Bi-Component Fibers and Nonwoven Materials Produced Therefrom

Abstract

A method can include (a) extruding a bi-component fiber comprising: a first component comprising a first polypropylene homopolymer; and a second component comprising a blend that comprises a propylene-based elastomer and a second polypropylene homopolymer, wherein the blend has a melt flow rate that is at least 20% greater than or at least 20% less than a melt flow rate of the first polypropylene homopolymer; (b) cooling the bi-component fiber; and (c) thermally and/or mechanically activating the bi-component fiber to cause the bi-component fiber to curl.

1 . A method comprising:
 extruding a bi-component fiber comprising:   a first component comprising a first polypropylene homopolymer; and   a second component comprising a blend that comprises a propylene-based elastomer and a second polypropylene homopolymer, wherein the blend has a melt flow rate that is at least 20% greater than or at least 20% less than a melt flow rate of the first polypropylene homopolymer;   cooling the bi-component fiber; and   activating the bi-component fiber to cause the bi-component fiber to curl wherein the step of activating is performed thermally, mechanically, or through a combination of thermal and mechanical action.   
     
     
         2 . The method of  claim 1 , wherein a weight ratio of the propylene-based elastomer and the second polypropylene homopolymer in the blend is 10:90 to 90:10. 
     
     
         3 . The method of  claim 1 , wherein a weight ratio of the propylene-based elastomer and the second polypropylene homopolymer in the blend is 40:60 to 90:10. 
     
     
         4 . The method of  claim 1 , wherein the bi-component fiber is thermally activated by exposing the bi-component fiber to 50° C. to 150° C. for 1 second to 5 minutes. 
     
     
         5 . The method of  claim 1 , wherein the bi-component fiber is thermally activated by exposing the bi-component fiber to 90° C. to 115° C. for 5 seconds to 15 seconds. 
     
     
         6 . The method of  claim 1 , wherein the bi-component fiber is mechanically activated by exposing the bi-component fiber to a force of 0.01 N to 10 N. 
     
     
         7 . The method of  claim 1 , wherein the bi-component fiber is mechanically activated by exposing the bi-component fiber to a force of 0.1 N to 5 N. 
     
     
         8 . The method of  claim 1 , wherein the bi-component fiber after cooling is substantially straight and after activating has a shrinkage of a least 25%. 
     
     
         9 . The method of  claim 1 , wherein the bi-component fiber after cooling is substantially straight and after activating has a shrinkage of a least 45%. 
     
     
         10 . The method of  claim 1 , wherein a weight ratio of the first component and the second component in the bi-component fiber is 10:90 to 90:10. 
     
     
         11 . The method of  claim 1 , wherein a weight ratio of the first component and the second component in the bi-component fiber is 40:60 to 80:20. 
     
     
         12 . The method of  claim 1 , wherein a compositional cross-section is side-by-side, segmented, sheath/core, or island-in-the-sea. 
     
     
         13 . The method of  claim 1  further comprising producing a nonwoven article with the bi-component fiber. 
     
     
         14 . The method of  claim 1  further comprising producing a laminated article with the bi-component fiber. 
     
     
         15 . A bi-component fiber comprising:
 a first component comprising a first polypropylene homopolymer; and   a second component comprising a blend that comprises a propylene-based elastomer and a second polypropylene homopolymer, wherein the blend has a melt flow rate that is at least 20% greater than or at least 20% less than a melt flow rate of the first polypropylene homopolymer.   
     
     
         16 . The bi-component fiber of  claim 15 , wherein a weight ratio of the propylene-based elastomer and the second polypropylene homopolymer in the blend is 10:90 to 90:10. 
     
     
         17 . The bi-component fiber of  claim 15 , wherein a weight ratio of the first component and the second component in the bi-component fiber is 10:90 to 90:10. 
     
     
         18 . The bi-component fiber of  claim 15 , wherein a compositional cross-section is side-by-side, segmented, sheath/core, or island-in-the-sea. 
     
     
         19 . A nonwoven article comprising the bi-component fiber of  claim 15 . 
     
     
         20 . A laminated article comprising the bi-component fiber of  claim 15 .