The influence of process variables on the preparation and properties of spherical granules by the process of extrusion and spheronisation

Abstract

The influence of spheronisation process variables of time, load, speed of rotation and plate texture on the properties of size, shape and density of granules has been assessed with a standard extrudate produced by a cylinder extruder. It was found that optimum conditions of load and speed of rotation existed in that too low a speed produced no significant shape changes in the extrudate, while too high a speed resulted in a size reduction of the particles. A low load appeared to give poor particle/particle interaction while a high load produced poor plate/particle interaction. Increase in the length of the die in the cylinder extruder resulted in the inability to spheronise the extrudate under what had been previously optimum conditions of speed and load. No such loss of spheronisation performance occurred with processing of extrudate from two lengths of die of a ram extruder on a spheroniser with different plate textures. The granules produced, however, were significantly larger than those obtained for the same wet mass processed by the cylinder extruder.