Achieving Optimal Paint Performance: Rheological Modifiers for Water-Reducible OEM Coatings
An optimal rheology package should provide the at-rest viscosity necessary to keep pigments from settling, resulting in a more homogeneous coating with good appearance. During application by brush, dip tank, spray or curtain coat, the viscosity needs to be at the appropriate level to provide for proper film deposition, atomization and curtain coat integrity. Once applied, the coating needs to flow and level, providing a smooth film without defects.
Industrial water-reducible (WR) coatings based on WR alkyds, acrylics and polyesters are typically supplied at 25-35% volume solids. Consequently, they are often applied at high wet film thickness. The rheology (viscosity as a function of applied shear) of these systems determines many properties of the paint. These properties include anti-settling of pigments, color stability, application performance (including sag), and flow and leveling. WR coatings, unlike water-based latex systems, are true solutions of resins and rheological modifiers, and are more like those used in solventborne systems.