Viscosity index improver and lube oil containing the same

Abstract

A viscosity index improver, which comprises a polymer (A) having a solubility parameter of 8.6-9.4, a crystallizing initiation temperature of equal to or less than −15° C., and a steric hindrance factor (F) of 0-13, said factor F being defined by the following equation: F=4X+Y (1) wherein X and Y represent the total numbers of atoms at the 6th position and the 7th position, respectively, in the side chains; said polymer (A) having a Mw of 5,000-2,000,000 and comprising units of at least one monomer selected from the group consisting of: (a) a monomer represented by the general formula: CH 2 ═C(R 0 )—COO—(AO) n —R (2) wherein R 0 is hydrogen atom or methyl group, R is a C 1-40 alkyl group, n is 0 or an integer of 1-20 giving 0-10 on average, A is an alkylene group containing 2-4 carbon atoms, plural A's in case of n being at least 2 are the same or different, and the polyoxyalkylene moiety (AO) n in case of the plural A's being different comprises random-wise or block-wise distributed oxyalkylene groups; (b) an alkyl alkenyl ether; (c) an alkenyl carboxylate; and (d) a nitrogen-containing unsaturated monomer. The suitable monomers, 2-decyl-tetradecyl methacrylate and 2-decyl-tetradecyl acrylate compose the polymer (A), are also described.

What is claimed as new and desired to be secured by letters patent is:  
     
         1 . A viscosity index improver, which comprises a polymer (A) having a solubility parameter of 8.6-9.4, a crystallizing initiation temperature of equal to or less than −15° C., and a steric hindrance factor (F) of 0-13, said factor F being defined by the following equation:  
       F=4X+Y   (1)  wherein X and Y represent the total numbers of atoms at the 6th position and the 7th position, respectively, in the side chains, counted from the backbone; said polymer (A) having a weight-average molecular weight of 5,000-2,000,000 and comprising units of at least one monomer selected from the group consisting of: 
 (a) a monomer represented by the general formula:  
                     
   wherein R 0  is hydrogen atom or methyl group, R is a C 1-40 alkyl group, n is 0 or an integer of 1-20 giving 0-10 on average, A is an alkylene group containing 2-4 carbon atoms, plural A's in case of n being at least 2 are the same or different, and the polyoxyalkylene moiety (AO) n  in case of the plural A's being different comprises random-wise or block-wise distributed oxyalkylene groups; 
 (b) an alkyl alkenyl ether;  
 (c) an alkenyl carboxylate; and  
 (d) a nitrogen-containing unsaturated monomer.  
   
     
     
         2 . The improver of  claim 1 , wherein said polymer (A) contains units of said monomer (a), said monomer (b) or said monomers (a) and (b) in an amount of at least 30% by weight, with or without 0-45% by weight of units of said monomer (c), 0-12% by weight of units of said monomer (d) and 0-20% by weight of units of another monomer.  
     
     
         3 . The improver of  claim 1 , wherein said polymer (A) is a copolymer (A1), comprising units of at least one monomer (a1) represented by the general formula (2) wherein R is a branched alkyl group containing 16-40 carbon atoms.  
     
     
         4 . The improver of  claim 3 , wherein said copolymer (A1) comprises 5-90% by weight of units of said monomer (a1) , and 10-60% by weight of units of an alkyl acrylate or methacrylate (a2) containing 1-4 carbon atoms in the alkyl group, with or without 0-85% by weight of units of at least one selected from the group consisting of an alkyl acrylate or methacrylate (a3) containing 8-15 carbon atoms in the alkyl group and a straight-chain alkyl acrylate or methacrylate (a4) containing 16-18 carbon atoms in the alkyl group.  
     
     
         5 . The improver of  claim 4 , wherein said copolymer (A1) further comprises 0.1-10% by weight of units of said monomer (d).  
     
     
         6 . The improver of  claim 5 , wherein said monomer (d) is at least one selected from the group consisting of dimethylaminoethyl acrylate, diethylaminoethyl acrylate, morpholinoethyl acrylate, and corresponding methacrylates.  
     
     
         7 . A viscosity index improver, which comprises a copolymer (A11) having a weight-average molecular weight of 5,000-2,000,000, comprising 5-90% by weight of units of at least one monomer (a11) and 5-95% by weight of units of at least one alkyl acrylate or methacrylate other than said monomer (a11): said monomer (a11) being capable of providing a homopolymer having a crystallizing initiation temperature of equal to or less than 5° C. and represented by the general formula:  
       
         
           
           
               
               
           
         
         wherein R 0  is hydrogen atom or methyl group, R is a branched alkyl group containing 20-40 carbon atoms, n is 0 or an integer of 1-20 giving 0-10 on average, A is an alkylene group containing 2-4 carbon atoms, plural A's in case of n being at least 2 are the same or different, and the polyoxyalkylene moiety (AO) n  in case of the plural A's being different comprises random-wise or block-wise distributed oxyalkylene groups.  
       
