Fibers comprising an aliphatic polyester blend, and yarns, tows, and fabrics formed therefrom

Abstract

The present disclosure provides thermoplastic fibers that comprise homogeneous blends of polylactic acid (PLA) polymers having different degrees of isomeric purity. The fibers exhibit reduced shrinkage and can be formed with increased productivity, specifically in relation to utilizing increased draw ratios. A homogeneous blend can comprise a first PLA polymer and a second PLA polymer, wherein the first PLA polymer has an isomeric purity for the D-isomer or the L-isomer of at least about 99% and the second PLA polymer has an isomeric purity for the D-isomer or the L-isomer of no greater than about 98.5%. The disclosure further encompasses yarns and fabrics formed from the fibers and compositions formed from the yams or fabrics, as well as methods of preparing PLA materials.

1 . A fiber comprising a homogeneous blend of:
 a first polylactic acid (PLA) polymer and a second polylactic acid (PLA) polymer, wherein the first PLA polymer has an isomeric purity for the D-isomer or the L-isomer of at least about 99%, and   a second PLA polymer has an isomeric purity for the D-isomer or the L-isomer of no greater than about 98.5%; or of about 40% to about 98.5%; or of about 60% to about 98.5%; or of about 98% to about 98.5%, and   optionally where the weight ratio of the first PLA polymer to the second PLA polymer in the homogeneous blend is about 50:50 to about 99:1, or about 50:50 to about 75:25,   optionally wherein the fiber is a multicomponent fiber,   optionally wherein the fiber comprises about 50% or greater by weight of the homogeneous blend, and   optionally wherein the fiber is a continuous filament, a staple fiber, a nanofiber, or a nanofilament.   
     
     
         3 . The fiber of  claim 1 , wherein the first PLA polymer has an isomeric purity for the D-isomer or the L-isomer of at least about 99%, the second PLA polymer has an isomeric purity for the D-isomer or the L-isomer of about about 98% to about 98.5%, and the weight ratio of the first PLA polymer to the second PLA polymer in the homogeneous blend is about 50:50 to about 75:25. 
     
     
         3 . The fiber of  claim 1 , wherein a fiber exhibits a shrinkage of less than about 20%, or up to about 17%, or up to about 13%, or up to about 10%, at a temperature of about 110° C. to about 130° C., or about 130° C. after the fiber has been heat-set at a temperature of about 90° C. A multicomponent fiber comprising:
 a first component in the form of a polylactic acid (PLA) homopolymer having an isomeric purity for the D-isomer or the L-isomer of at least about 99%, or L-isomer or D-isomer pure, wherein the PLA melts at a first temperature; and 
 a second component disposed on at least part of an exterior surface of the multicomponent fiber, wherein the second component has an isomeric purity for the D-isomer or the L-isomer of no greater than about 98.5%, optionally wherein the second component comprises a component that melts at a second temperature; 
 wherein when present the second temperature is less than the first temperature, and 
 optionally wherein the multicomponent fiber is in the form of a core/sheath arrangement, wherein the first component is a core component and the second component is a sheath component. 
 
     
     
         5 . The multicomponent fiber of claim  4 , wherein the second component is in the form of a homopolymer. 
     
     
         6 . The multicomponent fiber of claim  4 , wherein the second component is in the form of a blend. 
     
     
         7 . The multicomponent fiber of  claim 6 , wherein the blend is a homogeneous blend of a first polylactic acid (PLA) polymer and a second polylactic acid (PLM polymer, wherein the first PLA polymer has an isomeric purity for the D-isomer or the L-isomer of at least about 99% and the second PLA polymer has an isomeric purity for the D-isomer or the L-isomer of no greater than about 98.5%. 
     
     
         8 . A bundle of filaments comprising a fiber according to  claim 1 , wherein the bundle is in the form of a yarn or a tow, and
 optionally wherein a portion of the filaments are formed of fibers comprising the homogeneous blend, and wherein a portion of the filaments are formed of amorphous PLA.   
     
     
         9 . A fabric comprising a fiber according to  claim 1  or a multicomponent fiber according to claim  4 , and
 optionally wherein the fabric is a nonwoven fabric, a woven fabric, or a knit fabric. 
 
     
     
         10 . A composition formed from a fabric according to  claim 9 . 
     
     
         11 . A yarn or tow comprising a plurality of filaments comprising polylactic acid (PLA) polymer, wherein a first set of the filaments comprise semi-crystalline PLA having an L-isomer content of at least about 99%, and wherein a second set of the filaments comprise amorphous PLA having a D-isomer content of about 5% or greater. 
     
     
         12 . A filtration device comprising a fiber according to  claim 1 , a multicomponent fiber according to claim  4 , or the yarn or tow according to  claim 11 . 
     
     
         13 . The filtration device according to  claim 12  wherein the filtration device is a cigarette fitter. 
     
     
         14 . A cigarette comprising the filtration device according to  claim 13 . 
     
     
         15 . A method of preparing a low shrinkage, high productivity polylactic acid (PLA) material, the method comprising:
 forming a fiber comprising a homogeneous blend of a first polylactic acid (PLA) polymer and a second polylactic acid (PLA) polymer, wherein the first PLA polymer has an isomeric purity for the D-isomer or the L-isomer of at least about 99% and the second PLA polymer has an isomeric purity for the D-isomer or the L-isomer of no greater than about 98.5%;   drawing the formed fiber at a draw ratio of about 3:1 or greater; and   heat-setting the formed fiber at a temperature of up to about 110° C.;   wherein after the heat-setting step, the PLA material exhibits a shrinkage of less than about 20% at a temperature of about 115° C. to about 130° C.   
     
     
         16 . A method of preparing a multicomponent binder fiber exhibiting low shrinkage, the method comprising:
 providing a multicomponent fiber formed of a first, high melting polymer component and a second, tower melting polymer component, wherein the first polymer component is a PLA polymer with an isomeric purity for the L-isomer of at least about 99%, wherein the second polymer component is a PLA polymer with an isomeric purity for the L-isomer of no more than about 98.5%, and wherein the second component comprises at least a portion of an outer surface of the multicomponent binder fiber; and   heat-setting the multicomponent binder fiber at a temperature that is less than the activation temperature at which the second polymer component melts;   wherein the formed, heat-set multicomponent binder fiber exhibits a shrinkage of less than about 20% at a temperature greater than the activation temperature.