Development of VOC-Compliant Binders for Interior Wood Coatings
When applying conventional solventborne coating systems on an industrial coating line, organic solvents are released into the earth's atmosphere. To comply with European legislation, these emissions must be reduced by using expensive and complicated technical equipment and techniques such as solvent recovery, post-combustion, etc. Waterborne coatings contain very low quantities of solvents, or none at all. They allow for solvent-emission abatement by approximately 90%, provide a better working environment for the applicators and drastic pollution reduction. Furthermore, the liquid coatings are not flammable, offering increased workshop safety and reduced insurance costs (absence of spontaneous combustion). Finally, equipment can be washed with water instead of organic solvents. The wastewater can be conveniently treated so it poses no threat to the environment.
There are many types of crosslinking systems for coatings dried at ambient temperature. An example of a two-pack system is Setalux 6520, a waterborne acrylic polyol dispersion with 3.2% OH (calculated on non-volatiles). This product, in combination with water-reducible polyisocyanates, gives coatings having good drying, water resistance and mechanical properties. However, there are some drawbacks associated with the use of isocyanate-based systems. An alternative system that offers the performance of a two-pack system without the use of isocyanates is the waterborne, all-acrylic (AA) system. All the components of the AA system have acrylic backbones. The system is based on an epoxy-functional acrylic dispersion and an amino-functional emulsion with an acrylic backbone. Besides being isocyanate-free, the all-acrylic system does not have the short potlife and foam formation during curing that is associated with waterborne two-component isocyanate systems.