Recycling of Flexible Polyurethane Foam by Split‐Phase Alcoholysis: Identification of Additives and Alcoholyzing Agents to Reach Higher Efficiencies

Split‐phase alcoholysis of flexible polyurethane (PU) foam yields an apolar phase containing the recycled polyether polyol, and a lower, polar phase of the alcoholyzing agent and aromatic compounds. However, multiple purification steps are required to render the polyether polyol suitable for synthesis of new flexible PU foams; the unfavorable mass balance limits industrial applications. In this work, 2‐pyrrolidone was identified as a performant additive for accelerating the dissolution and depolymerization process. By applying a lactam to PU foam in a weight ratio of 0.1:1, the glycol to PU foam weight ratio can be decreased from 1.5:1 to only 0.5:1, without loss of purity or yield of the recycled polyether polyol. Diglycerol was discovered as a novel, promising alcoholyzing agent; it allows the recycling of the polyether polyol in high purity (97 %) and excellent yields (98 %), and after a single washing with diglycerol, a sufficiently low hydroxyl value (61 mgKOH g−1) is reached. The recycled polyether polyol can replace the virgin polyether polyol (48 mgKOH g−1) for up to 50 % in the synthesis of new flexible PU foams with effects on the foam quality that stay within the limits of generally accepted specifications. A first step towards the valorization of the lower phase was also taken by applying hydrolysis of the newly formed carbamates to toluenediamines, which are readily reintegrated in new PU foams. Making polyurethane anew: Split‐phase alcoholysis is a promising technique for the recycling of flexible polyurethane (PU) foam, with the potential to achieve a circular use of polyether polyol and aromatic components. The process was improved by employing new alcoholyzing agents such as diglycerol and a lactam co‐reactant, yielding a polyether polyol of high purity suitable for the synthesis of new flexible PU foams.