Preparation of Microsphere Wax by Supercritical Carbon Dioxide

Abstract

          This research studies preparation of microsphere wax by Rapid Expansion of Supercritical Solutions (RESS) method. Supercritical carbon dioxide was used as a solvent. scCO₂-paraffin wax homogeneous solution was sprayed into anti-solvent. Particle size and morphology of particle were analyzed by SEM. Microsphere wax with particle sizes of 400-7,000 nm could be prepared which depending upon experimental conditions. The obtained particles by spray into water were shown spherical shape and smaller than those produced by spray into air. Spraying into water impedes particle’s growth and agglomeration.  It could be described by We number. Increasing of pre-expansion temperature 70-90°C and pre-expansion pressure              120-160 bar resulted to the particle size reduction from 1,000 to 400 nm. It could be described by supersaturation ratio. Adding 0.3 wt% of sorbitol as a nucleating agent the particle sizes decrease from 1,000 to 400-600 nm with the narrow size distribution. In addition, scCO₂-Paraffin wax homogeneous solution was sprayed through spiral nozzle into 150 rpm spinning of 5-15 v/v% mixture of water and ethylene glycol solution as a surfactant and stabilizing of particles growth. It was found that paraffin wax become spherical shape and particle agglomeration can be retarded. The particle size was decreased from 7 to 1 µm when the concentration of ethylene glycol increased.