High viscosity index lubricating oil base stock and viscosity modifier combinations, and lubricating oils derived therefrom

Abstract

A lubricating composition including a first base stock component including: one or more metallocene catalyzed polyalphaolefins (mPAOs), each mPAO having a kinematic viscosity (Kv 100 ) from 40 cSt to 155 cSt and a viscosity index (VI) from 150 to 207; a second base stock including one or more polyalphaolefins (PAOs), each PAO having a kinematic viscosity (Kv 100 ) less than 10 cSt and a VI from 130 to 145; and a viscosity modifier including a copolymer having units derived from monomers of (i) an α-olefin and (ii) an ethylenically unsaturated carboxylic acid or derivatives thereof esterified with an alcohol. A lubricant including the above lubricating composition. A method for improving fuel efficiency, while maintaining or improving wear control, load carrying capacity and/or traction reduction in a driveline device, e.g., gears and transmissions, lubricated with a lubricating oil, by using as the lubricating oil the above lubricant.

What is claimed is: 
     
         1 . A lubricating composition comprising:
 a first base stock component comprising one or more metallocene catalyzed polyalphaolefins (mPAOs), each mPAO having a kinematic viscosity (Kv 100 ) from 40 cSt to 155 cSt and a viscosity index (VI) from 150 to 207;   a second base stock comprising one or more polyalphaolefins (PAOs), each PAO having a kinematic viscosity (Kv 100 ) less than 10 cSt and a VI from 130 to 145; and   a viscosity modifier comprising a copolymer having units derived from monomers of (i) an α-olefin and (ii) an ethylenically unsaturated carboxylic acid or derivatives thereof esterified with an alcohol;   wherein at least one of wear control (as determined by ASTM D4172), load carrying capacity (as determined by ASTM D2783) and traction reduction (as determined by Mini-Traction Machine (MTM) Ball-on-Disc apparatus) is improved in a driveline device lubricated with said lubricating composition as compared to at least one of wear control, load carrying capacity and traction reduction achieved with a lubricating composition containing a viscosity modifier other than said viscosity modifier copolymer, at an equal or lower kinematic viscosity (Kv@100° C.).   
     
     
         2 . The lubricating composition of  claim 1  wherein the lubricating oil base stock comprises a Group I, II, III, IV, V or VI base oil stock, or mixtures thereof. 
     
     
         3 . The lubricating composition of  claim 1  wherein the lubricating oil base stock comprises a synthetic polyalphaolefin (PAO) fluid, said PAO comprising a polymer of one or more C 8  to C 12  alphaolefin monomers. 
     
     
         4 . The lubricating composition of  claim 1  wherein the lubricating oil base stock has a kinematic viscosity (Kv 100 ) from 4 to 65 cSt at 100° C., and a VI from 140 to 200. 
     
     
         5 . The lubricating composition of  claim 1  wherein the viscosity modifier is represented by the formula: 
       
         
           
           
               
               
           
         
       
       wherein
 Formula (I) comprises a copolymer backbone (BB), and one or more pendant groups, wherein BB is derived from a copolymer of (i) an α-olefin and (ii) an ethylenically unsaturated carboxylic acid or derivatives thereof; 
 X is a functional group which either (i) contains a carbon and at least one oxygen or nitrogen atom, or (ii) is an alkylene group with 1 to 5 carbon atoms, connecting the copolymer backbone and a branched hydrocarbyl group contained within ( ) y ; 
 w is the number of pendant groups attached to the copolymer backbone, which is in the range of 2 to 2000; 
 y is 0, 1, 2 or 3, provided that in at least 1 mol % of the pendant groups, y is not zero; and with the proviso that when y is 0, X is bonded to a terminal group in a manner sufficient to satisfy the valence of X, wherein the terminal group is selected from hydrogen, alkyl, aryl, a metal or ammonium cation, and mixtures thereof; 
 p may be an integer in the range of 1 to 15; and 
 R′ and R″ are independently linear or branched hydrocarbyl groups, and the combined total number of carbon atoms present in R′ and R″ is at least 12. 
 
