Waterbased, UV-curable polyurethane dispersions are able to solve a number of problems at the same time: They are environmentally friendly as they use water as a solvent, they allow fast drying and they can easily be spray-applied. On top of that, they can more easily be matted compared to 100% solid UV-curing coatings. Waterbased UV-systems generally obtain a better adhesion to a wide range of substrates as well.
Due to their property profile these products are particularly suitable for substrates, that are not subjected to excessive heat during the application of the coating, like in plastics and wood coatings or resilient PVC floor coatings. Bayer MaterialScience offers UV-curing water-based polyurethane dispersions under the trade name Bayhydrol® UV.
A selection of products from the Bayhydrol® UV range
Bayhydrol® UV XP 2775 - with excellent chemical resistance
This is an aliphatic UV-curing polyurethane dispersion that has initially been developed for white pigmented waterbased UV wood coatings. It shows an outstanding chemical resistance particularly against coloring substances like coffee. In contrast to regular UV dispersions, this product maintains its property profile even with a high white pigment load in UV systems. This high property profile allows much more freedom in the formulation and application of the coating. On top of that, Bayhydrol® XP 2775 shows good hardness and does not need any co-solvent to obtain a proper film formation. It shows its excellent mechanical and chemical properties not only in white pigmented systems but also in clear coats.
Other applications like PVC floor coatings can also benefit from the stain resistance of Bayhydrol® UV XP 2775. Due to its good physical drying it is well suited for a stamping process before UV-curing.
Bayhydrol® UV XP 2721 - for resilient PVC and linoleum flooring
Bayhydrol® UV XP 2661 and Bayhydrol® UV XP 2721 are suitable for clear coats on semi-gloss or matt surfaces, have good adhesion and high abrasion, chemical and stain resistance properties and display high UV reactivity. Whereas XP 2661 has its strength in stain resistance, Bayhydrol® UV XP 2721 brings the benefits of improved hardness and physical drying (tack-free before UV), which allows improved embossing of the coated flooring before UV-curing. Both XP 2661 and XP 2721 can easily be combined with the other products from the Bayhydrol® UV product portfolio to achieve different property profiles.
Bayhydrol® UV XP 2690 - For exterior wood applications
Coatings based on this polyurethane dispersion are noted above all for their outstanding weather resistance, a claim that has been confirmed in a study by the Fraunhofer Institute for Wood Research (WKI), which shows that the wood surface remains absolutely free of damage during weather exposure and meets the requirements of DIN EN 927-3. The test results also show that when used outdoors, the timber can withstand the elements for eight years, before re-coating is required. An additional advantage is that Bayhydrol® UV XP 2690 is suitable for both clear coats and pigmented top coats.
Bayhydrol® UV XP 2687 - For use as a primer.
The product is recognized for its outstanding grain accentuation and adhesion to all wood types, even those containing oil. The polyurethane emulsion has a high solids content, which allows higher film thicknesses to be achieved in a single application. Due to its excellent resistance properties and high degree of hardness, it is also suitable for clear coats and can be formulated for both spray and roller application.