Bio-based chemicals: Greener paints improving coverage
Improving cost/performance ratios is driving demand for biobased paint and coatings raw materials
The paints and coatings industry is under increasing pressure from consumers and regulatory agencies to reduce the environmental impact of its products and processes.
Initial efforts were focused on reducing volatile organic compounds (VOCs) and have been quite successful. There is recognition today, however, of the need to improve environmental performance across the industry value chain and over the life cycle of paint and coating products.
The use of renewable raw materials is seen as one option for achieving this goal, as long as the cost/performance ratio is acceptable, the supply of bio-based raw materials is reliable and sufficient to meet growth expectations, and a measurable reduction of the environmental impact is achieved.
Commercialisation of advanced technologies for the production of bio-based versions of existing chemicals and newer bio-based compounds with new functionality is providing paint and coating manufacturers with the opportunity to explore that option.
Bio-based materials have, in fact, been used for the production of paints and coatings since the industry began. Natural oils, rosins, waxes, gums and polysaccharides are still important parts of many coating formulations today, according to Alistair Reid, manager of innovation, partnerships & bio-based materials with AkzoNobel.
“Interest in newer renewable technologies is therefore not only driven by the need to meet well-defined sustainability agendas, but also by the knowledge the bio-based raw materials can provide improved coating performance,” asserts Ludo Hart de Ruijter, industry director for coatings, adhesives, sealants and elastomers (CASE) at Corbion.
In addition, improved carbon and life-cycle performance combined with higher purity, enhanced water solubility and reduced toxicity are key trends and drivers for the use of bio-based paint ingredients, according to Timothy Staub, global vice president of business development with Green Biologics.
For some end users, there is also a desire to promote their commitment to sustainability by advertising that their products are coated with paint made from renewable resources, notes Brad Fogg, market segment manager, industrial coatings for agriculture, construction and earth moving (ACE) in BASF’s dispersions & pigments business.
The potential for unique functionality is another key factor driving interest in renewable raw materials for paints and coatings. Bio-based ingredients can be drop-in materials that are chemically the same as petrochemical-based products but produced from biomass instead of fossil resources. Alternatively, they can be novel materials that offer a desired functionality with the potential to impart new properties to coatings or enhance known and desirable performance characteristic.
“Bio-based feedstocks and innovative chemistries are introducing new molecules or producing new pathways to existing, useful molecules that can substantially improve the performance of coating additives, resins and solvents,” states Celene DiFrancia, senior vice president of engineering polymers and coatings for Elevance Renewable Sciences.
“As a result, coating formulators seeking to differentiate their products through increased performance are actively evaluating the use of these new, renewable compounds,” she says.
Functional bio-based additives comprised of enzymes, anti-microbial peptides, metal binding proteins/peptides, antibodies, protein/lipid receptors, protein ion channels, and nucleic acids are examples of bio-based materials with natural functionality that can be fixed/cured into coatings in a long-term, stable fashion and impart dynamic functionality that has not been possible in the past, according to Steve McDaniel, chief technology officer of Reactive Surfaces.
“Dynamic functionality delivered with bio-based materials in a cured resin system is unique, and its benefits are not generally available with other additives,” he says.
Generally speaking, if the coating survives, the functionality survives. Thus, as long as the downstream chemical process is not overly detrimental to the integrity of the coating, it will not be detrimental to the bio-based functional additive.
“The interest in coatings with novel functionality derived from natural and renewable resources will rapidly expand into a wide number of applications for which there is presently no equivalent technology,” he asserts.
The ability to reduce supply chain risk by creating additional feedstock sources that are not directly tied to the volatile price of oil is another important advantage of renewable raw materials, according to DiFrancia.
To be successful, however, bio-based paint and coating ingredients must provide an acceptable cost/performance ratio. Furthermore, to experience a strong pull from the market, the raw material must provide improved functionality, improved economics and decreased negative impacts, according to Rich Weber, global business leader for NatureWorks Performance Chemicals.
“The three-way intersection of more stable pricing, improved functionality, and the precepts of green chemistry – better for society and the environment – stimulates strong interest from brands that need all three of these qualities to deliver against their commitments of bringing better products to market,” he explains.
