Dispersant viscosity improvers for lubricating oil compositions

Dispersant viscosity modifiers (DVMs) are multi-functional lubricant additives combining in one additive composition, dispersancy and the ability to improve the viscosity of a lubricant, at high engine temperatures, sufficiently to maintain efficient lubrication. Compounds useful for this purpose are characterized by a polar group attached to a relatively high molecular weight hydrocarbon chain. Polymeric compounds that were studied for possible use as DVMs were maleated ethylene–propylene copolymers and copolymers containing an alkyl methacrylate and vinyl amine-containing monomers. The current method used by Lubrizol to prepare grafted polar monomers onto saturated polymers is a solvent-based chemical route, which involves precipitation, filtration, drying and then dissolution in base oil. Because of those drawbacks, an alternative synthesis needs to be found to get a much more cost-effective product. Therefore, the main objectives of this research were to apply melt techniques to replace the solvent-based free radical grafting reaction and to optimise the grafting level without product detriment. [Continues.]