Propylene polymer fibers and yarns

#This invention relates to propylene polymer fibers and yarns, articles of manufacture comprising the same, and manufacture thereof.

#Polypropylene fibers and yarns are well-known and are widely used in textile and other applications owing to a desirable combination of features. These include low cost, ease of processing, strength, chemical inertness and hydrophobicity. Examples of textile applications for the fibers and yarns include backing fabrics and pile or face yarns for carpets; upholstery fabrics; geotextile fabrics; walkover fabrics; automotive fabrics, such as carpets, trunk liners and kick panels; diaper cover stock; and apparel fabrics.

#There is, and has long been, a need for improved polypropylene fibers and yarns for use in applications in which the fibers, yarns or textile products containing them are subjected to bending, creasing, wrinkling, compression and the like. Examples include apparel fabrics, fiberfill, carpets, upholstery fabrics and automotive fabrics. Poor resilience of fibers and yarns used in such applications can result in limited recovery from forces to which fibers and yarns are subjected in use and, in turn, poor aesthetics and wear. These may limit or even preclude utility for certain end uses.

#Various aspects of the invention are described by reference to the accompanying Drawing, the six figures of which are as follows:

#FIG. 1, a longitudinal cross-sectional view of a fiber composed of oriented crystalline polymer showing a conceptual representation of the fiber's crystalline microstructure;

#FIG. 2, a transverse cross-sectional view of the fiber depicted in FIG. 1, again showing conceptualized crystalline microstructure;

#In greater detail, this invention provides fibers comprising propylene polymer characterized by a unique crystalline microstructure as determined by the small angle X-ray diffraction method utilized herein. The invention also provides yarns comprising such propylene polymer fibers and, in a more specific embodiment, BCF yarns comprising such fibers and characterized by improved resilience. Such BCF yarns are especially useful as carpet face yarns for both commercial and residential carpets. Indeed, in controlled carpet walkout tests, carpets tufted with such yarns have exhibited resistance to clumping and matting considerably better than carpets tufted with conventional propylene polymer yarns and only slightly less apparent wear than those tufted with nylon yarns.

#The invention also provides a method for heat treating textile products comprising fibers of crystaline propylene polymer comprising heating such products under particular conditions, including at least one temperature that is less than but within about 20° C. of the melting point of the propylene polymer. In one embodiment, heating is applied to textile products comprising oriented propylene polymer fibers that have been conditioned by heating at at least one lower temperature in the range of about 20 to about 40° C. below the propylene polymer melting point with the fibers in a substantially relaxed state. In another embodiment, heating within about 20° C. of the propylene polymer melting point is applied to fibers characterized by a particular crystalline microstructure as determined by the small angle X-ray diffraction method utilized herein. When applied to yarns predominantly comprising fibers of crystalline propylene polymer obtained by melt spinning, drawing and texturing under particular conditions, such heating can yield yarns having improved resilience as measured by the Plug Crush Recovery Test.

#While the invention is described largely by reference to carpets and carpet face yarns, it will be understood that neither the invention nor utility thereof is to be considered so limited. Indeed, the invented fibers and yarns are useful not only in the wide range of textile products in which propylene polymer fibers and yarns have heretofore been used, but also, due to their improved properties, in other applications and especially those calling for greater recovery from compression, bending, creasing, wrinkling and the like. Examples of other textile products in which the invented fibers and yarns are useful include fiberfill, such as for cushions, pillows, stuffed toys, sleeping bags, quilted bedspreads, comforters and the like; highloft nonwoven fabrics, such as needlepunched batts, insulation and filtration fabrics; apparel yarns and woven and knit apparel fabrics, such as for socks, thermal underwear and outerwear; automotive fabrics, such as automotive carpet yarns, trunk liners and kick panels; upholstery fabrics, such as velvets and velours; geotextile fabrics; industrial fabrics; and technical fabrics.