Oligomeric bisphosphate flame retardants and compositions containing the same

1. An oligomeric phosphate or mixture of oligomeric phosphates having the general formula I:

wherein R 1 , R 2 , R 3 and R 4 each independently is aryl or alkaryl and n has an average value of from about 1.0 to about 1.1 and wherein the oligomeric phosphate or mixture of oligomeric phosphates are in the form of a free-flowing powder having an average particle size of from about 10 μm to about 80 μm.

2. The oligomeric phosphate of claim 1 wherein R 1 , R 2 , R 3 and R 4 each independently is a phenyl group having the general formula II:

wherein each R independently is alkyl of 1 to 4 carbon atoms, each X independently is chlorine or bromine, p is 0 to 3 and q is 0 to 5 with the sum of p and q being 0 to 5.

3. The oligomeric phosphate a mixture of oligomeric phosphates according to claim 1 wherein R 1 , R 2 , R 3 and R 4 of formula I each is phenyl and n has an average value of 1.02.

4. A resin composition comprising;

(i) a flame retardant effective amount of an oligomeric phosphate or mixture of oligomeric phosphates having the following general formula I:

wherein R 1 , R 2 , R 3 and R 4 each independently is aryl or alkaryl and n has an average value of from about 1.0 to about 1.1 and wherein the oligomeric phosphate or mixture of oligomeric phosphates are in the form of a free-flowing powder having an average particle size of from about 10 μm to about 80 μm ; and

(ii) a resin.

5. The resin composition of claim 4 wherein R 1 , R 2 , R 3 and R 4 each independently is a phenyl group having the following general formula II,

wherein each R independently is an alkyl of 1 to 4 carbon atoms, each X independently is chlorine or bromine, p is 0 to 3 and q is 0 to 5 with the sum of p and q being 0 to 5.

6. The resin composition of claim 4 wherein the resin is selected from a group consisting of styrenic polymers and copolymers, polyphenylene oxide (PPO), acrylonitrile butadiene styrene (ABS), polycarbonates (PC), high impact polystyrene (HIPS) and mixtures thereof.

7. The resin composition of claim 6 wherein the resin is PC/ABS or PPO/HIPS.

8. The resin composition of claim 4 wherein said resin composition contains from about 2% to about 20% by weight, of the total composition, of oligomeric phosphate or mixture of oligomeric phosphates flame retardants of formula I.

9. The resin composition of claim 4 wherein the oligomeric flame retardant of formula I is hydroquinone bis (diphenylphosphate).

10. The resin composition of claim 9 wherein said hydroquinone bis-(diphenylphosphate) has an average n value of about 1.02.

11. The resin composition of claim 5 wherein the resin is selected from a group consisting of styrenic polymers and copolymers, polyphenylene oxide (PPO), acrylonitrile butadiene styrene (ABS), polycarbonates (PC), high impact polystyrene (HIPS) and mixtures thereof.

12. The resin composition of claim 11 wherein the resin is PC/ABS or PPO/HIPS.