A new water-based, low-VOC hybrid binder technology has recently been developed for decorative coatings, offering high gloss potential and a step forward in both applicability and open time versus conventional acrylics. This new binder also represents an alternative to solventborne resins, giving improvements toward sustainability. To quantify the environmental impact of this new binder, a Life Cycle Analysis (LCA) was performed, making comparisons with key competing technologies in the area of gloss decorative coatings.

Life Cycle Analysis: Key Results

A preliminary LCA was performed on interior gloss paints using the Boustead Model 5.0, comparing a paint based on the starting point formulation for our new hybrid binder to the reference paint that was a high-solids [80% (20% solvent/30% TiO2 + others)] solventborne alkyd. A paint based on a waterborne alkyd was also examined. The characteristics of both the solventborne alkyd and the new hybrid used for the LCA are described in Table 1. Most water-based alkyd emulsions, including the high-solids solventborne alkyd tested, develop significantly higher yellowing than the new hybrid after six months of application. Because of this proven higher-yellowing development, the assumption in our LCA analysis is made that paint applicators will need to repaint two more times with both water-based and solvent-based alkyd paints than with the new hybrid-based paint over a 20-year lifetime.

Environmental Advantages

The following environmental improvements are offered by the new hybrid technology.

  · Despite the higher potential price per kg of paint for the new hybrid versus the solvent-based technology, the hybrid ends up being around 40% more cost effective than the solventborne alkyd because of reduced maintenance re-coats. The waterborne alkyd, on the other hand, is less cost effective because it requires the same number of recoats as the solventborne alkyd and its price per kg is 30% higher than for the solventborne paint.

· The impact on humans and the environment for the new hybrid is reduced by approximately 40% due to the replacement of solvent by water and the reduction in maintenance.

· Emission and energy reductions for the new hybrid take into account the whole supply chain of raw materials and finished paint.

· The new hybrid technology enables a reduction of greenhouse gas emissions (ca. 20%) and energy consumed (ca. 15%). Note that these values are estimated via comparison with existing LCA comparing other solvent-based and water-based paints. A specific new hybrid LCA is in progress.

  The authors acknowledge that many assumptions need to be made when comparing a single product, such as a paint based on the new hybrid, with a range of products, such as that represented by the family of paints based on alkyds. Still, we believe that the general effect of durability on influencing the outcome of an LCA is correctly represented and that it is worthwhile sharing this preliminary study. Please note that while the information is provided in good faith, no representations or warranties are made with regard to its completeness or accuracy. Open debate is a necessary part of studying a subject as complex as the environmental impact of different paint chemistries and, in the spirit of improving the industry’s knowledge, the authors will greatly appreciate any correspondence or exchange on this subject.

Durability Measured by Yellowing Resistance

The indoor durability of the new hybrid is measured by its yellowing resistance and is taken as the base for our LCA. We used the b value of the “L, a, b” color system to compare the yellowing resistance of the new hybrid to alkyd emulsions (Figures 2, 3) and solventborne alkyds (Figure 4) exposed and non-exposed to light.

Our data shows that the new hybrid is superior to the alkyd emulsions tested. It also shows that the yellowing resistance for the new hybrid is the same exposed and unexposed to light, in contrast to alkyd emulsions, which yellow significantly more in the dark.

This characteristic presents a potential aesthetics issue as painted surfaces will be, for example, darker yellow behind hung pictures or other areas not directly exposed to light.

Solvent-based alkyds also yellow significantly, particularly in the dark. After 9 months of curing, the high-solids, solvent alkyd paint has a very high b value of 11.

Summary

The environmental profile of the hybrid acrylic binder is improved relative to the two types of alkyd resins. Thanks to its superior low-yellowing characteristics and water-based composition, less frequent repainting is required, leading to a lower use of non-renewable materials, resources and energy. Finally, and importantly, the new binder does not require heavy metal driers to develop film properties.

For more information, contact akoller@rohmhaas.com.