Patent ID: 7358294
Filing Date: 2008-04-15
Classification: C08F,C08G,C09D

Abstract:
1. An aqueous coating composition comprising a physical blend of a crosslinkable water-dispersible polyurethane oligomer(s) and 10 to 56 wt % of a dispersed vinyl polymer, 0 to 25% of co-solvent by weight of the composition, said polyurethane oligomer(s) having: a) a measured weight average molecular weight in the range of from 1,500 to 50,000 Daltons; and b) a solution viscosity ≦150 Pa·s, as determined from an 80% by weight solids solution of the crosslinkable polyurethane oligomer(s) in at least one of the solvents selected from the group consisting of N-methylpyrrolidone, n-butylglycol and mixtures thereof, using a shear rate of 90±5 s said dispersed vinyl polymer(s) having: a) a measured weight average molecular weight ≧90,000 Daltons; and b) an acid value up to 100 mgKOH/g; said composition when drying to form a coating having the following properties: i) an open time of at least 20 minutes; ii) a wet edge time of at least 10 minutes; iii) a tack-free time of ≦20 hours; iv) an equilibrium viscosity of ≦5,000 Pa·s, at any solids content when drying in the range of from 20 to 55% by weight of the composition, using any shear rate in the range of from 9±0.5 to 90±5 s wherein the crosslinkable water-dispersible polyurethane oligomer(s) is crosslinkable by autooxidation optionally in combination with silane or Schiff base condensation.