Synthesis of epoxy resins based on bisphenol‐S and its derivatives

Abstract

AbstractBisphenol‐S derivatives of five kinds such as bis[4‐(β‐hydroxyethoxy)‐phenyl]sulfone (HEPS), bis[4‐(β‐hydroxy(iso)propoxy)‐phenyl]sulfone (HPPS), 3,3′,5,5′‐tetrabromobisphenol‐S (TBS), bis[3,5‐dibromo‐4‐(β‐hydroxyethoxy)‐phenyl]sulfone (HEETBS) and bis[3,5‐dibromo‐4‐(β‐hydroxy(iso)propoxy)‐phenyl]sulfone (HPETBS) were successfully prepared by the reaction of bisphenol‐S with ethylene carbonate, 1,2‐propylene carbonate or bromine, respectively. Several sulfone‐containing epoxy resins were obtained by alkaline condensation of bisphenol‐S (bis(4‐hydroxyphenyl)‐sulfone) or its derivatives with epichlorohydrin using sodium hydroxide. The epoxy resins thus obtained were characterized by elemental analysis, IR and 13C‐NMR spectra. All epoxy resins are solid products except HPPS epoxy which contains oxypropylene units. The melting points (Tm) and glass transition temperatures (Tg) of epoxy resins which have flexible oxyethylene or oxypropylene units were lower than that of epoxy resin derived directly from bisphenol‐S. The increase of melting point which has been observed in brominated epoxy resins is attributed to the bulky bromine atom. The molar‐mass distributions of epoxy resins made by the direct addition of epichlorohydrin to bisphenol‐S (so‐called “taffy” process) or by the reaction of epoxy resin of low molar mass and of which the main constituent is the diglycidyl ether of bisphenol‐S in melt (so‐called “advancement” process) have also been compared. The “taffy” process leads to products containing both odd‐ and even‐numbered diepoxide oligomers in contrast to the “advancement” process which leads to products containing predominantly even‐numbered diepoxide oligomers. Epoxy equivalent and melt viscosity of epoxy resins increased with increasing amount of bisphenol‐S. This result is in accordance with the theoretical distribution calculated according to Flory statistics.