Patent ID: 8722754

Claim:
A process that comprises forming a pressurized, molten mixture of a melt-processable branched polylactide (PLA) resin containing about 3 to about 25% by weight of a blowing agent, based on the weight of the PLA resin, and extruding the molten mixture through a die to a region of reduced pressure such that the blowing agent expands and the PLA resin simultaneously cools to form a stable foam, wherein the PLA resin in the foam (1) is the reaction product of a linear PLA resin having a number average molecular weight of at least 80,000 with a reactive branching agent which contains multiple functional groups that can react with hydroxyl and/or carboxylic acid groups that terminate the PLA polymer chains, (2) has an absolute weight average molecular weight of from 550,000 to 1,500,000 as determined by dissolving 0.5 g samples of the PLA resin in 9.6 mL of methylene chloride, transferring 0.25 mL of the PLA resin solution into a 20 mL vial and diluting it with 9.75 mL tetrahydrofuran, filtering the diluted sample, measuring the refractive index, right angle light scatter and low angle light scatter using a multi-detector gel permeation chromatography (GPC) system comprised of a Viscotek GPCmax VE2001 GPC solvent/sample module, a Viscotek TDA 302 triple detector array module, a computer running Viscotek OmniSEC version 4.5 software, a Viscotek low molecular weight mixed-bed GPC column, and a Viscotek high molecular weight mixed-bed GPC column, and calculating the polymer concentration from the refractive index using a dn/dc of 0.045 ml/g for the PLA resin sample, and determining the absolute molecular weight from the right angle light scatter and the low angle light scatter in combination with the polymer concentration, (3) has an intrinsic viscosity of from 1.570 to 1.8 deciliters/gram, and (4) has an average of at least 10 branches/molecule.