Abstract
Solid pharmaceutical tablets can be manufactured via three processing technologies: direct compression, dry granulation and wet granulation before the final compaction process. Dry granulation using roll compaction generally involves production of ribbons, followed by milling to produce granules and the production of tablets. The mechanical properties of ribbons produced during roll compaction can influence breakage behaviour in a mill and hence the performance of a drug formulation. Therefore it is important to explore critical factors that determine the quality of ribbons. In this study, MCC Avicel PH-102 was used as the model powder for roll compaction and the critical operating factors affecting ribbon quality were studied. MCC 102 ribbons were manufactured at a range of process conditions (roll speed, feed screw speed and compaction pressure) using the TF mini roll compactor with a serrated die & punch (DPS), grooved roll surface. The key ribbon properties measured are the powder feed ratio (defined as the ratio of feed screw speed to that of roll speed) and mass throughput ratio (defined as the mass of ribbons produced in a given time to that of fines). The porosity of ribbons was observed to depend significantly on powder feed ratio into the compaction zone. Porosity remained constant at a fixed feed ratio irrespective of the absolute roll speed and the feed screw speed conditions used. Mass throughput ratio is another factor that was introduced to describe process efficiency i.e. to draw comparison between the amount of ribbons and fines. The amount of ribbons and fines generated at a given process condition depends significantly on the feed screw speed and the compaction pressure. In addition, ribbon porosity decreased with increasing pressure but there was negligible effect on ribbon porosity when excessively high pressure (> 60 bar) was used. Ribbon porosity was also observed to decrease with increasing feed screw speed but the converse is true with increasing roll speed. In conclusion, the impact of various roll compaction process parameters were critically investigated and a detailed insight into the main factors (powder feed and mass throughput ratios) that govern the behaviour of roll compacted ribbons was provided. In future, the focus is to relate these process properties (and ribbon porosity) to granule size distribution from a milling process.