Chemical recycling of aliphatic polyester by lipase

Cyclic oligomers obtained by the enzymatic degradation of aliphatic polyesters are attractive as raw materials for chemical recycling. In this report, molecularly pure cyclic oligomers of butylene adipate, which were obtained by the lipase-catalyzed degradation of poly (butylene adipate), were studied with respect to the polymerization by the enzyme. That is, poly (butylene adipate) was degraded in dry toluene using Candida antarctica lipase to produce cyclic oligomers mainly consisting of cyclic monomer to cyclic tetramer. It was found that cyclic dimer to tetramer were quickly polymerized by lipase to produce high-molecular weight polymers within 30 min. On the other hand, cyclic monomer was slowly polymerized, and it took longer than 120 min for complete conversion. Similar tendencies were observed for PCL and PBS degradation and polymerization.