Effect of process parameters on the melt granulation of pharmaceutical powders

Co-melt granulation of lactose and PEG was investigated in a fluidised bed granulator. The effect of process parameters such as binder content and binder viscosity were correlated to granulation time and particle size distribution. The experimental data indicated that after initial nucleation the granulation mechanism was dependent upon binder content and binder viscosity. When the binder content was increased above 18% (w/w) de-fluidisation of the bed occurred and granulation moved to the slurry regime. As the process involved the melt granulation of relatively high molecular weight (6–20 k) and thus high viscosity PEG (500–19000 mPa s), it was found that binder viscosity had a significant affect on the granule growth mechanism. Granulation with a binder viscosity of 500 mPa s resulted in granule growth by coalescence, however, an increase in binder viscosity resulted in less coalescence and a lower granule growth rate. Furthermore, the granulation data were characterised by Stokes number analysis.