A greener future for coatings

In the coatings industry, the initial focus was on reducing the release of volatile organic compounds (VOCs) into the atmosphere. The application of the sustainability idea has since been expanded to include the use of renewable materials, energy conservation, process efficiency enhancement, and waste minimization for the production of sustainable paint.

Companies must now consider the broader impact of their activities on society and move towards the concept of eco-efficiency. Eco-efficiency is the ability to satisfy customer needs in a way that minimizes adverse effects on the environment, natural resources, human health, and safety.

Compliance with local and international environmental regulations was once the sole motive behind the effort to formulate and manufacture more environment-friendly coatings. More recently, however, the consumer demand for greener solutions and evolution in corporate culture towards more responsible business behavior, have become the main drivers of the sustainability agenda. Even though the environmental legislation is now more stringent and comprehensive than before, the regulations only serve as the baseline that responsible manufacturers look to surpass.

The three key elements of the modern idea of sustainability are circularity, preventing climate change, and ensuring the health and safety of consumers and workers. These elements translate into the following actionable points for the coatings industry:

Consumers have shown a strong preference for low VOC paints that are environmentally friendly and pose no risk to health when applied inside their homes. Minimal VOC paint has virtually no odor and is hence perceived as safe and healthy. Reducing VOCs in coatings is therefore more than just a regulatory benchmark that must be achieved. Proactive paint and coatings companies either already have, or are actively engaged in the development of, a line of environmentally conscious, zero VOC bio-based coatings.

Bio-based materials are materials made from substances derived from living organisms. Bio-based raw materials can be divided into the following categories:

• Bio-based building blocks
• Bio-based solvents
• Renewable additives

Bio-based chemical building blocks are being increasingly employed to replace fossil fuel-based chemicals. The use of these sustainable alternatives is intended to reduce dependence on fossil feedstocks for chemicals. Replacing fossil-fuel-based chemicals with their bio-based counterparts reduces greenhouse gas emissions throughout the production chain. Plant-based raw materials such as vegetable oils have long been used in the coatings industry; incorporating additional bio-based chemicals into coating formulations can significantly enhance the total bio-based content.

Soy oil and castor oil are the two major raw materials used in the production of bio-based building blocks for the coatings industry. The unsaturated fatty acids in soy oil can be converted into hydroxyl groups or epoxy groups. The hydroxyl groups are used for the production of a variety of polyurethanes used in waterborne and solvent-less coatings.

The epoxy derivatives can be converted into acrylated esters used in the formulation of solvent-less UV curable coatings and other low VOC coatings. Vegetable-oil-based resin systems are typically hydrophobic and provide good moisture resistance.

Bio-based solvents provide a sustainable alternative to traditional petrochemical solvents. Consumers are increasingly concerned about the impact of solvent on the environment. They prefer the use of eco-friendly solvents or green substitutes over conventional products due to environmental benefits and safety. Bio-based solvents are mainly produced from corn, sugar, and beet. They are preferred as a safer alternative as they do not release toxic byproducts and volatile organic compounds during manufacturing.

In addition to binders and solvents, coating formulations also contain pigments and other additives. Although the percentage of additives is comparatively lower than other ingredients, renewable additives do present an opportunity to maintain and improve the green credentials of a coating formulation. Modern wetting agents, dispersing agents, coalescing agents, defoamers and even flash rust inhibitors may contain bio-based content of up to 85%.

Alkylphenol ethoxylates (APEs) is a group of chemicals commonly used as surfactants in acrylic paints. APEs include nonylphenol ethoxylates (NPEs) and octylphenol ethoxylates (OPEs), which are regarded as chemicals of concern by the EPA. The break-down products of NPEs and OPEs are not readily biodegradable and have been found to be highly toxic to fish and other aquatic organisms. Formulators of acrylic latex water-based paints must explore the use of safer alternatives to achieve an APE-free formulation.

In order to prevent climate change, coating manufacturers must aim to reduce their carbon footprint. The manufacturing process must be reengineered and optimized to:

• Reduce energy consumption
• Reduce waste material
• Reduce water consumption

Improving the performance of coatings is also an important step towards sustainability as it reduces the environmental impact from repeated coating applications. Technologies that improve performance and thus, the eco-efficiency, of coatings are considered environmentally friendly. These include self-healing coatings, nanoparticle-toughened coatings, sol-gel coatings, and photo-catalytic coatings among others.

Alkyd resins are recognized for their green credentials as they are largely based on natural fatty acids. Containing more than 50% natural oils and carboxylic acids from renewable plant sources, alkyd resins are an attractive choice for the formulation of sustainable coatings. Traditionally, alkyd resins have been solvent-based. The demand for VOC-free paint and the regulatory pressure to reduce VOC emissions has led to the development of water-based alternatives.

