Many plastic packaging materials manufactured today are composites made of distinct polymer layers (<i>i.e., </i>multilayer films). Billions of pounds of these multilayer films are produced annually, but no technologies exist to recycle them back into their pure resins without breaking the films down into their original monomers. We have demonstrated a new strategy we call Solvent-Targeted Recovery And Precipitation (STRAP) to deconstruct multilayer 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 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 is able to separate three representative polymer resins (polyethylene, ethylene vinyl alcohol, and polyethylene terephthalate) from a post-industrial multilayer film with near 100% material efficiency. In this process, a single polymer layer 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 chemically pure dry polymers that can be much more efficiently recycled. The FTIR spectra, GPC and melt flow index of the separated polymer fractions were comparable to the virgin resins. A techno-economic analysis of the process was performed and it was determined that the STRAP process can produce resins at costs comparable to virgin resins. Understanding polymer solubilities in mixtures of solvents and antisolvents would make the process more economically feasible, as a significant portion in the costs can come from the separation of solvents and antisolvents. This technology can be further used to recover plastic components from printed multilayer plastic films, face masks, and mixed plastic waste, which speak to the applicability of this process for different plastic waste feedstocks.

Recycling of multilayer plastic packaging materials by solvent-targeted recovery and precipitation (STRAP)

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