Phosphorus-containing flame retardants

1. A flame-retardant comprising one or more polymers comprising a unit represented by formula (I), (Ia) or (II):

where A is selected from O, S, SO 2 , a single bond, alkyl, and —CH 2 —P 1 ;

P 1 is a phosphorus-containing group of the formula:

wherein R 1 and R 2 together with a group Y form a group R 1 —Y—R 2 , which together with the phosphorus atom bound to R 1 and R 2 form a ring:

in which R 1 and R 2 are the same or different and each is selected from O-alkyl, O-aryl, alkyl and aryl, and Y is a linking group selected from direct bond, alkylene and —O—;

R 3 is H or alkyl;

each a is an integer individually selected from 0 to 4, provided that at least one a is at least 1; n is an integer from 4 to 100,000, and m is an integer from 0 to 100,000.

2. The flame-retardant according to claim 1 comprising one or more polymers comprising a unit represented by formula (I), or one or more polymers comprising a unit represented by formula (II) wherein m is from 1 to 100,000.

3. The flame-retardant according to claim 1 which comprises one or more compounds comprising a unit represented by formula (Ia) or (II).

4. The flame-retardant according to claim 1 comprising one or more polymers having a formula (VIIa), (VIIb), (VIIIa) or (IXa):

5. The flame-retardant according to claim 4 comprising at least one polymer of formula (VIIa) or (VIIb).

6. The flame-retardant according to claim 4 comprising at least one polymer of formula (Villa).

7. The flame-retardant according to claim 4 comprising at least one polymer of formula (IXa).

8. A flame retardant composition comprising a flame retardant according to claim 1 and a base resin selected from the group consisting of polyester resins, styrenic resins, polyamide resins, polycarbonate resins, vinyl resins, olefinic resins, acrylic resins, epoxy resins, blends of two or more of said resins, and blends of one or more of said resins with a polyphenylene oxide-series resin.

9. The flame retardant composition according to claim 8 wherein the base resin comprises a polyamide resin.

10. The flame retardant composition according to claim 8 wherein the flame retardant is present in an amount of from about 10% to about 40% by weight of the total flame-retardant composition.

11. The flame retardant composition according to claim 8 wherein the base resin comprises a polyester resin, styrenic resin, polyamide resin, polycarbonate resin or epoxy resin.

12. The flame retardant composition according to claim 11 wherein the base resin further comprises a glass reinforcing agent.

13. The flame retardant composition according to claim 12 wherein the base resin comprises a glass-filled polyamide resin, comprising from about 15 to about 40% glass by weight of the total weight of the polyamide and glass.

14. The flame retardant composition according to claim 8 further comprising at least one flame retardant adjuvant material selected from melamine condensation products, melamine salts, inorganic metal compounds, clay compounds, layered double hydroxide materials, and polyphenylene ether resins and mixtures thereof.

15. The flame retardant composition according to claim 14 , wherein the melamine salt comprises a melamine phosphate, polyphosphate, and/or melamine pyrophosphate.

16. The flame retardant composition according to claim 14 , wherein the melamine condensation product comprises one or more of melam, melem or melon.

17. The flame retardant composition according to claim 14 comprising at least one melamine salt and/or melamine condensation product and at least one adjuvant selected from the group consisting of metal oxides, metal hydroxides, clay compounds and layered double hydroxide materials.

18. The flame retardant composition according to claim 14 , wherein said at least one flame retardant adjuvant material is present in an amount of about 1 to about 20 wt % of the flame-retardant resin composition.

19. The flame retardant composition according to claim 14 , wherein the inorganic metal compound is selected from metal salts of inorganic acids, metal oxides and hydroxides, metal sulfides and mixtures thereof.

20. The flame retardant composition according to claim 19 , wherein the inorganic metal compound comprises a borate.