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.

What is claimed is:  
     
       1. A brominated polystyrene product made by the process comprising: 
       pretreating a solution of a polystyrene reactant comprising from about five to about  20  percent by weight of said 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;  
       subsequently adding a metal halide bromination catalyst to said solution, capable of effecting bromination of the ring without causing crosslinking of the polystyrene;  
       adding to said solution from about  1  to about  3 . 4  moles of a brominating agent, per mole of polystyrene repeating units;  
       reacting said polystyrene with said brominating agent at a temperature of from about − 20 ° C. to about  50 ° C., and isolating the brominated polystyrene.  
     
     
       2. A brominated polystyrene having a backbone halogen content of less than about  750  ppm and, a ΔE color as low as about  5 . 
     
     
       3. A brominated polystyrene, as in  claim 2 , having a bromine content of at least about  66  percent by weight. 
     
     
       4. A brominated polystyrene, as in  claim 2 , wherein said brominated polystyrene reactant is produced from a polystyrene having a weight average molecular weight of from about  500  to about  1 , 500 , 000 . 
     
     
       5. A brominated polystyrene, as in  claim 4 , wherein said polystyrene reactant is selected from the group consisting of homopolystyrene, polystyrene oligomers, halogenated polystyrenes and alkylated polystyrene. 
     
     
       6. A brominated polystyrene process as in  claim 2 , wherein said a backbone halogen content is  580  ppm. 
     
     
       7. A brominated polystyrene process as in  claim 2 , wherein said ΔE color is  8 . 5 . 
     
     
       8. A flame retardant additive comprising the brominated polystyrene, as in  claim 2 . 
     
     
       9. A brominated polystyrene flame retardant which is a derivative of polystyrene and which has a bromine content of at least about  66  wt % and a ΔE color of less than about  7 . 8  to as low as  5 . 
     
     
       10. The brominated polystyrene flame retardant of  claim 9  wherein the ΔE color is less than about  6 . 8  to as low as about  5 . 
     
     
       11. The brominated polystyrene flame retardant of  claim 9  wherein the ΔE color is less than about  7  to as low as about  5 . 
     
     
       12. A brominated polystyrene flame retardant which is a derivative of polystyrene and which has a bromine content of at least about  66  wt %, a ΔE color of less than about  7 . 8  to as low as  5  and a backbone halogen content from about  250  to about  750  ppm. 
     
     
       13. The brominated polystyrene flame retardant of  claim 12  wherein the ΔE color is less than about  6 . 8  to as low as about  5 . 
     
     
       14. The brominated polystyrene flame retardant of  claim 12  wherein the ΔE color is less than about  7  to as low as about  5 .