Waterborne polyurethane coatings for furniture and joinery with solventlike performance
Waterbased dispersions (Bayhydrol®) and hydrophylic poly-isocyanates (Bayhydur®) are used for high-performance furniture and joinery coatings. Coatings based on these raw materials show the same high quality properties of solventborne systems or even exceed them, while at the same time being more environmentally friendly and easy to process.
Waterbased coatings offer the same characteristics as solventbased systems
Coatings based on dispersions and hydrophilic poly-isocyanates fulfill the same high quality standards as solventbased coating, in some cases they perform even better. At the same time they are more environmentally friendly and easy to process. They show:
High to very high gloss
Outstanding mechanical resistance
Good resistance against virtually every household substance
Good grain wetting (Anfeuerung)
High productivity is possible with waterbased wood coatings
High throughput is required in the production of window- or industrial furniture coatings. Therefore, coatings need to dry as quickly as possible. It is of utmost importance that the primer is sandable fast and that the freshly coated parts are stackable in a minimum of time. Taking into account that the drying process can hardly be accelerated by higher temperatures, most furniture producers traditionally dry the coatings in ambient temperatures. Only in some cases large movable drying stacks can be employed that are exposed to temperature to 70°c max. A characteristic advantage of polyurethane coatings is the fact, that chemical crosslinking takes place at lower temperatures already.
Waterbased 1K systems - New grades for fast drying and good resistance
With 1K polyurethane coatings based on Bayhydrol® high quality and environmentally friendly wood coatings can be obtained. They are suitable for a broad range of application and drying conditions. In the past they were primarily used for parquet coatings, however, recently they have become popular in furniture manufacturing, too. With two new solventfree dispersions of the latest generation coatings can be formulated, that need only 2 hours at 40°C to obtain a good to very good blocking resistance. Freshly coated furniture panels can be stacked relatively quickly. Both grades feature a quick physical drying of the coating film, making coating application rather easy.
Coating films based on the new aliphatic polyurethane dispersion Bayhydrol® UH XP 2719 also show a particularly high resistance against detergents. No change can be detected even after an exposure of 24 hours with common household and window cleaners. They are equally resistant to alkaline substances. Also, the coating films are elastic and resistant to abrasion.
For more hardness and scratch resistance coatings can be formulated based on the fatty acid modified polyurethane dispersion Bayhydrol® UH 2593/1. They show a good chemical and mechanical resistance as well and an excellent wood warmth.
Waterbased 1K systems - New grades for fast drying and good resistance
The 2K water technology typically combines waterbased polyols with waterdispersible aliphatic poly-isocyanates. The polyol component usually being an OH-functional polyacrylate dispersion, in some cases it may also be an OH-functional polyurethane dispersion. In combination with elastifying hardeners based on an aliphatic hexamethylene diisocyanate (HDI) it is possible to utilize polyols with a very high glass transition temperature, this way obtaining the desired short drying times.
Emulsion dispersions and secondary dispersions
Polyacrylate dispersions (PAC - dispersions) are usually produced by emulsion polymerization. Polymers with a high molecular weigth are typically used in applications where short drying but gently drying is critical. Emulsion-polymerized acrylate dispersions are used for 1K clear coats or pigmented coats when drying times and a good chemical resistance are the essential properties looked for. (example: Bayhydrol® A 2427).
Contrary to emulsion polymers the polymers of the so-called secondary dispersions are produced in a homogenous organic phase. The resulting resin has a molecular weight that comes close to conventional solventbased acrylic resins. In a second step, the resin is dispersed in water. Secondary dispersions allow for furniture coatings that are typically associated with solventbased polyurethane coatings. Systems based on the low-VOC Bayhydrol® A 2651, for instance, are becoming more and more a standard system featuring high gloss, an excellent transparency, good wood wetting and wood appearance. On top of that, the highly reactive nature of polyacrylate dispersions and their easy miscability in combination with suitable crosslinkers allow even a manual mixing.
The new low-VOC Bayhydrol® U XP 2755 is a good example showing the performance of a polyurethane dispersion as the polyol component of a 2K wood or furniture coating. With this transparent and very reactive dispersion coatings can be formulated, that dry and cure exceptionally fast. Not only the speed of the initial hardness development is remarkable, but also its final hardness obtained. All of this with a gloos and chemical resistance usually attributed to the PAC dispersions above. Another advantage is the wet film transparency and its potlife of more than 6 hours.
The selection of the right poly-isocyanate is crutial: Anionic hydrophilized aliphatic grades like Bayhydur® XP 2655 are the best crosslinkers, when resistance against common household chemicals is the prime concern. At the same time a good wood appearance, transparency and a high gloss can be obtained, as well as good miscability properties.
Some dispersions and starting formulations for waterborne wood coatings
For 2K high-gloss, matte and clear pigmented topcoats, excellent grain wetting and high reactivity, very good mechanical and chemical resistance
(Product presentation)
Waterborne two-component, pigmented, glossy coating for furniture application (Bayhydrol® A 2651 / Bayhydur® XP 2655)
Additional starting formulations are available upon request.
UV-curing polyurethane dispersions
Feature: Self healing systems for Wood Coatings
Daily tear and wear can quickly tarnish a piece of valuable furniture. Wood coatings based on our 2K waterbased dispersions are "self-healing", meaning that abrasive forces that normally cause small scratches would merely have a deforming effect on the polyurethane coating. The shape memory effect causes the polymers to flow back to their original shape, the deformation disappears and there are no scratches on the surface. This effect is greatly enhanced at temperatures of 50-60° C. More.....
Feature: Environmentally friendly exterior wood coatings with good resistance
Long-term weathering stability, environmental friendliness and efficiency can be fullfilled at the same time. Have a look at this case study on the Lufthansa Aviation Center in Frankfurt.... more
Important environmental guidelines and environmental labels
UV-curing polyurethane dispersions
