化粧品用マイクロカプセルの開発と応用

Abstract

Microcapsules are minute containers in which individual entities of a solid, liquid, or gas are discretely enclosed, with shells made of natural or synthetic materials. These shells may be designed to protect from their environment, to aid in the storage, or to release their contents at specific rate or under a specific set of conditions. In the applications of microcapsules to cosmetics (particularly to cream), it may be necessary for microcapsules to have the following requirements; 1. the transparent shell film 2. the easy preparation process 3. insolubility in water or other solvents 4. easy breaking of shells on the palms of the hands upon usage 5. the composition of the innocuous ingredients for a human body. The shell materials and the preparation methods were studied to satisfy the above requirements. The most suitable microcapsules were prepared by a complex coacervation methods involving a phase separation in a gelatin-acacia mixture in aqueous phase. Their shells were composed of the crosslinked gelatin. Glutaraldehyde was selected as the crosslinking agent to denature gelatin into an insolble substance in water or other solvents. The particle sizes of the developed microcapsules were controlled by the stirring rate on preparation or the polarity of the oil enclosed within. Also, the breaking strength of microcapsule was controlled by mixing a liquid and a solid oil component in the suitable ratio. The stabilization of fragrance, vitamin A palmitate and ethyl linoleate was tried by microencapsulation in order to protect the enclosed materials from their environment. Microencapsulated substances showed an excellent in stability compared with emulsificated substances. Further, a more excellent stability could be exhibited by increasing the shell thickness of microcapsule or modifying the microcapsule's gelatin film by poly-lysin. From the measurments of the oxygen permiability coefficient of the plane modified geratin film, it was supposed that the fine matrix composed of gelatin and poly-lysin prevented the oxygen permeability and this gave an excellent stability.