Polyester bicomponent filament

Abstract

The invention provides an improved method for making a poly(ester) bicomponent fiber wherein at least one poly(ester) contains a styrene polymer.

What is claimed is:  
     
         1 . A process for making a side-by-side bicomponent filament comprising the steps of: 
 a) providing poly(trimethylene terephthalate);    b) providing a polyester selected from the group consisting of poly(ethylene terephthalate) and copolyesters of poly(ethylene terephthalate), in a weight ratio of about 30/70 to 70/30;    c) providing a styrene polymer having a number-average molecular weight of about 75,000 daltons to 300,000 daltons;    d) mixing the styrene polymer with at least one of the poly(trimethylene terephthalate) of step (a) and the selected polyester of step (b) to form a first melt-extrusion polymer and a second melt-extrusion polymer, respectively, wherein at least one melt-extrusion polymer contains from about 0.1 weight percent to about 5 weight percent styrene polymer;    e) melting the first melt-extrusion polymer;    f) melting the second melt-extrusion polymer;    g) spinning the first and second melt-extrusion polymers a filament;    h) quenching the filament with gas in a manner selected from the group consisting of cross-flow and co-current flow;    i) withdrawing the filament; and    j) winding up the filament.    
     
     
         2 . The process of  claim 1  further comprising, between steps h) and i) the steps of drawing the filament by at about 2.0X to 4.5X and heat-treating the filament at about 140° C. to 185° C. to form a fully-drawn filament, wherein step i) is carried out at a speed of at least about 4100 m/min when the quench gas is supplied as cross-flow and at least about 6200 m/min when the quench gas is supplied as co-current flow, and the wound-up filament has an after heat-set crimp contraction value of at least about 30%.  
     
     
         3 . The process of  claim 2  wherein winding step j) is carried out at about 5300 to 5800 m/min when the quench gas is cross-flow and at about 8200 to 9000 m/min when the quench gas is co-current flow.  
     
     
         4 . The process of  claim 1  wherein withdrawing step i) is carried out at a speed of about 3000 to 4500 m/min when the quench gas is cross-flow and at a speed of about 3600 to 5000 m/min when the quench gas is co-current flow, and the filament in step i) is partially oriented.  
     
     
         5 . The process of  claim 4  further comprising, after step i), the steps of drawing the filament by about 2.0X to 4.5X and heat-treating the filament at about 140° C. to 185° C.  
     
     
         6 . The process of  claim 4  wherein the withdrawing speed is about 3500 to 4500 m/min when the quench gas is cross-flow and the withdrawing speed is about 4100 to 5000 m/min when the quench gas is co-current flow.  
     
     
         7 . The process of  claim 1  wherein quenching step h) is carried out with cross-flow quench gas, withdrawing step i) is carried out at a speed of about 6000 to 8000 m/min, and a fully oriented filament is wound up in step j) at about 6000 to 8000 m/min.  
     
     
         8 . The process of  claim 7  wherein the filament has an after-heat-set crimp contraction value of at least about 30%.  
     
     
         9 . The process of  claim 1  wherein the styrene polymer is present at about 0.5 to about 4 weight percent based on the mixture.  
     
     
         10 . The process of  claim 1  wherein the styrene polymer is polystyrene having a number-average molecular weight of about 100,000 to 200,000 daltons.