Recycling of polyolefins using supercritical alkanes.

Polyolefins make up 80% of the plastics recycle stream. Mixed municipal plastics waste contains many grades of polyolefins none of which are compatible. For recycling or upcycling of plastics, separation of polyolefins from paper and polyester labels, adhesives, inks, pigments, fillers, water, food and other products is necessary if the plastics are to be processed into virgin quality materials. This can largely be achieved using supercritical alkanes such as butane and propane. Through careful control of pressure and temperature it is possible to grade and fractionate the various types of polyolefins to a dry product with narrow molecular weight distributions, variable branch content, and copolymer composition from unsegregated mixed municipal waste while recycling the distilled alkane solvent.