(529d) Solubility and Concentration Effects On Precipitation in Supercritical Antisolvent Processes

Studies were performed in a high magnification visualization system to determine the effects of solubility, concentration, and mass transfer on size distributions of particles produced using the supercritical antisolvent (SAS) precipitation process. The precipitation vessel includes clear windows for process visualization and filters for particle collection. Visualizations of the spray were obtained at various distances from the nozzle to measure the jet breakup lengths and droplet sizes. Solutions of polymethyl methacrylate in the solvents ethanol and acetone were processed via SAS using compressed carbon dioxide. Also, copolymers from the monomers methyl methacrylate and vinyl pyrrolidone were processed using SAS to observe the effects of their solubility in ethanol. The solubilities of the copolymers were influenced by the methyl methacrylate to vinyl pyrrolidone ratio. The process operating conditions (pressure, temperature, density) affects SAS spray characteristics and the resulting particles. Furthermore, studies have been conducted using planar laser induced fluorescence (PLIF) in SAS precipitation with a fluorescent molecule, poly[methylmethacrylate-co-(7-(4-trifluoromethyl)coumarin methacrylamide)], to obtain in situ concentration fields of the solute to characterize the mass transfer. The precipitated particles from these studies were analyzed with a scanning electron microscope and particle size distribution analysis. Relations between the process characteristics, the solvent-solute pairings, and the particle properties will be discussed.