A study of the mechanisms of wet spherical agglomeration of pharmaceutical powders

Spherical agglomeration of a number of chemical and pharmaceutical powders was effected in a stirred liquid mixture using the navel technique developed by Kawashima and Gapes, with modifications. The compounds were first classified into four groups on the basis of their solubilities in the liquid systems employed and, accordingly, agglomerated using appropriately developed methods. Each powdered material was first suspended in a liquid medium (external phase) and agglomeration was achieved by addition of a relatively small amount of ''bridging'' liquid (internal phase) which was immiscible with the (external) dispersion medium. The resulting spherical agglomerates were examined for size, binding strength, and surface topography. It appeared that a considerable number of the suspended particles initially underwent partial dissolution in the bridging liquid. The dissolved portion then collected the undissolved powder into spherical agglomerates under the influence of continuous stirring. Based on the trials and observations on a number of materials ranging from inorganics to organics, the general guidelines for spherical agglomeration of pharmaceutical powders were established. It is hoped that these guidelines will aid the application of this technique in the pharmaceutical and allied industries.