(124f) Evaluation of the Effect of Blade Angle On a High Shear Wet Granulation

Wet granulation is a widely used intermediate process in solid dosage manufacturing. It improves flowability of in-process materials, decreases segregation, reduces dust and modifies the appearance and properties of final product.

As well as other granulation methods, high shear wet granulation is very sensitive to operational and design parameters that have not been fully studied nor understood. The effectiveness of this process, particle growth behavior and dynamics are the result of different mechanisms that may take place simultaneously inside a granulator (e.g. wetting, coalescence, attrition), and these mechanisms are strongly affected by the energy provided to the system. In a high shear granulation the impeller plays a fundamental role since it determines the way in which the energy will be transmitted to the material. Therefore, the aim of this work is to study the effect of impeller design in the growth kinetics of a high shear granulation.

Experiments were performed in a laboratory-scale high shear granulator using a lactose-based formulation as model system and a diluted Povidone solution as binder. A factorial design was implemented using three-bladed impellers at different blade angles (42°, 90° and 127°) and agitation velocities (450 rpm, 620 rpm and 807 rpm). Early-stage growth kinetics was determined performing granulations at 6 different massing times from 15 s to 150 s after wetting stage. The study was supported using a Laser Diffraction Method (Insitec T, Malvern Inc.) and conventional sieving for particle size analysis and Powder Rheometry (FT4, Freeman Technology) to characterize final flowability of the material and other properties such as: compressibility and stability.

Experimental results show that as blade angle increase there is a tendency to decrease particle growth kinetics. Thus, a model was proposed to describe and quantify the influence of the blade angle and its interaction with the impeller velocity.