Glycolysis of PU Polymers

Glycolysis of a PU polymer is similar to a transesterification reaction, in fact a reaction between a carbamic ester (urethane) and a glycol (reaction 20.5). 

By glycolysis of urea groups a hydroxyalkyl carbamate (or hydroxyalkyl urethane) and an amine are formed (reaction 20.6). 

The glycolysis of urea groups takes place at a lower reaction rate than the glycolysis of urethane groups. The catalysts for both reactions, glycolysis and hydrolysis are alkali hydroxides (NaOH, KOH, LiOH) [11, 12, 25, 26, 30, 31], diethanolamine[ll, 26] and some titanium or tin compounds. One of the best catalysts is LiOH [11]. 

Urethane - polyisocyanuric foams (PU/PIR) foams) contain isocyanuric rings. Isocyanuric rings are glycolysed at lower reaction rates than the urea or urethane groups, with the formation of hydroxyalkyl carbamates and an amine (reaction 20.7) [11]  

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