As environmental regulations have tightened the VOC standards for architectural and industrial maintenance finishes, coatings manufacturers have long sought a means of reducing the VOC content of their products (as required by government regulations), yet still maintaining superior performance (as required by their customers). Recent developments in waterborne alkyd resin technology have enabled coatings manufacturers to meet performance demands while also meeting current and future environmental standards.
Evolution of Environmental Regulations for AIM Coatings
Governmental agencies on national, regional, state and local levels have issued a variety of regulatory rulings regarding the VOC content of coatings used in architectural and industrial maintenance (AIM) applications. Since many states and regional councils have established tighter requirements on VOC content than the federal government, the resulting patchwork of standards means that paint manufacturers must either attempt to formulate their products to meet the most stringent standards; or have different formulations for each specific geographic region covered by these standards. See Table 1 for a comparison of current and proposed VOC limits.National Regulations
As the nation’s primary regulatory agency for air quality, the EPA has established limits for VOC content for coatings sold into the U.S. market. Current EPA VOC limits for AIM coatings range from 550 g/L (for clear stain) to 380 g/L (for high gloss and semigloss paint), to 250 g/L (for flat paint).According to the EPA’s timeline, these national regulations are scheduled to be revised this year, although some delays are widely anticipated. The process will begin with publication of the new proposed rules in the Federal Register in 2009, a three-month public comment period, and final publication in the Federal Register by December 15, 2009. Compliance with the new regulations would be enforced as of January 1, 2011. Proposed changes will further limit VOC content in AIM coatings: 250 g/L for clear stain; 250/150 g/L for high-gloss/semigloss paint; and 100 g/L for flat paint.
Regional/State Regulations
With delays in the implementation of new national regulations, many state and regional groups have adopted their own VOC-limiting rules.OTC (Ozone Transport Commission)
Comprised of several states in the Northeast and mid-Atlantic regions, the Ozone Transport Commission (OTC) is responsible for advising EPA on transport issues as well as developing and implementing regional solutions to the ground-level ozone problems in the following states: Connecticut, Delaware, the District of Columbia, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont and Virginia. In addition, Illinois, Indiana and Ohio have also adopted a version of the OTC VOC limits for coatings sold in their states.
Current OTC standards limit VOC content for AIM coatings to 250 g/L (for clear stain); 250 g/L (for high gloss); 150 g/L (for semigloss paint), to 100 g/L (for flat paint). However, many of the OTC states are re-evaluating their VOC standards and are anticipated to revise these limits downward by sometime in 2010, and are likely to adopt even lower VOC limits, which will bring OTC’s regulations in line with statewide rules in California.
CARB (California Air Resources Board)
California has long been a bellwether for state air quality regulations, and has currently implemented VOC limits similar to the OTC standards. Starting in 2010, new CARB limits for VOC content will be established, including: 150 g/L (for high gloss); 100 g/L (for semigloss); and 50 g/L (for flat).
Local Regulations
Some of the most restrictive regulations are set for Southern California, where air quality has long been an issue. SCAQMD (South Coast Air Quality Management District) is the air pollution control agency for all of Orange County, California and the urban portions of Los Angeles, Riverside and San Bernardino counties.Strict VOC limits are imposed on coatings in the area covered by SCAQMD, with no more than 50 g/L allowed for high gloss, semigloss and flat paints. Many paint and coatings manufacturers use the SCAQMD standards as their baseline for VOC content, especially if they want to use a single formulation for paint sold into the United States.
Canadian Regulations
The Canadian government agency tasked with environmental issues, Environment Canada, is also adjusting its VOC limit regulations to generally conform to proposed new (January 1, 2011) EPA AIM rules. As with the EPA, the publication of these final regulations has been delayed, with publication expected in 2009, and an implementation date sometime in 2010.VOC Measurement
Typically measured in grams per liter (g/L) of the finished coating product (thinned to manufacturers’ specifications and excluding the volume of water, colorants and other exempt compounds), VOC content is regulated for more than 60 specific categories or types of coatings, and is determined in most cases by testing carried out by the paint manufacturers under EPA’s Method 24 (Ref. http://www.epa.gov/ttnemc01/methods/method24.html).
VOC Content for Waterborne Alkyds vs. Acrylic Latex Coatings
When waterborne acrylic latex technology was first introduced more than 50 years ago, it represented a significant reduction in the amount of VOCs needed as compared to traditional solventborne alkyd chemistries that comprised much of the coatings industry to that point. However, both traditional alkyds and acrylic latex coatings still required significant amounts of organic solvent additives, particularly for high-gloss and semigloss paint, as well as primers.The role of the organic solvent, in both chemistries, is to enhance the flow characteristics and adhesion of the coating to the substrate. Traditional solventborne alkyds exhibited a low molecular weight and a relatively flexible polymeric structure, giving them superior substrate-wetting properties, and the ability to penetrate deeply into porous surfaces. These characteristics provided excellent adhesion, gloss development, penetration and stain-blocking performance, but these factors were offset by the higher VOC content required by the need for organic solvents.
Acrylic latex, with its higher molecular weight and the structural properties of latex within the emulsion, was not able to meet alkyd-like performance levels for high-gloss and semigloss paints and primers without the addition of organic solvents, which in turn negated much of their low-VOC advantage.
The development of true waterborne alkyd technology has enabled coatings manufacturers to formulate high-gloss, semigloss and flat paints, as well as stain-blocking primers with near-zero VOC levels by using water as the primary carrier. An example of this technology is the Beckosol AQ family of alkyd resins introduced by Reichhold Chemicals. These surfactant-stabilized emulsions eliminate the need for expensive additives and co-solvents to enhance the coating performance, and produce paint with shelf stability of more than 12 months.
A comparison of the VOC content of high-gloss paints manufactured with traditional solventborne alkyd technology, acrylic latex technology and the new Beckosol AQ waterborne alkyd technology is shown in Figure 1.
Near-Zero VOC Resins Reduce Compliance Reformulation Need
By enabling coatings manufacturers to use a single resin across all paint categories (high gloss, semigloss, flat, stains and primers), the new waterborne alkyds greatly simplify the manufacturing processes, transportation, logistics and inventory systems needed to maintain different formulations of paint for different geographic regions of the country. In addition, manufacturers are relieved of the burden of constant reformulation of their product to meet VOC standards that are being tightened. Moving to a single resin also reduces factory downtime and cleaning processes involved in reformulation.
Alkyd Formulations - More Than 50% Renewable Resources
Because the base for the new alkyd coatings is derived from plant oils, the new waterborne alkyd formulations using Reichhold’s Beckosol AQ resins produce coatings that are more than 50% renewable resource-based (as a percentage of solids used), versus a renewable resource content of zero for most conventional acrylic latex formulations. A chart comparing typical waterborne alkyd composition with acrylic latex composition is show in Table 2.Superior Coating Performance Results in Lower VOC Emissions
While many coatings manufacturers have been able to produce paints that meet the tightening VOC limits, there have been tradeoffs in terms of higher costs and a degradation of paint performance and durability. If lower VOC coatings result in more frequent repainting, then the effect of the VOC regulations is negated through more VOC exposure. True waterborne alkyd technology, such as Beckosol AQ resin, provides the superior performance (high gloss, adhesion, weatherability) needed, along with the lower VOC content.Conclusion
The development of true waterborne alkyd technology has made it possible for paint and coatings manufacturers to produce high-performance coatings while meeting VOC limits for the foreseeable future.For more information see www.reichhold.com.
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