Four Ways Coating Materials Support UN Sustainability Goals

In a climate-friendly world, all organic components of coatings should ideally be derived from bio-renewable materials and not from fossil fuels. In recent years, the development of eco-friendly solvents and coating resins with increasing bio-content has accelerated. This is the result of significant investment in biotechnology over the last decade, where biomass is converted into biobased products that can be used as a direct replacement for, or as an alternative to, chemicals derived from fossil fuels. Biobased mono- and multifunctional alcohols and acids are increasingly incorporated into commercial coating resins to raise resin bio-content.

A number of low toxicity bio-solvents have entered the market either as direct replacements for non-sustainable organic solvents, such as bio-acetone or bio-ethanol, or as targeted replacements for more harmful solvents, such as dimethylformamide or N-methyl-2-pyrrolidone. Most of these green solvents are made from sugar, corn or beet, and do not release toxic by-products or volatile organic compounds during manufacturing. Some companies now supply blends of bio-solvents in order to provide a solvent closely matching the characteristics and performance of petrochemical-based solvents in terms of solvation and wetting, evaporation rate, flashpoint, or solution viscosity.

Other products with bio-renewable content being developed for coatings include biobased waxes (including renewably-sourced polyethylene wax), surfactants, defoamers, silicone release agents, organic pigments and dyes, epoxy curing agents, and plasticizers.

 

The nature of the ink and adhesive used on the packaging, such as the use of biobased materials and avoidance of heavy metals, is an important factor for the biodegradability, compostability, or recyclability of the packaging. 

 

A growing feature in the coatings industry is to reduce energy usage in manufacturing or application processes. Key examples are LED lamps for radiation curing and the development of lower temperature stoving systems (particularly powder coatings).

Probably the most important driver for the development of radiation curing systems was the speed of cure and the increased productivity, but the emergence of LED lamps has provided an opportunity to move away from mercury arc lamps, significantly reduce energy usage and increase lamp lifetimes. However, the spectral output of LED lamps in the near-UV/visible region and oxygen inhibition issues have led to developments in photoinitiator systems, monomers and oligomers. 

There has been considerable interest in the development of powder coating resins with lower stoving temperatures for some time, largely driven by the desire to use the 100% solids coatings on MDF, wood and other temperature-sensitive substrates. However, this trend towards using less energy in coatings processes, whether in application processes or manufacturing, is likely to strengthen in the coming years. 

The recent development of new pigment dispersants, easy-to-disperse pigments and thickeners has been at least in part driven by reducing the energy necessary for coatings manufacture. Indeed, dispersing pigments and fillers is a critical step both in terms of energy and production time.

The purpose of chemicals management regulations, such as REACH, TSCA and other national regulations around the world, is to improve the protection of human health and the environment from the risks posed by chemicals. Many of these regulations are now maturing:
 

• Toxic Substances Control Act (TSCA) was first signed into law in 1976 and
• The European REACH regulations came into force in 2007.

After years of chemicals testing and assessments, the focus of these regulations is increasingly shifting towards restricting the use of the more hazardous substances and encouraging substitution and the development of less harmful replacements. So clearly this is not a new theme for the coatings industry.

There were concerns about the use of lead decades ago and many companies have long stopped adding lead compounds (pigments and driers) to coatings. However, according to the 2020 update from UNEP and the Global Alliance to Eliminate Lead Paint, only 79 countries (41% of all countries) have legally binding controls to limit the production, import and sales of lead paints. Pigments in the same yellow-red color space or with anti-corrosion properties continue to be developed and launched to support the replacement of lead-based pigments. 

In more recent years there have been health concerns raised over, for example, the use of cobalt compounds (driers) and methyl ethyl ketoxime (anti-skinning agents) in coatings, prompting the development of a range of replacement products. New halogen-free flame retardants have been developed. There continues to be an interest in finding alternatives for bisphenol A-based resins especially in the can coatings market.

Download Brochure: Discover cobalt-free paint drier technology exceeding the performance of traditional cobalt containing products & cobalt-free systems »

 

Volatile organic compounds (VOCs) were identified as a health concern decades ago for their role in helping to produce ozone in the troposphere via photochemical reactions. Although there are a number of natural sources of VOCs, coatings were considered a notable source of VOCs, particularly in cities, and in a number of countries VOC emission regulations have been put in place to restrict VOC content in coatings and to limit VOC emissions from factory sites.

Ever since the first regulations restricting VOC emissions, there has been a drive to replace conventional solvent-borne coatings with the most appropriate low-VOC option (whether that is waterborne, high solids/solventless, or powder) and this has been supported by the development of products that have been specifically designed to improve the performance of low-VOC coatings or diminish their problem areas.

In the waterborne arena, this has led to low-VOC or VOC-free wetting, dispersing and defoaming agents; and easy-to-use low-VOC additives that improve matting, slip abrasion, mar or block resistance. There is an ever-increasing range of waterborne pigment dispersions and tinting systems; novel metallic effect pigments with improved optical properties and stability in aqueous systems; and easy-to-disperse pigments.

The matting of powder coatings and 100% solids radiation curing coatings is quite challenging. Unlike solvent-borne and waterborne coatings where coating shrinkage enables matting agents to broach the coating surface and achieve matting, there is minimal coating shrinkage during the application and cure processes for these solventless coatings. For both powder and UV coatings, one approach has been to modify the surface of a matting agent with a low surface energy material (such as a silane or other silicon-based compound) to encourage it to move to the air-coating interface in the short period that the coating is fluid.

Related Read: Overcome formulation challenges for low-VOC interior paints with new binder solutions »

 

The coatings industry and its supply chain have considerable experience at developing products that reduce the impact of coatings on health and the environment, and no doubt more will be asked of the coatings industry in the future. Future products will likely become increasingly dependent on developments in the biotechnology sphere. 

There are many companies and research consortia around the world now developing innovative biobased raw materials and products that may have value in coatings, inks and adhesives. However, the development of new biobased materials faces a number of barriers including finding financial support:
 

• For fundamental research, applied research and
• Then for piloting, demonstration and commercial scale-up.

Probably there also needs to be more policy-based market pull to overcome these barriers.