Interactions In Coating Colors Based On GCC Of Broad And Narrow Particle Size Distribution And Their Effect On Pore Structure, 2004 Coating and Graphic Arts Conference

The objective of this work was to relate interactions in coating colors to shrinkage during consolidation and drying, and to the final coating pore structure. Formulations were based on ground calcium carbonate of broad and narrow particle size distributions, two water-soluble binders: carboxymethyl cellulose and soy protein, and styrenebutadiene latex. The interactions between water-soluble binder, latex and pigment were systematically studied with the help of rheological measurements. Shrinkage and pore structure data were derived from porosity measurements on the filtercake and the dry coating, and from light scattering data. The results indicate that the carboxymethyl cellulose interacted with both pigment and latex to form a network structure. The soy protein interacted only with the pigment on which it was adsorbed, leading to a steric stabilization, without significant network formation. The sterically stabilized pigment particles were found to exist in a more aggregated state in the colors than the electrostatically stabilized particles in colors containing carboxymethyl cellulose. The porosity of the filtercakes was found to be governed by the state of aggregation in terms of relative plastic viscosity and by the size of the aggregates. The pore structures of the final dry coating layers were governed, not only by the parameters that controlled the filtercake structure, but also by the shrinkage during consolidation.