wo trends are evident in architectural paints today. Waterborne, or latex, paints continue to grow in use, and today's homes are increasingly being painted with deep, vibrant colors, both inside and out. While experience has shown that the best overall balance of rheology in waterborne coatings is achieved by using non-ionic associative rheology modifiers, when such coatings are tinted with high levels of colorants they often exhibit a significant decrease in viscosity. This decreased viscosity can manifest itself in a number of ways, including low sag resistance, poor brush loading and a "thin" appearance in the can. Although a number of approaches to formulating around these issues exist, there continues to be a need for viscosity-stable rheology modifiers. A new development in HEUR thickening offers significant improvements in these performance parameters.
Associative rheology modifiers consist of a water-soluble polymer backbone that contains two or more hydrophobic groups. This general structure is shown in more detail in Figure 1 for the specific case of the HEUR (hydrophobically modified ethylene oxide-based polyurethane) composition.