Lubricants Containing Olefin Copolymer and Acrylate Copolymer

Abstract

A lubricating oil composition comprising an oil of lubricating viscosity and a total of from about 1 to about 50% by weight of copolymers comprising (A) at least one ethylene-aliphatic olefin copolymer wherein the aliphatic olefins contain from 3 to about 24 carbon atoms, said copolymer (A) having M n ranging from about 600 to about 5000, and (B) at least one copolymer comprising units derived from alkyl acrylate ester monomers containing from 2 to about 25 carbon atoms in the ester group, and optionally, from about 0.1% to about 20% by weight of at least one member of the group consisting of vinyl aromatic monomers and nitrogen-containing vinyl monomers. said copolymer (B) having M n ranging from about 10,000 to about 350,000, wherein the weight ratio of (A):(B) ranges from about 99:1 to about 1:99.

1 . A method of lubricating a driveline using a lubricating oil composition comprising an oil of lubricating viscosity and a total of from about 1 to about 50% by weight of copolymers comprising: 
 (A) at least one ethylene-aliphatic olefin copolymer wherein the aliphatic olefins contain from 3 to about 24 carbon atoms, said copolymer (A) having  M   n  ranging from about 600 to about 5000; and    (B) at least one copolymer comprising units derived from    (a) about 35 mole % to about 95 mole % of alkyl methacrylate ester monomers containing from about 9 to about 25 carbon atoms in the ester group and    (b) about 65 mole % to about 5 mole % of alkyl methacrylate ester monomers containing from about 7 to about 12 carbon atoms in the ester group and wherein the alkyl moieties of the ester groups of alkyl methacrylate ester monomer (b) have 2-(C 1-4  alkyl) substituents, and    (c) optionally, from about 0.1 mole % to about 20 mole % of at least one member of the group consisting of alkyl methacrylate ester monomers containing from 2 to about 8 carbon atoms in the ester group, which esters are different from methacrylate esters (a) and (b), vinyl aromatic monomers and nitrogen-containing vinyl monomers, with the proviso that no more than 60% by weight of the esters contain not more than 11 carbon atoms in the ester group, said copolymer (B) having  M   n  ranging from about 10,000 to about 350,000; wherein the weight ratio of (A):(B) ranges from about 99:1 to about 1:99.    
   
   
       2 . The method of  claim 1  wherein monomer (b) comprises 2-ethylhexyl methacrylate.  
   
   
       3 . The method of  claim 1 , wherein the copolymer of the lubricating composition comprises: 
 (A) is an ethylene-alpha olefin copolymer wherein the ethylene content ranges from about 30 mole % to about 85 mole %; and    (B) is a polymethacrylate copolymer comprising units derived from    (a) about 35 mole % to about 95 mole % of alkyl methacrylate ester monomers containing from about 9 to about 25 carbon atoms in the ester group and    (b) about 65 mole % to about 5 mole % of alkyl methacrylate ester monomers containing from about 7 to about 12 carbon atoms in the ester group, and optionally    (c) about 0.2 mole % to about 10 mole % of at least one member of the group consisting of alkyl methacrylate ester monomers containing from 2 to about 8 carbon atoms in the ester group, which esters are different from methacrylate esters (a) and (b), vinyl aromatic monomers and nitrogen-containing vinyl monomers, with the proviso that no more than 60% by weight of the esters contain not more than 11 carbon atoms in the ester group, wherein the weight ratio (A):(B) ranges from about 25:75 to about 75:25.    
   
   
       4 . The method of  claim 1 , wherein the alkyl moieties of the ester groups of alkyl methacrylate monomer (b) have 2-(C 1-4  alkyl) groups and wherein (B) further comprises units derived from about 0.1% to about 10% by weight of at least one nitrogen containing vinyl monomer.  
   
