Waterborne self-crosslinkable polyurethane dispersions and polyurethane:acrylic hybrid dispersions

A composition comprising:

• (A) a dispersion of a crosslinkable polyurethane polymer in aqueous medium, and obtainable from a polyurethane prepolymer which is the reaction product of:
• (i) at least one polyisocyanate, and
• (ii) at least one organic compound containing at least two reactive groups which can react with isocyanates, and
• (iii) at least one compound which is capable to react with an isocyanate group and which contains at least one additional functional group which is susceptible either to dispersion in water and/or to a crosslinking reaction
• (iv) in an oxygenated solvent selected from the coalescing agents having a higher boiling point of from 150 to 250° C., under 760 mm Hg and being chemically inert towards isocyanates during the manufacture of the polyurethane;
• the so obtained polyurethane prepolymer being further neutralised and dispersed in water, and optionally then reacted with a chain extender or capping agent (v) having or not remaining functional groups after the capping;
• (B) a crosslinker which is a vinyl-type polymer having functional groups reactive with the functional groups of the polyurethane polymer (A).