Direct pelletization in a rotary processor controlled by torque measurements. II: effects of changes in the content of microcrystalline cellulose.

In the present study we investigated the effect of changes in the content of microcrystalline cellulose (MCC) on a direct pelletization process in a rotary processor in which the liquid addition was terminated once a certain increase in torque was produced. Nine different mixtures of MCC and lactose with MCC contents varying from 10% to 100% (w/w) were pelletized using 6 different torque increase levels, and the changes in pellet characteristics were investigated. The pellet characteristics investigated were pellet shape, size, and size distribution as well as the water content of the pellets at the end of liquid addition. To produce spherical agglomerates with suitable characteristics in a reproducible way, a content of at least 20% (w/w) MCC was found necessary. Linear correlations were found between the MCC content and the water content and between the torque increase and the water content, showing that the torque increase is suitable to control the process. A higher torque increase or a higher MCC content was found to increase the water content independently of each other.