Aqueous Gloss Solutions: Formula and Process Variables Effects on the Surface Texture of Film Coated Tablets

Abstract

A specially designed spray box was constructed that allows spraying aqueous based film coating formulas under carefully controlled and reproducible conditions. The process variables studied included: spray distance, drying temperature, air cap, atomizing air pressure, and spray rate. Aqueous film coating gloss solutions were prepared using hydroxypropyl methyl cellulose. The viscosity grade, surface tension and concentration of polymer in solution were the formula variables studied. The surface texture of film coated tablets before and after spraying with the gloss solutions was analyzed with a stylus type surface roughness analyzer. The effect of the formula and process variables was also assessed by measurement of the tristimulus color difference obtained from colorimeter readings on the tablets, excluding versus including the specularly reflected light from the glossed surface. Within the ranges of the variables studied, the most significant effects on the surface texture were from the nozzle set up used and the spray distance.