EFFECT OF CRYSTALLINITY OF MICROCRYSTALLINE CELLULOSE ON GRANULATION IN HIGH-SHEAR MIXER

Granulation was carried out using binary mixtures of microcrystalline cellulose (MCC) and cornstarch (CS); water was used as granulating liq uid. The effect of crystallinity of MCC on granulation was examined us ing MCC pulverized by a jet mill (J-MCC) and a vibrational rod mill (R -MCC). Crystallinity of J-MCC was nearly equal to that of intact MCC ( I-MCC), but that of R-MCC was remarkably low due to the mechanochemica l effect. The growth rate of granules with R-MCC was greater than thos e with I-MCC and J-MCC; the latter two had a grnule having a core (MCC and CS) around which CS was layered. R-MCC provided granules in which CS and abraded MCC were homogeneously mixed. In addition, R-MCC remar kably decreased the difference in drug content among the size fraction s of granules compared with I-MCC. These results suggest that the decr ease in crystallinity of MCC may increase the tendency of its abrasion by shear force of impeller, because of an increase of the fragile amo rphous region swollen by added water; this, in turn, results in a diff erence in the growth mechanism and in a greater growth rate.