Lubricating Oil Composition Having Improved Air Release

Abstract

The invention provides a lubricating oil composition comprising a ethylene/α-olefin copolymer and, optionally, and additive comprising an amine salt of a hydrocarbyl thiophosphoric acid ester. The invention also provides a method of improving air release of a lubricating oil composition by mixing an ethylene/α-olefin copolymer with an oil of lubricating viscosity.

What is claimed is: 
     
         1 . A lubricating oil composition comprising:
 (a) an oil of lubricating viscosity;   (b) 2% to 17% by weight of an ethylene/α-olefin copolymer; and   (c) 0.04% to 0.15% by weight of an additive comprising an amine salt of a hydrocarbyl thiophosphoric acid ester.   
     
     
         2 . The lubricating oil composition of  claim 1 , wherein the additive comprising an amine salt of a hydrocarbyl thiophosphoric acid ester is obtained by reacting a phosphorous sulfide with one or more alcohols having about 3 to about 13 carbon atoms to form a thiophosphoric acid ester, further reacting the thiophosphoric acid ester with an alkylene oxide to form a hydroxyl-substituted ester of thiophosphoric acid, and further reacting said hydroxyl-substituted ester of thiophosphoric acid with a phosphorous oxide to form a an acidic phosphoric acid intermediate, and salting said acidic phosphoric acid intermediate with one or more amines wherein said amines contain one or more hydrocarbyl groups having from 2 to 30 carbon atoms. 
     
     
         3 . The lubricating oil composition of  claim 1 , wherein the ethylene/α-olefin copolymer comprises ethylene monomer units and one or more α-olefin monomer units other than ethylene monomer, wherein the amount of ethylene monomer units is greater than 5 weight percent, wherein the α-olefin monomer units contain 3 to about 20, or 3 to about 6, or 3 to 4, or 3 carbon atoms or mixtures thereof. 
     
     
         4 . The lubricating oil composition of  claim 1 , wherein the α-olefin monomer units of the ethylene/α-olefin copolymer comprise propylene units and monomer units containing 4 to about 20 carbon atoms. 
     
     
         5 . The lubricating oil composition of  claim 1 , wherein the ethylene/α-olefin copolymer has a kinematic viscosity at 100° C. of at least about 35 mm 2 /s or at least 500 mm 2 /s. 
     
     
         6 . The lubricating oil composition of  claim 1 , further comprising:
 an industrial additive package.   
     
     
         7 . A method of lubricating an industrial gear comprising supplying to the industrial gear the lubricating oil composition of  claim 1 . 
     
     
         8 . A method of improving the air release of a lubricating oil composition, comprising:
 (i) providing (a) a base oil of lubricating viscosity, (b) 2% to 17% by weight of an ethylene/α-olefin copolymer, and (c) 0.04% to 0.15% by weight of an additive comprising an amine salt of a hydrocarbyl thiophosphoric acid ester;   (ii) mixing the base oil of lubricating viscosity, the ethylene/α-olefin copolymer, and the additive to obtain a functional fluid.   
     
     
         9 . The method of  claim 8 , wherein the additive comprising an amine salt of a hydrocarbyl thiophosphoric acid ester is obtained by reacting a phosphorous sulfide with one or more alcohols having about 3 to about 13 carbon atoms to form a thiophosphoric acid ester, further reacting the thiophosphoric acid ester with an alkylene oxide to form a hydroxyl-substituted ester of thiophosphoric acid, and further reacting said hydroxyl-substituted ester of thiophosphoric acid with a phosphorous oxide to form a an acidic phosphoric acid intermediate, and salting said acidic phosphoric acid intermediate with one or more amines wherein said amines contain one or more hydrocarbyl groups having from 2 to 30 carbon atoms. 
     
     
         10 . The method of  claim 8 , wherein the ethylene/α-olefin copolymer comprises ethylene monomer units and one or more α-olefin monomer units other than ethylene monomer, wherein the amount of ethylene monomer units is greater than 5 weight percent, wherein the α-olefin monomer units contain 3 to about 20, or 3 to about 6, or 3 to 4, or 3 carbon atoms or mixtures thereof. 
     
     
         11 . The method of  claim 8 , wherein the α-olefin monomer units of the ethylene/α-olefin copolymer comprise propylene units and monomer units containing 4 to about 20 carbon atoms. 
     
     
         12 . The method of  claim 8 , wherein the ethylene/α-olefin copolymer has a kinematic viscosity at 100° C. of at least about 35 mm 2 /s or at least 500 mm 2 /s.