Abstract: Bromination of styrenic polymer is carried out in a closed reaction system to retain HX coproduct (where HX is HBr or HCl, or both) in the bromination reaction mixture at superatmospheric pressure. Preferably, the reaction mixture which includes the brominated styrenic polymer and substantially all of the HX coproduct formed is discharged into an aqueous quenching medium. By operating in this manner, the reaction is terminated and the brominated styrenic polymer of desired bromine content and substantially all HX coproduct are captured in the same operation, process equipment costs are reduced, and processing of the reaction mixture is facilitated.

Abstract: Concurrently fed into a reaction zone held at about 10° C. or less are brominating agent, aluminum halide catalyst, and a solution of anionic styrenic polymer having a GPC Mn about 2000-30,000. The components are in at least two separate feed streams. The feeds are proportioned to maintain (a) the amount of aluminum halide being fed at about 0.8 mole percent or less based on the amount of aromatic monomeric units in the polymer being fed, and (b) amounts of brominating agent and unbrominated polymer in the reaction zone that produce a final washed and dried polymer product containing about 60-71 wt % bromine. The catalyst is deactivated, bromide ions and catalyst residues are washed away from the reaction mixture, and the brominated anionic styrenic polymer is recovered and dried. The dried polymer has a volatile bromobenzene content of about 600 ppm (wt/wt) or less as well as other beneficial properties.

Abstract: Preparing brominated styrenic polymer by maintaining a mixture formed from (i) brominating agent, (ii) a solvent solution of styrenic polymer, and (iii) aluminum halide catalyst, at ?20 to +20° C., and terminating bromination in 20 minutes or less. New brominated anionic styrenic polymers have better melt flow and/or lower initial ?E values than the best previously-known brominated anionic styrenic polymers. Other features of such new polymers include high thermal stabilities at 320° C. and/or very low initial color values. Brominated styrenic polymers, especially brominated anionic styrenic polymers, are useful as flame retardants for thermoplastic polymers.