Droitwich, UK -- Baxenden Chemicals Ltd, a subsidiary of Chemtura Corp., has introduced a new series of hydroxyl-functional polyurethane dispersions (PUDs) into the Witcobond range.
These anionic products are intended for two-component (2-K) coating systems, primarily for use in an industrial environment, where heat-curing or stoving conditions can be employed, Baxenden said in a 19 Oct news release.
The PUDs must be crosslinked with water-dispersible polyisocyanates, aqueous blocked isocyanates or melamine-formaldehyde resins typically used in the water-based coatings industry.
Baxenden said the new Witcobond products do not contain surfactants, N-methylpyrrolidone or triethylamine. Three initial grades are offered, each at 35 percent by weight solids and with a hydroxyl content of 2.5 percent (on solids).
The three grades have different chemical backbones giving compounders flexibility in use, Baxenden said. Witcobond 428-85 is based on aliphatic diisocyanate/polyether polyol and cosolvent-free. 434-55 434-55 is based on aliphatic diisocyanate/polyester polyol and is also cosolvent-free. Witcobond 434-65 is based on aliphatic diisocyanate/polycarbonate polyol and contains 4 percent glycol ether.