   
       5 . The method of  claim 1 , wherein (B) is a copolymer prepared by a process comprising reacting, in the presence of a free radical initiator 
 (1) from about 55% to about 99.9% by weight of one or more alkyl acrylate ester monomers containing from 2 to about 25 carbon atoms in the ester group, wherein at least about 50 mole % of the esters contain at least 6 carbon atoms in the ester group, and    (2) from about 0.1% to about 45% by weight of at least one monomer selected from the group consisting of acrylic acid esters containing from 2 to about 8 carbon atoms in the ester group and which are different from alkyl acrylate ester monomers (1), vinyl aromatic monomers and nitrogen-containing vinyl monomers, with the proviso that no more than 60% by weight of the esters contain not more than 11 carbon atoms in the ester group, and optionally, in the presence of a chain transfer agent, wherein monomer (1), the free radical initiator, and if used, the chain transfer agent, are first combined to form a mixture, whereupon from about 10% to about 80% of said mixture is mixed with monomer (2) to form a second mixture; from about 20% to about 100% of the mixture of monomers (1) and (2) is heated until an exotherm is noted, then while maintaining reaction temperature, first adding the balance, if any, of the mixture of monomers (1) and (2) over about 0.25 hour to about 5 hours followed by addition over 0.25 to about 5 hours of the remaining mixture of monomer (1) and initiator, optionally adding additional initiator, whereupon the reaction is continued to completion.    
   
   
       6 . The method of  claim 4 , wherein monomer (2) comprises a nitrogen containing vinyl monomer.  
   
   
       7 . The method of  claim 1 , wherein (B) is prepared by a process comprising reacting, in the presence of a free radical initiator 
 (a) the methacrylic acid esters containing from about 13 to about 25 carbon atoms in the ester group, and    (b) the methacrylic acid esters containing from 7 to about 12 carbon atoms in the ester group, and    (c) the at least one monomer selected from the group consisting of methacrylic acid esters containing from 2 to about 8 carbon atoms in the ester group and which are different from methacrylic acid esters (a) and (b), vinyl aromatic monomers and nitrogen-containing vinyl monomers, with the proviso that no more than 60% by weight of the esters contain not more than 11 carbon atoms in the ester group, optionally in the presence of a chain transfer agent, wherein monomers (a) and (b), the free radical initiator, and if used, the chain transfer agent, are combined to prepare a first mixture; from about 10% to about 80% by weight of the first mixture of monomers (a) and (b) is combined with monomer (c) to prepare a second mixture; from about 20% to about 100% of the second mixture is heated until an exotherm is noted; then while maintaining reaction temperature, first adding the balance, if any, of the second mixture over about 0.25 hour to about 5 hours followed by addition over 0.25 to about 5 hours of the remaining first mixture, optionally adding additional initiator, whereupon the reaction is continued to completion.    
   
   
       8 . The method of  claim 4 , wherein the lubricating oil composition comprising at least one member of the group consisting of pour point depressants, corrosion inhibitors, extreme pressure additives, antiwear additives, antioxidants, detergents, ashless dispersants, friction modifiers, and antifoam agents and wherein the oil of lubricating viscosity comprises at least one member selected from the group consisting of mineral oil, synthetic oil or mixtures thereof having kinematic viscosity at 1001° C. ranging from about 4 to about 10 centistokes.  
   
   
       9 . The method of  claim 1 , wherein the driveline is a gear.  
   
   
       10 . The method of  claim 1 , wherein the driveline is an automatic transmission or a manual transmission.  
   
   
       11 . The method of  claim 1 , wherein the copolymer of the lubricating composition comprises: 
 (A) is an ethylene-alpha olefin copolymer wherein the ethylene content ranges from about 30 mole % to about 85 mole %; and    (B) is a polymethacrylate copolymer consisting essentially of units derived from    (a) about 35 mole % to about 95 mole % of alkyl methacrylate ester monomers containing from about 9 to about 25 carbon atoms in the ester group and    (b) about 65 mole % to about 5 mole % of alkyl methacrylate ester monomers containing from about 7 to about 12 carbon atoms in the ester group, and optionally    (c) about 0.2 mole % to about 10 mole % of at least one member of the group consisting of alkyl methacrylate ester monomers containing from 2 to about 8 carbon atoms in the ester group, which esters are different from methacrylate esters (a) and (b), vinyl aromatic monomers and nitrogen-containing vinyl monomers, with the proviso that no more than 60% by weight of the esters contain not more than 11 carbon atoms in the ester group, wherein the weight ratio (A):(B) ranges from about 25:75 to about 75:25.