     
     
         8 . The improver of  claim 7 , wherein R is represented by the general formula:  
       
         
           
           
               
               
           
         
         wherein R 1  and R 2  are the same or different straight-chain alkyl groups containing 8-18 carbon atoms.  
       
     
     
         9 . The improver of  claim 7 , wherein said copolymer (A11) has a solubility parameter of 8.6-9.4, a crystallizing initiation temperature of equal to or less than −15° C., and a steric hindrance factor F of 0-13, said factor being defined by the following equation:  
       F=4X+Y   (1)  wherein X and Y represent the total numbers of atoms at the 6th position and the 7th position, respectively, in the side chains, counted from the backbone.    
     
     
         10 . The improver of  claim 9 , wherein said copolymer (A11) has a steric hindrance factor F of 0-10.  
     
     
         11 . The improver of  claim 7 , wherein said copolymer (A11) comprises 5-90% by weight of units of said monomer (a11), and 10-60% by weight of units of an alkyl acrylate or methacrylate (a2) containing 1-4 carbon atoms in the alkyl group, with or without 0-85% by weight of units of at least one selected from the group consisting of an alkyl acrylate or methacrylate (a3) containing 8-15 carbon atoms in the alkyl group, a branched alkyl acrylate or methacrylate (a12) containing 16-19 carbon atoms in the alkyl group, a straight-chain alkyl acrylate or methacrylate (a4) containing 16-18 carbon atoms in the alkyl group and a straight-chain alkyl acrylate or methacrylate (a5) containing 20-40 carbon atoms in the alkyl group.  
     
     
         12 . The improver of  claim 7 , wherein said copolymer (A11) comprises 10-45% by weight of units of 2-decyl-tetradecyl methacrylate, 20-45% by weight of units of methyl methacrylate, and 10-60% by weight of units of a straight-chain alkyl acrylate or methacrylate containing 10-18 carbon atoms in the alkyl group.  
     
     
         13 . The improver of  claim 7 , wherein said copolymer (A11) further comprises 0.1-10% by weight of units of a nitrogen-containing unsaturated monomer (d).  
     
     
         14 . The improver of  claim 13 , wherein said monomer (d) is at least one selected from the group consisting of N,N-dimethylaminoethyl acrylate, N,N-diethylaminoethy i acrylate, morpholinoethyl acrylate, and corresponding methacrylates.  
     
     
         15 . A viscosity improver concentrate, which comprises 10-90% by weight of said improver of  claim 1  and 10-90% by weight of a diluent.  
     
     
         16 . A viscosity improver concentrate, which comprises 10-90% by weight of said improver of  claim 7 , and 10-90% by weight of a diluent.  
     
     
         17 . A lube oil composition, which comprises a major amount of a base oil and 0.5-30% by weight of said improver of  claim 1 .  
     
     
         18 . The composition of  claim 17 , wherein the base oil has a kinematic viscosity of 1-15 mm 2 /s at 100° C. and a viscosity index of at least 80.  
     
     
         19 . A lube oil composition, which comprises a major amount of a base oil and 0.5-30% by weight of said improver of  claim 7 .  
     
     
         20 . The composition of  claim 19 , wherein the base oil has a kinematic viscosity of 1-15 mm 2 /s at 100° C. and a viscosity index of at least 80 .  
     
     
         21 . A compound of 2-decyl-tetradecyl methacrylate.  
     
     
         22 . A compound of 2-decyl-tetradecyl acrylate.  
     
     
         23 . A homopolymer having a weight-average molecular weight of 5,000-2,000,000, comprises units of a compound selecting from the group consisting of the compound o t  claim 21  and the compound of  claim 22 .  
     
     
         24 . A copolymer, having a weight-average molecular weight of 5,000-2,000, 000, comprises 5-90% by weight of units of a compound selecting from the group consisting of the compound of  claim 21  and the compound of  claim 22 , and 5-95% by weight of units of at least one monomer selecting from the group consisting of: an alkyl methacrylate or an alkyl acrylate other than the compound of  claim 21  or  claim 22;  an alkyl alkenyl ether; an alkenyl carboxylate; and a nitrogen-containing unsaturated monomer.