New Waterborne Epoxy Resin dispersion for Low-VOC, 2-Pack High-Performance Metal Primers Without Using Anticorrosion Pigments

By Ming Tsang, Martin Geisberger, Rosemaria Grasböck

A new waterborne, modified solid epoxy resin dispersion with good flexibility and improved shear stability is presented here. When this binder is used, high-performance metal primers can be formulated without the use of anticorrosion pigments. This is highly desirable since the toxicological effects of zinc phosphate and other zinc-based salts cause environmental concerns.

Primers formulated with this new resin provide equal or better corrosion resistance when compared to a number of waterborne and solventborne paint formulations (some of which contain anticorrosion pigments). Other advantages can be obtained, including the possibility of formulating metal primers with VOC content less than 100 g/L. In addition, direct pigment grinding is possible under processing conditions typical for other standard waterborne epoxy dispersions.

Solventborne 2-pack (2K) epoxy-amine coating systems have been commonly used to formulate high-performance metal primers. Crosslinkable at ambient temperatures, they provide excellent adhesion as well as corrosion protection to many metallic substrates. However, due to new, lowered VOC limits enacted in certain areas as well as other proposed regulation changes in North America and Europe, there is a need to reduce VOC by shifting to waterborne 2K epoxy systems.