(429a) The Use of Ribbon Attributes in the Scale-up of a Roller Compactor Process

The objective of this study was to develop the relationships between the ribbon attributes and downstream processing that will enable the use of an attribute centric strategy for scaling up a roller compaction manufacturing process.

Theoretical

A common method for scaling up a roller compaction process from development equipment to commercial equipment is to use a parametric strategy. The parametric strategy focuses on determining the equipment parameter values for the commercial equipment based process development work on smaller equipment, often by using manufacturer recommended equivalency factors. This approach neglects the importance of maintaining a similarity of the quality of the ribbons and granules produced between two different scales, and the potential effects on downstream processes. An alternative strategy, focusing on the attributes of ribbons, is proposed. It calls for adjusting the ribbon production parameters on the commercial equipment to attain ribbon attribute values equivalent to that produced in development.

Experimental

Two different sized roller compactors were run in automatic mode with the roll gap control turned on. In this mode the gap between the rolls and the maximum pressure on the rolls is set at predetermined levels. The feed screw speed floats to maintain a sufficient powder flow to produce ribbons at the preset thickness and density. A 2^(5-1) fractional factorial statistical design was used to identify the optimum ribbon attributes for a model powder on an Alexanderwerk WP120. The desired ribbon quality was then used for the scale-up to a commercial Alexanderwerk WP200.

Results

Relationships were established between ribbon thickness/density and downstream process intermediate attributes such as granule mean size/flow and compactability. In selecting the optimum ribbon attributes, three constraints were placed on the data set and solved simultaneously. The three constraints were a minimum mass flow, a minimum compactability, and a minimum process stability. The downstream intermediate attributes for the commercial operation were compared to that projected from development. The mean particle size of the commercial granulation was larger than projected, but the flow was in line with the prediction. The compactability of the commercial granulation was similar to that projected from development.

Conclusion

The use of ribbon attributes was successfully applied to scale-up the roller compaction process and produces granules with performance similar to that in development.