Biobased Technology for Improving UV-Curable Polyurethane Dispersions and Urethane Acrylates

Abstract

The developments of polyurethane dispersions and radiation curing techniques come together in UV-curable polyurethane dispersions (UV-PUD). The industry has welcomed the combination of the two techniques. The polyurethane dispersions technology gives the freedom of choice in the application, and high mechanical and chemical resistance. Furthermore a tack-free coating can be achieved before the UV curing, and the higher molecular weights of these UV-PUDs induce a lower shrinkage which leads to better adhesion. Their low viscosity compared to other UV formulations makes them ideal for spray applications. Moreover no co-solvents, reactive thinners or acrylic monomers are used which minimizes the effect on health and environment. The more critical application conditions for UV-PUD's, such as the removal of the water by a pre-drying step, and poor hydrolytic stability, are seen as an important drawback. We have countered these deficits through a range of hydrolytically stable polyester polyols based on dimerised fatty acids. In this paper, it is first demonstrated that the polyester polyols improve the hydrolytic stability of conventional polyurethane dispersions. Subsequently, we present results showing that properties of the conventional polyurethane dispersions can be translated to UV-curable polyurethane dispersions and their coatings. Additionally influences of the technology on urethane acrylate systems with respect to the adhesion were evaluated.