Methods of recycling polystyrene material comprising brominated contaminants

Method of recycling a polystyrene waste,

• the recycling comprising retention of a brominated polybutadiene polystyrene copolymer or removal of the brominated copolymer
• when the recycling comprises retention of the brominated copolymer, the method comprising
• dissolving the polystyrene waste in a first solvent, the first solvent being chosen from benzenes substituted with one or two substituents each chosen from C1 and C2 alkyl and mixtures thereof, to obtain a polystyrene/first solvent mixture,
• adding the polystyrene/first solvent mixture to a first portion of hydrocarbon polystyrene non-solvent under conditions to obtain precipitated polystyrene and a first portion of hydrocarbon waste solution, the hydrocarbon polystyrene non-solvent being chosen from C5 to C8 hydrocarbon and mixtures thereof,
• separating the precipitated polystyrene from the first portion of hydrocarbon waste solution, optionally repeating the dissolving, adding and separating,
• washing the precipitated polystyrene with a second portion of hydrocarbon polystyrene non-solvent under conditions to obtain washed polystyrene and a second portion of hydrocarbon waste solution,
• separating the washed polystyrene from the second portion of hydrocarbon waste solution,
• washing the washed polystyrene with a third portion of hydrocarbon polystyrene non-solvent under conditions to obtain a twice washed polystyrene and a third portion of hydrocarbon waste solution,
• separating the twice washed polystyrene from the third portion of hydrocarbon waste solution, and
• optionally drying the twice washed polystyrene;
• when the recycling comprises removal of the brominated copolymer, the method comprising
• dissolving the polystyrene waste in a solvent mixture comprising about 50 wt % to about 90 wt % of a first solvent as defined above or a second solvent;
• and about 10 wt % to about 50 wt % of a hydrocarbon polystyrene non-solvent as defined above, to obtain a polystyrene/second solvent mixture and a solid comprising the brominated copolymer,
• the second solvent being chosen from benzenes substituted with one or two substituents each chosen from C1 to C4 alkyl, wherein at least one of the one or two substituents is isopropyl,
• separating the solid comprising the brominated copolymer from the polystyrene/second solvent mixture,
• adding the polystyrene/second solvent mixture to a first portion of hydrocarbon polystyrene nonsolvent under conditions to obtain precipitated polystyrene and a first portion of hydrocarbon waste solution,
• separating the precipitated polystyrene from the first portion of hydrocarbon waste solution, optionally repeating the dissolving, adding and separating,
• washing the precipitated polystyrene with a second portion of hydrocarbon polystyrene non-solvent under conditions to obtain washed polystyrene and a second portion of hydrocarbon waste solution,
• separating the washed polystyrene from the second portion of hydrocarbon waste solution,
• washing the washed polystyrene with a third portion of hydrocarbon polystyrene non-solvent under conditions to obtain a twice washed polystyrene and a third portion of hydrocarbon waste solution,
• separating the twice washed polystyrene from the third portion of hydrocarbon waste solution, and
• optionally drying the twice washed polystyrene.