GB1444086A - Polyurethanes - Google Patents

Abstract

1444086 Polyurethanes DUNLOP Ltd 14 Sept 1973 [12 Aug 1972] 37731/72 Heading C3R Polyurethanes are prepared by reacting a mixture of a relatively low M.W. diol having a M.W. up to 400 and a relatively high M.W. diol having a M.W. of at least 750, in solution in an inert solvent, with from 100 to 120% of the stoichiometric equivalent of a polyisocyanate in a process comprising (a) reacting an initial charge of 90 to 99% of the stoichiometric equivalent of the polyisocyanate with the diol mixture, the initial concentration of the reactants in the solvent being 60 to 80% by weight; (b) adding the remainder of the polyisocyanate incrementally during or on completion of the reaction (a); and (c) adding additional solvent, as the polymerization proceeds, only when necessary to maintain the processibility of the reaction mixture. The relatively low M.W. diol may be ethylene glycol, propylene glycol, 1,4-butane diol or 1,6-hexane diol. Polyethers and polyesters are the preferred relatively high M.W. diols. The most preferred relative molar proportion of the relatively low M.W. diol to the relatively high M.W. diol is between 2 : 1 and 5 : 1. A triol may be included in the diol mixture. The solvent may be toluene, a ketone, e.g. methyl ethyl ketone, an ester, e.g. ethyl acetate or a chlorinated hydrocarbon. An adhesive may be prepared by mixing the polyurethane elastomer with a resin which may be phenol-formaldehyde, melamineformaldehyde, urea-formaldehyde, a rosin ester, a metal resinate, a vinyl chloride-vinyl acetate copolymer, a chlorinated rubber, an oxidized wood rosin, a coumarone resin or a furane resin.