Effect of Coating Powder Composition and Process Conditions on Dry Surface Treated Paper Properties, 2002 Coating Conference Proceedings

J. Maijala, K. Putkisto and J. Grön

Dry surface treatment of paper involves application of a dry coating powder and thermomechanical fixing onto the paper surface. The coating powder application utilizes an electric field to transfer the coating particles to the paper surface and to enable the preliminary adhesion through electrostatic forces. The final adhesion is completed with thermomechanical treatment. Since the process consists of application, fixing, and a smoothening phase without intermediate drying, the surface-treatment steps can be performed in a compact space. During the development of the dry surface-treatment process, it has become essential to optimize the required process conditions and coating powder composition in respect to coating layer adhesion to the paper surface. In this study, coating powders of different compositions were compared under different process conditions such as base moisture, fixing temperature, and linear load. It was possible to reduce the polymer content in the coating without losing the required surface strength. When compared to film-coated paper, it was possible to achieve similar levels of coating coverage, surface strength, and optical properties.