Aqueous coating compositions urethane-vinyl stain resistant

摘要

An aqueous coating composition comprising: (i) 20 to 80% by weight of polyurethane A obtained by reacting: (a) an isocyanate terminated prepolymer formed from components comprising: (1) 20 to 80% by weight of at least one polyisocyanate (2) 3 to 10% by weight of at least one reactive polyol with isocyanate weight average molecular weight 500 Daltons, containing at least one group of dispersion ionic or potentially ionic water; (3) 0 to 15% by weight of at least one isocyanate-reactive polyol containing dispersing groups 10 nonionic water; (4) 17-77% by weight of at least one isocyanate-reactive polyol other than (3) weight average molecular weight of = 500 Dalton; (5) 0 to 20% by weight of at least one isocyanate-reactive polyol other than (2) or (3) weight 500 Daltons average molecular weight; in which (1), (2), (3), (4) and (5) total 100%; wherein the polyols (a) (3) to (5) have a total content ring structure = 48% by weight; and (b) a chain-extending compound active hydrogen; wherein the polyurethane A has an acid number in the range of 8 to 40 mg KOH / g and a content of hard = 40% by weight by weight segment polyurethane A; and (ii) 80 to 20% by weight of a vinyl polymer B with a glass transition temperature = 20 ° C; wherein (i) and (ii) total 100%; composition, when in form of a film, exhibits a transmission rate of moisture vapor (MVTR) = 500 g / m2 / 24 h; and wherein the MVTR is measured as an average after 1 and 4 days by ASTM test method D1653-91a as described herein, measured under tropical conditions at a constant temperature of 38 ° C and a relative humidity ( RH) 90%; and a wet film thickness of 12 microns.