A novel approach of external lubrication in a rotary tablet press using electrostatics

PURPOSE: In powder compaction on rotary tablet presses, the addition of a lubricant is normally mandatory. However, the typical internal lubrication method tends toward overlubrication, resulting in an alteration of the critical quality attributes of the product. In this study, the feasibility of an external lubrication system only using electrostatics for the application was investigated. METHODS: Three well-established lubricants were analyzed regarding their ability to accumulate and retain charge. In subsequent tableting experiments, the impact of different lubrication methods on critical quality attributes and process parameters was investigated. RESULTS: Due to material characteristics, the charge on magnesium stearate particles was most stable over time. The application of this lubricant on the punches via external lubrication with electrostatic forces resulted in a significant reduction of the ejection forces. Furthermore, the tensile strength of the tablets produced in these trials was significantly higher compared to tablets that were produced with internal lubrication. CONCLUSION: The external lubrication method with an electrostatically charged lubricant is a promising method for reducing both the necessary amount of lubricant and the impact of the lubricant on the product.