Poly(trimethylene terephthalate) bicomponent fiber process

1. A process for preparing a poly(trimethylene terephthalate) bicomponent fiber comprising:

(a) providing two poly(trimethylene terephthalate) melts,

(b) altering the intrinsic viscosity of at least one of said polymers such that after alteration, said polymers have intrinsic viscosities that differ by at least about 0.03 dL/g;

(c) providing the two poly(trimethylene terephthalate) melts to a spinnerette, and

(d) spinning bicomponent fiber from the poly(trimethylene terephthalate) melts,

wherein the two poly(trimethylene terephthalate) polymer melts are prepared by

(i) providing two different remelt systems; and

(ii) remelting a poly(trimethylene terephthalate) in each of the remelt systems, wherein at least one of the remelt systems is operated so as to provide the poly(trimethylene terephthalate) melts having intrinsic viscosities that differ by at least about 0.03 dL/g.

2. The process of claim 1 , wherein at least one of the following is used to alter the intrinsic viscosity of a poly(trimethylene terephthalate):

(a) poly(trimethylene terephthalate) water content;

(b) melt temperature; and

(c) melt residence time.

3. The process of claim 1 , wherein in (b) the intrinsic viscosity of at least one polymer is decreased.

4. The process of claim 1 , wherein in (b) the intrinsic viscosity of at least one polymer is increased.

5. The process of claim 1 wherein the intrinsic viscosities of the poly(trimethylene terephthalate) melts differ by at least about 0.03 to about 0.5 dL/g.

6. The process of claim 5 , wherein the intrinsic viscosities of the poly(trimethylene terephthalate) melts differ by at least about 0.03 to about 0.3 dL/g.

7. The process of claim 1 wherein the intrinsic viscosity of the poly(trimethylene terephthalate) in one of the remelt systems is lowered by at least about 0.03 dL/g.

8. The process of claim 1 wherein the intrinsic viscosity of the poly(trimethylene terephthalate) in one of the remelt systems is lowered by at least about 0.03 to about 0.5 dL/g.

9. The process of claim 8 , wherein the intrinsic viscosities of the poly(trimethylene terephthalate) melts differ by at least about 0.03 to about 0.3 dL/g.

10. The process of claim 1 , wherein the fibers are side-by-side or eccentric sheath-core fibers.

11. The process of claim 10 , wherein the side-by-side or eccentric sheath-core bicomponent fibers are in the form of a partially oriented multifilament yarn.

12. The process of claim 1 , wherein the fibers are sheath-core fibers.

13. The process of claim 1 , wherein the fibers are island-in-the-sea or pie-shaped.

14. The process of claim 1 , wherein the two polymer melts in (a) are the same.

15. The process of claim 1 , wherein the two polymer melts in (a) are different.

16. The process of claim 1 , wherein the poly(trimethylene terephthalate) bicomponent fiber comprises a copolymer with up to 30 mole % comonomer.

17. The process of claim 16 , wherein the poly(trimethylene terephthalate) bicomponent fiber comprises a copolymer with about 0.5 to about 15 mole % comonomer.

18. The process of claim 17 , wherein the copolymer comprises copolyester made using 3 or more reactants, each having two ester forming groups.

19. The process of claim 16 , wherein the poly(trimethylene terephthalate) comprises a secondary amine, secondary amine salt, or tertiary amine in an amount effective to promote acid dyeability of the bicomponent fiber.

20. The process of claim 1 , wherein the poly(trimethylene terephthalate) is blended with up to 30 mole % of other polymers.

21. The process of claim 1 , wherein the poly(trimethylene terephthalate) comprises an acid-dyeable polyester composition.

22. The process of claim 1 , wherein each component comprises at least about 95% of poly(trimethylene terephthalate), by weight, of the polymer in the component.

23. The process of claim 1 , wherein each of the poly(trimethylene terephthalate)s contains at least 95 mole % trimethylene terephthalate repeat units.

24. The process of claim 1 , wherein the remelt temperature is in the range of from about 235° C. to about 295° C.

25. The process of claim 24 , wherein the remelt temperature is in the range of from about 235° C. to about 250° C.