High molecular weight polymers as viscosity modifiers

Abstract

A lubricating composition comprises a base oil and between 10 ppm and 1000 ppm by mass of a viscosity modifier, the viscosity modifier comprising a polymer having a number average molecular weight greater than 500,000. The polymer's side-chains may be branched or unbranched. The polymer is preferably selected from the group consisting of polyolefin, poly alpha olefin, poly internal olefin, ethylene-propylene copolymers, ethylene-propylene-diene copolymers, ethylene-propylene-acrylate copolymers, ethylene-propylene-methacrylate copolymers, ethylene-propylene-aromatic copolymers, ethylene-propylene-diene-acrylate copolymers, ethylene-propylene-diene-methacrylate copolymers, and combinations thereof.

What is claimed is: 
     
         1 . A lubricant composition, comprising:
 a base oil;   between 10 ppm and 1000 ppm by mass of a viscosity modifier, the viscosity modifier comprising at least one polymer having a number average molecular weight greater than 500,000.   
     
     
         2 . The composition according to  claim 1  wherein the polymer has side-chains that may be branched or unbranched, and wherein the polymer has a backbone that is at least ten times as long as the side-chains. 
     
     
         3 . The composition according to  claim 1  wherein the polymer comprises side-chains of different sizes, whereby at least 90% of the side-chains comprise 1 to 30 carbon atoms. 
     
     
         4 . The composition according to  claim 1  wherein the polymer comprises side-chains whereby at least 20% of the side-chains have the same length and comprise 1 to 30 carbon atoms. 
     
     
         5 . The composition according to  claim 1  wherein the polymer has a number average molecular weight greater than 1,000,000. 
     
     
         6 . The composition according to  claim 1  wherein the polymer has a number average molecular weight smaller than 100,000,000. 
     
     
         7 . The composition according to any  claim 1  wherein the polymer has a number average molecular weight of greater than 500,000. 
     
     
         8 . The composition according to any  claim 1  wherein the concentration of the polymer in the composition is between 10 ppm and 500 ppm by mass. 
     
     
         9 . The composition according to any  claim 1  wherein the polymer comprises ethylene and propylene. 
     
     
         10 . The composition according to  claim 9  wherein the polymer is selected from the group consisting of ethylene-propylene copolymers, ethylene-propylene-diene copolymers, ethylene-propylene-acrylate copolymers, ethylene-propylene-methacrylate copolymers, ethylene-propylene-aromatic copolymers, ethylene-propylene-diene-acrylate copolymers, ethylene-propylene-diene-methacrylate copolymers, and combinations thereof. 
     
     
         11 . The composition according to any  claim 1  wherein at least 50 weight percent of the polymer comprises ethylene and propylene. 
     
     
         12 . The composition according to any  claim 1  wherein the polymer comprises polyolefin and/or poly alpha olefin and/or poly internal olefin. 
     
     
         13 . The composition according to  claim 12  wherein at least 50 weight percent of the polymer comprises polyolefin and/or poly alpha olefin and/or poly internal olefin. 
     
     
         14 . The composition according to any  claim 1  wherein the composition has a viscosity index greater than 150. 
     
     
         15 . The composition according to any  claim 1  wherein the composition has a viscosity index greater than 175. 
     
     
         16 . The composition according to any  claim 1  wherein the composition further includes at least one additional component selected from the group consisting of additional viscosity modifiers, anti-wear additives, dispersants, detergents, pour point depressants, corrosion inhibitors, anti-oxidants, combustion enhancers, and anti-foam agents. 
     
     
         17 . The use of a composition according to  claim 1  as a lubricant for an engine. 
     
     
         18 . The use of a composition according to  claim 1  as a transmission oil. 
     
     
         19 . The use of a composition according to  claim 1  as a hydraulic oil. 
     
     
         20 . A method for reducing deposits in an engine comprising using a composition according to  claim 1  as a lubricant.