Method for improving nitrile seal compatibility with lubricating oils

Abstract

Provided are a lubricating engine oil and a method of improving nitrile seal compatibility with a lubricating oil in an engine lubricated with such lubricating oil. The method includes using as the lubricating oil a formulated oil comprising a lubricating oil base stock as a major component and one or more additives selected from the group consisting of (i) a sulfone, sulfolane, or derivative thereof; (ii) a borate ester, boron amide, or mixtures thereof; (iii) a sulfurized olefin; (iv) a thiadiazole or derivative thereof; and (v) a succinic anhydride or derivative thereof, as a minor component. Nitrile seal compatibility is improved as compared to nitrile seal compatibility achieved using a lubricating oil containing a minor component other than the one or more additives.

What is claimed is: 
     
         1 . A method of improving nitrile seal compatibility with a lubricating oil in an engine lubricated with the lubricating oil, said method comprising using as the lubricating oil a formulated oil comprising a lubricating oil base stock as a major component and one or more additives selected from the group consisting of (i) a sulfone, sulfolane, or derivative thereof; (ii) a borate ester, boron amide, or mixtures thereof; (iii) a sulfurized olefin; (iv) a thiadiazole or derivative thereof; and (v) a succinic anhydride or derivative thereof, as a minor component; wherein nitrile seal compatibility is improved as compared to nitrile seal compatibility achieved using a lubricating oil containing a minor component other than the one or more additives. 
     
     
         2 . The method of  claim 1  wherein the lubricating oil base stock comprises a Group I, II, III, IV, or V base oil stock, or mixtures thereof 
     
     
         3 . The method of  claim 1  wherein the lubricating oil base stock comprises a poly alpha olefin (PAO) or gas-to-liquid (GTL) oil base stock. 
     
     
         4 . The method of  claim 1  wherein the lubricating oil base stock is present in an amount from 80 weight percent to 99 weight percent, based on the total weight of the lubricating oil. 
     
     
         5 . The method of  claim 1  wherein (i) the sulfone, sulfolane, or derivative thereof comprises an alkyl sulfone or alkyl sulfolane; (ii) the borate ester, boron amide, or mixtures thereof comprises a mixture of borated alkyl diethanol amides and borated mono glycerides; (iii) the sulfurized olefin comprises sulfurized alpha-olefin, sulfurized isomerized alpha-olefin, sulfurized branched olefin, sulfurized cyclic olefin, or combinations of these; (iv) the thiadiazole or derivative thereof comprises an alkyl thiadiazole; and (v) the succinic anhydride or derivative thereof comprises polyisobutylene (PIB) succinic anhydride. 
     
     
         6 . The method of  claim 1  wherein the one or more additives are present in an amount from 0.01 weight percent to 2.0 weight percent, based on the total weight of the lubricating oil. 
     
     
         7 . The method of  claim 1  wherein the one or more additives are present in an amount sufficient for the lubricating oil to exhibit at least one of improved tensile strength (%) and elongation at break (%) as determined by Nitrile-NBR34 (MB VDA 675301 Method) or CEC L-39-96 elastomer test using RE-4 nitrile elastomer. 
     
     
         8 . The method of  claim 1  wherein the lubricating oil further comprises one or more of a viscosity improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, and anti-rust additive. 
     
     
         9 . The method of  claim 1  in which the lubricating oil is a passenger vehicle engine oil. 
     
     
         10 . A lubricating engine oil comprising a lubricating oil base stock as a major component and one or more additives selected from the group consisting of (i) a sulfone, sulfolane, or derivative thereof; (ii) a borate ester, boron amide, or mixtures thereof; (iii) a sulfurized olefin; (iv) a thiadiazole or derivative thereof; and (v) a succinic anhydride or derivative thereof, as a minor component; wherein the one or more additives are present in an amount sufficient for the lubricating oil to exhibit improved nitrile seal compatibility as compared to nitrile seal compatibility achieved using a lubricating oil containing a minor component other than the one or more additives. 
     
     
         11 . The lubricating engine oil of  claim 10  wherein the lubricating oil base stock comprises a Group I, II, III, IV, or V base oil stock, or mixtures thereof 
     
     
         12 . The lubricating engine oil of  claim 10  wherein the lubricating oil base stock comprises a poly alpha olefin (PAO) or gas-to-liquid (GTL) oil base stock. 
     
     
         13 . The lubricating engine oil of  claim 10  wherein the lubricating oil base stock is present in an amount from 80 weight percent to 99 weight percent, based on the total weight of the lubricating oil. 
     
     
         14 . The lubricating engine oil of  claim 10  wherein (i) the sulfone, sulfolane, or derivative thereof comprises an alkyl sulfone or alkyl sulfolane; (ii) the borate ester, boron amide, or mixtures thereof comprises a mixture of borated alkyl diethanol amides and borated mono glycerides; (iii) the sulfurized olefin comprises sulfurized alpha-olefin, sulfurized isomerized alpha-olefin, sulfurized branched olefin, sulfurized cyclic olefin, or combinations of these; (iv) the thiadiazole or derivative thereof comprises an alkyl thiadiazole; and (v) the succinic anhydride or derivative thereof comprises polyisobutylene (PIB) succinic anhydride. 
     
     
         15 . The lubricating engine oil of  claim 10  wherein the one or more additives are present in an amount from 0.01 weight percent to 2.0 weight percent, based on the total weight of the lubricating oil. 
     
     
         16 . The lubricating engine oil of  claim 10  wherein the one or more additives are present in an amount sufficient for the lubricating oil to exhibit at least one of improved tensile strength (%) and elongation at break (%) as determined by Nitrile-NBR34 (MB VDA 675301 Method) or CEC L-39-96 elastomer test using RE-4 nitrile elastomer. 
     
     
         17 . The lubricating engine oil of  claim 10  wherein the lubricating oil further comprises one or more of a viscosity improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, antifoam agent, inhibitor, and anti-rust additive. 
     
     
         18 . The lubricating engine oil of  claim 10  in which the lubricating oil is a passenger vehicle engine oil.