Process for preparing bicomponent fibers having latent crimp

1. A process for preparing polyester bicomponent fibers the process comprising combining at least two crystallizable polyester polymers, determining a maximum shrinkage spinning rate of said polymers, melting said polyester polymers, causing said molten polymers to flow through a spinneret having one or more apertures, said spinneret being suitable for preparing bicomponent fibers, thereby spinning at least one strand of 0.5 to 6 denier fiber said strand being spun at a linear rate of ±10% of the maximum shrinkage spinning rate, said two crystallizable polyester polymers differing from one another in crystallization rate under the spinning conditions.

2. The process of claim 1 wherein the at least two crystallizable polyester polymers are selected from the group consisting of polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate.

3. The process of claim 2 wherein one crystallizable polyester polymer is polyethylene terephthalate, and another crystallizable polyester polymer is polypropylene terephthalate.

4. The process of claim 2 or claim 3 wherein the weight ratio of the two polyesters in the bicomponent fibers made by the process of the invention is in the range of 30/70-70/30.

5. The process of claim 2 or claim 3 wherein the weight ratio of the two polyesters in the bicomponent fibers made by the process of the invention is in the range of 40/60-60/40.

6. The process of claim 2 or claim 3 wherein the weight ratio of the two polyesters in the bicomponent fibers made by the process of the invention is in the range of 45/55-55/45.

7. The process of claims 1 , 2 , or 3 wherein the at least two crystallizable polyester polymers differ in intrinsic viscosity.

8. The process of claim 1 or claim 3 further comprising the step of heating the thus prepared polyester bicomponent to a temperature above the glass-transition temperature of the less crystallized component to effect shrinkage and crimping of said fiber.