Urethane-acrylic hybrid polymer dispersion

A stable, precrosslinked urethane-acrylic hybrid polymer dispersion formed by:

• (a) blending:
• (i) an isocyanate terminated urethane prepolymer which is the reaction product of monomeric diisocyanate and active hydrogen containing materials having from 1.8 to 3.0 active hydrogens per molecule and a molecular weight of 62 to 5000, and having an NCO content of 1.0 to 1.9% by weight
• (ii) one or more vinyl monomers, inert to isocyanate functionality, and
• (b) reacting 0 to 100% of the isocyanate groups of the urethane prepolymer (i) in blend (a) with a mono-functional active hydrogen containing vinyl monomer
• (c) blending the reaction product of (b) with a polyisocyanate having an average isocyanate functionality of less than 4.0 and equal to 0.5 to 20% of the total weight of the solids of the polyurethane prepolymer (i) and polyisocyanate and
• (d) dispersing into water,
• (e) chain extending the residual isocyanate groups of the prepolymer with one or more active hydrogen containing compounds, and
• (f) reacting the vinyl groups of the blend by free radical polymerization.

A stable precrosslinked, urethane-acrylic hybrid polymer dispersion formed by:

• (a) blending:
• (i) an isocyanate terminated urethane prepolymer which is the reaction product of monomeric diisocyanate and active hydrogen containing materials having from 1.8 to 3.0 active hydrogens per molecule and molecular weight of 62 to 5000, and having an NCO content of 1.0 to 1.9% by weight;
• (ii) a polyisocyanate equal to 0.5 to 20% of the solids by weight of (i) and (ii), wherein the polyisocyanate is selected from the group consisting of biurets, isocyanurates and allophonates of hexamethylene diisocyanate and wherein the polyisocyanate has an average isocyanate functionality of less than 4.0, and
• (iii) one or more vinyl monomers inert to isocyanate functionality, and
• (b) reacting 0 to 100% of the isocyanate groups of the urethane prepolymer (i) and polyisocyanate (ii) in blend (a) with a monofunctional active hydrogen containing vinyl monomer, and
• (c) dispersing (b) into water,
• (d) chain extending residual isocyanate groups of the prepolymer with one or more active hydrogen containing compounds, and
• (e) reacting the vinyl groups of the blend by free radical polymerization.