Alkyd/Polyester Surface Coatings

Alkyd surface coatings continue to be one of the most highly consumed types of coatings used in the world, despite the increasing use of other film formers. The success of alkyd resin systems is a result of their relatively low cost, versatility and long familiarity with users. They can be tailored to meet a variety of end-use requirements through the choice and ratio of reactants and/or modifiers. Alkyds are used extensively in architectural coatings, product finishes and special-purpose coatings. Promoters of alkyd resins note that they are partly made from fatty acids or oils derived from renewable sources, making them greener than most competitive coating resins. Alkyds were the first synthetic coatings binder used in commercial practice, first used in large quantities in the 1930s.

Polyesters, also referred to as oil-free alkyds, are made in the same equipment as alkyds and use many of the same raw materials. Polyesters are used almost exclusively in industrial baking finishes.

The following pie chart shows world consumption of alkyd/polyester surface coatings.

Despite the continuing decline in the market in North America, Western Europe and Japan, alkyds remain one of the leading types of coatings used in the industrial marketplace.

In North America, Western Europe and Japan, consumption of alkyds has diminished over the last thirty years. In the architectural or decorative coatings market, solventborne alkyds have been steadily replaced with waterborne emulsions as a result of their lower odor, lower solvent content, easy cleanup and fast drying properties. However, in some applications, these emulsions do not display the same level of performance in leveling, adhesion, gloss and certain resistance properties. These drawbacks have stalled the conversion from most solventborne gloss trim, wood stains and light maintenance coatings, so solventborne alkyds still remain a sizable factor in the coatings industry. However, restrictions on the use of paints are becoming tighter in certain parts of the United States and in Europe, which will forbid the use of conventional low-solids (i.e., high-solvent-containing) solventborne coatings. As a result, the types of resins used in these regions in certain applications will change significantly.

Producers continue to develop new and improved systems for high-solids and waterborne formulations to meet increasingly stringent air pollution regulations. In recent years, producers of alkyd resins have developed waterborne latex resins that meet low VOC (volatile organic compound) levels required by recently enacted legislation in certain parts of the United States and Western Europe. Generally, though, these environmentally friendly systems are considerably more expensive than the conventional systems, and have some technical drawbacks. The industry has been blending waterborne alkyds with acrylic emulsions to combine the desirable properties of both systems. Polyesters are offered in high-solids, waterborne and powder coatings.

Japanese consumption of alkyd and polyester surface coatings has declined significantly during the 2000s, and is now less than half that of the peak year in 1990. The declining trend for alkyd surface coatings will likely stabilize over the next five years, as most high performance alternatives have already replaced alkyd surface coating applications; also, a slight recovery of the economy with an increase in construction is forecast. Polyester coatings consumption depends largely on the health of the construction industry. In recent years, polyesters have been used in lesser amounts in the automotive industry, having been mostly replaced with waterborne acrylics or urethanes.

China is the fastest-growing region in the world, and some multinational producers of resins and coatings have established production facilities there. In particular, the use of alkyd coatings for construction applications and of polyester-epoxy hybrid powder coatings on metal parts has grown rapidly.

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