Process technology for recovering brominated styrenic polymers from reaction mixtures in which they are formed and/or converting such mixtures into pellets or into granules or pastilles

A process for the preparation of a brominated styrenic polymer in the form of a melt or polymer flow, which process comprises:

• brominating a styrenic polymer under superatmospheric pressure in a vaporizable solvent and in the presence of a Lewis acid bromination catalyst, and in a closed reaction system in which substantially all of the hydrogen halide coproduct is retained in the reaction mixture;
• quenching the catalyst to thereby form (i) an organic phase containing dissolved brominated styrenic polymer and (ii) an aqueous phase containing hydrogen halide;
• separating phases (i) and (ii) from each other, and if phase (i) has a viscosity less than extrudable viscosity, concentrating organic phase of (i) to form an admixture of extrudable viscosity;
• continuously introducing organic phase of (i) or admixture of extrudable viscosity into the liquids inlet portion of an operating devolatilization extruder having a liquids inlet portion and a polymer melt or polymer flow outlet portion and at least two sections that can be operated (a) at temperatures that differ from each other, and (b) under pressures that differ from each other, one of the at least two sections being disposed upstream from the other of the at least two sections, the devolatilization extruder having vapor collecting apparatus adapted to collect volatiles formed in these at least two sections;
• and
• operating said section disposed downstream at higher temperature and lower pressure conditions than the temperature and pressure conditions of said section disposed upstream, so that (a) a flowable polymer melt or polymer flow of said polymer is formed within the devolatilization extruder and released from the at least one polymer melt or polymer flow outlet, and (b) volatiles composed predominately of the solvent released from the polymer in said at least two sections are collected by said vapor collecting apparatus, the polymer melt or polymer flow of such brominated styrenic polymer leaving from the outlet portion of the devolatilization extruder during steady-state operation of the devolatilization extruder containing an average of less than about 10,000 ppm (wt/wt) of the organic solvent used in the process.