Biodegradable fibers exhibiting storage-stable tenacity

Abstract

The invention provides a drawn and/or crimped fiber comprising a biodegradable polymer, such as polylactic acid, wherein the drawn and/or crimped fiber exhibits a storage-stable tenacity that does not decrease from an initial tenacity upon manufacture by more than about 10% after storage for 120 days in ambient conditions. The polymer composition used to form the fiber may comprise a softening agent. The fiber can be a drawn and crimped bicomponent fiber that is helically self-crimped and which comprises a first biodegradable polymer component and a second biodegradable polymer component, wherein the first polymer component and the second polymer component exhibit different polymer morphology such that each polymer component will undergo a different extent of longitudinal shrinkage upon application of heat. The outer surface of the fiber may carry a water-repellant coating. The invention also provides a method of forming a drawn and/or crimped fiber exhibiting storage-stable tenacity.

1 . A fiber that has been drawn or crimped or both, comprising a biodegradable polymer selected from the group consisting of polyvinyl alcohol, aliphatic polyesters, aliphatic polyurethanes, cis-polyisoprene, cis-polybutadiene, polyhydroxy alkanoates, and copolymers and blends thereof, the fiber exhibiting a storage-stable tenacity that does not decrease from an initial tenacity upon manufacture by more than about 10 percent after storage for 120 days in ambient conditions, wherein the initial tenacity is at least about 1.5 g/denier.  
   
   
       2 . The fiber of  claim 1 , wherein the internal stresses of the polymer are less than about 80% of the craze stress of the polymer.  
   
   
       3 . The fiber of  claim 2 , wherein the internal stresses of the polymer are less than about 70% of the craze stress of the polymer.  
   
   
       4 . The fiber of  claim 1 , wherein the biodegradable polymer is an aliphatic polyester.  
   
   
       5 . The fiber of  claim 4 , wherein the aliphatic polyester is selected from the group consisting of polyglycolic acid (PGA), polylactic acid (PLA), polyhydroxy butyrate (PHB), polyhydroxy valerate (PHV), polycaprolactone (PCL), and copolymers thereof.  
   
   
       6 . The fiber of  claim 4 , wherein the polyester is polylactic acid (PLA).  
   
   
       7 . The fiber of  claim 1 , wherein the fiber has an initial tenacity upon manufacture of at least about 3.0 g/denier.  
   
   
       8 . The fiber of  claim 1 , wherein the fiber has an initial tenacity upon manufacture of about 1.5 to about 15 g/denier.  
   
   
       9 . The fiber of  claim 1 , wherein the fiber is a staple fiber or continuous filament.  
   
   
       10 . The fiber of  claim 1 , wherein the tenacity does not decrease by more than about 5 percent.  
   
   
       11 . The fiber of  claim 1 , wherein the tenacity does not decrease by more than about 10 percent after 360 days of storage.  
   
   
       12 . The fiber of  claim 1 , wherein the fiber is a bicomponent self-crimping fiber.  
   
   
       13 . The fiber of  claim 12 , wherein the fiber comprises a first biodegradable polymer component and a second biodegradable polymer component, wherein the first polymer component and the second polymer component exhibit different polymer morphology such that each polymer component will undergo a different extent of longitudinal shrinkage upon application of heat.  
   
   
       14 . The fiber of  claim 13 , wherein said first polymer component and said second polymer component comprise the same biodegradable polymer, and wherein the difference in molecular weight between the first and second polymer components is at least about 15 percent of the higher molecular weight.  
   
   
       15 . The fiber of  claim 13 , wherein the heat history of said first polymer component is different from the heat history of said second polymer component.  
   
   
       16 . The fiber of  claim 13 , wherein said first polymer component and said second polymer component comprise polylactic acid (PLA).  
   
   
       17 . The fiber of  claim 16 , wherein said first polymer component and said second polymer component each comprise a mixture of L and D-isomers of poly(lactic acid), and wherein said first and second polymer components differ in the relative amounts of L and D-isomer.  
   
   
       18 . The fiber of  claim 1 , wherein the outer surface of the fiber carries a water-repellent coating.  
   
   
       19 . The fiber of  claim 1 , wherein the polymer is poly(lactic acid) having a weight average molecular weight of about 10,000 to about 100,000 Da.  
   
   
       20 . The fiber of  claim 19 , wherein the weight average molecular weight of the poly(lactic acid) is about 20,000 to about 50,000 Da.  
   
   
       21 . The fiber of  claim 1 , wherein the fiber comprises a softening agent.  
   
   
       22 . The fiber of  claim 21 , wherein the softening agent comprises an aromatic-aliphatic copolyester comprising butanediol, adipic acid and terephthalic acid monomers.  
   
   
       23 . A drawn and crimped bicomponent fiber, comprising a biodegradable polymer selected from the group consisting of polyvinyl alcohol, aliphatic polyesters, aliphatic polyurethanes, cis-polyisoprene, cis-polybutadiene, polyhydroxy alkanoates, and copolymers and blends thereof, the fiber exhibiting a storage-stable tenacity that does not decrease from an initial tenacity upon manufacture by more than about 10 percent after storage for 120 days in ambient conditions, wherein the initial tenacity is at least about 1.5 g/denier, and wherein the bicomponent fiber is helically self-crimped and comprises a first biodegradable polymer component and a second biodegradable polymer component, wherein the first polymer component and the second polymer component exhibit different polymer morphology such that each polymer component will undergo a different extent of longitudinal shrinkage upon application of heat.