in an inert gas flow to form dried over-indexed thermoplastic polyurethane elastomer precursor.

15. The method of claim 13 , wherein the cooled precursor pellets are partially dried to a moisture concentration less than about 1,000 ppm.

16. The method of claim 14 , wherein the cooled precursor pellets are partially dried to a moisture concentration less than about 800 ppm.

17. The method of claim 13 , wherein the dried over-indexed thermoplastic polyurethane elastomer precursor has a moisture content of 500 ppm.

18. The method of claim 17 , wherein the dried over-indexed thermoplastic polyurethane elastomer precursor has a moisture content of 300 ppm.

19. The method of claim 14 , wherein the dried over-indexed thermoplastic polyurethane elastomer precursor has a moisture content of 300 ppm.

20. The method of claim 15 , wherein the packaged pelletized precursor material has a moisture content of 300 ppm.

21. The method of claim 15 , wherein the partially dried precursor pellets are further dried at a temperature between about 70° C. and about 90° C. with inert gas flow.

22. The method of claim 14 , wherein the partially dried precursor pellets are further dried at a temperature between about 70° C. and about 90° C. with inert gas flow.

23. The method of claim 13 , wherein the over-indexed thermoplastic polyurethane elastomer precursor comprises a cross-linking agent.

24. The method of claim 13 , wherein the dried over-indexed thermoplastic polyurethane elastomer precursor has an NCO index of between about 1.05 and about 1.35.

25. The method of claim 24 , wherein the dried over-indexed thermoplastic polyurethane elastomer precursor has an NCO index of between about 1.06 and about 1.18.

26. A method for making an article comprising over-indexed thermoplastic polyurethane elastomer, said method comprising:

making an over-indexed thermoplastic polyurethane elastomer precursor having unreacted isocyanate moieties by combining reactants and reacting them to form an over-indexed thermoplastic polyurethane elastomer precursor,

cooling precursor in water and pelletizing cooled precursor to form precursor pellets,

drying the precursor pellets to a moisture concentration less than about 800 ppm to form dried precursor pellets,

processing the dried precursor pellets to form an article precursor, and curing the article precursor by contact with water to form the article.

27. The method of claim 26 , wherein the cooled, pelletized precursor is dried to a moisture concentration less than about 500 ppm.

28. The method of claim 26 , further comprising

packaging the dried precursor pellets in moisture-resistant packaging under conditions that essentially maintain the moisture content of the dried precursor pellets at or below about 800 ppm, and

removing the dried precursor pellets from the package before processing the dried precursor pellets to form an article precursor.

29. The method of claim 26 , wherein the packaged pelletized precursor material has a moisture content of 500 ppm.

30. The method of claim 26 , wherein the dried precursor pellets have an NCO index of between about 1.05 and about 1.35.

31. The method of claim 30 , wherein the dried precursor pellets have an NCO index of between about 1.06 and about 1.18.