Critical advancements in surfactant technology led to the launch of the first bio-sourced alkyd polymers and water-based paints in 2011. Initially, the water-based alkyd coatings ran into cost and formulation issues due to the high volume of surfactant required. Since then, however, the performance of water-based systems has constantly improved.

Today, low VOC, solvent-borne systems and water-based systems are both widely available which boast superior environmental credentials. Alkyd is a thoroughly tested technology that offers a number of performance benefits. It remains an attractive option for coating formulators, particularly for wood applications.

A major step forward, on the sustainable coatings front, was the introduction of waterborne paints. Emulsion polymerization technology driven by acrylic polymers enabled the formulation of water-based products that are easier to maintain and more economical to produce. Acrylic water-based paints have swiftly captured the lion’s share of the architectural coatings market.

The ingredients in the acrylic resin, however, are still largely fossil-based. Recent advancements have led to the production of acrylic resins from sustainably sourced plant-based materials. The new bio-based resins contain as much as 50% plant-based content, verifiable by the 14C analysis. The technology replaces fossil-based components with renewable materials, lowering the environmental footprint without compromising coating performance. Bio-based resins are made from safe ingredients; they contain low VOCs which makes them ideal for the production of low volatile organic compound paints.

Epoxy resins offer excellent adhesion and corrosion resistance properties. They are extensively used as binders in protective coatings because of their formulation flexibility. Basic epoxy resins have traditionally been produced from petroleum derivatives, namely epichlorohydrin (ECH) and bisphenol A (BPA). Renewable glycerin, obtained from vegetable oils, has been successfully used as a feedstock for the production of 100% bio-based ECH. Bio-based ECH can reduce the carbon footprint of epoxy coatings by more than 60%.

It is possible to further increase the percentage of bio-based ingredients by completely or partially replacing the curing agent with a 100% bio-based equivalent. Cardanol, extracted from the cashew nutshell, is commercially used in the preparation of epoxy curing agents known as phenalkamines. The Cardanol derivative provides a useful combination of chemical resistance, flexibility, and hydrophobicity that is desirable in several heavy-duty applications.

Polyurethanes (PU) are formulated using an isocyanate and a polyol component. Bio-based polyurethane coatings are increasingly replacing petrochemical-based coating due to their lower environmental impact. Bio-derived materials, such as cashew nut shell liquid (CNSL), vegetable oils, eucalyptus tar, terpene, and other plant-based sources, are being used to produce precursors for the synthesis of polyols and isocyanates.

CNSL based polyols and diols offer unique properties compared to polyester, polyether, and other natural oil-based polyols. Due to the long aliphatic chain of cardanol, CNSL-based polyols and diols are very hydrophobic. This hydrophobicity provides enhanced water resistance and lower moisture sensitivity for increased durability of the final polyurethane system

Sustainable alternatives to traditional architectural, decorative, industrial and automotive coatings are increasingly being sought by consumers and legislatively mandated by governments around the world. Coating manufacturers must carefully plan and proactively manage their transition to greener coatings. Consumers have a growing preference for products formulated with bio-based materials that are perceived as safer and more environment-friendly.

The increased use of naturally-derived raw materials in the binder component of coatings can improve the sustainability credentials of environmentally friendly paints and coatings. At Safic-Alcan we help formulators to understand how to replace petroleum-based ingredients in their formulations with bio-based building blocks, bio-based solvents, and renewable additives.

Reengineering of production technology, optimization of polymer chemistry, adjustments in polymeric coatings formulation, and improvements in coating application and curing procedures can all be used for improving the eco-efficiency of green coatings.

Eco-friendly paint and coating manufacturers must strive to achieve sustainability goals while remaining competitive in the market. The cost impact of eco-friendly modifications to the formulation and the manufacturing process must be minimized and should always be justifiable by the value it creates. Plan a meeting with Safic-Alcan’s experts to learn more about the solutions we can provide you.

• Four Ways Coating Materials Support UN Sustainability Goals
• Bio-based Raw Materials Form the Main Focus in Developing Bio-based Coatings
• Market Trends on Bio-based and Plant-based Resins
• 5 Trends Changing the Way Wood Coatings are Formulated
• The future is green – for the coatings industry too!
• An Update on Sustainability in the Coatings Industry
• Exploring the alkyd resin market to create a sustainable future for the European coatings industry
• Enabling sustainable epoxy resins
• Bio-based solvents on the rise
• It’s Not Just About VOCs: Select APE-free Paint, Too