METHOD FOR PREPARING LACTIDE USING MULTI-TUBE FALLING-FILM REACTOR

摘要

The present invention relates to a method for preparing lactide, comprising: step 1 of evaporating and concentrating lactic acid solution under a pressure of 50-700 torr and a temperature of 80-120°C; step 2 of polymerizing the lactic acid, which is concentrated to have a water content of 1% or less, into a small polymer at a temperature of 190-205°C; and step 3 of de-polymerizing the obtained small polymer of lactic acid under a pressure of 5-100 torr and a temperature of 200-270°C, wherein all the steps are conducted in a multi-tube falling-film apparatus. According to the present invention, a liquid reactant having a large viscosity is evenly distributed in individual vertical tubes of the multi-tube falling-film apparatus even at low pressure, and 100% of the liquid reactant flows down on the inner walls of the vertical tubes with even thickness in a circumferential direction. When this multi-tube falling-film apparatus is applied to all of the unit processes mentioned above, lactide can be continuously produced at high yields.;COPYRIGHT KIPO 2014