Implementation of powders - Humid granulation techniques and binders

In a first dossier [J 2 253] , we presented the basic principles and some theoretical concepts associated with wet granulation. In this dossier, we present the main wet granulation techniques, as well as the phenomena and growth mechanisms involved in the operation, and finally some criteria for choosing an appropriate granulation binder.

All wet granulation techniques are based on the movement and agitation of particles, followed by the introduction of the binding liquid. Thus, the main devices used in this field were originally powder mixing devices. Although, in principle, all agitation techniques can be used for wet granulation, some have become more widespread than others. The main difference between these techniques is the way in which the particles are brought into contact with each other:

• pneumatic agitation; this is the case with fluidized beds and their derivatives (jet bed, Wurster, granulator dryer, etc.);

• agitation by wall rotation: rotating plate and rotating drum;

• mechanical agitation: mixer-granulator .

In terms of stress, these different modes of action correspond to low, moderate and high shear rates respectively.