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EP-4317371-B1 - LUBRICATING OIL COMPOSITION

EP4317371B1EP 4317371 B1EP4317371 B1EP 4317371B1EP-4317371-B1

Inventors

  • FUJITA, Shoichiro
  • SUNAHARA, KENJI
  • YAMAGISHI, TSUKASA
  • KUBOTA, MASAYA

Dates

Publication Date
20260513
Application Date
20220304

Claims (16)

  1. A lubricating oil composition comprising a base oil (A) and a dispersant-type viscosity index improver (B), wherein the nitrogen atom content based on the solid content of the dispersant-type viscosity index improver (B) is 0.50 to 1.50% by mass, and the weight-average molecular weight (Mw) thereof is 100,000 or more, and the content in terms of the solid content based on the total amount of the composition of the dispersant-type viscosity index improver (B) is more than 0.05% by mass and less than 5.0% by mass, wherein the weight-average molecular weight (Mw) of the dispersant-type viscosity index improver (B) is 250,000 or less, the lubricating oil composition further comprises a non-dispersant-type viscosity index improver (C) having the weight-average molecular weight (Mw) of 200,000 or more, in an amount of 0.2 to 10.0% by mass in terms of the solid content based on the total amount of the composition, and the dispersant-type viscosity index improver (B) is selected from the group consisting of a nitrogen-containing poly(meth)acrylate and a nitrogen-containing polyolefin, wherein the Mw is a standard polystyrene-equivalent value measured by gel permeation chromatography.
  2. The lubricating oil composition according to claim 1, wherein the ratio of the content of the non-dispersant-type viscosity index improver (C) to the content of the dispersant-type viscosity index improver (B), [(C)/(B)] is, as a ratio by mass of the solid content, 0.50 to 30.0.
  3. The lubricating oil composition according to claim 1 or 2, wherein the kinematic viscosity at 100°C is 3.0 to 16.0 mm 2 /s, as determined according to JIS K 2283:2000.
  4. The lubricating oil composition according to any one of claims 1 to 3, wherein the viscosity index is 150 or more, as determined according to JIS K 2283:2000.
  5. The lubricating oil composition according to any one of claims 1 to 4, wherein the molecular weight distribution (Mw/Mn) of the dispersant-type viscosity index improver (B) is 3.0 or less, wherein the Mn is a standard polystyrene-equivalent value measured by gel permeation chromatography.
  6. The lubricating oil composition according to any one of claims 1 to 5, further comprising a molybdenum-based friction modifier (D).
  7. The lubricating oil composition according to claim 6, wherein the content of the molybdenum-based friction modifier (D) is 50 to 2,000 ppm by mass in terms of the molybdenum atom based on the total amount of the composition.
  8. The lubricating oil composition according to any one of claims 1 to 7, further comprising zinc dithiophosphate.
  9. The lubricating oil composition according to claim 8, wherein the content of the zinc dithiophosphate is 200 to 5,000 ppm by mass in terms of the phosphorus atom based on the total amount of the composition.
  10. The lubricating oil composition according to any one of claims 1 to 9, wherein the content of a dispersant-derived nitrogen atom is 0.10% by mass or less based on the total amount of the composition.
  11. The lubricating oil composition according to claim 10, wherein the content of the dispersant-derived nitrogen atom is a total amount of the nitrogen atom derived from a non-boron-modified succinimide and a boron-modified succinimide.
  12. The lubricating oil composition according to any one of claims 1 to 11, wherein the content of the base oil (A) is 60 to 99% by mass based on the total amount of the composition.
  13. Use of the lubricating oil composition according to any one of claims 1 to 12, to lubricate diesel engines.
  14. A method for producing the lubricating oil composition according to any one of claims 1 to 12, including a step of mixing the base oil (A) and the dispersant-type viscosity index improver (B).
  15. A diesel engine comprising the lubricating oil composition according to any one of claims 1 to 12.
  16. A method for lubricating an engine comprising applying the lubricating oil composition according to any one of claims 1 to 12.

