Propylene-based copolymers, a method of making the fibers and articles made from the fibers

Abstract

Fibers that exhibit good elasticity or extensibility and tenacity, and low modulus are prepared from propylene-based copolymers. The propylene-based copolymers comprise at least about 50 weight percent (wt %) of units derived from propylene and at least about 8 wt % of units derived from one or more comonomers other than propylene, e.g., ethylene. Particularly preferred propylene copolymers are characterized as having <SUP>13</SUP>C NMR peaks corresponding to a regio-error at about 14.6 and about 15.7 ppm, the peaks of about equal intensity. In one aspect of the invention, fibers are subjected to stress-induced crystallization by subjecting the fiber to tensile elongation during draw.

1 . A fiber comprising more than 80 weight percent of a reactor grade propylene copolymer, the copolymer having a MWD of less than 3.5, said copolymer comprising at least about 50 weight percent of units derived from propylene and at least about 5 weight percent of units derived from a comonomer other than propylene.  
     
     
         2 . The fiber of  claim 1  wherein the fiber is characterized as having a crystallinity index as measured by X-ray diffraction of less than about 30%.  
     
     
         3 . A fiber comprising a propylene copolymer, the copolymer comprising at least about 50 weight percent of units derived from propylene and at least about 5 weight percent of units derived from a comonomer other than propylene, the fiber characterized as having a crystallinity index as measured by X-ray diffraction of less than about 30%.  
     
     
         4 . The fiber of any of claims  1 - 3  in which the copolymer comprises at least about 84 weight percent of units derived from propylene, and the comonomer other than propylene is ethylene.  
     
     
         5 . The fiber of any of claims  1 - 4  in which the crystallinity index of the fiber is less than 27%.  
     
     
         6 . The fiber of any of claims  1 - 4  in which the crystallinity index of the fiber is less than about 20%.  
     
     
         7 . The fiber of any of claims  1 - 6  in which the copolymer is further characterized as having  13 C NMR peaks corresponding to a regio-error at about 14.6 and about 15.7 ppm, the peaks of about equal intensity.  
     
     
         8 . The fiber of any of claims  1 - 7  in which the copolymer is further characterized as having a DSC curve with a T me  that remains essentially the same and a T max  that decreases as the amount of the comonomer in the copolymer is increased.  
     
     
         9 . The fiber of any of claims  1 - 6  in which the copolymer is further characterized as having an X-ray diffraction pattern exhibiting more gamma-form crystals than a propylene copolymer comparable in weight average molecular weight except that it is prepared with a Ziegler-Natta catalyst.  
     
     
         10 . The fiber of any of claims  1 - 9  wherein the copolymer comprises at least about 98 weight percent of the fiber.  
     
     
         11 . The fiber of any of the preceding claims further comprising a nucleating agent.  
     
     
         12 . The fiber of any of the preceding claims in the form of a monofilament.  
     
     
         13 . The fiber of any of the preceding claims in the form of a bicomponent fiber.  
     
     
         14 . The fiber of  claim 13  in which the fiber has a sheath/core configuration.  
     
     
         15 . The fiber of  claim 14  in which the copolymer comprises the sheath.  
     
     
         16 . The fiber of  claim 14  in which the copolymer comprises the core.  
     
     
         17 - 42 . (canceled)