(131h) Recycling of Multilayer Plastic Packaging Materials By Solvent-Targeted Recovery and Precipitation (STRAP)

Many plastic packaging materials manufactured today are composites made of distinct polymer layers (i.e., multilayer films) which end up incinerated or in landfills at end of their useful life. We have demonstrated a new strategy called Solvent-Targeted Recovery And Precipitation (STRAP) to deconstruct multilayer rigid and flexible films into their constituent resins using a series of solvent washes that are guided by thermodynamic calculations of solvent-polymer solubility. Three computational methods were used for solvent selection and determining process conditions: Hansen Solubility Parameters (HSPs), Molecular Dynamics (MD) simulations, and COnductor-like Screening MOdel for Realistic Solvents (COSMO-RS). We show that the STRAP process can separate representative polymer resins (HDPE, LDPE, PP, EVOH, PET, PVC, PA6, PA66, and PA 6/66) from post-industrial multilayer films and mixed flexible packages with >95 wt% material efficiency. In this process, a single polymer component was selectively dissolved in a solvent system to be later separated from the insoluble layers and then precipitated by the addition of an antisolvent and/or decreasing the solvent temperature. This resulted in segregated streams of pure dry polymers that can be much more efficiently reused. A techno-economic and life cycle assessment of one example STRAP process with a flexible multilayer film were performed and it was determined that this approach can produce resins at costs comparable to market values and could reduce environmental impacts when compared to film production from virgin resins. In the same example, the FTIR spectra of the separated polymer fractions were comparable to the virgin resins and no significant changes in thermal and molecular properties were observed. Our team was able to produce and characterize a cast film using STRAP recovered PE and currently, we are in the process of scaling up the STRAP technology to a 25 kg/hr development unit which will produce sufficient quantities of material to make and qualify plastic films.