To recover a styrene monomer from a polystyrene resin efficiently and at a low cost by charging a polystyrene resin and a calcium-based catalyst having a weight or volume equal to or more than that of the polystyrene resin in a treatment bath and heating the same.
As the calcium-based catalyst, calcium oxide, calcium carbonate, calcium hydroxide, calcium sulfate and calcium phosphate are used and calcium oxide is preferable. When the specific gravity of the catalyst is below 1.5 times that of the polystyrene resin, a weight ratio is preferably used and, when the specific gravity of the catalyst is 1.5 times or more that of the polystyrene resin, a volume ratio is preferably used. Calcium oxide is preferably a sufficiently dried powder calcined at 1200-1400°C. The particle diameter is preferably 1 mm or less. A polymerization inhibitor, for example, such as a sulfur compound or 4-t-butylpyrocatechol, is preferably added in a treatment bath to prevent styrene monomer obtained by decomposition from re-polymerization. The heating temperature is about 230-360°C.
MASUNARI MITSUO
ASANO KENZO
