Abstract
Purpose
Most rotary tablet presses contain a feed frame to provide a continuous powder flow and to feed powder into the dies. The wide residence time distribution (RTD) of these feed frames is problematic, because it negatively affects material traceability in continuous manufacturing. In a rotary tablet press, different machine settings influence the RTD, which is characterized by the mean and the width of the distribution. This study focused on the effects of the rotational speed of the feed frame paddles and the rotary tablet press throughput on the RTD.
Methods
An in-line UV/Vis measurement method was developed for determining the RTD in the feed frame. A model based on a plug flow and a continuous stirred tank reactor was adapted to model the experimentally determined RTDs. Finally, the mixing capacity of a feed frame was evaluated and correlated with a model parameter of the RTD.
Results
Overall, the developed UV/Vis measurement method was suitable and could be used to obtain process information regarding content uniformity in real time. The experimentally-determined RTDs were described well by fitting an inverse mixing and a transport time. In addition, a correlation between the location and the shape of measured RTDs and tablet press throughput was found. In contrast, rotational feed frame paddle speed did not affect the RTDs. Split-feeding experiments indicated the mixing capacity of the rotary tablet press feed frame.
Conclusion
The inverse mixing time can be used as an initial indicator for estimating the mixing capacity.
Correction Statement
This article has been corrected with minor changes. These changes do not impact the academic content of the article.
Acknowledgements
The authors are grateful for the assistance of Elizabeth Ely (EIES, Lafayette, IN, USA) in preparing the manuscript. The authors also thank JRS Pharma and Meggle for providing Vivapur 102 and Tablettose 80, respectively.
Disclosure statement
The authors declare no conflict of interest.