Coatings material makers work to improve the ingredients’ profile as others try to replace them
By Marc S. Reisch
Isocyanates make possible the high-performance durable paint coatings on this fast train.
Love them or hate them, isocyanates are hard to beat. They make durable vehicle finishes that give new cars a shine that lasts for years. They also make industrial paints that are chemical resistant, flexible, and impervious to breakdown from the sun’s ultraviolet rays.
When reacted with polyester or acrylic resins, isocyanates cross-link to form a polyurethane. In coatings systems that also include pigments and other additives, polyurethanes are the industry benchmark for high performance. But isocyanates have a dark side too.
Reactive isocyanate oligomers are pulmonary and skin sensitizers until they fully cure, so they must be handled with care. Getting the most out of them often means that newly painted cars must cure in energy-hungry ovens. In addition, the oligomers are typically made with petrochemical raw materials in a hazardous phosgenation process that can hardly be called green.
But coating materials suppliers are moving to put a kinder and gentler face on polyurethanes. Some, such as Bayer MaterialScience and Vencorex Chemicals, are beginning to develop isocyanates out of biosourced raw materials. Others, such as Evonik Industries, Dow Chemical, Nuplex Industries, and Hybrid Coating Technologies, have developed alternative coating technologies that promise performance equal to or better than isocyanate-based polyurethanes.
The opportunities are big. Polyurethanes make up half of the $19.6 billion global high-performance coatings business, according to industry expert Phil Phillips, managing director of Chemark Consulting. Demand for high-performance coatings grows by 5% per year, Phillips says. The $115 billion coatings market grows at less than half that rate, he adds.
Paint makers are keenly interested in developing more environmentally benign polyurethane and other coatings systems. “Eliminating an oven or reducing oven cure temperatures can have a positive environmental impact,” says Ray Schappert, product management director for automotive coatings at the paint maker PPG Industries.
PPG, Schappert says, has developed a paint system that eliminates the need to put a new car body through a primer-curing oven. Thanks to resins that can be applied wet-on-wet, a car’s three top paint layers—primer, color coat, and clear topcoat—can be applied in succession and oven-cured.
Paint maker Axalta, which was DuPont’s coatings business until 2013, also has its eye on energy-saving technologies. Like PPG, it has designed paint packages for customers that use what Michael R. Koerner, an Axalta senior research fellow, calls a “three-wet system.” Advantages include a “smaller application footprint, reduced oven energy, and less environmental waste,” he says.