Block Arm Star Polymer Lubricant Viscosity Index
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Solution Overview
Problem
Existing lubricating compositions using star polymers often face challenges in achieving optimal viscosity index, low temperature viscometrics, fuel economy, and storage stability, particularly due to the waxy texture and reduced low temperature viscosity performance associated with certain monomer compositions.
Innovation Solution
A lubricating composition comprising an oil of lubricating viscosity and a block arm star polymer with specific monomer ratios and molecular weight distributions, where the polymer has at least three block arms with distinct inner and outer blocks, optimized to provide improved viscosity index, fuel economy, and storage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If C 16-30 alkyl (meth)acrylate monomer is used at 5 weight percent or more to improve viscosity index performance, then viscosity index is improved, but low temperature viscosity performance deteriorates due to waxy texture
Solution Approach 1:
The patent changes the monomer composition parameters by limiting C 16-30 alkyl (meth)acrylate to less than 5 weight percent while increasing C 4-12 alkyl (meth)acrylate content to 65-95 weight percent. This parameter adjustment eliminates the waxy texture problem while maintaining viscosity index improvement, resolving the contradiction between viscosity index and low temperature viscosity performance
Solution Approach 2:
The patent creates a composite polymer structure combining multiple (meth)acrylate monomers with different chain lengths (C 4-12 and C 16-30) in specific ratios. This composite approach allows the shorter chains to prevent wax crystallization while the longer chains provide viscosity index improvement, simultaneously achieving both performance targets
2Quantity of substance
If star polymer with high molecular weight is used to improve viscosity index, then viscosity index is improved, but fuel economy deteriorates due to excessive thickening
Solution Approach 1:
The patent optimizes the molecular weight parameter by specifying number average molecular weight Mn of 5,000-50,000 and weight average molecular weight Mw of 10,000-100,000. This controlled molecular weight range provides sufficient viscosity index improvement while preventing excessive thickening that would harm fuel economy, resolving the contradiction between viscosity index and fuel economy
3Temperature
If polymer with high concentration is used to improve viscosity performance, then viscosity is improved, but storage stability deteriorates due to phase separation
Solution Approach 1:
The patent optimizes the polymer concentration parameter by specifying 0.1-10 weight percent in the lubricating oil composition. This optimized concentration range provides adequate viscosity performance while preventing phase separation and maintaining storage stability, resolving the contradiction between viscosity performance and storage stability
Solution Approach 2:
The patent introduces dispersant units with specific functional groups (carboxyl, hydroxyl, amine) at localized positions within the polymer structure. These dispersant units improve oil solubility and prevent phase separation at the molecular level, enabling the use of higher polymer concentrations without sacrificing storage stability
Data Source
AI summary
The present invention relates to a lubricating composition containing an oil of lubricating viscosity and a star polymer that has at least two inner blocks, at least one of which is in turn bonded to one or more outer blocks. The invention further relates to methods of lubricating a mechanical device with the lubricating composition.