Description

Technical Field The present invention relates to a lubricating oil composition. Background Art Heretofore, there has been known a problem of a lubricating oil for use in internal combustion engines such as gasoline engines and diesel engines in that soot is generated with degradation of the lubricating oil, and for dispersing the soot in oil, a dispersant is often blended therein. In some lubricating oil compositions, a viscosity index improver is blended for the purpose of improving the viscosity index of the compositions, and a dispersant-type viscosity index improver given a dispersion performance by the use of a polar group-having comonomer is known. Regarding such a dispersant-type viscosity index improver, there are known ones having a nitrogen atom in the molecule, and for example, PTL 1 disclose a reaction product of an olefin copolymer, an acylating agent and a polyamine, and PTL 2 discloses a dispersant-type polyalkyl (meth)acrylate produced by copolymerizing an N-dispersant-type monomer. WO 2020/187954 A1 describes polyalkyl(meth)acrylate polymers, comprising the following monomers: (a) 10 to 25% by weight of esters of (meth)acrylic acid and a hydroxylated hydrogenated polybutadiene; (b) 30% to 65% by weight of C1-4 alkyl (meth)acrylates; (c) 10% to 30% by weight of styrene; (d) 10% to 43% by weight of C10-30 alkyl (meth)acrylates, preferably C10-15 alkyl methacrylates, more preferably C12-14 alkyl methacrylates; and (e) 0% to 7% by weight of N-containing monomers selected from the group consisting of N,N-dimethylaminoethyl methacrylate (DMAEMA), N-(3-(dimethylamino)propyl)methacrylamide (DMAPMAm) and N-vinylpyrrolidinone (NVP), preferably DMAEMA, wherein the weight-average molecular weight is in the range of 100,000 to 1,000,000 g/mol. US 2019/0270947 A1 describes lubricating oil composition having a HTHS viscosity at 150 °C in a range of about 1.3 to about 2.9 cP, comprising: (a) a major amount of an oil of lubricating viscosity having a kinematic viscosity at 100 °C in a range of 1.5 to 6.0 mm2/s; (b) a dispersant polymethacrylate (DPMA) VII having a Mw of from 200,000 g/mol to 450,000 g/mol; (c) a non-dispersant ethylene-based olefin copolymer viscosity index improver having a Mw of from 50,000 g/mol to 150,000 g/mol and a total ethylene content of about 50 wt % to about 70 wt %; (d) from about 50 to about 300 ppm of molybdenum from a molybdenum containing compound; and (e) a minor amount of a salicylate detergent. US 2017/0283732 A1 describes a specific method of making a multiple function dispersant graft polymer comprising two different functional groups, each directly grafted to a polymer backbone having graftable sites, in which: a first functional group comprises the reaction product of an acylating agent and a first amine, the first amine comprising an aromatic primary amine; and a second functional group comprises the reaction product of the acylating agent and a second amine, the second amine comprising an aliphatic primary amine; wherein the multiple function dispersant graft polymer has at least about 5 moles of each of said functional groups per mole of polymer backbone, and wherein the first functional group provides the multiple function dispersant graft polymer with a soot handling performance attribute and the second functional group provides the multiple function dispersant graft polymer with a sludge and varnish control performance attribute. Citation List Patent Literature PTL 1: JP2019-77864APTL 2: JP2016-534213A Summary of Invention Technical Problem However, as a result of investigations made by the present inventors, it has been proven that, when a lubricating oil contaminated with soot is used, wear resistance is not always good. The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a lubricating oil composition still excellent in wear resistance even in a condition contaminated with soot. Solution to Problem As a result of assiduous studies made by the present inventors, it has been found that a lubricating oil composition containing, as blended therein, a specific dispersant-type viscosity index improver can solve the above-mentioned problems, and the present invention has been thus completed. Specifically, the present invention is defined in the appended claims and provides the following. The present invention provides a lubricating oil composition containing a base oil (A) and a dispersant-type viscosity index improver (B), in which the nitrogen atom content based on the solid content of the dispersant-type viscosity index improver (B) is 0.50 to 1.50% by mass, and the weight-average molecular weight (Mw) thereof is 100,000 or more, and the content in terms of the solid content based on the total amount of the composition of the dispersant-type viscosity index improver (B) is more than 0.05% by mass and less than 5.0% by mass, as further defined in the claims. The present invention also provides a method