Flame retardant radiation curable compositions

1. A radiation curable flame retardant composition comprising

at least one polymer precursor selected from the group consisting of monomers and oligomers comprising one or more (meth)acryl groups,

at least one flame retardant (A) selected from cyclic phosphonate esters responding to formula (I)

wherein n is 1, 2 or 3, m is 0, 1 or 2 and p is 0 or 1 with the proviso that n+m+p=3,

R 1 represents an alkyl comprising from 1 to 4 carbon atoms, optionally substituted by a hydroxyl group,

R 2 represents an alkyl comprising from 1 to 4 carbon atoms,

R 3 and R 4 , each independently, represents an alkyl comprising from 1 to 8 carbon atoms, phenyl, optionally substituted by one or more halogen or hydroxyl, tolyl, xylyl, benzyl, phenethyl, hydroxyethyl, phenoxyethyl or dibromophenoxyethyl;

and

at least one flame retardant (B) selected from organic phosphorus compounds different from the cyclic phosphonates of formula (I)

wherein the polymer precursor comprises at least 5% by weight of one or more oligomers that are selected from the group consisting of urethane (meth)acrylates, polyester (meth)acrylates and epoxy (meth)acrylates.

2. The radiation curable composition according to claim 1 wherein flame retardant (A) is selected from the compounds of formula (I) wherein n is 1 or 2, m is 0 or 1 and p is 1.

3. The radiation curable composition according to claim 2 wherein flame retardant (A) is selected from the group consisting of the compounds of formula (II) and (III) as well as mixtures

thereof

4. The radiation curable composition according to claim 1 wherein flame retardant (B) is selected from the group consisting of phosphates, phosphonates, phosphinates, phosphites and phosphine oxides.

5. The radiation curable composition according to claim 4 wherein flame retardant (B) is selected from the group consisting of alkylphosphate esters, aryl phosphate esters, alkylarylphosphate esters, alkylphosphonate esters, aryl phosphonate esters, and alkylarylphosphonate esters.

6. The radiation curable composition according to claim 5 wherein flame retardant (B) is selected from polyarylphosphate esters derived from bisphenol A.

7. The radiation curable composition according to claim 1 comprising from 25 to 94% by weight of one or more polymer precursor, from 3 to 40% by weight of flame retardant (A) and from 3 to 35% by weight of flame retardant (B).

8. The radiation curable composition according to claim 7 wherein the polymer precursor comprises at least 20% by weight of one or more monomers selected from the group consisting of mono-, di-, tri-, tetra-(meth)acrylates, and mixtures thereof.

9. The radiation curable composition according to claim 7 wherein the monomers are selected from mono(meth)acrylates.

10. The radiation curable composition according to claim 1 wherein the polymer precursor comprises at least one oligomer and at least one monomer.

11. A method of producing a laminate comprising the steps of (i) providing a flame retardant composition according to claim 1 ; (ii) placing the flame retardant composition between two panes, at least one of which is glass, and (iii) letting the composition cure to form the polymer which forms the interlayer between the panes.

12. A glass laminate comprising at least one interlayer comprising the flame retardant composition according to claim 1 .

13. The radiation curable composition according to claim 7 wherein the polymer precursor comprises at least 5% by weight of one or more oligomers with a number average molecular weight from 1000 to 10000.

14. The radiation curable composition according to claim 13 wherein the oligomers are selected from the group consisting of urethane (meth)acrylates, polyester (meth)acrylates and epoxy (meth)acrylates.

15. The radiation curable composition according to claim 1 , wherein the polymer precursor comprises at least one oligomer selected from urethane (meth)acrylates.