Effects of Multiple Process Variables on the Quality of Double Coated Fine Paper, 1995 Coating Conference Proceedings

Vilho Nissinen

Valmet Paper Machinery Inc.

The idea of this study was to select a sufficiently wide and representative set of variables from the many areas of the paper finishing process to get a good picture of the interplay between the parameters. The described target can not be reached, if the scope of trial runs is limited and narrow sets of test variables are chosen. Our trial plan is based on so called Taguchi factor analysis and its orthogonal matrix L16. The effects of 15 variables on two alternate levels were analyzed by running 16 separate test rolls on a Valmet pilot coater in Jävenpää, Finland. Topcoating process variables, such as moisture levels and drying strategy, seem to be more significant than the precoating ones. Both precoating and topcoating quality, especially the deviation of measured values in the top coat, are influenced by the type of the application method. Paper and print gloss quality can be positively affected by top coat drying and by softcalendering the coated sheet before supercalendering. Precoat softcalendering adds to paper stiffness and considerably improves the smoothness of the coated sheet, which is most important on many grades.