Novel Dry Coating Method for Paper, 2001 Coating Conference Proceedings

Juha Maijala, Kaisa Putkisto, Timo R. Nyberg--The traditional pigment coating of paper involves application of an aqueous suspension, e.g. coating color, onto the paper. After applying the coating color, the coating layer is dried and finished. A large proportion of the coating costs comes from raw materials, drying and other energy consumption. A novel method has been developed, where a dry coating is applied onto the paper. It eliminates the need for further web drying and thus reduces drying costs. The dry coating method utilizes an electric field to apply the powder of the coating material to the paper surface, and a mechanical or thermomechanical treatment to complete the adhesion or fixing process. One important aspect here is the anchoring or adhesion of the coating layer to the paper surface. For example, the mechanical bonding of the coating layer should be strong enough to resist stresses in the printing process. This paper introduces the dry coating method and some preliminary indications regarding the color fixing to the paper. The effect of fixing temperature on adhesion strength during thermomechanical treatment was studied through bonding strength and surface strength.