Recycling of flexible polyurethane foams with a low aromatic amine content

The glycolysis process is the basis for a controlled degradation of crosslinked polyurethane for recycling. Flexible water-blown polyurethanes are polymers with repeating urethane and urea groups. When they undergo heating in presence of glycols and selective catalysts, the reaction of these groups leads to products that are liquid at room temperature. The transesterification reaction of the urethane groups, that leads to the formation of new carbamate is faster than that of the urea groups that leads to the formation of carbamates and amines. The carbamates in turn undergo aminolysis due to the amines formed in the glycolysis of the urea groups to give insoluble products. The possibility of transforming the free aromatic amines by means of a reaction with formaldehyde into products with methylol end groups has been studied. At the same time the formation of a solid phase, mainly of urea groups, has been avoided. The use of ethylene glycol (EG) allows the process to be carried out with high polymer/glycol ratio (up to 4:1) even if a biphase product is obtained. The top phase is mainly formed by the polyether polyol from the polymer, the bottom phase is formed by the solution of carbamates, ureas and amines in EG.