New High Solids Acrylic Technologies for High Performance Topcoats: Alternatives to Acrylic Urethane Coatings

Abstract Acrylic urethanes have set a standard for high performance topcoats by virtue of their long lasting resistance and appearance properties. Such a high level of performance has made acrylic urethanes attractive to an ever increasing share of various coatings markets, including maintenance coatings. Naturally, this technology is not without its shortcomings, not the least of which are the health concerns associated with the isocyanate resins (HDI prepolymers) used in these coatings. These urethane paint vapors and mists can irritate the respiratory tract and repeated overexposure can lead to a respiratory sensitization reaction. Alternative technologies are being developed that take advantage of the light stability of acrylics and achieve resistance properties by using crosslinking resins other than these isocyanate resins. Three distinct chemistries are involved: The goals during the development of these new acrylic technologies were to demostrate coatings with performance that approach that of current acrylic urethanes at VOCs at least as low as 3.5 pounds per gallon. (420 grams per liter). Laboratory tests have indicated that these goals have been achieved, but to varying degrees, depending on the desired VOC and balance of properties. Conventional and low VOC acrylic urethanes are compared to these three alternative chemistries in laboratory tests and relative performance trade-offs are presented. Acrylic FunctionalityCrosslinkerCatalyst1. HydroxylTMXDI Isocyanate Prepolymer (as opposed to HDI prepolymer)Organo-metallic2. CarboxylAliphatic or Aromatic EpoxyTertiary Amine3. AcetoacetylUnsaturated PolyesterStrong Base