Copolymers as dewaxing additives

1. A method for solvent deparaffinization of paraffinic mineral oil distillates, comprising:

adding a dewaxing additive and a solvent to said paraffinic mineral oil distillates, to obtain a solvent-paraffinic mineral oil mixture;

stirring until a clear solution results;

cooling the solution to below −20° C. at a defined rate, thereby forming paraffin crystals which form a filter cake which is porous and permeable to the solution; and

separating said paraffin crystals from said solution by filtration;

increasing a filtration volume per filtration time compared to the filtration volume per filtration time using no dewaxing additive; and

obtaining deparaffinized mineral oil distillates;

wherein said dewaxing additive comprises a copolymer of the following free-radically polymerizable monomers of Formulae A and B:

wherein

R 1 =H or CH 3 ,

R 2 =phenyl, benzyl, naphthyl, anthranyl, phenanthryl, N-pyrrolidonyl, N-imidazolyl, 2-pyridyl, 4-pyridyl or an alkyl-substituted aromatic substituent or

R 2 =COOR 3 where R 3 =H or R 3 is a linear or branched alkyl radical of C 1 -C 10

or

R 3 is a heteroatom-substituted radical —(CH 2 ) n X where X=OH or X=N(R 4 ) 2 wherein n=1-10 and R 4 is in each case independently H or R 4 =C 1 -C 4 -alkyl

or

R 3 is —(CH 2 CH 2 O) m R 5 wherein m=1-90 and R 5 =H or R 5 =C 1 -C 18 or R 3 is a benzyl, phenyl or cyclohexyl radical

or

R 2 =CONHR 6 wherein R 6 =H or R 6 is a linear or branched alkyl radical of C 1 -C 10

or

R 6 is a heteroatom-substituted radical —(CH 2 ) n X where X=OH or X=N(R 4 ) 2 wherein n=1-10 and R 4 is in each case independently H or R 4 =C 1 -C 4 -alkyl;

wherein R 7 =H or CH 3 , and

R 8 radical=linear or branched alkyl radicals of C 12 -C 40 , and,

optionally further customary dewaxing additives.

2. The method according to claim 1 , wherein the addition rate of the copolymer is 0.005-0.5%.

3. The method according to claim 1 , wherein said paraffin crystals grow epitaxially.

4. The method according to claim 1 , comprising:

adding said dewaxing additive to said paraffinic mineral oil distillates at a temperature above the cloud point of said mineral oil.

5. The method according to claim 1 , wherein the proportion by weight of the monomer A in the total weight of the copolymer is 0.1-70%.

6. The method according to claim 1 , wherein at least 50% of the monomers B contain alkyl radicals R 8 of chain length greater than or equal to C 16 .

7. The method according to claim 1 , wherein the monomers of formula A consist of one or more monomers selected from the group consisting of styrene, butyl methacrylate, methyl methacrylate, 2-ethyihexyl methacrylate and mixtures thereof.

8. The method according to claim 1 , said dewaxing additive further comprising one or more homo- or copolymers which are polyalkyl methacrylates and have alkyl substituents of chain length C1-C24.

9. The method according to claim 8 , wherein the homo- or copolymers which are polyalkyl methacrylates have alkyl substituents of chain length C 12 -C 18 .

10. The method according to claim 8 , wherein a ratio of the copolymers and the homo- or copolymers which are polyalkyl methacrylates is 1:20 to 20:1.

11. The method according to claim 8 , wherein the homo- or copolymer is a polyalkyl methacrylate which contains up to 20% by weight of C 1 -C 10 methacrylates.

12. The method according to claim 1 , wherein the dewaxing additive is a solution of the copolymer in an oil of the paraffinic or naphthenic type, or in an organic solvent.

13. The method according to claim 12 , wherein the organic solvent is selected from the group consisting of toluene, methyl-ethyl-ketone, xylene, naphtha and mixtures thereof or wherein the organic solvent is propane.

14. The method according to claim 1 , wherein the dewaxing additive comprises

a copolymer of behenyl acrylate and styrene.

15. The method according to claim 1 , wherein the dewaxing additive comprises

a copolymer of behenyl acrylate and at least one member selected from the group consisting of n-butyl methacrylate, isononyl methacrylate, and benzyl methacrylate.

16. The method according to claim 1 , wherein the dewaxing additive consists of:

a copolymer of behenyl acrylate and styrene.

17. The method according to claim 1 , in which the obtained deparaffinized mineral oil distillates show an increased degree of dewaxing compared to a method in which a styrene-free dewaxing aid is used.

18. The method according to claim 1 , wherein said filtration volume per filtration time is increased by at least 10% compared to the filtration volume per filtration time using no dewaxing additive.

19. The method according to claim 1 , wherein said filtration volume per filtration time is increased by at least 20% compared to the filtration volume per filtration time using no dewaxing additive.

20. The method according to claim 1 , wherein said filtration volume per filtration time is increased by at least 30% compared to the filtration volume per filtration time using no dewaxing additive.