The interest for hydroxyl-functional acrylic resins as a component in polyurethane coatings has increased not only because of improved performance through crosslinking, but also because of higher non-volatile content. Hydroxyl functionality may be introduced in acrylic resins by the use of a hydroxyl-functional monomer. However the range and latitude of choice are limited as commercial monomers have a limited portfolio.
Another approach is functionalization of the acrylic backbone, in most cases acid functional, to a hydroxyl-functional one, in which case the hydroxyl functionality is a secondary group.
The approach allows a larger latitude of formulation, targeting a lower or higher mobility of the hydroxyl group, related to the length of the R' chain. In most cases propylene glycol, ethylene glycol, 1,6-hexane diol and 1,4-butane diol may be used but also cyclohexane dimethanol, 1,4- or a commercial blend with the 1,3- isomer. However the limitation of the method resides in the risk for looping and interchain esterification that may lead to gellation.