PREDICTION OF COATING STRUCTURE CHANGE DURING CALENDERING, 2008 Advanced Coating Fundamentals Symposium

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The final coating structure is important in terms of coating gloss and opacity, print gloss, and ink setting characteristics. Much empirical experience has moved coatings towards optimum levels, but when there is a raw material change or grade change, there is much expense in predicting the final coating structure. Many recent computer models have advanced our abilities to predict coating structure from particle packing models, but little has been done to describe the calendering operation that is known to determine coating gloss.

Here, a particle level model to describe the compression of pigments to simulate the calendering operation is proposed. Particles are placed into a structure with a drainage flow field and compressed with a row of particles that represent the calender surface. The results are compared to pilot scale experiments for two pigment size distributions. The gloss increase due to calendering and the pore size distributions are well predicted before and after calendering. The modeling technique should help predict the gloss response of coating suspensions with various pigment size distributions.