     
     
         6 . The lubricating composition of  claim 1  wherein the alphaolefin is selected from the group consisting of 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-hepta-decene 1-octadecene, and mixtures thereof. 
     
     
         7 . The lubricating composition of  claim 1  wherein the ethylenically unsaturated carboxylic acid or derivative thereof is selected from the group consisting of acrylic acid, methyl acrylate, methacrylic acid, maleic acid or anhydride, fumaric acid, itaconic acid or anhydride or mixtures thereof, and substituted equivalents thereof. 
     
     
         8 . The lubricating composition of  claim 1  wherein the alcohol is selected from the group consisting of 2-ethylhexanol, 2-butyloctanol, 2-hexyldecanol, 2-octyldodecanol, 2-decyltetradecanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, eicosanol, and mixtures thereof. 
     
     
         9 . The lubricating composition of  claim 1  wherein the viscosity modifier is a copolymer derived from monomers of (i) an α-olefin and (ii) an ethylenically unsaturated carboxylic acid or derivatives thereof,
 wherein 0.1 to 99.89 percent of the carboxylic acid units are esterified with a primary alcohol branched at the β- or higher position, 
 wherein 0.1 to 99.89 percent of the carboxylic acid units are esterified with a linear alcohol or an alpha-branched alcohol, and 
 wherein 0.01 to 10 percent of the carboxylic acid units has at least one of an amino-, amido- and/or imido-group. 
 
     
     
         10 . The lubricating composition of  claim 1  wherein the viscosity modifier copolymer has a weight average molecular weight of 45,000 or less. 
     
     
         11 . The lubricating composition of  claim 1  wherein the first base stock component is present in the amount from 10 weight percent to 60 weight percent, the second base stock component is present in an amount from 30 weight percent to 60 weight percent, and the viscosity modifier is present in an amount from 2 weight percent to 46 weight percent, based on the total weight of the lubricating composition. 
     
     
         12 . A process for producing the lubricating composition of  claim 1 , said process comprising:
 providing a first base stock component comprising one or more metallocene catalyzed polyalphaolefins (mPAOs), each mPAO having a kinematic viscosity (Kv 100 ) from 40 cSt to 155 cSt and a viscosity index (VI) from 150 to 207;   providing a second base stock comprising one or more polyalphaolefins (PAOs), each PAO having a kinematic viscosity (Kv 100 ) less than 10 cSt and a VI from 130 to 145;   providing a viscosity modifier comprising a copolymer having units derived from monomers of (i) an α-olefin and (ii) an ethylenically unsaturated carboxylic acid or derivatives thereof esterified with an alcohol; and   blending the first base stock component, second base stock component and viscosity modifier in amounts sufficient to produce the lubricating composition.   
     
     
         13 . A lubricant comprising the lubricating composition of  claim 1 . 
     
     
         14 . The lubricant of  claim 13  further comprising one or more of an antioxidant, detergent, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, antiwear, extreme pressure agent, friction modifier, and antirust additive. 
     
     
         15 . A method of lubricating a mechanical device comprising supplying to the device a lubricating composition of  claim 1 , wherein the mechanical device comprises a driveline device. 
     
     
         16 . The method of  claim 15  wherein the driveline device comprises gears or transmissions. 
     
     
         17 . The lubricant of  claim 13  which comprises an axle fluid or manual transmission fluid (MTF). 
     
     
         18 . A method for improving fuel efficiency or shear stability, while maintaining or improving wear control, load carrying capacity and/or traction reduction in a driveline device lubricated with a lubricating oil, by using as the lubricating oil a lubricant of  claim 13 . 
     
     
         19 . The method of  claim 18  wherein the driveline device comprises gears or transmissions. 
     
     
         20 . The method of  claim 18  wherein the lubricant comprises an axle fluid or manual transmission fluid (MTF).