A New Generation of High Performance Viscosity Modifiers Based on Comb Polymers

Viscosity index improvers based on poly(alkyl methacrylates) as well as polyolefins have been well known to the industry as key additives to formulate lube oils for decades. Recent efforts to combine these two chemistries to prepare well-defined comb polymer architectures have led to a performance breakthrough. Specifically, the concept of temperature dependent comb polymer coil expansion and collapse allows to achieve extraordinary viscosity temperature properties. Viscosity indices and thickening efficiencies are well beyond the levels achievable by conventional chemistries at the same shear stability level.

After a general introduction of viscometric key properties, the paper describes synthetic pathways towards these novel comb polymers. Standard radical polymerization of polyolefin macromonomers with alkyl methacrylate backbone comonomers is the most straightforward process for their preparation, and allows for an easy transfer to manufacturing. This versatile chemistry enables the design of comb polymers for all kinds of modern base fluids and lubricant applications. The superior viscometric properties of these copolymers are illustrated for selected lube oil formulations such as modern driveline fluids and fuel economy engine oils. The unique viscometric properties of these materials lead to a number of significant performance advantages, for instance improved low temperature viscosity as well as improved efficiency and reduced fuel consumption. Consequently, the novel technology helps meet the stringent current and future requirements of automobile manufacturers regarding fuel economy and CO₂ emissions.