| abstract |
Oil-soluble, derivatized ethylene copolymers derived from about 15 to 90 wt. % ethylene, and one or more C3 to C28 alpha-olefins, e.g. propylene, which are grafted, preferably solution-grafted under an inert atmosphere and at elevated temperatures and in the presence of a high-temperature decomposable free-radical initiator, with an ethylenically-unsaturated dicarboxylic acid material and thereafter reacted with a polyamine having at least two primary amine groups, e.g. an alkylene polyamine such as diethylene triamine, to form carboxyl-grafted polymeric imide, usually maleimide, derivatives are subsequently reacted with a C12 to about C18 hydrocarbyl substituted dicarboxylic acid anhydride, preferably a C12 to about C18 hydrocarbyl substituted succinic anhydride, to yield an oil-soluble stable imide of said carboxyl-grafted copolymeric imide whereby oil solutions thereof are characterized by minimal viscosity change over an extended period of time. Useful number average molecular weights (Mn) of said copolymers range from about 700 to 500,000; however, if the molecular weight is from about 10,000 to 500,000 then these copolymers are also useful as multi-functional viscosity index improvers. |