Oxidation occurs when aluminum foil is
manufactured and exposed to air. The oxidation manifests
itself in a thin layer of aluminum oxide, which deposits on the
surface of the foil. In this state, the aluminum oxide
prevents the ink film from wetting the surface, causing ink beading
and poor adhesion. To prevent this, a primer prints over
the foil surface to promote adhesion and positive printability
characteristics for the ink. There are many primers depending
on the specific resin used. Further, the primer can be
formulated as a color or it can be made opaque or transparent,
depending upon the customers' specifications. International
Ink Company's Inter-Prime Series can be formulated in either a
Solvent-Based or Water-Based system and are available in the
following resin systems: acrylic, nitrocellulose, polyurethane,
polyester, vinyl and polyamide.
Primarily, the Rotogravure method of printing is employed to print the Primer Coat, to improve the ink wetability and adhesion. The Gravure cylinder is etched to a range of 150 to 250 lines to obtain an even and level Primer Coat across the web. The clear Primers can be formulated to exhibit either a high gloss or matte finish. Other printing methods, such as Flexographic can be employed.
Foil Primers are packaged in 1-gallon and 5-gallon containers and 55-gallon drums.