Combination of Colloidal Silicon Dioxide with Spray-Dried Solid Dispersion to Facilitate Discharge from an Agitated Dryer

Abstract

A feasibility evaluation of the addition of fumed silica (SiO 2 ) into an agitated dryer to aid spray-dried solid dispersion intermediate (SDSDi) flow during secondary drying and discharge is described. The quantity of SiO 2 to enhance the flow character of SDSDi was assessed by measuring particle size distribution, bulk density, and flow-through-an-orifice. Results indicate that the addition of the SiO 2 did not alter the drying kinetics and did not impact the bulk particle size distribution of the SDSDi. While bulk density of SDSDi increased with the addition of SiO 2 , the flow, and thus the recovery of the SDSDi-SiO 2 batch from the secondary dryer, was significantly higher than that for the intermediate alone. Imaging indicated uniform distribution of SiO 2 in the bulk powder and coating on intermediate particles. Premixing and co-sieving of the SiO 2 with a portion of pre-dry SDSDi promotes the uniform distribution of SiO 2 within the bulk powder bed.