Tackling the Challenge of Finding True Green Chemical Solutions

Green chemistry industry sign on black wooden background. 3D rendering.

The global market for green coatings, including waterborne, powder, high-solids solvent-based, and radiation-cure coatings, is estimated by Allied Market Research to be valued at $80 billion in 2016 and growing at a compound annual growth rate (CAGR) of 5.8% to reach $119 billion in 2023. Grand View Research, meanwhile, projects the green coatings market will expand at a CAGR of 6.9% to reach $209 billion by 2025. Drivers of this growth include increasingly strict environmental regulations, growth in the popularity of green building standards, and a rise in consumer awareness regarding sustainable products in both the construction and automotive sectors. Expanding use of solar-reflective coating technology is one important factor in the construction industry. Waterborne technology dominated the green coatings market and will continue to grow at a high rate. Powder coatings will also experience significant demand growth over the next several years. Architectural/decorative coatings account for the largest portion of the market, while on a geographic basis, more green coatings (approximately one-third of the total) are sold in Europe than other parts of the world. The Asia-Pacific region is, however, witnessing the highest growth rate.

While much of the emphasis on green coating developments focuses on the move to waterborne and high-solids solvent-based coatings and the resin and additive technologies required to achieve high performance levels for these formulation types, advances have also been made with respect to other green materials used in more sustainable coating solutions. InKemia Green Chemicals was founded in 1997 by chief scientific officer, Carles Estévez to help companies in many industries find green chemical solutions. For over 20 years, the company has been designing, developing, and commercializing new green chemistry products and processes and identifying existing green chemicals that can replace less sustainable alternatives.

Grand View Research projects the green coatings market will expand at a CAGR of 6.9% to reach $209 billion by 2025.

When identifying potential green chemicals for use in paints and coatings, there are several factors that must be considered. “The chemicals must not only be green, but they must offer the desired level of performance, efficacy, and function at an acceptable cost,” Estévez says. The real challenge, he notes, is to achieve the best compromise between all of these different and important factors simultaneously. “The more values and parameters applied as constraints—to be within certain specifications such as viscosity, film formation temperature, volatility, appearance, color, stability, and so on—the more difficult that challenge becomes. In addition, any material—solvent, coalescent, diluent, etc.—must also meet toxicological and ecotoxicological requirements, which involves another layer of constraint.

Another challenge is the limited number of choices available that can be considered green and that have the potential to meet all of these complex performance and cost efficiency goals, according to Estévez. InKemia Green Chemicals is dedicated to addressing this shortage. “We are focused on expanding the variety of green chemicals that are available for use in coatings and many other applications,” he explains. That involves identifying potential candidates with good tox and ecotox profiles that already exist, some of which may be cost-effective and others that have high costs that preclude their use. For the latter materials, which are attractive from a sustainability and technical perspective, the company seeks to develop new production processes that will enable their manufacture at an acceptable cost.

While InKemia is not an expert at formulating coatings, the company does know chemistry and how to identify and synthesize green chemicals that can fulfill a number of required functional properties, according to Estévez. “We understand the relationship between the chemistry and the function, and build on that through partnerships and collaborations with experts in various industries,” he observes. Most of its clients have been in Europe, but the company is currently building many connections in the United States as well.

The first step is to identify the problem that needs to be solved, which is generally completed in partnership with the client. InKemia then screens its libraries of compounds with low or negligible health hazards to identify any potential candidates based on the desired functionality and specific constraints of the formulation. Some of these chemicals are biobased materials, but being biobased in and of itself is in many occasions insufficient, as there are biobased chemicals that do not have desirable functional or toxicity properties, according to Estévez. “It is also important to conduct a lifecycle assessment and consider the sum of all of the environmental impacts over the lifetime of a chemical. Some biobased options have attractive sustainability profiles, while others do not,” he adds. Cost is also often an issue for biobased alternatives—and in some cases for compounds that are chemically synthesized. “Paints and coatings have cost structures that carry small margins; any increase in the price of raw materials quickly has a measurable impact on the overall cost. It is essential to take cost into account at the design stage so that any solutions that are developed will have a reasonable cost for the formulator,” Estévez states.

In one example, the client was seeking a replacement for butyl glycol in a waterborne system. The primary goal was to reduce the quantity of solvent in the formulation to 30% by weight without changing the viscosity or the environmental, health, and safety profile. InKemia identified 10 different candidates that met criteria including the rate of evaporation, chemical aggressiveness on plastic substrates (ABS polymers), miscibility with water, compatibility with the target emulsion, etc. The candidates were evaluated in the formulation using multilevel design of experiments to evaluate the influence of temperature, solvent concentration, and other factors on film formation along with the quality of the resultant films. As a result, one of the 10 candidates was found to have properties comparable to butyl glycol. In fact, the minimum film forming temperature was better than the reference chemical, according to Estévez. The coalescent efficiency of the one-component aqueous clearcoat was improved by as much as 50% at 20°C. InKemia then tested the candidate in a two-component epoxy acrylic coating and confirmed that the results were similar for the new and existing formulations in terms of film formation, applicability, sandability, and appearance, even though there was 20% less solvent in the new formulation. “This project is a good example of how InKemia can help companies find greener chemicals that can meet even challenging performance requirements,” Estévez asserts.

We are focused on expanding the variety of green chemicals that are available for use in coatings and many other applications.

In a different case, the client formulation was a waterborne marine coating based on an acrylic resin that also contained white spirits. The VOC content needed to be reduced. The solution proposed by InKemia was to replace the white spirits with a reactive diluent that becomes incorporated into the coating during the drying process rather than evaporating. The chemical chosen was VOC-exempt and did not pose any health hazards. “We evaluated several different properties, including viscosity, leveling, film formation, appearance stability (no yellowing), drying time, hardness, gloss, adhesion, and chemical resistance. In all cases except gloss, the formulation with the reactive diluent performed similarly to the existing coating containing white spirits,” says Estévez. The higher gloss obtained with the reactive diluent was successfully adjusted with a matting agent. In addition, the diluent was biobased and a fairly inexpensive ingredient.

In a third case, InKemia was charged with developing a more cost-effective route to a more sustainable coalescent that would allow for its sale at half the current cost. The company took two to three years to develop the chemistry for manufacturing the glycerine derivative, evaluate its functional properties with respect to required performance in paints and coatings, and confirm the scalability and ultimate cost of the process. Within two years, the product will be commercially produced within a biorefinery at nearly one-third the cost of material available today, according to Estévez. “This solution is very attractive because it supports the concept of the circular economy through the use of bioproducts from biodiesel production,” he notes. Overall it would have taken InKemia just four to five years to go from early-stage R&D to introduction of tonnes of product into the market.

CoatingsTech | Vol. 16, No. 4 | April 2019

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