Microwave assisted drying of cellulose derivative (HPMC) granular solids

Drying constitutes a critical unit operation in the manufacturing of pharmaceutical powders and their associated products. In this work, the drying processes of cellulose derivative (hydroxypropyl methyl cellulose, HPMC) granules were investigated. Granules of HPMC powders were produced by a wet granulation process using a hydro-alcoholic solution as binder phase, then they were dried with different drying methods based on traditional (by convective heating) and innovative (by microwave heating) techniques. To compare drying kinetics, experimental data were fitted by Lewis equation obtaining drying coefficients, and time/temperature process parameters were investigated. Microwave assisted drying showed reduced process times and, under some conditions, it allowed no drastic process temperatures. Since granular solids have a great relevance in pharmaceutical solid dosage form preparations, novel methods of drying with better performances appeared an issue of great interest for industry.