Covestro will highlight the new hardener Bayhydur quix 306-70 at the European Coatings Show (ECS) 2019, which will be held from 19 – 21 March 2019 in Nuremberg, Germany. The company said the product makes it possible for the first time to formulate water-based, two-component polyurethane coatings for wood and furniture that have drying properties similar to solvent-based systems, but cause less volatile organic compounds (VOC) emissions.
According to Covestro, when it comes to wood coatings, solvent-based polyurethane systems dominate the world market. Because the water-based PU coatings produced thus far dry at a slower rate, it is difficult for wood and furniture manufacturers to switch to these systems with a lower content of VOC, since it takes longer for them to further process their goods. Covestro said with Bayhydur quix 306-70, it has now overcome this obstacle to switching technologies.
“Water-based wood coatings that are based on the new hardener and selected polyol components achieve a sand dry after just 35 minutes, and therefore must no longer be protected from dust. In less than two hours, T4 drying time is achieved, meaning the film is fully dried,” said Dr. Eva Tejada, wood coatings expert in the Coatings, Adhesives, Specialties segment at Covestro. That means a reduction of the drying time by up to 60 % over standard water-based PU systems, said the company. The pot life is quite unaffected by this: depending on the formulation, the coating can be processed for more than 7 h after mixing in the components. Dr. Eva Tejada will present a detailed properties profile of the new hardener at the ECS conference (on 19 March 2019, from 2:00 p.m.) as well as at a product presentation on 20 March 2019 from 12.10 p.m.
Water-based wood coatings based on Bayhydur quix 306-70 are said to have similar chemical-resistance properties to solvent-based systems in the same quality category. Extensive comparison tests, in which coffee, red wine, mustard, ethanol or water came into contact with the coatings, are proof of this. In terms of appearance, no compromises must be made either: water-based clear coatings with the new hardener shine just as much as mainstream solvent-based PU wood coatings, said Covestro.
From a chemical perspective, the new hardener is an anionic modified isocyanate, comprising both an aromatic and an aliphatic part. Despite the aromatic part, white-pigmented wood coatings based on Bayhydur quix 306-70 do not turn yellow faster than standard solvent-based systems when exposed to UV light or heat. Overall, the product enables coatings manufacturers to formulate dual-component wood coatings with a VOC content below 100 g per liter that are just as effective and efficient as comparable solvent-based systems, said the company.