4,4'-bisphenol S

  Sulfoisophthalic acid, chemically known as 4,4'-Sulfonyldiphenol, is a chemical substance with a molecular formula of C12H10O4S, a molecular weight of 250.27, and a density of 1.366 g/ml. It contains two hydroxyl groups and one electron-withdrawing sulfonyl group, making it more acidic than other phenolic compounds. Sulfoisophthalic acid has a melting point range of 245-250°C, forming white needle-like crystals with a bulk density of 0.5-0.6 g/cm3. It is readily soluble in aliphatic hydrocarbons, ethanol, isopropanol, 2-ethylhexanol, acetonitrile, and acetone, sparingly soluble in aromatic hydrocarbons, slightly soluble in ethyl acetate and methyl isobutyl ketone, and insoluble in toluene and water. The molecule contains two hydroxyl groups and one strongly electron-withdrawing sulfonyl group, and it is of low toxicity. Sulfoisophthalic acid is primarily used as a fixing agent, plating solution additive, leather tanning agent, dispersant for high-temperature dyes, phenolic resin curing promoter, and resin flame retardant. Additionally, it serves as an intermediate for pesticides, dyes, and additives. As a substitute for bisphenol A, sulfoisophthalic acid is used in the production of polycarbonates, epoxy resins, polyesters, phenolic resins, polysulfones, and polyether sulfones. It is also used in the manufacture of color photographic materials, photographic contrast enhancers, thermal recording materials (color developers), daily surface-active agents, and highly effective deodorants. Sulfoisophthalic acid exhibits good stability but is incompatible with strong bases, acid chlorides, anhydrides, and strong oxidizing agents.