Process for preparing bicomponent fibers comprising poly(trimethylene terephthalate)

Abstract

Disclosed is a process for preparing crimpable bicomponent fibers from two poly(trimethylene terephthalate) starting materials that differ from one another in intrinsic viscosity. One starting material is characterized by an intrinsic viscosity ≦0.7 dL/g. The relatively low intrinsic viscosity allows the employment of a low melt temperature, with concomitant reduction in the evolution of acrolein, and without significant degradation in the properties or processibility of the bicomponent fiber.

What is claimed is: 
     
         1 . A process comprising melting a first poly(trimethylene terephthalate) starting material characterized by an intrinsic viscosity of ≦0.7 dL/g to form a first melt stream characterized by a melt temperature less than 250° C., said first melt stream being characterized by an intrinsic viscosity that is no more than 0.03 dL/g lower than the intrinsic viscosity of said first starting material;
 melting a second poly(trimethylene terephthalate) starting material characterized by an intrinsic viscosity >0.7 dL/g to form a second melt stream, with the proviso that the difference between the intrinsic viscosity of said first and second melt streams is >0.1 dL/g; providing said first and second melt streams to a spinneret therein contacting said first melt stream with said second melt stream; 
 extruding a molten fiber from said spinneret; and, quenching said molten fiber to form a solid bicomponent fiber characterized by a first component and a second component disposed with respect to one another in a configuration suitable for the formation of crimp. 
 
     
     
         2 . The process of  claim 1  wherein the first fiber component and the second fiber component are disposed with respect to one another in the bicomponent fiber in a side by side configuration. 
     
     
         3 . The process of  claim 1  wherein the first fiber component and the second fiber component are disposed with respect to one another in the bicomponent fiber in an eccentric sheath/core configuration. 
     
     
         4 . The process of  claim 1  wherein the first starting material is characterized by an IV in the range of 0.60 to 0.68. 
     
     
         5 . The process of  claim 1  wherein the second starting material is characterized by an IV>0.8 dL/g. 
     
     
         6 . The process of  claim 5  wherein the second starting material is characterized by an IV>0.9 dL/g. 
     
     
         7 . The process of  claim 1  wherein the first melt stream is at a temperature in the range of 240 to 245° C. 
     
     
         8 . The process of  claim 1  wherein the difference between the intrinsic viscosity of the first and second melt streams is >0.2 dL/g. 
     
     
         9 . The process of  claim 1  wherein the first starting material is characterized by an intrinsic viscosity in the range of 0.60 to 0.68 dL/g, the second starting material is characterized by an intrinsic viscosity >0.8 dL/g, and the difference between the intrinsic viscosity of the first and second melt streams is >0.2 dL/g. 
     
     
         10 . The process of  claim 9  wherein the first melt stream is at a temperature in the range of 240 to 245° C. 
     
     
         11 . The process of  claim 10  wherein the the second starting material is characterized by an intrinsic viscosity >0.9 dL/g. 
     
     
         12 . The process of  claim 1  further comprising subjecting the bicomponent fiber to elevated temperature thereby developing crimp therein.