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US 11,261,398 B2Granted
Hydraulic fluid composition
AssigneeThe Lubrizol Corporation
InventorsDaniel J. Knapton, David Cressey, Daniel C. Visger
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Abstract
A hydraulic fluid includes an oil of lubricating viscosity and at least 2 wt. % of an ester of a carboxy group-containing interpolymer comprising units derived from a vinyl aromatic monomer and units derived from a carboxylic acid monomer. The interpolymer also contains nitrogen functionality. The hydraulic fluid is at least substantially free of polyacrylates and polymethacrylates.
Claims17
A hydraulic fluid comprising:
- (a) at least 60 wt. % of a Group I or Group II base oil;
- (b) 3.4 to 5.2 wt. % of an ester of a carboxy group-containing interpolymer comprising units derived from a vinyl aromatic monomer, the vinyl aromatic monomer comprising styrene, and units derived from a carboxylic acid monomer, the carboxylic acid monomer comprising maleic anhydride, the interpolymer also comprising nitrogen functionality provided by a nitrogen-containing moiety which comprises at least one of aminopropylmorpholine and dimethylaminopropylamine, the ester of the carboxy group-containing interpolymer having a weight average molecular weight of 30,000 to 70,000, the ester of a carboxy group-containing interpolymer including up to 0.44 wt. % nitrogen;
- and
- (c) at least one phosphate compound comprising zinc;
- wherein the hydraulic fluid is at least substantially free of polyacrylates and polymethacrylates that contain, in total, at least 30 mol. % of at least one of acrylate and methacrylate units and have a weight-average molecular weight of at least 1500, such that said polyacrylates and polymethacrylates, in total, amount to no more than 0.3 wt. % of the hydraulic fluid;
- and
- wherein the hydraulic fluid includes, in total, less than 0.1 wt. % of nitrogen-containing ashless dispersants, other than the esterified interpolymer, the nitrogen-containing ashless dispersants being characterized by a nitrogen-containing functional group attached to a polymeric hydrocarbon backbone.
4 more elements
A method for lubricating a hydraulic system comprising pressurizing a hydraulic fluid in the hydraulic system, the hydraulic fluid comprising:
- (a) at least 60 wt. % of a Group I or Group II base oil;
- (b) 3.4 to 5.2 wt. % of an ester of a carboxy group-containing interpolymer comprising units derived from a vinyl aromatic monomer and units derived from a carboxylic acid monomer, the interpolymer also comprising nitrogen functionality, the ester of the carboxy group-containing interpolymer having a weight average molecular weight of 30,000 to 70,000, the ester of a carboxy group-containing interpolymer including up to 0.44 wt. % nitrogen;
- and
- (c) 0.05-0.5 wt. % of a zinc dialkyldithiophosphate,
- wherein the hydraulic fluid is at least substantially free of polyacrylates and polymethacrylates that contain, in total, at least 30 mol. % of at least one of acrylate and methacrylate units and have a weight-average molecular weight of at least 1500, such that said polyacrylates and polymethacrylates, in total, amount to no more than 0.3 wt. % of the hydraulic fluid;
- and
- wherein the hydraulic fluid includes, in total, less than 0.1 wt. % of nitrogen-containing ashless dispersants, other than the esterified interpolymer, the nitrogen-containing ashless dispersants being characterized by a nitrogen-containing functional group attached to a polymeric hydrocarbon backbone.
4 more elements
Dependencies are inferred from the claim text.