Valorization of the Isocyanate-Derived Fraction from Polyurethane Glycolysis by Synthesizing Polyureas and Polyamides

The isocyanate-derived fraction resulting as the bottom phase from the split-phase glycolysis of conventional polyurethane flexible foams has been given a new life based on the formation of amine-based polymers (polyureas and polyamides). For that purpose, the bottom phase was first hydrolyzed, producing toluenediamine and diethylene glycol, and further subjected to controlled vacuum distillation in order to recover both products separately. The hydrolysis reaction and the separation process conditions were determined and optimized, obtaining products with a purity comparable to that of commercial ones. Then, the recovered diethylene glycol was used in a new glycolysis process, obtaining a split-phase product with properties similar to those obtained using commercial diethylene glycol. Finally, the recovered toluenediamine was used in the synthesis of polyureas and polyamides. Both syntheses were modified with respect to the state of the art, replacing benzene with limonene in the synthesis of polyamides, which implies environmental improvements.