Shaped capillary production of homofilament crimp fibers

Abstract

Robust homofilament fibers are meltspun from specially shaped capillaries to induce differential shear to induce crimping. Crimping may further be aided by directed quenching and drawing of the fibers.

We claim:  
     
         1 . A spinneret design for producing a crimped homofilament fiber comprising: 
 a) an extruder for forcing a liquid polymer through a spinneret capillary;    b) the capillary having one of a substantially circular or elliptical cross sectional shape with a cut out of less than 25 percent of a surface area of the cross sectional shape; and    c) the cut out area being contiguous with an outer boundary of the cross sectional shape and forming at least one point on an outer surface of the fiber.    
     
     
         2 . The spinneret design of  claim 1  wherein the capillary has a length to width ratio of between about 6:1 to about 10:1.  
     
     
         3 . The spinneret design of  claim 1  wherein the capillary is connected to a polymer supply passage by a counterbore.  
     
     
         4 . A nonwoven web comprising: 
 a plurality of crimped fibers,    each fiber having one of a substantially circular or elliptical cross sectional shape with a cut out of less than 25 percent of a surface area of the cross sectional shape; and    the cut out area being contiguous with the outer boundary of the cross sectional shape and forming at least one point on an outer surface of the fiber.    
     
     
         5 . The nonwoven web of  claim 4  wherein the fibers are polypropylene.  
     
     
         6 . A process for making crimped fibers, comprising the step of: 
 extruding each of the fibers through a capillary having one of a substantially circular or elliptical cross sectional shape with a cut out of less than 25 percent of a surface area of the cross sectional shape; and    the cut out area being contiguous with the outer boundary of the cross sectional shape and forming at least one point on an outer surface of the fiber.    
     
     
         7 . The process for making crimped fibers according to  claim 6 , further comprising the step of: directing quenching fluid primarily at the cutout area of the fiber.  
     
     
         8 . The process for making crimped fibers according to  claim 7 , further comprising the step of: drawing the fibers while in their plastic state to produce fibers with a substantially round cross section.  
     
     
         9 . The process for making crimped fibers according to  claim 6 , further comprising the step of: drawing the fibers while in their plastic state to produce fibers with a substantially round cross section.  
     
     
         10 . The process for making crimped fibers of  claim 6  wherein the fibers are polypropylene.  
     
     
         11 . The process for making crimped fibers of  claim 8  wherein the fibers are polypropylene.