Comb Polymethacrylate Viscosity Modifiers for Low-Viscosity Engine Oil
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Solution Overview
Problem
Current lubricating oils face challenges in simultaneously achieving wear protection, deposit control, and improved fuel economy, particularly for spark-ignited engines, as additives like organic or organometallic friction modifiers can lead to increased deposit formation and wear, and viscosity modifiers may degrade under high temperature and stress conditions.
Innovation Solution
A lubricating oil composition with a Kinematic Viscosity at 100°C of less than 9.3 mm²/s, comprising a major amount of lubricating viscosity oil, 0.4 wt.% to 2.0 wt.% non-dispersant comb polymethacrylate with a weight average molecular weight of 390,000 to 460,000 g/mol, and 0.08 wt.% to 0.4 wt.% non-dispersant ethylene-based olefin copolymer with a weight average molecular weight of 90,000 to 160,000 g/mol, which provides enhanced anti-wear performance and fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If viscosity is decreased to improve fuel economy, then fuel efficiency improves, but wear protection deteriorates
Solution Approach 1:
The patent changes the chemical structure parameters of the viscosity modifier from conventional linear or star-shaped polymers to a specific comb-shaped architecture with side chains containing aromatic rings. This structural parameter change enables the polymer to maintain effective viscosity modification at lower concentrations, allowing use of lower overall additive packages while maintaining fuel economy benefits. The comb structure with aromatic side chains provides better thermal stability and resistance to shear degradation, maintaining wear protection at lower viscosities.
Solution Approach 2:
The invention uses a composite approach by combining the comb-shaped polymethacrylate viscosity modifier with specific friction modifiers and anti-wear additives in a formulated blend. The viscosity modifier itself has a composite-like structure with a polymethacrylate backbone and aromatic side chains. This composite material approach allows simultaneous achievement of low viscosity for fuel economy and sufficient film strength for wear protection that cannot be achieved with single conventional additives.
2Use of energy by moving object
If organic or organometallic friction modifiers are added to reduce surface friction, then fuel economy improves, but deposit formation increases
Solution Approach 1:
The comb-shaped polymethacrylate acts as an intermediary substance that mediates between the friction modifier's need to adsorb on metal surfaces and the tendency to form deposits. The aromatic side chains of the comb structure provide controlled interaction with metal surfaces, enhancing the effectiveness of friction modifiers at lower concentrations while the polymethacrylate backbone prevents excessive aggregation and deposit formation. This intermediary structure allows friction reduction without the severe deposit problems of conventional friction modifiers.
3Stability of the object's composition
If viscosity modifiers are used to improve viscosity index, then viscosity stability improves, but degradation under high temperature and stress occurs
Solution Approach 1:
The invention fundamentally changes the structural parameters of the viscosity modifier by introducing a comb architecture with aromatic side chains at regular intervals along the polymethacrylate backbone. This structural parameter change dramatically improves thermal stability and resistance to shear degradation. The aromatic rings provide rigid structural support that prevents chain collapse at high temperatures, while the comb structure distributes stress more evenly, reducing degradation under high shear conditions compared to conventional linear viscosity modifiers.
Data Source
AI summary
Provided is a lubricating oil composition, for example a composition having a SAE 0W-20 viscosity grade or lower, comprising: (a) a major amount of an oil of lubricating viscosity, (b) a non-dispersant comb polymethacrylate (PMA), and (c) a non-dispersant ethylene-based olefin copolymer. Also provided is a method for reducing wear in an internal combustion engine by lubricating the engine with the lubricating oil composition.