Regime map development for co-rotating twin screw granulation

Abstract

Continuous granulation is an important process for the future PAT (Processes analytical technology) initiative for the FDA. Therefore it is important to investigate the relationship between operating conditions and the granules. This thesis focused on one of the main equipments – twin screw extruder and attempted to develop the regime maps and the granulation hypothesis for twin screw granulation. In order to compare the mechanism with high-shear granulation that has been studied [1], the same materials were chosen (MCC (Microcrystalline cellulose) 102 and aqueous Polyethylene Glycol (PEG) 6000) and the regime maps were plotted by following similar operating conditions with reference [1]. One regime (granulation behaviour) was recognised for the short mixing geometry (16 mm, 30°), while three regimes (granulation, extrudates and blocked behaviours) were recognized for the long mixing geometry (64 mm, 30°). The regime maps suggested that the optimal granulation (narrow GSD (granule size distribution) and large mean granule size) can be achieved with a higher LS (Liquid-to-solid) ratio and a higher screw speed. The GSD was found further improved by reprocessing the same granules and/or manufacturing with aggressive mixing conditions.