The Hiding Power of Various Coating Pigments

The purpose of this thesis is to analyze various coating pigments, used in the coating formulations of coated paperboard, by determining their hiding power and cost effectiveness in coating 100% recycled paper used in the top layer of coated paperboard. The main consideration will be the ability of the various coating pigments to cover or hide the dirt and ink spots associated with 100% recycled paper. The base coat chosen was #2 clay due to its relative cheapness, good brightness, and good flow characteristics. It was held at a constant coat weight (+- 1 g/m2 ) throughout the trial. The three pigments used in the top coat formulations were: TiO2, Calcined clay, and #2 Clay. They were selected due to their large use in the coated paperboard industry and their physical coating and opacifying characteristics. The experiment consisted of coating 100% recycled paperboard with a double coating. Once the base coat weight was determined to be constant, three coating formulations, each using an equal amount (20 parts) of the three pigments, were. applied onto the base coating. The double coat weight was targeted to be 20 g/m2. Tappi dirt count, brightness, and relative costs were the determining factors in finding the hiding power of the various coating pigments and how cost effective each one was. Gloss and IGT Pick were also used to help tabulate the results and find the optimum coating formulation with the best hiding power of the three pigments used, #2 clay showed the best effectiveness based on cost and was determined to be the most cost-effective pigment of the three. Calcined clay was second based on cost, had the highest gloss, but also had the highest dirt count. TiO2 showed the best brightness with the lowest dirt count, but was the least cost effective due to it\u27s large cost. IGT pick and wax pick showed trends of decreasing surface strength with increasing Tappi dirt count. Dirt count had no significant effect on smoothness