High-Strength Coating Binders Based on Molecular Design of Styrene-Butadiene-Acrylontrile Latices, 2005 TAPPI Coating Conference

Optimizing raw materials utilization is currently high priority for nearly every coated papermill. An effective way to achieve this is by improving coating latex strength in order to maximize binding strength without sacrificing other critical coated paper properties. Previous studies have demonstrated how latex emulsion features, latex chemistry, and solubility influence the picking strength of paper coatings. In this paper, we demonstrate how intrinsic polymer physics of a latex influence coated paper -offset ink interactions, effectively increasing the passes to fail (strength) of a paper coating. A novel approach developed a correlation between molecular weight between chain crosslinks (Mc) of polymeric latex and coated paper-ink performance, with the intent that in the future we can predict latex performance in a formulated coating from selected latex film testing and its viscoelastic properties. Examples are shown using experimental polymers made with a modified emulsion polymerization process that changes polymer architecture and Mc, the latter estimated from dynamic viscoelasticity measurements of latex films. Paper coating application methods included laboratory drawdowns, CLC and papermill trials. Results indicated that there is an influence of the latex film viscoelasticity, and therefore Mc, in ink setting onto papers coated with formulations containing the latex. We found that latex films with relatively lower storage modulus and higher tangent delta increased pigmented coated paper strength. Differences in viscoelasticity were attributed to molecular weight (Mc) between polymeric chain crosslinks. A high Mc of a latex correlates with improved passes to fail in the laboratory paper-ink interaction test.