Powder Coated Tough - Spring 2008 - (Page 30) Powder Technologies POWDER SPRAY ZONE TOUCH UP ZONE AIR SEAL BAKE OVEN 4 3 2 1 TACK OFF VESTIBULE FIGURE 1. BODY POWDER APPLICATION IN-LINE CONCEPT Conceived as a lower cost route for manufacturing powder coatings, the Vedoc Advanced Manufacturing Process (VAMP) supercritical CO2 high pressure process for facilitating dispersion of pigments/additives into the resin was highly publicized but never commercialized. Diagram courtesy Akzo Nobel form thin film coating applications (figure 1). While ingenious from a theoretical standpoint, commercialization of the VAMP process indicates a major continued research and financial commitment. Another unsuccessful low cost process was an attempt to develop friable polyester resins that could be intimately mixed with curing agent, pigments, etc, in a high intensity blender for ES powder application. Several very early unsuccessful attempts were also made to develop and apply powders as a liquid or as a dispersion in water. One process involved precipitating powders from a solvent solution in an aqueous dispersion, which for large-scale production might be economical if the technology could be worked out. A promising patented acrylic-urethane powder aqueous slurry process has since been commercialized in Europe as a clear top coat for Mercedes car bodies with recent improvement in appearance and intercoat adhesion. This technology is in competition with GMA acrylic/dode- canedioic acid powder clearcoat commercially applied to BMW autobodies on five lines in Germany. We understand next-generation automotive clear top coat developments are looking at UV curing powders for improved scratch and mar resistance. In conclusion, no new powder chemistry is seen on the immediate horizon that will challenge existing thermosetting epoxies, polyesters, hybrids and acrylics currently in use. Progress will be made, though, in modifying these resincuring agent binder systems for particularly lower UV cure ES powder thin film decorative and protective coating applications. Corona charging ES guns will continue to dominate application equipment with more improvements anticipated in higher first pass transfer efficiency and faster color change recovery-recycling systems. No replacement of the melt-mix or extrusion manufacturing process by a mechanical method such as dry blending is also foreseen. However, with today’s research advancements, some of the foregoing alternate powder coating technologies may well warrant more thorough investigation for future commercialization. Gordon Cole was PCI’s charter executive secretary as well as marketing director of DSM Resins, U.S., prior to which he authored and presented worldwide a number of articles promoting the benefits of powder coating. He can be reached at 772-231-7440 or via e-mail at gcolegca @cs.com. Acknowledgements The author extends sincere appreciation to Hani Azzam, Sam Dawson, Eric Dumain, Ron Farrell, Ken Kreeger, Chris Merritt and Doug Richart for their valued contributions to this article. Have an article idea or comment? Please send to sspielman@ powdercoating.org. 30 Powder Coated Tough
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