| 摘要 |
AQUEOUS POLYURETHANE-UREAS DISPERSIONS AND THEIR USE FOR THE PRODUCTION OF COATINGS HAVING IMPROVED HUMIDITY RESISTANCE The present invention is directed to stable, aqueous dispersions of polyurethane-ureas which are formed by a) preparing isocyanate-terminated prepolymers containing about 5 to 190 milliequivalents per 100 grams of polyurathane-urea of chemically incorporated potential anionic groups and/or anionic groups and up to about 10% by weight, based on the weight of the polyurethane-urea, of lateral and/or terminal hydrophilic chains containing ethylene oxide units, b) converting a sufficient amount of the potential anionic groups to anionic groups either before, during or after preparing the prepolymer such that the blend of step (c) can be stably dispersed in water, wherein at least about 50% of the counterions of the anionic groups are derived from volatile organic compounds, c) blending said prepolymer either before, during or after step (b) with an epoxy resin which is not dispersible in water and contains at least one epoxide group, such that the equivalent ratio of potential anionic groups and anionic groups having counterions derived from volatile organic compounds to epoxide groups, is about 0.2 to 20.0, d) dispersing the blend of prepolymer and epoxy resin in water and e) chain extending said dispersed blend with a polyamine having an average functionality of about 2.0 to 6.0 in an amount sufficient to provide a ratio of amino groups to isocyanate groups of about 0.6:1.0 to 1.0:1.0. The present invention is also directed to the use of the aqueous polyurethane-urea dispersions for the production of coated substrates having improved humidity resistance. |
