The application of lower punch vibration to improve the tableting process of a rotary tablet press

Abstract

Because of the economically attractive production possibilities, the good physicochemical properties and the high patient compliance, tablets are advantageous and present an attractive approach for API application. According to the regulatory quality requirements, high standards are expected for the tablet formulation as such and for the respective production process. Therefore, expensive and specially particleengineered excipients as well as upstream production processes such as granulation are often necessary to meet the required tableting properties such as flowability, compressibility, and compactibility of the powders to be tableted. One possibility to improve the tableting process is the application of ultrasonic tool vibration during tablet compaction. However, the vibration systems developed so far show a limited applicability and may only be used on a laboratory scale. For this reason, the present thesis deals with the development of an innovative pneumatic vibration system that improves the tableting process and especially the die filling step. By means of a targeted pneumatic lower punch vibration within the filling cam, the die filling may be improved, the powder bed within the die may be densified, and entrapped air within the powder bed may be removed. For this purpose, in a first study a pneumatically operating vibration system for laboratory scale was developed and investigated with regard to its performance characteristics and a subsequent scale-up. The powder bed densification within a die was recorded with a high-speed camera system and subsequently quantified with an image analyzing program. It was observed that the two investigated vibration systems met the required properties to allow a fast and significant densification of the powder bed within the die. In a second study, a respective vibration system was developed and implemented on a rotary tablet press. Subsequently, the performance characteristics of both vibration systems were investigated during tablet production. It was shown that the application of lower punch vibration led to improved die filling as the consequence of the rearrangement of the powder particles within the die. Furthermore, new contact surfaces between the powder particles are created, which positively influence the bondability and thus the resulting mechanical tablet stability. In a third project, the applicability of lower punch vibration was investigated with regard to the avoidance of production errors such as capping and/or lamination. The occurrence of capping and/or lamination during or after tablet manufacturing is often caused by entrapped air within the tablet. By lower punch vibration, it was possible to remove the entrapped air prior to the compaction step and thus the occurrence of capping and/or lamination was partially or completely prevented. The last study dealt with the influence of lower punch vibration on various tableting properties of the powders to be tableted (e.g. bondability, compactibility) and the resulting quality attributes of the manufactured tablets (e.g. crushing force, friability). The results clearly showed that depending on the used powder formulation, important tableting properties are positively influenced by the application of pneumatic lower punch vibration, thus leading to an increased mechanical tablet stability. In summary, the application of pneumatic lower punch vibration is a promising and innovative approach to improve the tableting process as well as to meet the quality requirements of the tablets.