PURPOSE: To effectively remove sulfates, etc., formed as a by-product and obtain polyphenylene ether (PPE) stable to thermal oxidation, by initially treating the PPE with sulfuric acid and subjecting the treated PPE to steam distillation in separating and purifying the PPE from the reaction product.
CONSTITUTION: A 2,6-disubstituted phenol (e.g. 2,6-dimethylphenol) is subjected to oxidative polymerization in the presence of a catalyst consisting of copper ions, halogen ions and an amine. An alcohol, such as methanol, is normally added to the resultant reaction product to deposit polyphenylene ether (PPE). Sulfuric acid in an equivalent amount of normally 1W5 times based on the sum of the amine and copper which is the catalyst is added. Filtration treatment is subsequently carried out and the obtained PPE is dispersed in methanol and neutralized with sodium hydroxide, etc. the resultant impregnated PPE is then dispersed in water or hot water and steam is blown into the system to carry out steam distillation. Thereby the aimed PPE is obtained. Furthermore, the above-mentioned steam distillation is preferably carried out at 50W150°C for 10minW3hr.