Extruded polylactide foams blown with carbon dioxide
AssigneeNatureWorks LLC
InventorsKevin Cink, Jeffrey C. Smith, James F. Nangeroni, Jed Richard Randall
Life of this patent
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Abstract
This invention provides a process for extruding a PLA resin using high levels of CO2. Excellent quality, low density foam is produced easily and reproducibly. The foams arc capable of being heat-annealed to induce significant crystallinity, even when an ordinarily amorphous PLA resin is used.
Claims6
A process that comprises forming a pressurized, molten mixture of a melt-processable polylactide resin containing about 5 to about 15% by weight, based on the weight of the polylactide resin, of carbon dioxide, and extruding the molten mixture at an extrusion temperature through a die to a region of reduced pressure such that the carbon dioxide expands and the polylactide resin simultaneously cools to form a stable foam, wherein the foam has least 70% closed cells and a crystallinity of about 13-24 J/g measured by differential scanning calorimetry, and wherein the polylactide resin contains at least 80% by weight polymerized lactic acid units.
A process that comprises forming a pressurized, molten mixture of a melt-processable polylactide resin containing 7-11% by weight, based on the weight of the polylactide resin, of carbon dioxide, and extruding the molten mixture at an extrusion temperature through a die to a region of reduced pressure such that the carbon dioxide expands and the polylactide resin simultaneously cools to form a stable foam having at least 70% closed cells, wherein the polylactide resin contains at least 80% by weight polymerized lactic acid units.
Dependencies are inferred from the claim text.