US Patent 7915379 Extraction process utilzing liquified carbon dioxide

A method for removing contaminants from synthetic resin material includes contacting a particulate synthetic resin material containing at least one contaminant with a solvent other than carbon dioxide. At least a portion of the contaminant is removed from the particulate synthetic resin material and becomes dispersed in the solvent. The solvent, with the contaminant dispersed therein, is then removed from the particulate synthetic resin material. Thereafter, at least a portion of the solvent still contained on the synthetic resin material is removed by contacting the particulate synthetic resin material with liquid carbon dioxide to dissolve the solvent into the carbon dioxide.