The Effect of Water Retention and Rheology Modifiers (WRRM’s) on the Formation of Coating Structure and Migration of Particles, 2006 TAPPI Advanced Coating Fundamentals Symposium

Dewatering properties of coating colors and the coating layer structure have been determined for formulations comprising of engineered calcium carbonate particles with narrow particle size distribution, styrene/butadiene latex and different water retention and rheology modifiers (WRRM’s). The WRRM’s used in the study were sodium carboxymethylcellulose and different types of synthetic polymers. Different analytical techniques were used to gather information about the effect of WRRM’s on the dewatering and formation of the wet and dry macrostructures, respectively.

It was concluded that the chemistry of WRRM’s can be used to tune the water retention properties, but also to impact the wet and dry structure, respectively. TOF-SIMS and X-ray tomography analysis of the latex distribution implied that the WRRM’s play an important role, particularly in latex depletion. The material flow in the continuous phase and dissimilar particle interactions induced by the chemistry of the WRRM’s was found to be a key variable for controlling local and overall latex concentration gradients. Interesting observations regarding the porosity and pore size distribution were also found, which could be related to the WRRM chemistry and their behavior at different coating solids.