Ethylene copolymer viscosity index improver-dispersant additive useful in oil compositions

Abstract

Oil soluble viscosity index improving ethylene copolymers, such as copolymers of ethylene and propylene; and ethylene, propylene and diolefin; etc., are reacted or grafted with ethylenically unsaturated carboxylic acid moieties, preferably maleic anhydride moieties, and reacted with polyamines having two or more primary amine groups and a carboxylic acid component, preferably alkylene polyamine and alkenyl succinic anhydride such as polyisobutenyl succinic anhydride. Or the grafted ethylene copolymer can be reacted with already formed salts, amides, imides, etc. of said polyamine and acid component, preferably imides of alkylene polyamine and alkenyl succinic anhydride. These reactions can permit the incorporation of varnish inhibition and dispersancy into the ethylene copolymer while inhibiting cross-linking with resulting viscosity increase, haze or gelling. The aforesaid grafting reaction may be carried out thermally, or more preferably with a free radical initiator such as a peroxide in a mineral lubricating oil, in which case the acid component, preferably also acts to solubilize insoluble compounds formed by side reactions, such as maleic anhydride grafted oil molecules reacted with amine, to thereby inhibit haze formation, particularly when preparing oil concentrates of the V.I.-dispersant additive for later addition to lubricating oils. The invention also includes preferred methods of grafting maleic anhydride onto the ethylene copolymer by periodic or continuous addition of maleic anhydride and initiator charge, so as to maintain the maleic anhydride in solution during the grafting reaction.

Dependencies are inferred from the claim text.