Leverkusen, Germany-Bayer MaterialScience AG has developed a range of radiation-curing, water-based polyurethane systems for wood finishes which, it claims, are both economical and environmentally friendly. The basic PU dispersions contain little or no solvent apart from water, so they emit only minimal quantities of volatile organic compounds (VOCs), Bayer points out, adding that the systems cure very quickly under UV light, which means that the finished wood products can be stacked immediately after leaving the production line. The latest polyurethane system of this kind, Bayhydrol® UV XP 2420, is very easy to apply, says Bayer. It dries on wood within a few minutes and then takes only a few seconds under UV radiation to cure. It also adheres very well indeed on metals and plastics, the firm adds.The finishes themselves may be either transparent or pigmented and are highly flexible, even at low temperatures. They also have very good chemical and mechanical resistance properties, Bayer claimed in a 21 March statement. Above all, the firm claims, the finishes are noted for their outstanding weather stability. Their chemical backbone is formed by special aliphatic polyurethanes that remain virtually unaffected by sunlight, Bayer explained.The speed of cure "makes for maximum productivity, which is a major advantage over other solvent-based and waterborne outdoor wood finishes," says Christoph Irle, the expert for polyurethane wood finishes at Bayer MaterialScience. Furthermore, "We now have a tailor-made polyurethane system for outdoor applications," he added, in the statement. Irle sees window frames and shutters, doors, and all kinds of exterior wood panelling as potential applications for the new systems.UV-curing polyurethane dispersions of this kind are experiencing high growth rates on the world market, mainly because there is no need for the user to mix the polyol and polyisocyanate before application, making life that much easier, Bayer explains.In addition to the new product for outdoor applications, Bayer MaterialScience says it also has its proven product line centring on Bayhydrol UV VP LS 2282. This universal grade is suitable for clear and coloured primers and topcoats. Other products in the Bayhydrol range include UV VP LS 2348 and UV VP LS 2280. The former is noted for its outstanding adhesion on 'critical' wood types and its ability to accentuate the wood grain which, Bayer suggests, more or less predestines it for use on furniture and parquet flooring. The other product was developed specifically for pigmented formulations and also adheres very well to metal. Last but not least, there is Bayhydrol UV VP 2317 which is characterised by its excellent wet film transparency, which means that it is also clear during application, and can be re-emulsified without problem. The latter property is an advantage for recycling any overspray, Bayer says, adding that the excess material can be collected easily with water or the coating system and returned to the application cycle.Further information about Bayer's wood coatings, including detailed descriptions of applications, and contact details can be found on the Internet at http://www.bayercoatings.com or obtained by sending an e-mail to [email protected]"