Compression behaviour of granules produced via twin-screw melt granulation: Effect of initial particle size on granulation efficiency

This study focuses on the impact of initial particle size on the tabletability and the deformation behaviour (i.e. plasticity) of granules produced by twin-screw melt granulation (TSMG). As model substances, three different grades of anhydrous dicalcium phosphate (aDCP) were melt-granulated with polyethylene glycol 6000 (PEG) using a twin-screw granulator. Compaction performance of the granules and the corresponding physical mixtures (PM) was evaluated by in-die and out-of-die compaction analysis. A major impact on granules deformation behaviour was found for the relation of the specific surface area of the filler material to the binder content.

Highlights

• Melt granulation effectively changed brittle into plastic deformation behaviour.

• Efficiency linked to binder distribution quantified by EDX-mapping and filler PSD.

• Tabletability correlated with the achieved solid fraction after compression.

• For physical mixtures solid fraction followed a modified Kawakita model.

• Granules deviation from the model correlated with the plasticity performance factor.

A relative yield pressure (YP) was introduced to describe the enhancement in plastic deformation behaviour, defined as the plasticity performance factor (PPF). Furthermore, a modified Kawakita model was used to describe the granulation efficiency, compared to a calculated physical mixture model. Granules under investigation showed an increased plastic deformation, enhanced tabletability and reduced elastic recovery (ER). The binder was shown to be finely distributed and to fill the voids between the aDCP particles (image analysis of the carbon energy dispersive X-ray maps). A small initial particle size of filler material (DI-CAFOS®A7 and A12) was more efficient than a larger particle size (DI-CAFOS® A60). A very low particle size (DI-CAFOS® A7) required the addition of 1% (w/w) colloidal silicon dioxide to enable feeding of the material into the granulator. Moreover, due to the larger surface area of these particles, a higher amount of binder was necessary to achieve a low PPF and a high tensile strength (TS). Continue on Compression behaviour of granules produced via twin-screw melt granulation

Keywords:  Twin-screw melt granulation, Tabletability, Primary particle size, Plasticity performance factor, Kawakita model, Heckel analysis, anhydrous dicalcium phosphate (aDCP), Polyethylene glycol (PEG) 6000, colloidal silicium dioxide (AEROSIL® 200)