Stabilized amide-imide graft of ethylene copolymeric additives for

Abstract

Oil-soluble, derivatized ethylene copolymers derived from about 2 to 98 wt. % ethylene, and one or more C.sub.3 to C.sub.28 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 firstly reacted with from 0.1 to 0.9 molar equivalents of a t-amino-amine compound containing only one primary amino group to form imido groups and then secondly reacted with from 0.1 to 0.9 molar equivalents of a .alpha.,.omega. primary diamine having at least two primary amine groups, e.g. a poly(alkylene amine) such as diethylene triamine, to form carboxyl-grafted polymeric imide, usually succinimide, intermediate and thirdly reacted with an anhydride of a C.sub.1 -C.sub.30 hydrocarbon substituted acid, preferably acetic anhydride, to yield an oil-soluble stable amide derivative of said polyamine whereby oil solutions of said amide derivative are characterized by minimal viscosity change over an extended period of time. Useful number average molecular weight (M.sub.n) of said copolymers range from about 700 to 500,000; however, if the molecular weight is from 10,000 to 500,000 then these copolymers are multifunctional viscosity index improvers of enhanced sludge dispersant activity. It is preferred to treat these derivatized copolymers with oil-soluble hydrocarbyl substituted acids, preferably with long chain alkylaryl sulfonic acids with an average side chain carbon number of about 20-40, to yield haze-free hydrocarbon concentrate useful as an additive solution for lubricating oils.