Author(s)

P. Alam, C. Stoor & M. Toivakka

Abstract

Blade coating is a high speed (~ 20ms-1) coating operation that involves the squeezing of shear thinning coating slurry between a base paper substrate and a steel metering blade. The gap between the blade and the paper can be as small as 1μm and mineral pigments in the slurry can become trapped, giving rise to streaks and scratches on the coating surface. The objective of the research presented herein is to develop a model for simulating the process of blade metering and to use the model to investigate operational anomalies connected to the process. The effects of specific variables were studied notably; blade shape and backing roll stiffness. Virtual experimentation was undertaken to study the deformation of the paper surface, the coating colour thickness and the position of the stagnation point (where pigments may gather). The choice of blade type was found to have a highly localised influence on the area close to the nip. The backing roll stiffness was shown to be one of the most important parameters in blade metering. Lowering the stiffness decreases the coating thickness and pushes the stagnation point further away from the heel region. Keywords: solid mechanics, fluid dynamics, multiphysics, modelling simulation, metering, coating, time dependent non-Newtonian hyperelastic process engineering. 1 Introduction The coating of paper is a process by which coating colour is applied to one or both sides of the paper. Paper and board are primarily coated in order to improve the optical and printing properties. Though, functional coatings might be coated on a variety of speciality papers, such as greaseproof paper for food packaging [1]. Blade coating is currently the most commonly used method for pigment

Keywords

solid mechanics, fluid dynamics, multiphysics, modelling simulation, metering, coating, time dependent non-Newtonian hyperelastic process engineering