Isophthalic acid is a colorless crystalline solid. It is used as an intermediate primarily for unsaturated polyester resins and alkyd and polyester coating resins; other applications include use in aramid fibers, as a component of copolyester resins and in high-temperature polymers. Nearly pure isophthalic acid has a purity of >99.8%. This material is called purified isophthalic acid or PIA.
Currently, there is significant global overcapacity for isophthalic acid, with sufficient spare capacity for the next five years.
Isophthalic acid (1,3-benzenecarboxylic acid) is the meta form of phthalic acid. It is a white crystalline solid subliming at 345°C. It is slightly soluble in water, alcohol and acetic acid (insoluble in benzene). Isophthalic acid is obtained by oxidizing meta-xylene with chromic acid, or by fusing potassium meta-sulphobenzoate, or meta-brombenzoate with potassium formate. IPA has excellent performance characteristics including exceptional hardness, corrosion and stain resistance, hydrolytic stability of coatings and gel coats, outstanding thermal stability and low resin color in coatings industry.
Isophthalic acid is a key ingredient in FRP (Fiberglass Reinforced Plastics) markets for such products as marine, automotive, and corrosion resistant pipes and tanks. Polyesters containing isophthalic acid are also used extensively in industrial coatings applications for home appliances, automobiles, aluminum siding, and metal office furniture. It used as an intermediate for polyesters, polyurethane resins, plasticizers.