A mixing model for multicomponent reactions in twin screw extruders applied to the polymerization of urethanes

Abstract

To understand the performance of multicomponent reactions in twin screw extruders the mixing mechanism in the extruder had to be understood. Therefore, two new relevant mixing parameters are defined; the mixing efficiency, which is the average number of passages of material through a high shear region: and the mixing deficiency, which is the fraction of material that does not pass through a high shear region. With' these parameters an analysis can be made of the mixing circumstances in the extruder. The new model was applied to the polymerization of urethanes in a counter-rotating twin screw extruder.The results agreed very well with the theoretical expectations.

Reactive extrusion of poly(urethane‐isocyanurate)

“…This is explained as a change in the screw speed causing changes in the mean residence time and the mixing parameters of the extruder. 13 At a higher rotation speed (25 rpm) the mixing efficiency was enhanced, however the residence time of the materials in the extruder was not sufficient for reaction completion. Also, at a lower rotation speed (15 rpm), there was a poor mixing efficiency, even though the residence time of the materials in the extruder was relatively higher, hence a lower amount of conversion was achieved.…”

“…The effects of various reaction and process parameters on the mixing efficiency have also been investigated in their work. 13 In spite of the above-mentioned reports on the reactive extrusion of linear PUs, there is no fundamental study on the formation of poly(urethaneisocyanurate)s (PUIR) in the TSE. These polymers are of great industrial interest, thanks to their good mechanical and physical properties.…”

Numerical simulation of reactive extrusion processes for activated anionic polymerization

“…Michaeli et al used the ideal "cascade of continuous stirred tank reactors" and "pipe reactor" models to develop the numerical simulation of the anionic polymerization of polystyrene and nylon 6 and the copolymerization of styrene-isoprene in a closely intermeshing co-rotating twin screw extruder Michaeli et al, 1993aMichaeli et al, , 1993b. Janssen et al carried out the numerical simulations of reactive extrusion processes for polymerization in a counter-rotating twin screw extruder (Ganzeveld and Janssen, 1992;Ganzeveld et al, 1994;de Graaf et al, 1997;Janssen et al, 2001). Gimenez et al numerically simulated the anionic polymerization process of -caprolactone in a co-rotating twin screw extruder (Gimenez et al, 2000a(Gimenez et al, , 2000bPoulesquen et al, 2001;Gimenez et al, 2000aGimenez et al, , 2000b.…”

In‐situ reactive blending of polyethylene and polypropylene in co‐rotating and counter‐rotating extruders

“…where vfis the number of filled chambers, Ql the total of leakage flows, and Q the throughput (25). Moreover, a minimal amount of residence time is also an important factor for the compatibilizjng effect.…”