Effect of thickener structure on paper-coating color properties

Physical and chemical properties of clay-based paper-coating colors have be en characterized. The "surface potential" (zeta potential) of kaolin partic les used in paper-coating formulations was determined as functions of pH an d sodium polyacrylate (used as a dispersant) concentration. The optimal pH and dispersant concentration have been established. The effect of adsorptio n of two different thickeners on the kaolinite particle potential was also investigated. The rheological properties of coating colors, thickened with an associative polymer and a commonly used thickener, have been compared. T he rheological behavior of all the coating colors studied was found to be s imilar, except for the magnitude of the elastic modulus, which was consider ably larger for the more hydrophobic thickener. The water-retention propert ies of the colors could be qualitatively correlated with the molecular stru cture of the thickeners. An interaction mechanism (e.g. formation of hydrop hobic micellar domains) between kaolinite particles and the associative pol ymer has been proposed.