Operating Parameters Investigation On The Preparation Of Microcapsule By Supercritical Impinging Stream

Microcapsules with narrow particle size distributions are widely used in many field, such as biochemistry, materials, pharmaceuticals, etc. Supercritical fluid assisted technologies allow the generation of particles that are difficult or even impossible to be achieved by general methods, particularly for substances with thermal sensitivity, structure instability or bioactivity. In this paper, a rapid expansion of supercritical solution combined with impinging stream technology was proposed for the coating of ultrafine particles. The process combined the advantages of RESS and the Impinging stream process, could vary operating conditions such as pressures, temperatures and impinging distances, to control particles morphology, size distribution and coating rate.Firstly, glass bead was taken as the model for the experimental study of preparing glass bead-paraffin microcapsules in this paper. The morphology, the size distribution and coating rate of microcapsules were characterized by a laser diffraction size analyzer, a scanning electron microscope (SEM) and a differential scanning calorimeter (DSC). The effect of the operation conditions, such as the pressure, temperature, impinging distance as well as the temperature before expanding were investigated. In the condition of experiments, P:20 MPa; T:75℃; Pre-T:140℃; D:70 mm, the microcapsules with uniform distribution of particle size were prepared. Simultaneous, the coating rate was 57.4%. The result shows that this way is a feasible method to prepare microcapsules.As a continuation, the process was employed to prepare the amoxicillin/PEG microcapsules. The morphology and the internal structure were tested by transmission electron microscope, simultaneous the size distribution and coating rate of microcapsules were characterized by a laser diffraction size analyzer, a scanning electron microscope and a uv-spectrophotometer. The effect of operation conditions, such as the pressure, temperature, impinging distance as well as the temperature before expanding were investigated. The result confirmed that the morphology could be controlled by varying the operation conditions. Increasing pressure and the impinging distance properly can increase the coating rate and make the particle size distribution of microcapsules more narrow. In the condition of experiments, P:12 MPa; T:60℃; Pre-T:80℃; D:70 mm, the microcapsules with uniform distribution of particle size were prepared. Simultaneous, the coating rate was 31.4%. The result shows that this way is a feasible method to prepare microcapsules.Base on the studying the improved RESS technology, it provides a novel method to prepare microcapsules (composite microparticles). Simultaneous, the effects of the operation conditions on the particle size distribution and coating rate are understood more deeply, which establishes the foundation for further study.