| abstract |
The invention relates to the use of graft polymers obtained by polymerization in two stages. In a first stage, at least one graft basis is produced by radically polymerizing a monomer composition A) containing 0 to 40 percent by weight of one or several ethylenically unsaturated ester compounds of formula (I), wherein R represents hydrogen or methyl, R1 represents a linear or branched alkyl radical comprising 1 to 5 carbon atoms, R2 and R3 independently represent hydrogen or a group of formula -COOR', wherein R' represents hydrogen or an alkyl group comprising 1 to 5 carbon atoms, 60 to 100 percent by weight of one or several ethylenically unsaturated ester compounds of formula (II), wherein R represents hydrogen or methyl, R4 represents a linear or branched alkyl radical comprising 6 to 40 carbon atoms, R5 and R6 independently represent hydrogen or a group of formula -COOR", wherein R" represents hydrogen or an alkyl group comprising 6 to 40 carbon atoms, and 0 to 40 percent by weight of comonomers, the percentages being relative to the weight of monomer composition A). In a second stage, a monomer composition B) containing 20 to 100 percent by weight of at least one monomer that comprises at least one nitrogen-containing group is grafted onto the graft basis in order to reduce wear in lubricant oil compositions. Said graft polymer comprises a maximum of 200 ppm of sulfur while the weight ratio between monomer composition A) and monomer composition B) ranges between 99.7:0.3 and 80:20. |