Improving the Process Runnability and FCO Quality by Optimizing the Coating Color Composition, 1997 Coating Conference Proceedings

In this study, we evaluated the effect of the coating color composition on the process runnability and also the final coated surface. A comparison was performed between latex/starch and latex/CMC hinder systems in clay based coating colors. It was seen that a reduction of the starch content made it possible to run the coating color at a higher solids content. By running the color at a higher solids content. both its runnability and the paper gloss were improved. The improved runnability can partly be explained as a higher color transfer to the paper due to a thinner non-immobilized layer color at the nip outlet promoting a less color mist. An increased color solids will naturally have a direct effect on the premetered film amount. Where a higher solids will demand a higher rod load to keep the film amount on a desired level. The starch system also gave a higher viscosity at high shear forces. which are present at the rod premetering. compared to the latex/CMC colors. A difference in the high shear viscosity will determine the solids content at which the color has to be run to avoid a too high rod pressure. The lower solids content for starch colors will increase the demand for premetered film amount to achieve the desired coatweight. By increasing the film amount. the transfer ratio will be reduced due to more color to dewater and a thicker non-immobilized layer. Keywords; Metered film press. coating color. Starch. CMC. Solids content. Runnability. Film transfer. Misting. Gloss. Ink transfer.