Synthesis of high purity o-cresol novolac epoxy resins

O-cresol novolac epoxy resins are used widely as electronic encapsulating materials. When the pitch wires in electronic systems are more slender, there are pressing demands for high purity o-cresol novolac epoxy resin which are with little content of hydrolyzable chloride. In this paper, o-cresol novolac resin was synthesized from para-formaldehyde and o-cresol in the presence of a mixed catalyst (oxalic acid and another co-catalyst). Then, the resultant resin was further reacted with epichlorohydrin to prepare o-cresol novolac epoxy resin. The performances and structure of o-cresol novolac resin and o-cresol novolac epoxy resin were characterized by epoxy equivalent weight, softening point, the content of hydrolyzable chloride and inorganic chlorine, FTIR, ¹³CNMR. And the relationships between the performances and the reaction conditions were also studied. The results indicate that, o-cresol novolac epoxy resins were synthesized with certain performances through the adjustment of the reaction conditions, which were suited for the pressing demands for high purity applications.