In addition to reducing the dependence on petrochemicals, products made from biologically produced carbon-containing materials reduce the amount of new carbon released, thereby enabling better management of the carbon cycle, according to Scott Cooley, North American Coatings Technology director with Reichhold.
“This benefit will obviously become smaller in the formulated paint or coating. It is therefore vital that all participants in the paint and coating industry fulfil their responsibility to make the entire value chain more sustainable,” says Corbion’s Hart de Ruijter.
AkzoNobel’s Reid also stresses that bio-based does not mean the same thing as sustainable. “Most often, bio-based materials offer a sustainability improvement over the comparable fossil material, but we cannot forget about the impacts of agricultural inputs or environmental and social consequences of land use.
“Whether bio-based or fossil, we must look at a life-cycle analysis (LCA) to compare alternatives. A life-cycle assessment is standard practice at AkzoNobel, and we only source bio-based materials if they offer lower total environmental impact vs incumbent raw materials,” he explains.
It is also important that the entire supply chain embrace the bio-based concept and prove that paints and coatings made from renewable raw materials perform equally or better than their petroleum based counterparts, according to Yasmin Sayed-Sweet, vice president of sales & marketing for Alberdingk Boley. She also notes that bio-based raw materials need to be readily available in large quantities. That can be difficult for newer bio-based products that are being introduced to the market because they are not yet produced at a fully commercial scale.
“Establishing manufacturing and supply chains for new performance chemicals at large scale, including aligning supply quantities with market adoption of the technology to address any customer concerns about bio-based sources not keeping up with the market adoption rate, is a real issue,” agrees Weber.
Fogg adds that, at least in North America, the use of bio-based materials in coatings is of interest as long as the performance is equal to or better than existing technology and the cost is equal to or lower than that of existing options. “The market will not pay more for bio-based materials unless regulations force the issue,” he says.
Misconceptions in the marketplace that bio-based means higher cost and lower performance can be a challenge, according to Cooley. “We have the ability to raise the bio-based content in our polymers to offer a more attractive profile, but if the balance of performance and cost is not favourable, the market has been resistant to move to greener products,” he adds.
Reichhold is meeting this challenge by developing low-VOC waterborne products using vegetable oils that meet current customer needs. The required investment in coating resin and coating formulation development and longer adoption times for bio-based products that are not one-on-one replacements of existing petro-based raw materials can pose difficulties, according to Hart de Ruijter.
Novel functionality requires a complete rethink of a formulation, agrees Reid, but he also notes that even a drop-in replacements requires checks that it is fit for purpose. In addition, different sourcing may result in different impurities and sources of variation. The fact that the bioeconomy does not yet have a feedstock base or logistics is yet another issue.
“Agricultural and forestry by-products, cover crops, food processing, municipal and water wastes have all been proposed as feedstocks, but many of these materials are dispersed, low density or otherwise difficult to obtain in quantity. Demand for feedstocks for energy and fuel applications, which in some regions also have regulatory drivers or subsidies, exacerbates this issue,” Reid says.
Inertia and resistance to change also present barriers to the adoption of new functional bio-based ingredients for paints and coatings, according to Reactive Surfaces’ McDaniel, particularly if any alterations, no matter how slight, to an established process are required. “We have seen that this resistance is particularly notable when the benefit of the bio-based material provides a solution to a long-existent but never-before-answered need. Initially there is incredulity over the remarkable results, partly because of a general unfamiliarity with the bio-based chemicals themselves, and at least partly because of the paradigm shift upsetting existing markets.
“In the case of enzymes, peptides, and antibodies there also has been a misperception that such raw materials, being biologically-derived, are unstable, sensitive to environmental challenges, and hard to work with. All of these perceptions have gradually given way to the overwhelming evidence to the contrary,” McDaniel observes.
In addition, he notes that consumers are willing to pay for increased functionality. “For instance, they seem quite willing to pay more for a self-cleaning cell phone screen coating than they already do for one that merely prevents scratching of the glass screen. We expect this trend to grow as consumers come to expect dynamic functionality from coatings in their environments.”
