Study on the drying process of pigment coated paper webs.

摘要

Simulation models have been developed for the drying process of pigment coated webs. Both one-sided and simultaneous double sided coating processes can be simulated. The models have been verified through measurements made on pilot coaters and on full-scale production machines. The model used for describing water drainage rate from the coating color seems to explain satisfactorily the influence of coat weight and temperature. Reduced concentration and/or lower viscosity grade of the soluble binder showed to increase the drainage rate. Sorption isotherms were measured for different pigment coating colors. The coatings showed hygroscopic properties only at very low moisture contents. Binders had more influence on the sorption isotherms than type of pigment. In the simulation model tile coating is approximated as nonhygroscopic material. Very little is known how the drained water is distributed through the thickness of the base stock in different phases of drying. An uniform moisture distribution is assumed here. Heat transfer coefficients for different air flotation dryer nozzles were determined both with a static test bench and trial runs made utilizing pilot coating machines