Associative thickeners play an important role in defining the rheology of waterborne latex paints. These materials include hydrophobically modified ether-urethane (HEUR) polymers, hydrophobically modified cellulosics and hydrophobically modified alkali-swellable emulsions (HASE). In comparison to water-soluble thickeners such as cellulose or acrylic copolymers (alkali-swellable emulsions), paints made with associative thickeners show better performance in sag and leveling, moisture resistance, spatter resistance and coverage (Figure 1). In addition, mixtures of associative thickeners allow one to tailor the rheological profile to provide superior paint performance.
However, one of the most difficult problems to solve with associative thickeners has been the viscosity instability with the addition of colorants. This phenomenon is known in the industry as “viscosity loss” and has resulted in poor coating properties and increased formulation complexity.