Continuous Reactive Extrusion for TPU

As part of BIOMAC project, a tandem extrusion set-up will be used as a continuous reactor for the polymerization of various bio-based non-isocyanate polyurethanes (NIPUs) and the subsequent dispersion of various bio-based functional fillers.

Compared to standard batch reactions, the advantages of reactive extrusion (REx), a continuous and solvent-free process, include increased polymerization speeds, enhanced mixing of components, and the ability to work with highly viscous materials. Pilot line 9 consists of two 18 mm twin-screw extruders that may be connected in tandem and equipped with a side feeder, various solid and liquid feeders, vacuum venting and combined with relevant post-processing equipment (cooling belts, cooling baths, grinders). When complemented by extrusion simulation software, it is possible to simulate up-scaling to larger twin-screw extrusion lines as well. In addition to the ease with which this system may be controlled, it provides great flexibility and may be readily adapted to a range of synthetic conditions; adjustable parameters include the following:

  • output starting at 1 kg/h
  • temperatures up to 450 °C
  • screw speed up to 1200 rpm
  • large diversity of complementary screw profiles
  • length of extrusion from 44 to >100 L/D (longer residence times)
  • reduced torque limitations
pilot lines templates cover 1
pilot lines templates cover 2

Online monitoring of functional group concentrations is of great interest in polymerizations in general and in the case of reactive extrusion in particular. Additionally, controlling dispersion quality in reinforced thermoplastics is also possible and of particular interest in the context of the BIOMAC project.

With this in mind, a near infra-red (NIR) spectrometer will be connected through multiple probes to monitor inline REx polymerizations. In this way (and following careful, in-depth calibration prior to use), the degree of advancement of NIPU synthesis along the length of the tandem set-up will be determined in situ and in real-time, facilitating process optimization and saving time and materials.