Process for applying a topcoat to a porous basecoat

Abstract

A process is provided that allows the production of multi-layer coatings in which one or more topcoats can be applied to a porous basecoat to produce a uniform and defect-free coating layer. Specifically, a process is provided in which a liquid is applied to the basecoat prior to topcoating such that the air in the basecoat is removed prior to topcoating. This process can occur in-line with a simple apparatus described herein. An added benefit of this method is that it also allows the possibility of adding functionality or performing chemistry to a basecoat after the basecoat is dried and before the topcoat is applied in a single process. For example, the wetting fluid may contain, but is not limited to, surfactants, pH modifiers, polymers, crosslinkers, pigments, and/or dye stabilizers. Advantages over what has been done before include the use of re-wetting process that allows a topcoat to be applied to a porous basecoat that is coated on a non-porous substrate such that bubbles are not formed in the topcoat. In addition, there is added flexibility of incorporating functionality or chemistry in the re-wetting process. Finally, the process is simple to implement and is compatible with many general coating methods, such as slot-die coating, rod coating, blade coating, gravure coating, knife-over-roll coating, or the like.