Abstract: The present invention relates to a flame retardant waterborne coating composition comprising: a) water dispersed hydroxyl-terminated polyurethane particles, and b) isocyanate crosslinker, wherein (i) the hydroxyl-terminated polyurethane contains phosponate oligomer as a building block in an amount of from 3 to 75 parts by weight relative to the hydroxyl-terminated polyurethane, wherein the phosphonate oligomer contains units according to the following structural formula in which n is an integer from 1 to 20, R is a C1-20 alkyl, C2-20 alkene, C2-20 alkyne, C5-20 cycloalkyl or C6-20 aryl, and R2 is an aliphatic or aromatic group, (ii) the hydroxyl number of the hydroxyl-terminated polyurethane is from 5 to 180 mg KOH/g polyurethane, (iii) the molar ratio of hydroxyl groups present in the hydroxyl-terminated polyurethane to isocyanate groups of the crosslinker is from 0.2 to 2.0.

Abstract: This invention relates to a new two-component 100% solids polyurethane coating composition characterized by being free of volatile organic compounds (hence “VOC-free”). The coating composition is used to provide a durable coating on a substrate. The coating is produced by reacting a liquid polyester polyol with a polyfunctional isocyanate. Optionally, the polyol component contains a short chain polyol to provide hard segments in the resulting coating. The coating is particularly useful for providing a top coat on concrete form panels, such as plywood form panels, that are widely employed in the construction industry.