Aqueous not gelation ability which end, anionic polyurethane - dispersions and process for their preparation

摘要

Aqueous dispersion adhesives of anionic polyurethanes which have high heat resistance and low activation temperature, even when employed without addition of a cross-linker. The polyurethane is the reaction product of an isocyanate terminated polyurethane prepolymer, and water. The polyurethane prepolymer is the reaction product of a polyol component and a diisocyanate component, the polyolcomponent including: a sulfonated polyester polyol, a hydroxy carboxylic acid of the formula: (HO)xR (COOH)y wherein (R) represents a straight or branched, hydrocarbon radical containing 1 to 12 carbon atoms, and x and y represent values from 1 to 3, and optionally, a low molecular weight aliphatic diol having a molecular weight of from 60 to 400, a non-sulfonated polyol, and the diisocyanate component being selected from the group consisting of aromatic diisocyanates, isopherone diisocyanate, hexamethylene diisocyanate and mixtures thereof. The dispersions are prepared by mixing prepolymer and water at a temperature of at least 60 DEG C for sufficient time to fully react the isocyanate groups in a prepolymer self-extension reaction with water, typically at least 0.5 hour. The dispersions of the invention provide higher strength adhesive bonds than identical prepolymer dispersions extended with diamine chain extender, instead of water, after dispersion. The adhesive composition may also be modified to include a dispersed polymer or copolymer of an ethylenically unsaturated monomer. Such compositions may be obtained by preparing the sulfonated polyurethane in the presence of an ethylenically unsaturated monomer and subsequently subjecting the mixture to free-radical polymerization.