Multi-stage granulation : an approach to enhance final granule attributes

A new method in a high shear wet granulation process was implemented to enhance the final granule attributes. The granulation process in this method is divided into stages. In each stage different impeller speed was used. For this reason, this method of wet granulation is named here as multi-stage granulation (MSG) to be distinguish from the normal granulation (NG) in which the impeller speed is fixed throughout the granulation process. The experimental work revealed that by following the multi-stage granulation a noticeable change in the granules attributes has been observed. In this work, a high shear mixer (Eirich EL1) has been used. Calcium carbonate and melted polyethylene glycol (PEG1000) were used as a primary powder and binder respectively. The speed of impeller has been changed in a pulse mode throughout the granulation process from moderate speed to high speed in different intervals of time. Analysis of the produced granules showed that the granule characteristics with the multi-stage granulation were different to that with the normal granulation process. The granule median size affected clearly during the process. However, the granule porosity did not influence enormously during the process. The surface area of the granules also increased to some extent after the pulse change in the impeller speed. This increase in the surface area is reflected on the granules dissolution process. The collected granules after the pulse change were dissolving a slightly faster than the granule samples before the pulse change. This may due to the increase in the surface area of the granules.