Method for making shapeable microcellular poly lactic acid articles

Abstract

A method for making a shapeable article from poly(lactic acid) includes treating solid poly(lactic acid) that results in the solid poly(lactic acid) having a crystallinity of at least 20% by weight based on the weight of the solid poly(lactic acid) and a gas concentration of 6% to 16% by weight based on the weight of the solid poly(lactic acid); and heating the solid poly(lactic acid) having said minimum crystallinity and gas concentration to produce a cellular poly(lactic acid) article that is shapeable. The shapeable cellular poly(lactic acid) article is advantageous in that the article can be further shaped by heat and/or pressure (or vacuum), such as via thermoforming, into a variety of useful products.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
         1 . Poly(lactic acid) having cells less than 100 microns, a maximum density relative to the density of solid poly(lactic acid) of 40%, a percent tensile elongation before break of 10% to 50%, and a minimum crystallinity of 20%. 
     
     
         2 . The poly(lactic acid) of  claim 1 , having the form of a sheet or rod. 
     
     
         3 . The poly(lactic acid) of  claim 1 , wherein the poly(lactic acid) has a cellular poly(lactic acid) structure within the interior and a noncellular poly(lactic acid) layer at the surface. 
     
     
         4 . The poly(lactic acid) of  claim 1 , wherein the density is greater than 5% to 40% relative to the density of solid poly(lactic acid). 
     
     
         5 . The poly(lactic acid) of  claim 1 , which has been treated with heat while being shaped. 
     
     
         6 . The poly(lactic acid) of  claim 5 , which has a milky white color.