Method for producing recycled styrene monomer

Abstract

The chemical recycling of polystyrene suffers from a low yield of recycled styrene monomer. The purpose of this invention is to provide a method for manufacturing recycled styrene monomer, comprising a thermal decomposition step in which waste styrene-based resin composition is thermally decomposed in the presence of a metal compound to obtain a thermal decomposition product containing recycled styrene monomer; the content of the metal compound is 1 to 25 parts by mass relative to 100 parts by mass of styrene monomer units in the aforementioned waste styrene-based resin composition, and the metal compound is at least one selected from the group consisting of zinc compounds, iron compounds, potassium compounds, and sodium compounds.