Method for improving nitrile seal compatibility with lubricating oils

Abstract

Provided is a method of improving nitrile seal compatibility with a lubricating oil in an engine lubricated with the lubricating oil. The method includes using as the lubricating oil a formulated oil comprising a lubricating oil base stock as a major component and an alkylated aromatic base stock 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 alkylated aromatic base stock, e.g., an ester. A lubricating engine oil comprising a lubricating oil base stock as a major component and an alkylated aromatic base stock as a minor component. The alkylated aromatic base stock is 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 alkylated aromatic base stock.

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 an alkylated aromatic base stock 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 alkylated aromatic base stock. 
     
     
         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 the alkylated aromatic base stock comprises an alkylated naphthalene, an alkylated benzene, or mixtures thereof. 
     
     
         6 . The method of  claim 1  wherein the alkylated aromatic base stock is selected from the group consisting of alkyl benzenes, alkyl naphthalenes, alkyl diphenyl oxides, alkyl naphthols, alkyl diphenyl sulfides, alkylated bis-phenol A, alkylated thiodiphenol, and mixtures thereof. 
     
     
         7 . The method of  claim 1  wherein the alkylated aromatic base stock is mono-alkylated, dialkylated, or polyalkylated. 
     
     
         8 . The method of  claim 1  wherein the alkylated aromatic base stock is an alkyl naphthalene selected from the group consisting of mono-, di-, tri-, tetra-, or penta-C 3  alkyl naphthalene, C 4  alkyl naphthalene, C 5  alkylnaphthalene, C 6  alkyl naphthalene, C 8  alkyl naphthalene, C 10  alkyl naphthalene, C 1-2  alkyl naphthalene, C 1-4  alkyl naphthalene, C 1-6  alkyl naphthalene, C 1-8  alkyl naphthalene, C 10 -C 14  mixed alkyl naphthalene, C 6 -C 18  mixed alkyl naphthalene, or mono-, di-, tri-, tetra-, or penta C 3 , C 4 , C 5 , C 6 , C 8 , C 10 , C 12 , C 14 , C 16 , C 18  or mixture thereof alkyl monomethyl, dimethyl, ethyl, diethyl, or methylethyl naphthalene, and mixtures thereof. 
     
     
         9 . The method of  claim 1  wherein the minor component other than the alkylated aromatic base stock comprises an ester. 
     
     
         10 . The method of  claim 1  wherein the alkylated aromatic base stock is present in an amount from 1 weight percent to 15 weight percent, based on the total weight of the lubricating oil. 
     
     
         11 . The method of  claim 1  wherein the alkylated aromatic base stock is 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). 
     
     
         12 . The method of  claim 1  wherein the lubricating oil further comprises one or more of a viscosity index improver, antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, antifoam agent, inhibitor, anti-wear, friction modifier, and anti-rust additive. 
     
     
         13 . The method of  claim 1  in which the lubricating oil is a passenger vehicle engine oil. 
     
     
         14 . A lubricating engine oil comprising a lubricating oil base stock as a major component and an alkylated aromatic base stock as a minor component; wherein the alkylated aromatic base stock is 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 alkylated aromatic base stock. 
     
     
         15 . The lubricating engine oil of  claim 14  wherein the lubricating oil base stock comprises a Group I, II, III, IV or V base oil stock, or mixtures thereof. 
     
     
         16 . The lubricating engine oil of  claim 14  wherein the lubricating oil base stock comprises a poly alpha olefin (PAO) or gas-to-liquid (GTL) oil base stock. 
     
     
         17 . The lubricating engine oil of  claim 14  wherein the alkylated aromatic base stock comprises an alkylated naphthalene, alkylated benzene, or mixtures thereof. 
     
     
         18 . The lubricating engine oil of  claim 14  wherein the alkylated aromatic base stock is selected from the group consisting of alkyl benzenes, alkyl naphthalenes, alkyl diphenyl oxides, alkyl naphthols, alkyl diphenyl sulfides, alkylated bis-phenol A, alkylated thiodiphenol, and mixtures thereof. 
     
     
         19 . The lubricating engine oil of  claim 14  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, and the alkylated aromatic base stock is present in an amount from 1 weight percent to 15 weight percent, based on the total weight of the lubricating oil. 
     
     
         20 . The lubricating engine oil of  claim 14  wherein the alkylated aromatic base stock is present in an amount sufficient for the lubricating oil to exhibit at least one of improved change in tensile strength (%) and elongation at break (%) as determined by Nitrile-NBR34 (MB VDA 675301 Method).