Cold flow improvers for vegetable or animal fuel oils

1 . A fuel oil additive comprising

A) a copolymer of ethylene and from 18 to 35 mol % of at least one acrylic ester or vinyl ester having a C 1 -C 18 -alkyl radical and a degree of branching of less than 5 CH 3 /100 CH 2 groups, and

B) a comb polymer comprising structural units formed from

B1) at least one olefin as monomer 1, which bears at least one C 8 -C 18 -alkyl radical on the olefinic double bond, and

B2) at least one ethylenically unsaturated dicarboxylic acid as monomer 2, which bears at least one C8-C 16 -alkyl radical bonded via an amide and/or imide group,

in which the parameter Q

Q

=

∑

i





w

1



i

·

n

1



i

+

∑

j





w

2



j

·

n

2



j

in which

w 1 is the molar proportion of the individual chain lengths n, in the alkyl radicals of monomer 1,

w 2 is the molar proportion of the individual chain lengths n 2 in the alkyl radicals of the amide and/or imide groups of monomer 2,

n 1 are the individual chain lengths in the alkyl radicals of monomer 1,

n 2 are the individual chain lengths in the alkyl radicals of the amide and/or imide groups of monomer 2,

i is the serial variable for the chain lengths in the alkyl radicals of monomer 1, and

j is the serial variable for the chain lengths in the alkyl radicals of the amide and/or imide groups of monomer 2

assumes values of from 23 to 27.

2 . The fuel oil additive as claimed in claim 1 , wherein Q assumes values of from 24 to 26.

3 . The fuel oil additive as claimed in claim 1 , wherein constituent A) comprises from 18.5 to 27 mol % of at least one vinyl ester.

4 . The fuel oil additive of claim 1 , wherein constituent A) comprises from 0.5 to 10 mol % of olefins having from 3 to 10 carbon atoms.

5 . The fuel oil additive of claim 1 , wherein the degree of branching of constituent A) is less than 4 CH 3 /100 CH 2 groups, determined by means of 1 H NMR spectroscopy.

6 . The fuel oil additive of claim 1 , wherein the at least one olefin which forms constituent B1) is an α-olefin.

7 . The fuel oil additive of claim 1 , wherein a molar ratio of comonomer B1) to comonomer B2) in copolymer B) is between 1.5:1 and 1:1.5.

8 . The fuel oil additive of claim 1 , wherein copolymer B, as well as comonomers B1) and B2), further comprises up to 20 mol % of a further comonomer other than B1) and B2), selected from the group consisting of an olefin having from 2 to 50 carbon atoms, an allyl polyglycol ether, a C 1 -C 30 -alkyl (meth)acrylate a vinylaromatic or a C 1 -C 20 -alkyl vinyl ether, and a polyisobutene having molecular weights of up to 5000 g/mol.

9 . The fuel oil additive of claim 1 , wherein constituent A) has a melt viscosity V 140 of from 5 to 100 mPas.

10 . The fuel oil additive of claim 1 , wherein constituent A) has a molecular weight of from 1000 to 10 000 g/mol.

11 . The fuel oil additive of claim 1 , in which constituent B) has a molecular weight Mw of from 1200 to 200 000 g/mol.

12 . A fuel oil composition comprising a fuel oil of vegetable or animal origin and the fuel oil additive of claim 1 .

13 . The fuel oil composition as claimed in claim 12 , wherein the fuel oil further comprises a mixture of fatty acid esters of C 1 - to C 4 -alcohols.

14 . The fuel oil composition as claimed in claim 13 , wherein the fatty acid esters include stearic acid methyl ester and palmitic acid methyl ester in a proportion of at least 7% by weight.

15 . A process for improving the cold behavior of fuel oils of vegetable or animal origin, said process comprising admixing a portion of the fuel oil additive of claim 1 with said fuel oil.