Stable polyurethane latices, emulsifiable prepolymers therefor and

Abstract

Novel emulsifiable prepolymers for polyurethanes comprising an isocyanate prepolymer a minor proportion of the terminal isocyanate groups of which have been reacted with a quaternized tertiary amino alcohol, storage stable polyurethane latices produced therefrom and methods of making them are described. In a preferred embodiment a conventional isocyanate terminated prepolymer is first produced by the reaction of a polyol, preferably a diol of polyether or polyester origin, with a stoichiometric excess of a polyisocyanate, preferably a diisocyanate such as toluene diisocyanate; this prepolymer is then reacted, under anhydrous conditions, with a small amount, usually from about 1% to 5%, preferably about 1% to about 2%, by weight of a quaternized tertiary amino alcohol. Alternatively, a small amount of the quaternized tertiary amino alcohol may be included in the mixture of polyol and excess isocyanate used for making the prepolymer. In both cases there is obtained a prepolymer a minor proportion of the terminal isocyanate groups of which have been reacted through an urethane (carbamic ester) linkage with the quaternized tertiary amino alcohol. The thus obtained prepolymer is readily emulsifiable in water, without added surfactant type emulsifiers, whereby chain extension is effected by reaction of the free isocyanate groups of the prepolymer with the water, or an added diamine such as propylene diamine, to thereby produce storage stable, fully polymerized polyurethane latices useful, inter alia, for the production of films and coatings on a variety of both porous and non-porous substrates.