Scale-up Polymerization of L-Lactide in Supercritical Fluid

For the purpose of the pre-industry production of poly (L-lactide) (PLLA) and full understanding of the supercritical polymerization system, large scale polymerization of L-lactide initiated by 1-dodecanol/stannous 2-ethyl-hexanoate (DoOH/Sn(Oct)(2)) was carried out in supercritical chlorodifluoromethane under various reaction conditions (time, temperature and pressure) and reactants (monomer and supercritical solvent) concentrations. A 3 L sized-reactor system was used throughout this study. The monomer conversion increased to 72% on increasing reaction time to 5 h. The molecular weight of PLLA product also increased to 68000 g/mol over the same period. An increase in monomer concentration resulted in a higher molecular weight, up to 144000 g/mol and 97% of monomer conversion. Raising the reaction pressure from 130 to 240 bar also resulted in an increased monomer conversion and molecular weight. To increase heat resistivity of PLLA, methanol treatment and heat-vacuum methods were evaluated. Both of them successfully improved the heat resistivity property of PLLA.