Chemical Recycling of Mixed Polyurethane Foam Stream Recovered from Shredder Residue into Polyurethane Polyols

Tons of shredder residue (SR), a complex mixture of plastics, foams, rubber, metals, and glass, are generated each year as a by-product from the recycling of obsolete vehicles. The Vehicle Recycling Partnership (VRP), along with our CRADA partners, is investigating ways to enable the optimum recovery and recycling of these materials. This study investigates the feasibility of recycling (PU) foam using a new chemical process by glycolysing [1, 2] two types of polyurethane (PU) foams, “dirty” and “clean”, which were recovered from SR via an industrial scale process specifically designed to separate PU foams from SR [3, 4]. In stage one of this process, the polyurethane foam is subjected to glycolysis, followed by filtration of the liquid glycolyzed product. In stage two, the glycolyzed products are used as initiators in reaction with propylene oxide to prepare novel polyurethane polyols. A number of successful laboratory glycolyses were carried out utilizing the two different types of PU foams recovered from shredder residue: (1) the best case scenario - hand-picked PU foams from shredder residue with >80% conversion into liquid initiator and (2) the worst case scenario - mixed PU materials separated by an automated separation process from shredder residue with ∼50% conversion into a liquid initiator. Both toluene diisocyanate (TDI) and polymeric diphenylmethane diisocyanate (PMDI) based flexible foams were prepared from the novel recycled polyols by propoxylation of the glycolyzed products (initiators) obtained from the mixed PU materials [1, 2].