Alcoholysis of polylactic acid (PLA) for the production of biopolyols

In this work, we studied the feasibility of a chemical process to recycle polylactic acid (PLA) through an alcoholysis process with 1,4-butanediol. This glycol was used as the coreactant and solvent because it can be produced from bio-based sources. This makes the recycled product completely biobased polyol. The alcoholysis reaction yields hydroxy-terminated PLA oligomers that were employed in the production of polyisocyanurate foams due to their relatively low hydroxyl value. The effect of polymer-to-solvent ratio, temperature, and catalyst concentration was studied on variables of interest such as dynamic viscosity, hydroxyl value, and acid value. We observed that potassium acetate is a suitable catalyst for this process, present in a concentration of 1 to 50 mmol/100gPLA, with a polymer-to-solvent ratio of 4 kg/kg, working at 200°C.. However, what was observed is that the dynamic viscosity of the final biopolyol increases by increasing the catalyst concentration while the hydroxyl number decreases. So the concentration of 1 mmol/100gPLA was considere for the production of foams. Other catalysts have been studied but none of them have shown the performance of potassium acetate. This biopolyol was used to produce the polyisocyanurate foams at NCO index of 250. The foams were made with an increasing percentage of recycled polyol (up to 50%). Their properties were then verified by comparing them with the properties of a reference foam obtained using a mixture of polyols commonly used in an industrial formulation.