Bio-based raw materials with assured availability and cost structures will be incorporated into sustainable supply chains, and as large global raw material suppliers engage in research and development of bio-based raw materials with these types of commitments, they will be able to create market demand and consumer understanding, according to Sayed-Sweet.
Products that are most likely to succeed will offer a performance benefit as well as satisfy regulatory concerns and sustainability needs at an acceptable price-to-performance ratio, concludes DiFrancia.
Resins based on vegetable oils remain popular. Alberdingk Boley and Reichhold are both expanding this technology to include low-VOC, water-based options, the former as bio-based building blocks for poly-urethane dispersions (PUDs) and solvent-free polyols for cross linked urethane systems, and the latter as alkyd latex, oil-modified urethane and epoxy ester resins. BASF offers a range of natural oil-based, solvent-free polyols specially designed for use in two-component PU coatings and adhesives that have low viscosity combined with good hydrophobicity and hydrolysis, chemical and UV resistance, according to Fogg.
BIO-BASED MONOMER DEVELOPMENT
Bio-based monomers for the preparation of coating resins are also being developed. Biosuccinic acid is offered by several companies (Myriant, BioAmber, Corbion/BASF, Reverdia (a DSM/Roquette joint venture) as a raw material for coating resins.
BioAmber and Ecoat are evaluating penta-erythritol alkyd resins containing BioAmber’s bio-based succinic acid (SA). Preliminary findings suggest bio-based SA can replace between 20-35% of the PA with retention of performance.
Myriant has produced a line of developmental 100% bio-based polyester polyols using its bio-SA that are comparable to adipic acid polyols, with more price stability, according to the company. Myriant will not produce the polyols; they are being offered to polyol producers for evaluation.
Elevance, has commercialised octadecanedioic acid, produced from natural oils using its proprietary metathesis technology. The diacid is being explored as a bio-based raw material for new additives and resin systems for paints and coatings with improved hydrophobicity, flexibility and chemical resistance. Elevance is starting to explore adjacent opportunities for zero/low VOC coalescents for waterborne coatings.
Bio-based materials need large support
Copyright: Rex Features
Corbion offers a high-purity lactide monomer (PURALACT B3) that reduces the viscosity of solvent born resins and thus allows for a higher solids content in paint and coating formulations. The use of PURALACT B3 also reduces the drying time in decorative coatings and increasing the hardness and flexibility of coil coatings, says Hart de Ruijter. The company is also developing a process for the microbial production of 2,5-furandicarboxylic acid for the synthesis of various coating resins.
NatureWorks recently introduced a high-purity, polymer-grade lactide rich in meso-lactide for the production of amorphous copolymers, adhesives, coatings, emulsions, printing toners and surfactants. According to Weber, the product has a lower melting point and is more susceptible to ring-opening than racemic and pure L- and D-lactide for easier processing with lower energy consumption.
The company recently expanded lactide production at its Blair, Nebraska, facility from 140,000 tonnes/year to 150,000 tonnes/year and is in the engineering stage for a second manufacturing facility in Southeast Asia.
Croda offers a range of bio-based building blocks for coatings and resin modification, including, dimer-based polyester polyols, 36 carbon diols and diamines, polymerised fatty acids, azelaic acids and fatty acid amides.
According to Bryan Danek, Croda’s sales director for North America, “These technology platforms are allowing formulators to improve coating properties such as moisture resistance, adhesion to low energy substrates, and flexibility compared to those of traditional polyurethane dispersions (PUDs).”
Several companies are working towards the production of key paint and coatings raw materials. While BASF recently elected to exit its R&D collaboration with Novozymes and Cargill to develop a bio-based process for 3-hydroxypropionic (3-HP) and acrylic acid, the latter two companies are proceeding with the project and hope to find a new commercialisation partner.
Academic research groups are investigating potential new materials for formulation of bio-based coatings. For example, research groups at North Dakota State University (NDSU) are investigating derivatives of low viscosity, sucrose-based fatty esters as raw materials for epoxide resins and coating binders prepared by esterifying soybean oil with a vinyl ether alcohol, removing the glycerol byproduct, and then polymerising the new vinyl ether.
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