Toughened polylactic acid polymers and copolymers

Abstract

Toughened compositions of PLA and PLA copolymers are disclosed, which also have low tensile modulus values and greater elongation to break. These toughened compositions are prepared by blending PLA and PLA copolymers with poly-4-hydroxybutyrate, and copolymers thereof. Blending of poly-4-hydroxybutyrate with PLA and its copolymers has been found to impart advantageous properties to the resulting blend. These compositions, and objects formed from these compositions, have improved toughness and lower stiffness than polylactic acid polymers or copolymers alone.

We claim: 
     
         1 . A medical device comprising a toughened polymer composition comprising poly-4-hydroxybutyrate homopolymer or copolymer thereof wherein the composition further comprises at least one polylactic acid homopolymer or copolymer, and the amount of poly-4-hydroxybutyrate homopolymer or copolymer added is sufficient to increase the elongation to break of the composition to greater than the elongation to break of the polylactic acid homopolymer or copolymer. 
     
     
         2 . The medical device of  claim 1  wherein the composition has been oriented. 
     
     
         3 . The medical device of  claim 1  wherein the elongation to break of the composition is greater than 3%. 
     
     
         4 . The medical device of  claim 3  wherein the elongation to break of the composition is between 3% and 281%. 
     
     
         5 . The medical device of  claim 1  wherein the Young's modulus of the composition is less than the Young's modulus of the polylactic acid homopolymer or copolymer. 
     
     
         6 . The medical device of  claim 5  wherein the Young's modulus of the composition is less than 700 kgf/mm 2 . 
     
     
         7 . The medical device of  claim 1  wherein the ratio of the polylactic acid homopolymer or copolymer to the poly-4-hydroxybutyrate homopolymer is between 9:1 and 1:9 by weight. 
     
     
         8 . The medical device of  claim 1  wherein the polylactic acid homopolymer is poly-L-lactic acid. 
     
     
         9 . The medical device of  claim 1  wherein the device is a suture, suture fastener, meniscus repair device, rivet, tack, staple, screw, bone plate, bone plating system, biocompatible coating, rotator cuff repair device, surgical mesh, medical textile, repair patch, sling, cardiovascular patch, tissue engineering scaffold, vascular graft, vascular closure device, catheter balloon, anti-adhesion device, drug delivery device, embolization particle, orthopedic pin, adhesion barrier, stent (including coronary stents, peripheral stents, carotid stents, biliary stents, gastroenterology stents, urology stents, and neurology stents), embolization coil, guided tissue repair/regeneration device, articular cartilage repair device, nerve guide, tendon repair device, intracardiac septal defect repair device (including, but not limited to, atrial septal defect repair devices and PFO closure devices and left atrial appendage (LAA) closure devices), pericardial patch, bulking and filling agent, vein valves, bone marrow scaffold, meniscus regeneration device, ligament graft, tendon graft, ocular cell implant, spinal fusion cage, imaging device, skin substitute, dural substitute, bone graft substitute, bone dowel, would dressing, or a hemostat. 
     
     
         10 . A process for preparing the medical device of  claim 1 , comprising blending poly-4-hydroxybutyrate homopolymer or copolymer thereof with at least one polylactic acid homopolymer or copolymer, wherein the poly-4-hydroxybutyrate homopolymer or copolymer thereof and at least one polylactic acid homopolymer are mixed in the molten state at a temperature between 110° C. and 230° C., and extruded. 
     
     
         11 . The process of  claim 8  further comprising extruding the toughened composition, wherein the composition is dried to a water content of less than 0.01% (w/w) prior to extrusion, and wherein the composition is extruded at a temperature between 140° C. and 250° C. 
     
     
         12 . The process of  claim 9  wherein the extrudate is oriented by drawing it with stretch ratios of 1X to 11X.