PURPOSE: To obtain polyphenyl ethers having improved heat resistance and oxidation resistance, by a method in which polyphenyl ethers containing impurities are subjected to an oxidation treatment and then to a heat treatment in the presence of an alkali metal hydroxide.
CONSTITUTION: Polyphenyl ethers containing impurities are first treated by oxidation at 250W350°C in a container for approx. 1hr or more while blowing air into the reaction system preferably. Then, an alkali metal hydroxide is added to the reaction system which is in turn subjected to a heat treatment under a reduced pressure of approx. 100mmHg or less. The said treatment can apply to commerically available high-temperature synthetic lubricants or their waste oils to advantage, particularly to those containing meta(metaphenoxyphenoxy)diphenyl.
NAKANISHI HIROSHI
YAGI TETSUYA
