Additives for improving the cold properties of fuel oils

1. A polymer of ethylene, a single ethylenically unsaturated ester and propene, which comprises:

a) from 12.0 to 16.0 mol% of structural units derived from the single ethylenically unsaturated ester,

b) from 1.0 to 4.0 methyl groups derived from propene per 100 aliphatic carbon atoms, determined by 13 C NMR spectroscopy, and

c) fewer than 6.5 methyl groups stemming from chain ends per 100 CH 2 groups, wherein the polymer has a sum G of molar content of unsaturated ester a) and the number of methyl groups derived from propene per 100 aliphatic carbon atoms of the polymer b), according to the formula

G=[mol % of unsaturated ester]+[propene-CH 3 ]

and wherein G is between 14.5 and 18.0.

2. The polymer as claimed in claim 1 , in which the ethylenically unsaturated ester is the vinyl ester of a carboxylic acid having from 2 to 12 carbon atoms.

3. The polymer of claim 1 , in which the ethylenically unsaturated ester is vinyl acetate.

4. The polymer as claimed in claim 3 , in which the polymer comprises between 28.0 and 36.0% by weight of the vinyl acetate.

5. The polymer of claim 1 , which further comprises structural units derived from at least one moderator having a carbonyl group.

6. The polymer as claimed in claim 5 , which further comprises from 0.5 to 7.0% by weight of at least one structural unit derived from a moderator comprising carbonyl groups.

7. A process for preparing the polymer of claim 1 , by reacting a mixture of ethylene, propene and the single ethylenically unsaturated ester under elevated pressure and elevated temperature in the presence of a free radical-forming initiator, and in which the molecular weight is adjusted by a moderator comprising carbonyl groups.

8. The process as claimed in claim 7 , in which a high-pressure bulk polymerization is performed at the elevated pressure of at least 100 MPa.

9. The process as claimed in claim 7 , in which a high-pressure bulk polymerization is performed at a peak temperature below 220° C.

10. A composition comprising at least one polymer as claimed in claim 1 and at least one further ethylene copolymer.

11. The composition as claimed in claim 10 , wherein the total comonomer content of the further ethylene copolymer is at least two mol % lower than that of the at least one polymer.

12. A composition comprising at least one polymer as claimed in claim 1 and at least one oil-soluble polar nitrogen compound.

13. A composition comprising at least one polymer as claimed in claim 1 and at least one alkylphenol-aldehyde resin.

14. A composition comprising at least one polymer as claimed in claim 1 and at least one comb polymer.

15. The composition comprising at least one polymer as claimed in claim 1 , and at least one polyoxyalkylene compound.

16. A free-flowing additive concentrate having an intrinsic pour point of −10° C. or lower for improving the flowability of middle distillates, said concentrate containing 20-40% by weight of at least one polymer as claimed in claims 1 and 60-80% by weight of at least one solvent.

17. A process for improving the cold flow properties of a fuel oil, by adding to the fuel oil a formulation containing at least 20% by weight of at least one polymer as claimed in claim 1 at a temperature of 0° C. or lower.

18. A fuel oil comprising a middle distillate and at least one polymer as claimed in claim 1 .

19. The composition of claim 1 , further comprising at least one component selected from the group consisting of a further ethylene copolymer, an oil-soluble polar nitrogen compound, an alkylphenol-aldehyde resin, a comb polymer, a polyoxyalkylene compound, and mixtures thereof.