POLYURETHANES

摘要

1294450 Polyurethanes INMONT CORP 2 Dec 1969 [2 Dec 1968 25 April 1969] 58797/69 Headings C3C and C3R Solutions of thermoplastic polyurethanes dissolved in a liquid amide solvent are prepared by reacting at least one compound having hydroxyl groups and at least one compound having isocyanate groups, in solution in the solvent, the proportions of the reactants being such that their average functionality is at most 2, the reaction being carried out at a temperature above 30‹ C. and the solvent used being selected or treated so that it does not have a free tertiary amine content of more than 5 gram atoms of tertiary amino nitrogen per 109 grams of solvent, and the reaction being continued in solution until the intrinsic viscosity of the resulting dissolved polyurethane produced by the reaction is at least 0À8 (measured in the solvent at 25‹ C.) and terminating the reaction by adding an isocyanate reactive end capping reagent in an amount at least sufficient to react with all the remaining isocyanate groups. The solvent is suitably treated by including therein a monofunctional monosulphonic or monophosphonic acid in amounts to provide at least one acid group per tertiary amino group present in the solvent. The polyurethane is suitably prepared by reacting a hydroxyl-terminated linear polymer, e.g. a polyether or polyester, a diisocyanate and a diol chain extender in a first stage to provide an NCO group containing polymer and then reacting this polymer in a second stage with further diol chain extender. The diol chain extender in the first stage may be replaced by a polyfunctional reagent plus a monofunctional reagent so that the average functionality remains at 2 or less. The polyurethane-containing solutions may be converted into water-vapour permeable sheet materials by conventional techniques, suitably by mixing the solution with a microparticulate pore-forming material, followed by coagulation with water and removing the pore-forming material. These sheet materials may be used in the preparation of shoe uppers.