Process for producing lubricating grease

1. A process for producing a lubricating grease, comprising:

adding a polymeric structure improver to a dispersion which has a grease structure, wherein

the dispersion comprises at least one thickener and at least one lubricating oil, and wherein the polymeric structure improver is added in the form of a composition which is a liquid at 25° C., and

wherein the polymeric structure improver is obtained by polymerizing a monomer composition comprising:

a) 0 to 40% by weight, based on the weight of the monomer compositions for preparing the polymeric structure improvers, of one or more ethylenically unsaturated ester compounds of the formula (I)

wherein R is hydrogen or methyl, R 1 is a linear or branched alkyl radical having 1 to 5 carbon atoms, R 2 and R 3 are each independently hydrogen or a group of the formula —COOR′ where R′ is hydrogen or an alkyl group having 1 to 5 carbon atoms,

b) 50 to 100% by weight, based on the weight of the monomer compositions for preparing the polymeric structure improver, of one or more ethylenically unsaturated ester compounds of formula (II)

wherein R is hydrogen or methyl, R 4 is a linear or branched alkyl radical having from 6 to 30 carbon atoms, R 5 and R 6 are each independently hydrogen or a group of the formula —COOR″, where R″ is hydrogen or an alkyl group having 6 to 30 carbon atoms, and

c) 0.01 to 20% by weight, based on the weight of the monomer compositions for preparing the polymeric structure improvers, of acid-bearing monomers or salts thereof comprising at least one monomer selected from the group consisting of methacrylic acid and acrylic acid or salts thereof.

2. The process according to claim 1 , wherein said composition has a viscosity within the range of from 1 mm 2 /s to 10,000 mm 2 /s.

3. The process according to claim 1 , wherein said composition comprises a lubricating oil.

4. The process according to claim 3 , wherein said lubricating oil is compatible with the lubricating oil of the lubricating grease.

5. The process according to claim 1 , wherein said polymeric structure improver has a weight-average molecular weight within the range of from 15,000 g/mol to 1,000,000 g/mol.

6. The process according to claim 1 , wherein the concentration of said polymeric structure improver in the lubricating grease is within the range of from 0.1 to 20% by weight.

7. The process according to claim 1 , wherein the ratio of the weight of said dispersion to the weight of said composition is within the range of from 100:1 to 1:1.

8. The process according to claim 1 , wherein said acid-bearing monomers or salts thereof which are present in component c) comprise at least one phosphonic acid group and/or at least one sulphonic acid group.

9. The process according to claim 1 , wherein component c) comprises 0.1 to 10% by weight, based on the weight of the monomer compositions for preparing the polymeric structure improvers, of acid-bearing monomers or salts thereof.

10. The process according to claim 1 , wherein said composition comprises additives.

11. The process according to claim 1 , wherein said composition is a solution.

12. The process according to claim 1 , wherein said composition is a dispersion.

13. The process according to claim 1 , wherein said composition is added at a temperature which is below the dropping point of the lubricating grease before the addition of said composition.

14. The process according to claim 1 , wherein said composition is added at a temperature which is at least 60° C. below the dropping point of the lubricating grease before the addition of said composition.

15. The process according to claim 1 , wherein said composition is added at a temperature within the range of from 20° C. to 75° C.

16. The process according to claim 1 , wherein said thickener is selected from the group consisting of a soap thickener, an inorganic thickener and a polymeric organic thickener.

17. The process according to claim 1 , wherein the lubricating grease, after the addition of said composition, has a water resistance of 1 to 50%.

18. The process according to claim 1 , wherein the lubricating grease, after the addition of said composition, has a cone penetration within the range of from 175 dmm to 385 dmm.

19. The process according to claim 1 , wherein said composition is added to the dispersion having a grease structure by stirring, mixing, kneading, rolling or homogenizing.