Tert-Amyl Alcohol-Mediated Deconstruction of Polyurethane for Polyol and Aniline Recovery

Abstract

Polyurethane (PU) is a highly engineered and cross-linked polymer found in a plethora of materials such as mattresses, shoes, windmills, and insulation of refrigerating appliances and buildings. Because of PU’s inherent stability, chemical recycling is difficult and often affords a secondary feed with different characteristics and properties compared to the original input. In this work, a simple chemical recycling of PU via a solvolysis process using tert-amyl alcohol both as the solvent and reagent is demonstrated. The devised methodology is showcased for the deconstruction of 20 different PU materials with examples of all four cornerstones of PU (rigid solid, rigid foamed, flexible foamed, and flexible solid). The solvolysis affords both polyol and dianiline fractions, constituting monomeric precursors of PU. The methodology is used for the depolymerization of 50 g flexible PU foam affording a polyol within specification of the original virgin polyol (OH value) and an aniline fraction isolated as the precipitated di-HCl salt with a combined mass recovery of 89 wt%. As the solvolysis process provides access to both the polyol and the aniline precursors of the original isocyanate of PU, the procedure presented in this study could pave the way toward a viable circular economy for PU. A further potential utilization of the method is showcased by valorization of a waste stream from split-phase glycolysis, which is another promising method for recovering polyol from flexible PU foam. Finally, preliminary mechanistic investigations are undertaken to probe the intriguing utility of a hindered tertiary alcohol in a solvolysis procedure.