Non-ionic associative rheology modifiers such as hydrophobically-modified ethylene oxide urethanes (HEURs), are used widely in waterborne coatings because they deliver desirable rheological and applications properties, like excellent flow, good water-resistance and low spatter. To achieve practical viscosities of the supplied material, associative rheology modifiers are often supplied in water/solvent solutions, and thus contribute volatile organic compounds (VOC) to the coating. Continued regulatory and consumer pressure to reduce VOC has made it undesirable for even small levels of incidental VOC, such as that which comes in with the rheology modifier, to be introduced to the formulation. The development of low and zero VOC coatings therefore relies on innovative technologies to enable such VOC levels, while achieving high performance coating systems that are cost effective. We report here a new ACID SUPPRESSION~(?) technology that utilizes pH to reversibly activate the thickening of associative polymers, thereby allowing a wide range of efficient thickeners to be supplied at low viscosity without additional solvents.
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