Use of Particle Packing Modeling with Lognormal Particle Size Distributions to Develop a Strategy to Improve Blade Coating Runnability, 2004 Coating and Graphic Arts Conference

Coating with precipitated calcium carbonate (PCC) has optical and in some situations printability advantages in comparison to ground calcium carbonate (GCC). PCC has been hindered in its implementation by the fact that it doesn’t run as well on blade coaters as GCC does. The advantages in optics and printability and the disadvantage in ease of running is mostly caused by the fact that the particle size distribution is much narrower for PCC in comparison to GCC. In order to understand this effect better and to develop a coating formulation that will run better on a blade coater, particle packing simulations were done. Unique to our work was the use of a lognormal particle size distribution model to represent the PCC particles. Mono-sized particle distribution simulations give dramatically different optimums for the blend ratios between two different mean particle sizes in comparison. Correlation of the results of these simulations with latex properties was done with rheological measurements. Hypotheses were then made of what would run well on a blade coater and what would not. These hypotheses were verified in a pilot coater trial. A key finding was the verification of a long held belief that smaller sized latex lowers the high shear viscosity and so improves the runnability of a coating on a blade coater.