Abstract: A water soluble laminate may be prepared comprising one or more relatively water insoluble layers of polymers such as polyvinyl alcohol or crosslinked polyvinyl alcohol and one or more relatively more water soluble layers such as linear uncrosslinked sulphonated vinylaromatic polymers.

Abstract: High molecular weight polylactic acid is generally produced by the polymerization of lactide. Lactide is prepared by the depolymerization of low molecular weight polylactic acid. There are difficulties in the preparation of high molecular weight polylactic acid and high purity lactide isomers due to the equilibrium between lactic acid, low molecular weight polylactic acid, high molecular weight polylactic acid, lactide and water. Further it has never been proposed to provide a continuous process to produce high molecular weight polylactic acid from lactic acid. The present invention overcomes the equilibrium problem and provides a continuous process.

Abstract: Generally, polylactic acid is prepared by the ring opening polymerization of lactide. However, to obtain a high molecular weight polylactic acid it is necessary to start with a lactide having a high degree of purity. Lactide may be economically brought to the required degree of purity using melt recrystallization techniques.