Liquid-liquid emulsification by rotor/stator homogenization

Liquid-liquid emulsification is a critical step in the double emulsion microencapsulation process (W/O/W or O/W/O). This study focuses on the preparation of the primary emulsion (W/O or O/W) using rotor/stator homogenization. These homogenized emulsions were characterized based on the emulsion droplet size. Emulsion droplet size was mainly determined by the shear forces generated in the turbulent zone within the gap between the spinning rotor and the stationary stator. It was found that the size of these droplets decreases with increasing homogenization intensity and duration. The dependence of emulsion droplet size on viscosity, total volume size, volume ratio of the continuous phase to the dispersed phase. and the rotor/stator design was also investigated. The scaleability of rotor/stator homogenization is limited by the internal circulation determined by the rotor/stator assembly. Experiments using a large-scale rotor/stator homogenizer were conducted and the circulation rate was estimated using a simple flow model. As an alternative approach, an externally circulated flow-through homogenization process was used and compared to the batch operation. The results, derived from this study can serve as a basis for the evaluation of large-scale liquid-liquid emulsification in a microencapsulation process.