PROCESS OF PURIFYING POLYMERS AND OLIGOMERS OF ALIPHATIC HYDROXY- ACIDS

摘要

The process of purifying polymers and oligomers of aliphatic hydroxyacids is based on dissolving the raw polymerisation product in a solvent with relative permittivity of epsilon r from 10.0 to 33.5 making a solution with 5 to 50 % by weight of oligomers at 35 degrees C up to the boiling point of the solvent. After dissolving the oligomers and filtration the clear solution is cooled to 35 to - 50 degrees C. The solid phase or coacervated layer is separated off. The coacervated layer is then plasticised with a polar liquid, whose relative permittivity epsilon r is higher than 25.0. The liquid phase is separated off and the solid phase is desiccated under a vacuum of 0.1 to 1.0 kPa.