Laser Triangulation Based In-Line Elastic Recovery Measurement for the Determination of Ribbon Solid Fraction in Roll Compaction

Abstract

Process Analytical Technology (PAT) plays a crucial role in the design of today's manufacturing lines as continuous manufacturing becomes more important. Until now PAT tools to measure the ribbon solid fraction (SF_ribbon) in-line are not commonly used in roll compaction. The aim of this study was therefore to establish a new approach as PAT for in-line ribbon solid fraction determination. Different placebo formulations with different binders and one formulation containing active pharmaceutical ingredient were investigated using in-line laser triangulation measurement to detect the ribbon thickness after compaction. With this the ribbon elastic recovery was determined in-line (ER_in-line) while the ribbons are attached to the roll surface. It was found that the ratio (ER_ratio) between the total elastic recovery and ER_in-line is formulation specific and not influenced by any process parameters. This enables ER_ratio as prediction tool for SF_ribbon, if the solid fraction at gap (SF_gap) width is known. SF_gap was determined with ribbon mass flow measurement or based on the Midoux model, a simplified Johanson model, gaining two prediction models for SF_ribbon. Both models showed good agreement of the predicted SF_ribbon and the measured one.

Keywords: Elastic recovery; In-line; Laser triangulation; Process analytical technology (PAT); Ribbon solid fraction; Roll compaction.