Methods for producing cyclic phenol sulfides

A method for producing a cyclic phenol sulfide which comprises the step of reacting a phenol compound of the following formula (1) as a raw material:

• wherein R1 represents a straight or branched alkyl group having 1 to 6 carbon atoms, in a one-step reaction, with 1.7 to 2.5 molar equivalent of sulfur and 0.25 to 0.75 molar equivalent of an alkali metal reagent per 1 mol of the phenol compound to obtain a mixture of cyclic phenol sulfide wherein m =4 and at least one kind(s) of cyclic phenol sulfides wherein m =5 to 9, or each separate cyclic phenol sulfide comprised in the mixture, the cyclic phenol sulfide being represented by the following formula (2):
• wherein R1 represents a straight or branched alkyl group having 1 to 6 carbon atoms, and m is an integer from 4 to 9;
• and wherein the reaction is conducted under the temperature conditions that the reaction temperature is risen to 120 to 140° C. and kept at the same temperature for 0.5 hour or more;
• then, it is risen to 160 to 180° C. and kept at the same temperature for 0.5 hour or more;
• and then it is risen to 210° C. or higher.