Depolymerization of polylactic acid

摘要

The invention provides energy efficient depolymerization of polyesters such as post-consumer polylactic acid. Ultrasonic induced implosions can be used to facilitate the depolymerization. The expanding market of polylactic acid-based plastic products, such as water bottles and packaging materials, has raised concerns of contaminating the recycling stream, which is largely filled with petroleum-based plastics. Thus the development of an energy efficient and economically viable PLA recycling process is urgently needed. Post consumer PLA was exposed to methanol as the suspension media in the presence of organic or ionic salts of alkali metals such a potassium carbonate and sodium hydroxide as depolymerization catalysts to provide high quality lactic acid monomers in high yield.

主权项

1. A method to convert polylactic acid to lactic acid comprising:
contacting solid particles of polylactic acid and an alcoholic solution, wherein the solution comprises less than about 5 wt. % water, and wherein the alcoholic solution comprises an alkali metal hydroxide, an alkali metal carbonate, or both, and methanol or ethanol, to form a first mixture; and maintaining the temperature of the first mixture at about 30° C. to about 90° C.; for a period of time sufficient to depolymerize the polylactic acid of the solid particles, thereby providing a second mixture comprising lactic acid monomers or salts thereof.