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UV curable coatings are one of the fastest growing sectors in the coatings industry. In recent years,
UV technology has made inroads into a number of market segments like fiber optics, optical and pressure sensitive adhesives, automotive applications like UV cured topcoats, and UV curable powder coatings. The driving force of this development is mostly the quest for an increase in productivity of the coating and curing process. In automotive refinish applications where minor repairs need to be performed swiftly and at ambient temrerature, UV technology promises to significantly increase the throughput of cars in a body. The development of refinish applications breaks new ground in UV technology. Safety concerns associated with the use of UV lamps in body shops as well as economic constraints will likely preclude the use of high intensity light sources. Relatively inexpensive low intensity lamps that emit only in the UV-A region of the electromagnetic spectrum are taking their place thus posing new challenges to resin developers and formulators. A typical build-up of a refinish system consists of wash primer, primer/surfacer, base and clear coat
(Figure 1). A UV clear coat system can be either based on Dual 5 or monocure technology. In this
paper, we report on our developments of UV refinish primer and clear coat guide formulations based on yer Polymers acrylate resin technology. In the primer development, high throughput experimentation was employed to select resin combinations exhibiting optimum UV reactivity under low intensity UV-A irradiation. To this end, 480 combinations of resins, photoinitiators, and reactive diluents were screened for surface cure and through cure at various lamp distances and irradiation times resulting in the testing of more than 25,000 coating films. The clear coat development involved the syntheses of novel flexible urethane acrylates as well as extensive blending studies to yield formulations exhibiting the targeted balance of hardness, flexibility, formulation color, film color, and reactivity. Again, high throughput experimentation tools and statistically guided experimentation to explore the complex parameter space were critical success factors.
