Copolymers comprising ester groups and use thereof in lubricants

Abstract

The present invention relates to copolymers comprising ester groups and having at least one nonpolar segment P and at least one polar segment D, the polar segment D having at least 8 repeat units and the proportion by weight of dispersing repeat units in the polar segment D being at least 30%, based on the weight of the polar segment D, wherein the copolymer comprising ester groups is obtainable by NMP (nitroxide mediated polymerization). The invention further relates to lubricant oils having improved friction properties and comprising said copolymers.

1 . A copolymer, comprising:
 an ester group,   a nonpolar segment P, and   a polar segment D,   wherein   the polar segment D comprises at least 8 repeat units,   a proportion by weight of dispersing repeat units in the polar segment D is at least 30%, based on a weight of the polar segment D, and   the copolymer is obtained via a nitroxide mediated polymerization.   
     
     
         2 . The copolymer according to  claim 1 , wherein the copolymer is obtained via a multistage polymerization comprising a first stage and a last stage, with the nonpolar segment P prepared in the first stage and the polar segment D prepared in the last stage. 
     
     
         3 . The copolymer according to  claim 1 , wherein a transferrable nitroxyl radical compound in the nitroxide mediated polymerization comprises a phosphorus atom. 
     
     
         4 . The copolymer according to  claim 2 , wherein a transferrable nitroxyl radical compound in the multistage polymerization comprises a phosphorus atom, and the transferrable nitroxyl radical compound is attached to an end of the polar segment D. 
     
     
         5 . The copolymer according to  claim 1 , wherein the copolymer comprises repeat units derived from styrene and methacrylate. 
     
     
         6 . The copolymer according to  claim 5 , wherein a proportion of the repeat units derived from styrene is of from 0.5 to 10% by weight. 
     
     
         7 . The copolymer according to  claim 1 , wherein a weight ratio of the nonpolar segments P to the polar segments D is of from 100:1 to 1:1. 
     
     
         8 . The copolymer according to  claim 1 , wherein the nonpolar segment P is obtained by a process comprising: 
 polymerizing a monomer composition comprising, based on a total weight of the monomer composition:   a) 0 to 40% by weight of one or more ethylenically unsaturated ester compounds of formula (I)   
       
         
           
           
               
               
           
         
         b) 5 to 100% by weight of one or more ethylenically unsaturated ester compounds of formula (II) 
       
       
         
           
           
               
               
           
         
         c) 0 to 80% by weight of one or more ethylenically unsaturated ester compounds of formula (III) 
       
       
         
           
           
               
               
           
         
       
       and
 d) 0 to 50% by weight of a comonomer, 
 wherein: 
 R is hydrogen or methyl, 
 R 1  is a linear or branched alkyl radical comprising 1 to 6 carbon atoms, 
 R 2  and R 3  are each independently hydrogen or a —COOR′ group, wherein R′ is hydrogen or an alkyl group comprising 1 to 6 carbon atoms, 
 R 4  is a linear or branched alkyl radical comprising 7 to 15 carbon atoms, 
 R 5  and R 6  are each independently hydrogen or a —COOR″ group, wherein R″ is hydrogen or an alkyl group comprising 7 to 15 carbon atoms, 
 R 7  is a linear or branched alkyl radical comprising 16 to 30 carbon atoms, and 
 R 8  and R 9  are each independently hydrogen or a —COOR′″ group, wherein R′″ is hydrogen or an alkyl group comprising 16 to 30 carbon atoms. 
 
     
     
         9 . The copolymer according to  claim 1 , wherein the dispersing repeat units are derived from one or more ethylenically unsaturated, polar ester compounds of formula (IV) 
       
         
           
           
               
               
           
         
         wherein 
         R is hydrogen or methyl, 
         X is oxygen, sulfur or an amino group of —NH— or —NR a —, wherein R a  is an alkyl radical comprising 1 to 40 carbon atoms, 
         R 10  is a radical comprising 2 to 1000 carbon atoms and at least one heteroatom, and 
         R 11  and R 12  are each independently hydrogen or a —COX′R 10′  group, wherein X′ is oxygen or an amino group of —NH— or —NR a′ —, wherein R a′  is an alkyl radical comprising 1 to 40 carbon atoms, and R 10′  is a radical comprising 1 to 100 carbon atoms and optionally from a heterocyclic vinyl compound. 
       
     
     
         10 . The copolymer according to  claim 9 , wherein R 10  comprises a —CO— group. 
     
     
         11 . The copolymer according to  claim 10 , wherein R 10  comprises at least two —CO— groups. 
     
     
         12 . The copolymer according to  claim 11 , wherein the at least two CO— groups are bonded to one another via atoms of not more than four. 
     
     
         13 . The copolymer according to  claim 1 , wherein the dispersing repeat units in the polar segment D are derived from 2-acetoacetoxyethyl (meth)acrylate. 
     
     
         14 . A lubricant, comprising the copolymer according to  claim 1 . 
     
     
         15 . The lubricant according to  claim 14 , further comprising at least 10% by weight of group III oil. 
     
     
         16 . A method for improving a coefficient of friction of a lubricant, the method comprising: including the copolymer according to  claim 1  in a lubricant in need thereof. 
     
     
         17 . The method according to  claim 16 , wherein the coefficient of friction is improved in a boundary lubrication range. 
     
     
         18 . The method according to  claim 16 , wherein the coefficient of friction determined by a high frequency reciprocating rig value is improved. 
     
     
         19 . A method for reducing wear, the method comprising: employing the copolymer according to  claim 1 .