Comparison of three different dry coating devices for fine API bulk property enhancements: The effect of device intensities and processing parameters

As predicted by the multi-asperity particle contact model, powder cohesion can be significantly reduced through dry coating of silica using a high-intensity vibratory mixer (HIVM). To promote industry adoption of dry coating, industry-relevant devices, a low-intensity V-blender and a medium-intensity comil, were evaluated against HIVM as a benchmarking control. Since low/medium intensity devices could lead to less effective silica dispersion, the contact model was extended to account for silica agglomeration. Three model APIs, belonging to very cohesive and cohesive flow category, were coated with two silica types (A200 and R972P) for enhancing flow (flow function coefficient - FFC) and conditioned bulk density (CBD). The V-blender exhibited least improvements in FFC and CBD. Corresponding SEM images revealed poor silica dispersion and presence of large porous agglomerates on coated API surfaces. Comil, at one and five passes with different-sized screens, performed better than V-blender. While FFC and CBD improved, some silica agglomeration on API surfaces was evident. HIVM, due to well-dispersed silica coating, achieved the most significant, 2-3 category enhancements in FFC and CBD at higher intensities. These results, in line with the extended model predictions, indicated that whereas V-blender would be unsuitable for dry coating due to excessive silica agglomeration, comil with finer screens would be a promising continuous manufacturing option for enhancing fine powder flowability. Device equivalence analysis identified lower intensity HIVM operating conditions that could achieve performance comparable to best outcomes from V-blender or comil; potentially enabling HIVM as a surrogate material sparing screening device.