The invention relates to a method for producing polylactic acid, comprising
the steps of obtaining lactic acid from starchy agricultural products by
fermentation, ultrapurification of the lactic acid by ultrafiltration,
nanofiltration and/or electrodialysis, concentration of the lactic acid
and production of a prepolymer, cyclizing depolymerization to dilactide,
purification of the dilactide, ring-opening polymerization of the
dilactide and demonomerization of the polylactide.
