Preparations having improved efficacy as flame retardants

1. A preparation comprising:

i) a mixture comprising poly(alkylene phosphates) of formula (I)

in which

R 1 , R 2 , R 3 and R 4 each independently of one another represent an n-butyl radical or a 2-methylpropyl radical,

A represents a radical of formula —CHR 5 —CHR 6 —(O—CHR 7 —CHR 8 ) a —,

in which

a represents an integer from 1 to 5 and

R 5 , R 6 , R 7 and R 8 independently of one another represent hydrogen or methyl,

and

n represents an integer from 0 to 100,

with the proviso that the poly(alkylene phosphates) of formula (I) present in the mixture differ from one another at least in the number n of repeating units and

the weighted average of the number of repeating units n of the poly(alkylene phosphates) of formula (I) is 1.10 to 4.00,

and

ii) at least one cyclic phosphonic ester of formula (II)

in which

R 9 , R 10 and R 11 each independently of one another represent a straight-chain or branched C 1 - to C 4 -alkyl radical and

m represents the number 0 or 1.

2. The preparation according to claim 1 , wherein in the radical of formula —CHR 5 —CHR 6 —(O—CHR 7 —CHR 8 ) a —, a represents the number 1.

3. The preparation according to claim 1 , wherein R 5 , R 6 , R 7 and R 8 are all identical and represent hydrogen.

4. The preparation according to claim 1 , wherein R 1 , R 2 , R 3 and R 4 are all identical and represent n-butyl radicals.

5. The preparation according to claim 1 , wherein R 1 , R 2 , R 3 and R 4 are all identical and represent 2-methylpropyl radicals.

6. The preparation according to claim 1 , wherein the weighted average of the number of repeating units n of the poly(alkylene phosphates) of formula (I) is in the range from 1.20 to 3.00.

7. The preparation according to claim 1 , wherein the mixture comprising poly(alkylene phosphates) of formula (I) has a molar mass distribution as determined by gel permeation chromatography against polystyrene standards with tetrahydrofuran as the eluent, wherein in the molar mass distribution the area fraction of poly(alkylene phosphate) of formula (I) where n=1 is 10 to 70 area percent.

8. The preparation according to claim 1 , wherein R 9 , R 10 and R 11 independently of one another represent methyl or ethyl.

9. The preparation according to claim 1 , wherein R 9 and R 10 both represent methyl and R11 represents ethyl.

10. The preparation according to claim 1 , wherein the preparation contains at least one cyclic phosphonic ester of formula (II) where m=0 and at least one cyclic phosphonic ester of formula (II) where m=1.

11. The preparation according to claim 1 , wherein the preparation contains 60% to 99.9% by weight of the mixture comprising poly(alkylene phosphates) of formula (I) and 0.1% to 40% by weight of the at least one cyclic phosphonic ester of formula (II) based on the total preparation.

12. The preparation according to claim 11 , wherein the preparation contains 70% to 99% by weight of the mixture comprising poly(alkylene phosphates) of formula (I) and 1% to 30% by weight of the at least one cyclic phosphonic ester of formula (II) based on the total preparation.

13. The preparation according to claim 1 , wherein the preparation has a dynamic viscosity of 20 to 1000 mPa·s at 23° C.

14. The preparation according to claim 1 , further comprising one or more auxiliaries selected from the group consisting of solvents, antioxidants, stabilizers and dyes.

15. The preparation according to claim 1 , further comprising one or more flame retardants distinct from the poly(alkylene phosphates) of formula (I) and from the at least one cyclic phosphonic ester of formula (II).

16. A process for producing polyurethanes, comprising reacting organic polyisocyanates with compounds having at least 2 isocyanate-reactive hydrogen atoms in the presence of the preparation according to claim 1 and in the presence of one or more blowing agents, stabilizers, and/or activators at 20° C. to 80° C.

17. A method of providing flame retardancy to a polyurethane, comprising preparing the polyurethane in the presence of the preparation according to claim 1 .