In-line dynamic torque measurement in twin-screw extrusion process

Extrusion technology has been a focus of pharmaceutical research for many years. Extrusion processes are used for improvement of drug bioavailability, for bead manufacturing as well as for continuous granulation. Besides these, there are also several research efforts regarding the use of process understanding as a tool in quality management. Several initiatives of the Food and Drug Administration (FDA) about this issue such as Process Analytical Technology (PAT) and Quality by Design (QbD) are becoming more and more accepted.In the present study, a corotating twin-screw extruder was equipped with a torque gauge as a tool for process monitoring. The experimental setup was qualified in accordance with the ICH guidelines. The torque of extrusion correlated linearly with the water content in a wet extrusion process. Moreover, a pelletisation process was performed using different formulations in wet extrusion/spheronisation. A relationship between the torque on the screws and the shape of the pellets was found. In conclusion, the torque was found to be a suitable extrusion parameter for monitoring wet extrusion processes.