Lubricating composition

Abstract

A lubricating composition for use in the crankcase of an engine comprising a base oil and one or more additives, wherein the base oil comprises a Fischer-Tropsch derived base oil and wherein the lubricating composition comprises one or more comb polymers. The lubricating composition of the present invention has been found to improve sustained fuel economy properties whilst obtaining improved piston cleanliness properties and improved dispersancy properties.

1 . A lubricating composition for use in the crankcase of an engine comprising a base oil and one or more additives, wherein the base oil comprises a Fischer-Tropsch derived base oil and wherein the lubricating composition comprises one or more comb polymers. 
     
     
         2 . A lubricating composition according to  claim 1 , wherein the comb polymer comprises, in the main chain, at least one repeat unit which is obtained from at least one polyolefin-based macromonomer, and at least one repeat unit which is obtained from at least one low molecular weight monomer selected from the group consisting of styrene monomers having 8 to 17 carbon atoms, alkyl(meth)acrylates having 1 to 10 carbon atoms in the alcohol group, vinyl esters having from 1 to 11 carbon atoms in the acyl group, vinyl ethers having 1 to 10 carbon atoms in the alcohol group, (di)alkyl fumurates having 1 to 10 carbon atoms in the alcohol group, (di)alkyl maleates having 1 to 10 carbon atoms in the alcohol group and mixtures thereof, where the molar degree of branching is in the range of 0.1 to 10 mol % and the comb polymer comprises a total of at least 80% by weight, based on the total weight of repeat units of the comb polymer, of the at least one repeat unit which is obtained from the at least one polyolefin-based macromonomer and the at least one repeat unit which is obtained from the at least one low molecular weight monomer. 
     
     
         3 . A lubricating composition according to  claim 2 , wherein the comb polymer has a molar degree of branching in the range of 0.3 to 3.6 mol %. 
     
     
         4 . A lubricating composition according to  claim 2 , wherein the comb polymer has 8 to 30% by weight of the at least one repeat unit which is derived from the at least one polyolefin-based macromonomer, and the molar degree of branching of the comb polymer is in the range of 0.3% to 1.1%. 
     
     
         5 . A lubricating composition according to  claim 2  wherein the comb polymer has 11 to 26% by weight of the at least one repeat unit which is obtained from the at least one polyolefin-based macromonomer. 
     
     
         6 . A lubricating composition according to  claim 2 , wherein the at least one repeat unit which is obtained from the at least one polyolefin-based macromonomer has a number-average molecular weight in the range of 700 to 10000 g/mol. 
     
     
         7 . A lubricating composition according to  claim 2  wherein the comb polymer comprises at least 90% by weight of repeat units which are obtained from at least one polyolefin-based macromonomer and from at least one low molecular weight monomer selected from the group consisting of styrene monomers having 8 to 17 carbon atoms, alkyl(meth)acrylates having 1 to 10 carbon atoms in the alcohol group, vinyl esters having from 1 to 11 carbon atoms in the acyl group, vinyl ethers having 1 to 10 carbon atoms in the alcohol group, (di)alkyl fumurates having 1 to 10 carbon atoms in the alcohol group, (di)alkyl maleates having 1 to 10 carbon atoms in the alcohol group and mixtures thereof. 
     
     
         8 . A lubricating composition according to  claim 2  wherein the polydispersity index Mw/Mn is in the range of from 1 to 5. 
     
     
         9 . A lubricating composition according to  claim 2  wherein the molar degree of branching of the comb polymer is in the range of from 0.4% to 1.0%. 
     
     
         10 . A lubricating composition according to  claim 2  wherein the at least one repeat unit obtained from the at least one polyolefin-based macromonomer comprises a group which is obtained from monomers selected from the group consisting of C 2 -C 10  alkenes and C 4 -C 10  alkadienes. 
     
     
         11 . A lubricating composition according to  claim 2  wherein the at least one repeat unit obtained from the at least one polyolefin-based macromonomer comprises at least 80% by weight of groups which are derived from monomers selected from the group consisting of C 2 -C 10  alkenes and C 4 -C 10  alkadienes, based on the weight of the at least one repeat unit derived from the at least one polyolefin-based macromonomer. 
     
     
         12 . A lubricating composition according to  claim 2  wherein the melting point of the at least one repeat unit obtained from the at least one polyolefin-based macromonomers is less than or equal to 10° C. 
     
     
         13 . A lubricating composition according to  claim 2  wherein no melting point of the at least one repeat unit obtained from the at least one polyolefin-based macromonomer is measured. 
     
     
         14 . A lubricating composition according to  claim 2  wherein the comb polymer has repeat units, preferably in a proportion of at least 50% by weight, which are obtained from at least one of n butyl methacrylate and n butyl acrylate. 
     
     
         15 . A lubricating composition according to  claim 2  wherein the comb polymer has repeat units which are obtained from styrene, preferably in a proportion in the range of from 5 to 25% by weight. 
     
     
         16 . A lubricating composition according to  claim 2  wherein the comb polymer has a weight-average molecular weight in the range of 100,000 to 500,000 g/mol. 
     
     
         17 . A lubricating composition according to  claim 2  wherein the comb polymer has repeat units which are obtained from alkyl(meth)acrylates having 11-30 carbon atoms in the alkyl radical, preferably in a proportion in the range of from 1 to 10% by weight. 
     
     
         18 . A lubricating composition according to  claim 1  wherein the Fischer-Tropsch derived base oil has a kinematic viscosity at 100° C. in the range of 2 mm 2 /s to 10 mm 2 /s. 
     
     
         19 . (canceled) 
     
     
         20 . (canceled) 
     
     
         21 . A method comprising:
 applying a lubricating oil composition to a surface in relative movement to another surface in the crankcase of an engine, wherein the lubricating oil composition comprises a base oil and one or more additives, wherein the base oil comprises a Fischer-Tropsch derived base oil and wherein the lubricating composition comprises one or more comb polymers.   
     
     
         22 . The method according to  claim 21 , wherein the comb polymer comprises, in the main chain, at least one repeat unit which is obtained from at least one polyolefin-based macromonomer, and at least one repeat unit which is obtained from at least one low molecular weight monomer selected from the group consisting of styrene monomers having 8 to 17 carbon atoms, alkyl(meth)acrylates having 1 to 10 carbon atoms in the alcohol group, vinyl esters having from 1 to 11 carbon atoms in the acyl group, vinyl ethers having 1 to 10 carbon atoms in the alcohol group, (di)alkyl fumurates having 1 to 10 carbon atoms in the alcohol group, (di)alkyl maleates having 1 to 10 carbon atoms in the alcohol group and mixtures thereof, where the molar degree of branching is in the range of 0.1 to 10 mol % and the comb polymer comprises a total of at least 80% by weight, based on the total weight of repeat units of the comb polymer, of the at least one repeat unit which is obtained from the at least one polyolefin-based macromonomer and the at least one repeat unit which is obtained from the at least one low molecular weight monomer.