Purification of post-consumer polyolefins via supercritical CO2 extraction for the recycling in food contact applications

Throughout their lifecycle or first use, polyolefins can be exposed to contaminating media which limit their recyclability, especially in food industry, such as packaging. Supercritical carbon dioxide (SCCO2) extraction in dynamic mode is studied as a possible method to purify post-consumer polyolefins. As a first approach, the strategy was to remove the well-known conventional additives (i.e., antioxidant) which are already present in food grade polypropylene (PP) and linear low density polyethylene (LLDPE). The extraction yields and kinetics have been obtained by gas chromatography. A systematic study of the influence of the shape (pellets or films) and the thickness of the materials shows that it is possible to increase the speed of extraction with a thinner material: high yields (100%) are obtained with films at 300 bar, 50 degrees C and 5 min of extraction. Finally, the potential of SCCO2 extraction was compared to that of traditional liquid extraction with methylene chloride. (C) 2015 Elsevier B.V. All rights reserved.