Microemulsions Generation Using PGSS (Particles from Gas Saturated Solutions) Technique

摘要

High pressure technology e.g. PGSS (Particles from Gas Saturated Solutions) allows to produce powders with properties difficult to achieve by classical methods like milling, crystallization or spray drying. In the last years, research for the PGSS process was focused on the production of single component systems but another very promising possibility is to use the PGSS process to obtain filled micro particles, solid - solid or solid-liquid composites. For powder production the shell and core materials are melted if necessary and pumped into a static mixer. Here these substances are mixed with supercritical carbon dioxide (CO_2). Subsequently the mixture is expanded through a nozzle into a spray tower. Due to the Joule-Thomson effect of the expanding carbon dioxide, a cooling of the droplets occurs and this leads to the formation of particles when they under-run the solidifying temperature. These particles can be gathered in the spray tower. Encapsulation of sensitive substances forms an effective protection against stress factors. Besides protection, encapsulation opens furthermore new possibilities for the controlled release of active substances or for increased bioavailability. This can be, for example, achieved in the case of micro emulsions. Thus an active substance can be solved in water that is subsequently encapsulated in a fatty matrix. The system can be stabilized with the help of an emulsifier. The obtained powderous emulsions have tailor made properties like bulk density, size, morphology and water content. The properties of the micro emulsion can be adjusted by the process parameters of the PGSS process.