of 1 7 the parameters of the twin screw extruder were set as follows screw speed 150 rpm vacuum 1 kpa aspect ratio 48 material feed rate 1 0 kg h the temperatures of various barrel sections were set as follows section i 145 u00b0 c section ii 185 u00b0 c section iii 200 u00b0 c section iv 165 u00b0 c u00b0 c l lactide 2016 g 14 mol the co 2 adduct of carbene i 7 87 g 0 028 mol and benzyl alcohol 6 05 g 0 056 mol were evenly mixed and fed into the twin screw extruder at a constant rate one thousand nine hundred and eighty three grams 1983 g of polylactic acid was extruded using the above described operating parameters and cooled by air cooling the polylactic acid thus obtained had a molecular weight of 31 000 and a molecular weight distribution of 1 4 the parameters of the twin screw extruder were set as follows screw speed 125 rpm vacuum 0 8 kpa aspect ratio 48 material feed rate 1 5 kg h the temperatures of various barrel sections were set as follows section i 165 u00b0 c u00b0 c section ii 200 u00b0 c section iii 250 u00b0 c section iv 185 u00b0 c l lactide 2016 g 14 mol the co 2 adduct of carbene m 4 44 g.