New Development Results of Curtain Coating for Various Paper Grades, 2005 Coating Conference

For many years paper makers have dreamt of non-impact coating: Applying a perfect layer of coating on the surface without any mechanical impact on the paper. Curtain coating is now opening new possibilities for coated papers. During the late 1990’s, it has become a state-of-the-art technique for specialty paper such as carbonless paper (micro-capsules for “coated back”). Today the operating window for curtain coating is being extended for many other applications such as pigmented coatings or barrier coatings.

The fundamentals of curtain coating will be presented with special regard to new development results. Important rheology features such as curtain stability at low flow rates and stretchability of the coating color to eliminate film breaks will be discussed. The rheological properties of the coating color play a major role in this new technique.

The primary part of this paper is followed by results from pilot machine trials, demonstrating the applicability and the advantages of the curtain principle for lightweight coated (LWC) paper, white top liner and woodfree paper grades. The work includes investigations of color properties as well as the possibility of reducing the number of coating stations.