Halogen-free flame retardant compositions, thermoplastic compositions comprising the same and methods of producing the compositions

1. A halogen-free or substantially halogen-free flame retardant composition comprising a blend of (i) at least one highly charring polymer, (ii) at least one low volatility phosphate ester and (iii) at least one compound which splits off a high volatility phosphorus-containing fragment.

2. The composition according to claim 1 , wherein said (i) at least one highly charring polymer is selected from the group consisting of phenol-formaldehyde resins, substituted phenols, substituted diphenols, polycarbonates, polyphenylene ethers, polyimides, polysulfones, polyether sulfones, polyphenylene sulfides, polyether ketones, and mixtures thereof.

3. The composition according to claim 1 , wherein said (i) at least one highly charring polymer is polyphenylene ether.

4. A flame retarded thermoplastic composition comprising an effective amount of the flame retardant composition of claim 3 and an effective amount of (iv) at least one polystyrene resin.

5. The composition according to claim 1 , wherein (ii) at least one low volatility phosphate ester has the general formula:

where R is a linear, branched or cyclic C 2 to C 15 alkylene group, phenylene, or bisphenylene with an alkylene, ether or sulfone bridge, Ar is an unsubstituted or substituted phenyl group, and where n can range from about 1 to about 10.

6. The composition according to claim 5 , wherein said (ii) at least one low volatility phosphate ester is selected from the group consisting of resorcinol bis(diphenyl phosphate), bisphenol A bis(diphenyl phosphate), hydroquinone bis(diphenyl phosphate) and mixtures thereof.

7. A flame retarded thermoplastic composition comprising an effective amount of the flame retardant composition of claim 6 .

8. A flame retarded thermoplastic composition comprising an effective amount of the flame retardant composition of claim 5 .

9. The composition according to claim 1 , wherein said (iii) at least one compound which splits off a high volatility phosphorus-containing fragment is a metal salt of an alkyl alkylphosphonic acid.

10. The composition according to claim 9 , wherein said metal salt of alkyl alkylphosphonic acid is a metal salt of an alkyl alkylphosphonic acid, said alkyl groups having 1-5 carbon atoms, branched or straight chain, wherein the metals are selected from Groups II, III, or IV of the Periodic Table or transition metals.

11. The composition according to claim 9 , wherein said (iii) at least one compound which splits off a high volatility phosphorus-containing fragment is a metal salt of an alkyl alkylphosphonic acid wherein the metal is selected from the group consisting of Mg, Ca, Zn, Al, Ti and Zr.

12. The composition according to claim 11 , wherein the metal salt of alkyl alkylphosphonic acid is an aluminum salt of methyl methylphosphonic acid.

13. The composition according to claim 1 , wherein said (iii) at least one compound which splits off a high volatility phosphorus-containing fragment, splits off said high volatility phosphorous-containing fragment at a temperature above about 300° C.

14. The process for manufacturing the flame retarded thermoplastic composition according to claim 13 wherein said (i) at least one low volatility phosphate ester has the general formula:

where R is a linear, branched or cyclic C 2 to C 15 alkylene group, phenylene, or bisphenylene with an alkylene, ether or sulfone bridge, Ar is an unsubstituted or substituted phenyl group, and where n can range from about 1 to about 10.

15. The composition according to claim 1 , wherein said composition comprises about 5 percent to about 35 percent by weight of said (iii) at least one compound which splits off a high volatility phosphorus-containing fragment.

16. The composition according to claim 15 , wherein said composition comprises about 2 percent to about 15 percent by weight of said (iii) at least one compound which splits off a high volatility phosphorus-containing fragment.

17. The composition according to claim 1 further comprising poly(tetrafluoroethylene).

18. A flame retarded thermoplastic composition comprising an effective amount of the flame retardant composition of claim 1 .

19. The composition according to claim 1 further comprising a polystyrene resin.

20. The composition according to claim 19 wherein the polystyrene resin is high impact polystyrene.

21. A process for manufacturing a halogen free or substantially halogen-free flame retardant composition, said process comprising blending together (i) at least one highly charring polymer, (ii) at least one low volatility phosphate ester and (iii) at least one compound which splits off a high volatility phosphorus-containing fragment.

22. A process for manufacturing a flame retarded thermoplastic composition comprising blending (iv) at least one polystyrene resin with the blended flame retardant composition of claim 21 .

23. The process for manufacturing the flame retarded thermoplastic composition according to claim 22 wherein a sufficient amount of said flame retardant composition is mixed with a sufficient amount of said (iv) at least one polystyrene resin to provide a flame retarded thermoplastic composition comprising about 20 percent to about 50 percent by weight of said flame retardant composition.

24. The process for manufacturing the flame retarded thermoplastic composition according to claim 22 wherein a sufficient amount of said flame retardant composition is blended with a sufficient amount of said (iv) at least one polystyrene resin to produce a flame retarded thermoplastic composition comprising about 20 percent to about 35 percent by weight of said flame retardant composition.

25. The process for manufacturing the flame retarded thermoplastic composition according to claim 22 wherein said (i) at least one highly charring polymer is selected from the group consisting of phenol-formaldehyde resins, substituted phenols, substituted diphenols, polycarbonates, polyphenylene ethers, polyimides, polysulfones, polyether sulfones, polyphenylene sulfides, polyether ketones, and mixtures thereof.

26. The process for manufacturing the flame retarded thermoplastic composition according to claim 22 wherein said (i) at least one highly charring polymer is polyphenylene ether.

27. The process for manufacturing the flame retarded thermoplastic composition according to claim 22 wherein said (ii) at least one low volatility phosphate ester is resorcinol bis(diphenyl phosphate), bisphenol A bis(diphenyl phosphate), hydroquinone bis(diphenyl phosphate) and mixtures thereof.

28. The process for manufacturing the flame retarded thermoplastic composition according to claim 22 wherein said (iii) at least one compound which splits off a high volatility phosphorus-containing fragment is a metal salt of an alkyl alkylphosphonic acid, said alkyl groups having 1 to 5 carbon atoms, branched or straight chain, wherein the metal is selected from Groups II, III, or IV of the Periodic Table or transition metals.

29. The process for manufacturing the flame retarded thermoplastic composition according to claim 22 , wherein said (iii) at least one component which splits off a high volatility phosphorus-containing fragment is a metal salt of an alkyl alkylphosphonic acid wherein the metal is selected from the group consisting of Mg, Ca, Zn, Al, Ti and Zr.

30. The process for manufacturing the flame retarded thermoplastic composition according to claim 29 wherein said metal salt of alkyl alkylphosphonic acid is an aluminum salt of methyl methylphosphonic acid.

31. The process for manufacturing the flame retarded thermoplastic composition according to claim 22 wherein said (iii) at least one compound which splits off a high volatility phosphorus containing fragment splits off said high volatility phosphorous-containing fragment at a temperature above about 300° C.

32. The process for manufacturing a flame retarded thermoplastic composition according to claim 21 wherein poly(tetrafluoroethylene) is blended with the blended flame retardant composition.