The effect of the physical states of binders on high-shear wet granulation and granule properties: a mechanistic approach toward understanding high-shear wet granulation process. Part II. Granulation and granule properties.

The objective is to provide mechanistic understanding of a preferred wet granulation process that a binder is added in a dry state. Blends of CaCO(3) and binders were prepared and used as model systems, and they were exposed to either 96% RH (rubbery/solution state) or 60% RH (glassy state) at room temperature to control the physical state of the binders, followed by high-shear granulation and particle size measurement. The blends of PVP K12, PVP K29/32, and HPC showed a significant increase in particle size after exposure to 96% RH. An increase of aspect ratio was also observed for the blend of HPC. In contrast, the blends being exposed to 60% RH did not exhibit any increase in particle size or aspect ratio. Regarding the effect of binder molecular weight on the mechanical strength of granules, granules of PVP K29/32 had higher strength than granules of PVP K12. This can be explained using polymer entanglement theory, in which the degree of polymerization (DP) of (N ∼ 440-540) of PVP K29/32 is above the critical value (N(c)  ∼ 300-600) for entanglement; while DP of PVP K12 (N ∼ 20-30) is below it. Finally, a water sorption-phase transition-diffusion induced granule growth model for granulation has been suggested.