Coating EPA-complying Waterborne and 100% Solid Flexible Laminating Adhesives

Flexible packaging converters are increasingly using U.S. Environmental Protection Agency (EPA)-complying adhesives, in aqueous and 100% solid forms. Aqueous grades are applied with the same direct gravure coating stations used for solventborne systems; 100% solid types are applied by offset gravure. In both cases, new variables are introduced related to these less familiar forms. Wet-out, the coating quality, and the initial bond strength are affected. The variables must be understood and adjusted for optimum results. These variables fall into three groups. Some directly involve the adhesive, such as surface tension and vehicle-release characteristics; others involve the substrate, most important, the surface free energy. Coating equipment variables such as heat transfer at the laminating nip make up the third group.