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Recycling of Flexible Polyurethane Foam by Split‐Phase Alcoholysis: Identification of Additives and Alcoholyzing Agents to Reach Higher Efficiencies
Author(s) -
Vanbergen Thomas,
Verlent Isabel,
De Geeter Joke,
Haelterman Bart,
Claes Laurens,
De Vos Dirk
Publication year - 2020
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.202000949
Subject(s) - polyurethane , phase (matter) , identification (biology) , materials science , chemical engineering , polymer science , chemistry , organic chemistry , composite material , engineering , botany , biology
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 mg KOH g −1 ) is reached. The recycled polyether polyol can replace the virgin polyether polyol (48 mg KOH 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.