Influence of cellulose type on the properties of extruded pellets - II. Production and properties of pellets

Pelletization using various types of cellulose was performed in a twin scre w extruder followed ed by a spheronization step. Most types of untreated mi crocrystalline cellulose and a silicified type behaved similarly during the extrusion process and imperceptible differences in the properties of resul tant pellets were observed. The only exception was the microcrystalline cel lulose type which had a higher density and yielded pellets with unsatisfact ory properties after the spheronization process. In contrast, a treated typ e of microcrystalline cellulose with colloidal grade was easily extruded, b ut the pellets produced were of poor quality under all the processing condi tions investigated. The different types of powder cellulose did not constit ute appropriate excipients for extrusion. Only one type of powder cellulose produced an extrudate which could be spheronized. This therefore shows cle arly that the behavior of cellulose material during the extrusion/spheroniz ation process depends to a considerable extent upon its physicochemical pro perties, since all the types investigated had the same original chemical st ructure.