Brominated polystyrene having improved thermal stability and color and process for the preparation thereof

Abstract

In a process for the suppression of backbone halogenation during the bromination of polystyrenes comprising the step of pretreating a solution of a polystyrene reactant comprising from about five to about 20 percent by weight of a polystyrene reactant, in a halogenated hydrocarbon solvent with at least about 0.1 percent by weight of an additive to suppress halogenation of the polystyrene backbone prior to brominating the polystyrene in the presence of a catalyst; adding a metal halide bromination catalyst to the solution, capable of effecting bromination of the ring without causing crosslinking of the polystyrene; adding to the solution from about 1 to about 3.4 moles of a brominating agent, per mole of polystyrene repeating units; reacting the polystyrene reactant with the brominating agent at a reaction temperature of from about −20° C. to about 50° C., and isolating the brominated polystyrene. A brominated polystyrene is also provided having a backbone halogen content of less than about 750 ppm and, a ΔE color as low as about 5.

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