Continuous production of thermoplastic polyurethane elastomers, for extrusion, injection molding, calendering or powder-slush process, involve determining the amount of diisocyanate for a maximum melt viscosity in the initial phase

摘要

Continuous production of thermoplastic polyurethane elastomers (I) from linear hydroxyl-terminated polyols (II), organic diisocyanates (III), diol chain extender(s) (IV) at an isocyanate/OH ratio of (0.9-1.2):1. Comprises determining amount of (III) to give maximum melt viscosity and adding this and 0.3-6 mol.% H-acid compound w.r.t. (IV) to give constant melt viscosity = 90% of maximum. Continuous production of thermoplastic polyurethane elastomers (I), with high thermal stability and as constant melt flow as possible, uses linear hydroxyl (OH)-terminated polyols (II) of molecular weight 600-5000, organic diisocyanates (III), diol and optionally triol chain extender(s) (IV) of molecular weight 62-500, with the overall isocyanate (NCO)/OH ratio adjusted to (0.9-1.2):1. The process comprises: (1) determining the amount of (III) needed to give the maximum melt viscosity by varying the amount of (III) within the cited range in the initial phase; and (2) keeping this amount constant and also simultaneously adding H-acid compound in small amounts of 0.3-6 mole-% with respect to (IV) to adjust the melt viscosity to a constant value less than 90% of the maximum.