The Waterborne Symposium 2025

Abstract

Grinding pigments and fillers using cowles dissolver is a standard practice for breaking down agglomerates and aggregates into primary particles during the production of waterborne paints, especially architectural paints. Serrated disc introduced at the appropriate peripheral speed forces a specific flow in the vessel, which causes the agglomerated particles to rub against each other and collide with each other. The wetting and dispersing additive introduced to this process is supposed to build a double electrical layer according to the DVLO theory, but this is only a theory that has little to do with practice. Of course, the theory of wetting, significant zeta potential and other properties of dispersing additives are true, but their correct use in mill-base formulations and further influence on the parameters of the grinding process itself and the parameters of the paints depends solely on the effectively found dose and balance between mill-base concentration allowing grinding at low viscosity and maximum solids loading, without adding any rheology additives during grinding. The paper discusses examples of grinding of various pigments and fillers used in architectural paints and discusses how to properly balance the ingredients and the grinding process to achieve the lowest possible viscosity, low energy consumption and donut-shaped flow, without using rheological additives that prevent proper grinding and breaking down of pigments and fillers into primary particles. It also presents how to properly control the mill-base slurries obtained after the grinding process and how to combine them with latex polymer dispersions in the let-down process to obtain stable architectural paints.