Two component waterborne crosslinkable polyurethane/acrylate-hybrid systems

摘要

An improved two component coating system based upon crosslinkable hydroxy containing polymers and a polyisocyanate crosslinker. The improvement resides in the utilization of a water-borne hydroxy-terminated polyurethane prepolymer/acrylate hybrid, preferably a hydroxy acrylate hybrid, in combination with a water-dispersible polyisocyanate. The two component coating composition can be prepared by: a) forming a carboxy-containing, water-dispersible, isocyanate-terminated polyurethane prepolymer, b) adding at least one acrylic monomer which contains a hydroxy-group to the carboxy-containing, water-dispersible, isocyanate-terminated polyurethane prepolymer to form a prepolymer/monomer mixture, c) adding an alkanolamine to the prepolymer/monomer mixture to introduce hydroxy functionality into the polyurethane prepolymer, d) dispersing the prepolymer/monomer mixture in water, e) adding an oil-soluble free radical initiator and a hydroxy- containing chain extender to the aqueous dispersion, f) polymerizing the acrylic monomers and completing the chain extension of the prepolymer by heating the aqueous dispersion, and g) mixing the resulting hybrid dispersion with a water-dispersible polyisocyanate.