Rheological Properties of the Coating Colour Influencing Variations in Surface Properties of Coated Paper, 1993 Coating Conference Proceedings

This study was performed in order to evaluate the properties of coating colours that determine the quality of coated and printed papers. The study was divided into a rheological evaluation of the coating colours and a study of coated as well as printed paper in order to find a correlation.

A series of coating colours were prepared using a #l clay and three latexes of different carboxylation degrees but similar particle size and glass-transition temperature (Tg). To each of these coatings a series of viscosity modifiers and water holding agents were added (CMC, an alginate, a polyacrylate, an ethylated corn starch and oxidized corn starches). The coating colours were evaluated for different rheological properties as well as dewatering properties and applied to a wood free stock of medium sized paper using a pilot blade coater with application roll at Abe Akademi University. The paper was dried with either hot air driers or a combination of IR and hot air driers during the coating operation. The resulting coated paper was then printed in a lithographic offset press at Western Michigan University and the coated as well as printed papers were analysed for surface properties that it was felt could be related to the coating colour properties.

The analysis of the coating colours showed differences that could be related to the use of different water holding agents. There was also a correlation between certain coating colour properties and surface properties of the coated paper such as porosity and roughness. This correlation provides us with further information about the pigment-binder interactions and the formation of the coating structure in the final dry coating layer.