New Additive to Eliminate Pinholes for Water-based Coating Formulations

By Jim Reader, Jos vanOosterwijk, Caixuan Xu, Ye Dai, Ruediger Mertsch, Shauna McAuliffe, Jianchang Tang

Pinholes are a problem for formulators developing fast-drying, water-based coatings, especially in coatings cured at high temperature and applied at high wet fi lm thickness. Pinholes are often caused by air or solvent vapor release from the film when the coating is too viscous to flow back and repair the holes. Pinholes also occur in baked coatings, as the trapped vapor regains mobility when the coating soft-ens under heating, before crosslinking hardens the film, preventing flow back into the voids.

Hydrocarbon-based defoamers help eliminate the foam and pinholes in these formulations, but their limited compatibility results in lower gloss, poor leveling and surface appearance. This paper describes a new additive that combines both deaeration of micro-foam and modifi ed surface drying for pinhole elimination. This new additive shows comparable pinhole elimination compared with hydrocarbon-based defoamers, but without compromising formulation compatibility or final coating appearance.