PURPOSE: To effectively avoid dioxane formation during depolymerization of polyester into glycol and ester components by adding a base to neutralize any acid catalyst for formation of the dioxane formed from contaminants.

CONSTITUTION: The formation of dioxane when a superheated methanol is passed through a reaction mixture comprising (A) a polyester, (B) an oligomer and (C) a contaminant capable of forming an acid catalyst for forming dioxane under a depolymerizing condition to depolymerize the polyester to a glycol and an ester component, is avoided by adding a base (e.g. sodium hydroxide) in an amount sufficient to neutralizing the acid formed from the component C.