Investigation of new open time extenders for low/zero-VOC latex paints and aqueous coatings

With strict environmental legislation seeking to reduce the amount of volatile organic compounds (VOC), new latex binders are being developed with low glass transition temperatures, to be used in formulating low- and zero- VOC paints. Lower-VOC paints are expected to meet the same performance requirements as traditional paints. However, the open time or wet-edge time of low/zero-VOC aqueous coatings is a major challenge during application when cosolvents or coalescing agents are eliminated from the formulations. In this study, a series of new additives was developed to extend the open time of low/zero-VOC binders and latex paints. The effects of this additive on the open time of low/zero-VOC waterborne paints with different binders were investigated. Factors related to open time, including viscosity, PVC, film thickness, and substrates, were studied. The results indicated that the additives are effective in extending open time by two to five times. In addition, other properties of low/zero-VOC paints such as freeze/thaw stability, film gloss, stain removal, tint strength, wet adhesion, and scrub resistance were evaluated. Various techniques have been employed to characterize open time and wet-edge time. A new method was developed to characterize open time/wetedge time and the film formation process. Correlations among film formation, physical properties, and coating performances are discussed.