Phthalic anhydride is the cyclic carboxylic anhydride of ophthalmic acid. Phthisic anhydride appears as a colorless to white lustrous solid in the form of needles with a mild distinctive odor. It is an important industrial chemical, especially for the large-scale production of plasticizers for plastics.
· The primary use of phthalic anhydride (PA) is as a chemical intermediate in the production of plastics from vinyl chloride. Phthalate esters that function as plasticizers are derived from phthalic anhydride.
· Phthalic anhydride has another major use in the production of polyester resins and other minor uses in the production of alkyd resins used in paints and lacquers, certain guys, insect repellents, and urethane polyester polios.
· Phthalic anhydride has also been used as a rubber scorch inhibitor and retarder.
· The second largest outlet for PA is in unsaturated polyester resins (UPR) which are usually blended with glass fibers to produce fiberglass-reinforced plastics. Principal markets are construction, marine and transportation.
· The third largest outlet is PA-based alkyd resins that are used in solvent-based coatings for architectural, machinery, furniture and fixture applications.
· Small volume uses for PA include the manufacture of dyes and pigments, detergents, herbicides and insecticides, fire retardants, saccharin and polyester resin cross-linking agents.