Water-Borne Coatings Prepared from High Molecular Weight Epoxy Resins

As air pollution controls tighten, as fuel reserves dwindle and as industrial hazards are explored, solvents become increasingly unattractive as diluents for coatings. Industry has formulated several alternative coating technologies, probably the most advanced and easily substituted being water-borne. Our water-borne investigations led us recently to the discovery of techniques for preparing oil-in-water emulsions of our highest molecular weight epoxy resins. Known commercially as ARALDITE ® 488, these resins have weight average molecular weights of 15,000-20,000 and are ideal for applications requiring excellent adhesion and formability. Emulsions of these resins with relatively high solids content can be prepared while the corresponding solvent cuts have viscosities too high for use in coatings. For example, at 40% solids in Cellosolve acetate, ARALDITE 488 has a viscosity of 6000 cP. while the water-borne emulsion at the same solids level is only 1000 cP. For most methods of application the solids content of the