MICROENCAPSULATION BY MAINTAINING THE TEMPERATURE OF AN AQUEOUS SOLUTION OF A POLYVINYL ALCOHOL ABOVE THE CLOUD POINT

摘要

The specification discloses a process for producing microcapsules having walls comprising a polyvinyl alcohol type polymer. The process includes the steps of: (I) dispersing a water insoluble nucleus material in an aqueous solution of a polyvinyl alcohol type polymer, which solution has a cloud point, (II) causing phase separation and deposition of a concentrated aqueous solution of the polyvinyl alcohol type polymer as a separated phase around the nucleus material by maintaining the temperature of the system at or above the cloud point of the aqueous polyvinyl alcohol type polymer solution, and (III) solidifying the so-formed microcapsules under such conditions that the separated phase of concentrated aqueous solution of the polyvinyl alcohol type polymer as formed around the nucleus material is subjected to solidification or gelation, but that no solidification or gelation action is exerted upon the diluted aqueous solution of the polyvinyl alcohol type polymer forming a continuous phase. In this way, microencapsulation can be carried out without the need for the addition of a phase separation medium to the aqueous solution of the polyvinyl alcohol type polymer, which medium tends to increase the porosity of the resulting microcapsules.