Process for preparing thermoplastic polyurethanes

Production of thermoplastic polyurethane elastomers (TPU) involves (A) mixing (a) linear hydroxyl (OH)-terminated polyol(s) (molecular weight (Mw) 500-5000) with (b) organic diisocyanate in isocyanate (NCO)-reactive/NCO group equivalent ratio of (1.1-5.0):1 in mixing aggregate with high shear energy; (B) over 90% conversion to OH-terminated prepolymer (I) by reaction at over 80[deg]C; (C) mixing (I) with (c) chain extender(s) (Mw 60-490); (D) conversion to TPU by reaction with (b) to adjust overall equivalent ratio of NCO/NCO-reactive groups to (0.9-1.1):1. Production of thermoplastic polyurethane elastomers (TPU) with improved processability uses a multistage reaction comprising (A) mixing (a) linear hydroxyl (OH)-terminated polyol(s) of weight average molecular weight 500-5000 with (b) an organic diisocyanate in an equivalent ratio of isocyanate (NCO)-reactive groups to NCO groups of (1.1-5.0):1 in a mixing aggregate with high shear energy; (B) reacting the resultant mixture at temperatures above 80[deg]C to over 90% conversion with respect to (b), to a OH-terminated prepolymer (I); (C) mixing (I) with (c) chain extender(s) of molecular weight 60-490; (D) conversion to the TPU by reacting the mixture with component (b) in such an amount that the overall equivalent ratio of NCO/NCO-reactive groups is adjusted to (0.9-1.1):1. Stages (A) to (D) may take place in the presence of catalyst and with addition of 0-20 wt.% ancillaries and additives with respect to the total amount of TPU. An independent claim is included for use of the TPU for producing injection molded and extruded articles.