Effervescent atomization of aqueous polymer solutions and dispersions

The purpose of this paper is to characterize the performance of effervescent atomizers via the effects of Air-to-Liquid-Mass-Ratio, (ALMR), feed pressure, and liquid viscosity on spray droplet size. Water and aqueous solutions having varying concentrations of polyvinylpyrrolidone, (PVP), (Kollidon 30, 90, and the copolymer VA 64), hydroxypropyl methylcellulose, (HPMC), (Pharmacoat 603, 606, and 615), and aqueous polymethacrylate dispersions, (Eudragit RS 30 D, RL 30 D, and L 30 D-55) were sprayed over a range of ALMRs from approximately 0.1 to 0.8 at feed pressures ranging from approximately 550 to 1590 kPa. Fluid viscosities ranged from 1 to 228 mPa.s. The ALMR of the spray was shown to be the most important factor influencing the Sauter mean diameter (SMD) of the droplets, while feed pressure was shown to have only a minor effect on droplet size. Sprays with SMDs between 7 and 12 microns were produced for the polymethacrylates, 13 to 24 microns for the PVPs, and 15 to 20 microns for the HPMCs, all at an ALMR of 0.4 and a feed pressure of 1172 kPa. A higher liquid viscosity lead to larger droplets. The correlation between viscosity and droplet size was found to be dependent on the type of polymer.