抄録
So-called Aerosol Solvent Extraction System (ASES), one of Supercritical Anti Solvent (SAS) processes, was applied to produce nanoparticles of yellow pigments (Hansa Yellow 5G). The ASES process involves spraying the liquid solution of solute+organic solvent through an atomizing nozzle as fine droplets into flowing supercritical CO2 under high pressure. When in contact with the supercritical CO2, CO2 dissolves into the liquid droplets and brings phase change of the liquid solvent very rapidly when temperature and pressure in a particle formation cell are controlled in supercritical region for the CO2+solvent binary mixture. Due to the rapid phase change and the high supersaturation of solute in mixed solution, solid nanoparticles can be precipitated. Using acetone solution of Hansa Yellow 5G, we already have reported that particle sizes were affected by experimental condition such as pressure, temperature, flow rate of the liquid solution and solute concentration. In this work we present how particle size and morphology would vary by changing spraying length and pressure in the cell. Spraying length is a distance between the nozzle and the glass plate placed in a cell for collection of particles. Pigment particles produced by the ASES process are collected by both a slide glass and polyethylene membrane filter. The particle size distribution and its morphology were observed by the SEM. The particle size became smaller as spraying length was longer. The spherical particle sizes of the Yellow Pigment 5G were distributed between 60-300 nm.
