Cleaning device for separating dilactide from mixtures, polymerisation device, method for separating dilactide from mixtures and use thereof

A method for continuous production of polylactide, the method comprising:

• obtaining or providing a starting material mixture comprising mesodilactide having a chemical structure of Formula I
• and the starting material mixture further comprising at least one of D-lactic acid and L-lactic acid of Formula II
• separating cleaned mesodilactide from the starting material mixture with a cleaning device, the separating comprising
• a) feeding the material mixture into a cleaning device comprising a dividing wall column, the cleaning device comprising at least the following components which are arranged from top to bottom in the sequence
• aa) at the top, at least one dephlegmator and also at least one outlet,
• bb) at least one mass transfer packing which fills the diameter of the device at least partially,
• cc) the dividing wall column which is divided into two zones by a vertical dividing wall, each zone comprising at least two mass transfer packings which are separated from each other respectively by a gap, the first zone comprising a prefractionation zone comprising at least one inlet for supplying the material mixture and the second zone comprising a main fractionation zone comprising at least one side outlet for removing the cleaned product, and the at least one inlet and also the at least one side outlet being located respectively in the region of the at least one gap,
• dd) at least one further mass transfer packing which fills the diameter of the device at least partially,
• ee) on a sump side, at least one evaporator and at least one outlet, a length ratio of the dividing wall column to a total length of the cleaning device comprising approximately 0.5 to 0.9,
• b) separating the material mixture, the acid of Formula II leaving the column in a vaporous aggregate state and
• c) removing the cleaned mesodilactide via the at least one side outlet;
• and
• polymerizing the cleaned mesodilactide, providing polylactide comprising at least about 90 wt % poly-mesodilactide.

A method for continuous production of polylactide, the method comprising:

• obtaining or providing a starting material mixture comprising mesodilactide having a chemical structure of Formula I
• and the starting material mixture further comprising at least one of D-lactic acid and L-lactic acid of Formula II
• separating cleaned mesodilactide from the starting material mixture with a cleaning device, wherein the cleaned mesodilactide has a concentration of free carboxylic acid groups of at most about 20 mmol/kg, the separating comprising
• a) feeding the material mixture into a cleaning device comprising a dividing wall column, the cleaning device comprising at least the following components which are arranged from top to bottom in the sequence
• aa) at the top, at least one dephlegmator and also at least one outlet,
• bb) at least one mass transfer packing which fills the diameter of the device at least partially,
• cc) the dividing wall column which is divided into two zones by a vertical dividing wall, each zone comprising at least two mass transfer packings which are separated from each other respectively by a gap, the first zone comprising a prefractionation zone comprising at least one inlet for supplying the material mixture and the second zone comprising a main fractionation zone comprising at least one side outlet for removing the cleaned product, and the at least one inlet and also the at least one side outlet being located respectively in the region of the at least one gap,
• dd) at least one further mass transfer packing which fills the diameter of the device at least partially,
• ee) on a sump side, at least one evaporator and at least one outlet, a length ratio of the dividing wall column to a total length of the cleaning device comprising approximately 0.5 to 0.9,
• b) separating the material mixture, the acid of Formula II leaving the column in a vaporous aggregate state and
• c) removing the cleaned mesodilactide via the at least one side outlet;
• and
• polymerizing the cleaned mesodilactide, providing polylactide comprising at least about 70 wt % poly-mesodilactide.