Patent ID: 7435772

Claim:
A method of treating a thermoplastic resin composition, the thermoplastic resin composition comprising a thermoplastic resin, a bromine-including flame retardant and an antimony-including flame retardant auxiliary, the method comprising: a step (a) of heating and agitating said thermoplastic resin composition together with a first solvent at a temperature ranging from a glass transition temperature of said thermoplastic resin to a boiling point of said first solvent inclusive; and separating and recovering said first solvent in a liquid state in which at least part of said bromine-including flame retardant is dissolved from said thermoplastic resin composition, so that at least part of said bromine-including flame retardant is separated and removed from said thermoplastic resin composition, and a step (b) of heating and agitating said thermoplastic resin composition together with a second solvent containing at least one selected from ethylene glycol and propylene glycol at a temperature ranging from a glass transition temperature of said thermoplastic resin to a boiling point of said second solvent inclusive; and separating and recovering said second solvent in a liquid state in which at least part of said antimony-including flame retardant auxiliary is dissolved from said thermoplastic resin composition, so that at least part of said antimony-including flame retardant auxiliary is separated and removed from said thermoplastic resin composition, wherein: said step (b) is performed after said step (a) or said step (a) is performed after said step (b); said thermoplastic resin comprises any one of polystyrene, poly-α-methyl styrene, poly-(styrene-butadiene), poly-(styrene-acrylonitrile), poly-(styrene-butadiene-acrylonitrile), poly-(styrene-maleic anhydride), and impact-resistant high-impact polystyrene; and said first solvent is selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol propyl ether, diethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, triethylene glycol methyl ether, triethylene glycol ethyl ether, triethylene glycol propyl ether, triethylene glycol butyl ether, tripropylene glycol methyl ether, tripropylene glycol ethyl ether, tripropylene glycol propyl ether, tripropylene glycol butyl ether, ethyl lactate, butyl lactate, and mixtures thereof.