Optimal design and operation of reactive extrusion processes: application to the production and scale-up of polyurethane rheology modifiers for paints

Abstract

In this work, the methodology for the optimal design, operation and scale-up of reactive extrusion processes in twin-screw extruders previously presented in Reference (Cegla and Engell, 2023). is applied to the production of hydrophobically ethoxylated urethanes (HEURs). The new process is a promising alternative to the current batch technology in large reactors with long residence times. We demonstrate the use of model-based design and scale-up for this case. A novel mechanistic finite volume twin-screw extruder model is used as the process model, which is adapted to the process at hand by embedding a detailed description of the HEUR chemistry and rheology. An economic cost function is used to examine the scale-up process from an 18 mm extruder to a 27 and 75 mm extruders, considering a selected range of products. The comparison between the optimization results obtained for the individual products with the optimization results for the production of multiple material grades using the same screw setup shows the high flexibility of the extruder-based process. Significant energy savings compared with the conventional batch process can be achieved using reactive extrusion. To quantify the effort for the transition to a purely continuous production in terms of flexibility and process logistics, product changeovers are investigated.