Multistage Chemical Recycling of Polyurethanes and Dicarbamates: A Glycolysis–Hydrolysis Demonstration

Abstract

The use of polyurethanes and, therefore, the quantity of its scrap are increasing. Considering the thermoset characteristic of most polyurethanes, the most circular recycling method is by means of chemical depolymerization, for which glycolysis is finding its way into the industry. The main goal of polyurethane glycolysis is to recover the polyols used, but only limited attempts were made toward recovering the aromatic dicarbamate residues and derivates from the used isocyanates. By the split-phase glycolysis method, the recovered polyols form a top-layer phase and the bottom layer contain transreacted carbamates, excess glycol, amines, urea, and other side products. The hydrolysis of carbamates results in amines and CO2 as the main products. Consequently, the carbamates in the bottom layer of polyurethane split-phase glycolysis can also be hydrolyzed in a separate process, generating amines, which can serve as feedstock for isocyanate production to complete the polyurethane material cycle. In this paper, the full recycling of polyurethanes is reviewed and experimentally studied. As a matter of demonstration, combined glycolysis and hydrolysis led to an amine production yield of about 30% for model systems. With this result, we show the high potential for further research by future optimization of reaction conditions and catalysis.

Deactivation and Regeneration of Zeolite Catalysts Used in Pyrolysis of Plastic Wastes—A Process and Analytical Review

“…If purity is not sufficient for polymer synthesis, these recycled monomers can possibly be purified or mixed with conventionally obtained monomers. Different processes have been investigated for plastic monomer recovery and several processes follow this principle using different solvents: hydrolysis with water [34], alcoholysis using methanol (methanolysis [35]) or ethylene glycol (glycolysis [36]), along with phosphorolysis, ammonolysis and aminolysis [37][38][39]. Solvents are chosen in function of their affinity for the different polymers and their ability to cleave particular bonds.…”

Effect of Conditioning on PU Foam Matrix Materials Properties

“…After prolonged conditioning, plasticization patterns in mechanical behavior were found, as indicated in Figure 4 b. After 24 h of conditioning at 80 °C and 80% RH, the foam elasticity was decreased in the frequency range of 200 to 600 Hz in comparison with the virgin PU sample indicating the probable start of the hydrolysis process of the wall material decomposition [ 31 , 32 ].…”

Recent Advances in Development of Waste-Based Polymer Materials: A Review

“…The solubility of the polyols in the glycol plays an important role in the separation of two phases. By this method, the upper phase consists mostly of the recovered polyols and the bottom phase is the excess glycol and other products of the reaction [185].…”