Copolymer compositions usable as additives for lubricating oils

摘要

Compositions of copolymers are disclosed containing 10 to 35% by weight of units derived from at least one vinylaromatic monomer, 5 to 15% by weight of units derived from at least one linear or branched alkyl methacrylate with 1 to 4 carbon atoms, 20 to 50% by weight of units derived from at least one linear alkyl methacrylate with 8 to 14 carbon atoms and 15 to 50% by weight of units derived from at least one linear alkyl methacrylate with 16 to 22 carbon atoms. The copolymer compositions have a weight average molecular weight of 100,000 to 400,000 and a polydispersity index in general of less than 5. They are prepared by any free-radical copolymerization method using for example azo or peroxide initiators. These compositions have the advantage of providing a better compromise between the characteristics required of a viscosity additive for lubricating oils.