Lubricating Composition Containing Viscosity Modifier Combination

Abstract

The present invention relates to a lubricating composition containing (a) an oil of lubricating viscosity, (b) a star polymer and (c) a substantially linear polymer with a weight average molecular weight of 45,000 or less. The invention further provides a method of lubricating a mechanical device, typically a manual transmission with the lubricating composition. The invention further provides for the use of the lubricating composition to provide a number of benefits including lower operating temperatures and fuel economy

1 - 22 . (canceled) 
     
     
         23 . A lubricating composition comprising (a) an oil of lubricating viscosity, (b) a star polymer, and (c) a substantially linear polymer with a weight average molecular weight of 45,000 or less, wherein the substantially linear polymer is a copolymer comprising units derived from monomers (i) an α-olefin and (ii) an ethylenically unsaturated carboxylic acid or derivatives thereof esterified with an alcohol. 
     
     
         24 . The lubricating composition of  claim 23 , wherein the substantially linear polymer has a weight average molecular weight of 8000 to 25,000. 
     
     
         25 . The lubricating composition of  claim 23 , wherein the substantially linear polymer has a weight average molecular weight of 12,000 to 20,000. 
     
     
         26 . The lubricating composition of  claim 23 , wherein the substantially linear polymer is a copolymer derived from monomers (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, 
 wherein 0.01 to 10% of the carboxylic acid units has at least one of an amino-, amido- and/or imido-group, and 
 wherein the copolymer has a reduced specific viscosity of up to 0.08. 
 
     
     
         27 . The lubricating composition of  claim 23 , wherein the substantially linear polymer is a copolymer comprising units derived from monomers (i) an α-olefin and (ii) an ethylenically unsaturated carboxylic acid or derivatives thereof esterified with a primary alcohol branched at the β- or higher position, wherein the copolymer, prior to esterification has a reduced specific viscosity of up to 0.15. 
     
     
         28 . The lubricating composition of  claim 27 , wherein the substantially linear polymer prior to esterification has a reduced specific viscosity of 0.02 to 0.07. 
     
     
         29 . The lubricating composition of  claim 27 , wherein the substantially linear polymer prior to esterification has a reduced specific viscosity of 0.04 to 0.06. 
     
     
         30 . The lubricating composition of  claim 23 , wherein the substantially linear polymer is present at 5 wt % to 30 wt % of the lubricating composition. 
     
     
         31 . The lubricating composition of  claim 23 , wherein the substantially linear polymer is a copolymer comprising units derived from monomers (i) an α-olefin and (ii) an ethylenically unsaturated carboxylic acid or derivatives thereof esterified with a primary alcohol branched at the β- or higher position; and wherein the substantially linear polymer is present at 5 wt % to 30 wt % of the lubricating composition. 
     
     
         32 . The lubricating composition of  claim 23 , wherein the ethylenically unsaturated carboxylic acid or derivatives thereof is at least one of maleic anhydride or maleic acid. 
     
     
         33 . The lubricating composition of  claim 23 , wherein the star polymer is a poly(meth)acrylate, and wherein the star polymer is derived from a monomer composition comprising:
 (a) 50 wt % to 100 wt % of an alkyl (meth)acrylate, wherein the alkyl group of the (meth)acrylate has 10 to 20 carbon atoms, or mixtures thereof;   (b) 0 wt % to 40 wt % of an alkyl (meth)acrylate, wherein the alkyl group of the (meth)acrylate has 1 to 9 carbon atoms, or mixtures thereof; and   (c) 0 wt % to 10 wt % of a nitrogen-containing monomer.   
     
     
         34 . The lubricating composition of  claim 23 , wherein the star polymer is a poly(meth)acrylate, and wherein the star polymer is derived from a monomer composition comprising:
 (a) 65 wt % to 95 wt % of an alkyl (meth)acrylate, wherein the alkyl group of the (meth)acrylate has 12 to 18 carbon atoms, or mixtures thereof;   (b) 5 wt % to 30 wt % of an alkyl (meth)acrylate, wherein the alkyl group of the (meth)acrylate has 1 to 9, carbon atoms, or mixtures thereof; and   (c) 0 wt % to 5 wt % of a nitrogen-containing monomer.   
     
     
         35 . The lubricating composition of  claim 23 , wherein the star polymer is a polymethacrylate and is present at 2 wt % to 30 wt % of the lubricating composition 
     
     
         36 . The lubricating composition of  claim 23 , wherein the star polymer is a polymethacrylate and present at 5 wt % to 20 wt %, of the lubricating composition. 
     
     
         37 . The lubricating composition of  claim 23 , wherein the star polymer is a polymethacrylate and is present at 0.5 to 10 wt % of the lubricating composition. 
     
     
         38 . The lubricating composition of  claim 23 , wherein the lubricating composition contains 0.3 wt % to 15 wt % of star polymer and 1 wt % to 35 wt % of the substantially linear polymer. 
     
     
         39 . The lubricating composition of  claim 23 , wherein the lubricating composition contains 0.45 wt % to 5 wt % of star polymer and 2 wt % to 25 wt % of the substantially linear polymer. 
     
     
         40 . A method of lubricating a mechanical device comprising supplying to the device the lubricating composition of  claim 23 . 
     
     
         41 . The method of  claim 40 , wherein the mechanical device is a manual transmission. 
     
     
         42 . The method of  claim 40 , wherein the mechanical device is an automatic transmission.