Improvement of tabletability via twin-screw melt granulation: Focus on binder distribution

In this study, the impact of binder distribution on the tabletability and compactibility of granules produced by twin-screw melt granulation was investigated. To this end, two grades of dicalcium phosphate anhydrous (fine and coarse) were used as model substances (filler) in combination with two grades of poloxamer (fine and coarse) as melt binder at three concentrations. For the fine filler, granule forming followed the immersion mechanism, whereas a distribution mechanism was observed in case of the coarse filler. Compared to the granules prepared with the coarse filler, the tabletability of granules prepared with the fine filler increased more pronouncedly compared to the corresponding physical mixtures (PM). In general, tabletability, compressibility and compactibility depended predominantly on the distribution of the binder in the tablet, and the homogeneity of distribution correlated with increased tensile strength. Binder distribution was analysed using scanning electron microscopy combined with energy-dispersive X-ray analysis (SEM/EDX) and quantified by image-analysis of the tablet surface. PMs in general varied in tabletability. However, even at tabletability similar to the granules, all PMs suffered from poor flow and/or segregation.