This invention relates to a process for condensing phenols to form polyphenylene oxides useful as thermoplastics. More particularly, this invention relates to the preparation of polyphenylene oxides by reacting substituted phenols with oxygen or an oxygen-containing gas in the presence of a catalyst consisting of a copper compound, a primary amine and iodine or an iodine-containing compound.
Heretofore, there have been known processes which employ a cuprous salt with a tertiary amine, a basic cupric salt with a primary amine or a secondary amine, and a cupric salt with an amine and a base as a copper salt-amine catalyst in the preparation of polyphenylene oxides. However, the polymers which are obtained by employing the above-mentioned catalysts, are generally somewhat discolored and the intrinsic viscosity, which represents the polymerization degree of the condensation products, rarely exceeds 1.3 dl./g. but shows generally figures less than 0.8 dl./g. Furthermore, the time for absorption of a theoretical volume of oxygen is more than 20 minutes and the yield of polymer rarely exceeds 90%.