Claude Monet once commented that "Color is my day-long obsession, joy and torment", a sentiment that resonates with formulators of waterborne architectural paints who need to design base paints that can accept a variety of liquid colorants, enabling a paint line with the broadest possible color palette. With the advent of point-of-sale (POS) tinting systems, many paint manufacturers now produce only a small number of base paints to which the colorants are added at the store. Smaller quantities allow paint manufacturers and stores to manage inventories by stocking fewer materials, and it significantly decreases the amount of unused paint that goes to waste each year. However, the colorants used in POS tinting systems must have excellent compatibility with different base paints to ensure consistent, reproducible colors under all conditions. This remains one of the toughest challenges facing the waterborne architectural paint formulator today. Difficulties occur when the additives used to stabilize the pigments in the colorant interact with additives in the base paint, causing loss of pigment stabilization and flocculation leading to an immediate or gradual color change that can be observed in a rub-out test in the laboratory. Problem pigments such as PV23, PBk7 and PB15:3 give rise to the most challenges with regards to colorant acceptance. This paper will describe the mechanisms involved in colorant stabilization and, using chemical structure-property relationships, explain how specific surface active agents are used within the base paint formulation to prevent destabilization of the colorant, ensuring that it performs as intended.
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