Zero etch clear — a new modular clear coat system with excellent scratch/mar performance

Abstract

The aggravated demands regarding the etch/mar resistance of clear coats due to aggressive atmosphere pollution has led to new clear coat systems with extraordinary etch performance. One of the most promising key-chemistries is based on the epoxy/acid reaction. In contrast to the introduced clear coats on this chemistry basis, this new clear coat system has changed the former drawbacks, storage stability and scratch resistance to advantageous properties. Key ingredients are an epoxyfunctional acrylic resin and an acidic polyester resin. By incorporation of latent acidic groups into the epoxy acrylate and by branching of the resin during synthesis a high cross-linking density even at lower baking temperatures is realised. Although a high reactive system is obtained the material shows excellent storage stability. The scratch resistance is attributed to the structure of the tailor-made high-functional, highly branched acidic polyester. Furthermore, there is an extraordinary broad application field: waterborne, solventborne, high solids and powder clear formulations have been developed. The superior etch performance of the waterborne as well as the solventborne epoxy/acid clear coats is proven in laboratory etch tests and especially in outdoor weathering tests in aggressive atmosphere, e.g. at Jacksonville.