Materials & Chemicals
RECYCLING OF PLASTICS BY SOLVENT-TARGETED RECOVERY AND PRECIPITATION (STRAP)
Inventors: George Huber, Kevin Sanchez-Rivera, Reid Van Lehn, Theodore Walker, Panzheng Zhou
UW-Madison researchers have developed a process to recover the components of printed multilayer plastic films. As an example, a film composed of polyethylene (PE), ethylene vinyl alcohol (EVOH), and polyethylene terephthalate (PET) was subjected to a solvent-targeted recovery and precipitation (STRAP) process which uses the selective dissolution of the plastic components guided by thermodynamic calculations of polymer solubility. Before the STRAP process, the films were shredded to sizes <5mm. A deinking step is done before targeting any of the polymers, removing the inks from the film. The polymer is separated from the other components and precipitated after each dissolution step. The polymers are later dried and recovered in pure streams that can be more efficiently recycled. As an alternative to pure solvents, solvent mixtures were used for separation, which allowed for subsequent precipitation via a decrease in temperature instead of requiring an antisolvent.