THE MECHANICS OF WEB RELEASE FROM A ROLL DURING SIZE PRESS OPERATION, PaperCon 2010 Conference

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In printing, size press, and metered size press coating operations, the paper web passes between two rolls and exits the nip causing a film to split between the web and the roll. The physics of the film split location is not well understood. If coating both sides of the web, the web release point can oscillate from top and bottom rolls generating non-uniform product. A pilot scale metered size press coating unit was run at various speeds, coat weights, and coatings. The location of the web release from the roll was recorded with a camera. A model, based on the thin film equations and a web tension equation, was developed to predict the pressure distribution in the liquid film between the web and the roll as well as the web trajectory. The influence of web speed, coating viscosity, and the web tension are included in the model. All of these parameters are found to influence the web release location. The model predictions agree with trends seen in the pilot scale trial and with other pilot scale results given in the literature.