The paper, film, and foil surface coating process can be described as a web coating
process, which is a process that applies a continuous layer of coating material across essentially the entire width or any portion of the width of a web substrate to: (1) provide a covering, finish, or functional or protective layer to a substrate; (2) saturate a substrate for lamination; or (3) to provide adhesion between two substrates for lamination. The web coating operations and emission control techniques do not vary significantly among the sectors of the paper, film, and foil surface coating industry.
A typical coating line consists of a series of one or more unwind/feed stations; one or more coating applicators; the flash-off area (the area between two or more consecutive coating applicators or between the coating applicator and the drying oven); one or more drying ovens; and one or more rewind/cutting stations.
There are several different types of coating applicators that may be used to apply coatings. The most common types of applicators include: rotogravure, reverse roll, slot die, knife, flexography, Mayer rod, dip and squeeze, and extrusion/calendering. The type of coating applicator used may differ among coating application stations in the same coating line.