Process for improving thermoplastic polyurethanes

An improved process for the preparation of thermoplastic polyurethane elastomers by a one-shot reaction of an organic diisocyanate, a polymeric diol, and a diol extender is disclosed wherein the diol components, either singly or together, are treated with a trivalent phosphorus compound prior to their reaction with the diisocyanate in the presence of a stannous tin urethane catalyst. The process when carried out with pure urethane grade diol components results in very efficient catalysis which in turn requires lower levels of stannous tin catalyst than would otherwise be employed. Moreover, the process can be carried out with diol components that are not urethane grade materials but which are contaminated by high levels of peroxidic impurities and which materials would otherwise be useless for the preparation of high grade elastomer products.