Low VOC interior wall coatings use new hybrid resins to create conditions for the use of daylight lighting

China Coatings Online News
A new hybrid resin for low VOC interior wall coatings in public places that meet the requirements of UV-resistant and chemical resistance
Unfortunately, however, exposure to ultraviolet light can lead to problems such as powdering, yellowing and reduced gloss. Therefore, this has also been restricting the application of epoxy system in the exterior coating system. At present, for the inner wall coating system, also led to a similar new problem, that is, the increasing popularity of lighting indoors.
the Department of Energy (DOE), indoor spaces with natural light lighting can reduce total energy costs by up to one-third1. Other studies have shown that exposure to sunlight can improve health and productivity of people in buildings, increase retail sales, and even improve student test scores2. However, over time, the widespread use of natural light for building lighting can also darken and yellowen epoxy coatings that protect floors, walls and ceilings.
to improve coating durability and UV resistance, Dow Coatings Has developed a low VOC hybrid resin for dual component (2K) coating systems3. MAINCOTE™ AEH-10 acrylic epoxy hybrid dispersions combine the weather and UV resistance of acrylic resins with the chemical resistance of epoxy resins. When used with acrylic curing agents, the technology VOC<100 g/L, when used with amine curing agent VOC<50 g/L.
the application of concrete
as shown in Figure 1, water-based epoxy concrete coatings are usually used in one of the following three types. The Type I system consists of pure liquid epoxy resin (LER) and water-based amine curing agents. They require surfactants to increase the emulsification of liquid epoxy resins (LER), solvents or thinners to reduce viscosity. The type I systems are designed to provide high hardness and resistance and are the most cost-effective for commercial use;
type II system uses pre-dispersed water-based epoxy resins. They are easier to use because epoxy resins do not need to be emulsified in the mixing procedure. Typical performance includes better flexibility and faster hardness formation after drying through physics (spraying). However, these pre-dispersed epoxy systems often bring some VOC solvents and have a higher cost than type I systems. Their application period is also short, often only one to three hours.
type III system also uses a pre-dispersed epoxy resin (usually LER) as an A part, but an acrylic emulsion as a B part.
these systems need to rely on acid-epoxy reactions to cure them and catalysis them. Although Type I and Type II systems are commonly used in concrete flooring, Type III systems are the leading technology for concrete walls. They provide excellent chemical resistance, but slow reaction times take longer to form all properties.
2 shows the MAINCOTE AEH resin technology, which introduces a fourth type of epoxy system to achieve a low VOC formulation without affecting curing speed, application period or performance formation. This versatile technique has epoxy groups inside acrylic emulsion particles. During the wet phase, acrylic emulsion acts as a barrier between curing agents and epoxy resins, which helps to extend the application period. When the formulated coating comes into contact with air, the water in the formulation evaporates, bringing the hybrid resin into contact with the curing agent. Crosslinking is rapidly forming, and the demand for curing agents is reduced due to the relatively high EEW value of hybrid resins. The amount of film-forming additives required is also low, as epoxy resins in emulsion particles help reduce the minimum film-forming temperature (MFFT) of acrylic polymers. Curing agents can be amine curing agents, or acrylic polymers containing pyric acid groups, such as MAINCOTE AE-58 acrylic curing agents.Test Results
In order to prove the performance advantages of the new acrylic-epoxy hybridization technology, a two-part (2K) coating system was developed with MAINCOTE AEH-10 acrylic epoxy hybrid resin and MAINCOTE AE-58 acrylic curing agent, which was tested together with five municipal concrete water-based wall coating systems. In Table 1, these bodies evaluate the five main properties of concrete wall coatings: adhesion, wear resistance, chemical resistance, color preservation and gloss preservation. The results show that MAINCOTE AEH-10 provides an excellent balance of these important properties, while the VOC<100 g/L of the formula has better gloss hold and color preservation without the addition of UV stabilizers. An example of chemical resistance is shown in Figure 3, which shows a photograph of the coating after exposure to a 10% sodium hydroxide solution, showing the obvious advantages of an acrylic-epoxy hybridization system. The results in Table 2 also show that hybridization systems have the same or better chemical resistance as commercially available formulations for commonly used cleaning agents. Table 3 shows a variety of test results such as Taber's wear resistance, scrub resistance, impact resistance, and shaft rod flexibility, which describe how easily coatings can withstand mechanical damage.
UV-resistant and durability
A significant advantage of the new resin technology over standard water-based epoxy systems is its extra UV resistance. As shown in the data in Figures 4 and 5, the MAINCOTE AEH-10-10-based coating system has been shown to have excellent color and gloss hold throughout the 1600-hour test.Conclusion
The growing use of daylight lighting in low VOC coatings and buildings to reduce building energy consumption is driving the development of low VOC acrylic system products that provide significant UV-resistant performance while meeting the durability needs of commercial and public buildings with high traffic. Regular cleaning and use of corrosive cleaners requires a two-component (2K) coating with high chemical resistance, and MAINCOTE™AEH acrylic epoxy hybrid resins provide good durability, low VOC, and improved UV resistance.
References
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3, Fu, Z. Dombrowski, G.; Hejl, A.; Swartz, A.; Tepe, T.; Procopio, L. Proc. American Coatings Conf. 2014.
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