Alkyd resins: From down and out to alive and kicking

Alkyd resins have been introduced in the 1930s as binders for paints. Their compatibility with many polymers and the extremely wide formulating latitude made them suitable for the production of a very broad range of coating materials. This includes do-it-yourself paints and varnishes for wood and metal, road marking paints, anticorrosive paints, nitrocellulose lacquers, two-component isocyanate curing coatings, acid curing coatings, stoving enamels, etc. Except for phthalic anhydride, being of petrochemical origin, the other raw materials used in the synthesis of the alkyds are from biologically renewable sources. This, combined with their biological degradability, makes them very interesting binders from an ecological point of view. Solvents which are used to reduce and adjust the paint viscosity are the only concern with respect to the ecological aspects of the alkyd paints. In recent years, however, we witness quite an activity in designing alkyd emulsions and high solids alkyds which can serve as binders for environmentally friendly coatings.It can be expected that in coming years the contribution of common low(er) solids alkyds in organic solvents will decrease, those products being replaced with high solids alkyds, alkyd emulsions and other high end waterborne binders. High end in this respect means all waterbased systems that exhibit a performance substantially higher than common thermoplastic latices used for wallpaints.When properly formulated, alkyd emulsions can be considered as candidates to formulate paints with a zero VOC level. This paper summarizes the new developments in alkyd emulsions and high solids alkyd paints and compares these paint systems with paints based on acrylic dispersions as other environmentally friendly alternatives to conventional paints.