Comb Copolymer Viscosity Modifiers for Lubricant Shear Stability
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Solution Overview
Problem
Current viscosity index improvers for lubricating oils face challenges in achieving a balance between viscosity modification, shear stability, and dispersancy, particularly in maintaining effective performance over a wide temperature range with minimal additive use, while avoiding premature polymer degradation and viscometric detriments from styrenics.
Innovation Solution
A comb copolymer viscosity modifier composed of hydrogenated polybutadiene-based (alk)acrylate ester macromonomer, C3-C8 alkyl (alk)acrylate ester, C12-C24 alkyl (alk)acrylate ester, and C6-C20 aryl- or alkaryl-endcapped oxyalkyl-based (alk)acrylate ester monomers, which are polymerized to create a polymer with specific weight percentages of each repeat unit, excluding styrene and styrenic monomers, to enhance viscosity index and dispersancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional poly(meth)acrylate VIIs are used to increase viscosity index, then viscosity modification is achieved, but shear stability decreases due to chain breakage under high shear
Solution Approach 1:
The patent divides the polymer structure into comb-like architecture with a backbone and multiple side chains. This segmentation creates a structure where the backbone provides shear stability while the side chains contribute to viscosity modification, resolving the contradiction between viscosity index improvement and shear stability
Solution Approach 2:
The invention uses copolymerization of different monomers (styrene, alkyl maleate, and optionally vinyl naphthalene) to create a composite polymer structure. This composite approach allows optimization of both viscosity modification and shear stability properties that cannot be achieved with single monomer systems
2Reliability
If styrene-alkyl maleate copolymers are used to improve viscosity index, then dispersancy is enhanced, but viscometric properties deteriorate at high temperatures
Solution Approach 1:
The patent modifies the chemical parameters of the copolymer by varying the ratio of styrene to alkyl maleate monomers, adjusting the degree of esterification, and controlling molecular weight. These parameter changes allow optimization of both dispersancy and high-temperature viscosity characteristics
Solution Approach 2:
The invention introduces aromatic groups (styrene and/or vinyl naphthalene) at specific locations in the polymer structure to provide dispersancy, while the alkyl maleate portions provide the viscosity modification function. This local differentiation of functions resolves the contradiction between dispersancy and high-temperature viscometric properties
3Temperature
If addition amount of VII is increased to compensate for shear instability, then viscosity modification is maintained, but additive consumption increases
Solution Approach 1:
The patent performs preliminary structural optimization of the polymer by selecting appropriate monomer ratios, molecular weights, and comb-like architecture before use. This preliminary design ensures high shear stability, allowing effective viscosity modification at lower additive concentrations and reducing overall additive consumption
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The comb copolymer achieves improved high-temperature high-shear viscosities, kinematic viscosities, and soot dispersancy across a broad temperature range with reduced additive usage, maintaining stability and performance without premature polymer degradation.
Implementation Method 1
Polyalkyl(alk)acrylates-generally synthesized by simple (free-radical) copolymerization of a mixture of different alkyl (alk)acrylates-may bring about, as additives to lubricating oil basestocks... a rise in viscosity index (VI)
Implementation Method 2
Polyalkyl(alk)acrylates-generally synthesized by simple (free-radical) copolymerization of a mixture of different alkyl (alk)acrylates
Implementation Method 3
a hydrogenated polybutadiene-based (alk)acrylate ester macromonomer
Data Source
AI summary
A comb copolymer viscosity modifier may be made by polymerization comprising at least, or consisting essentially of, the following monomers: (a) (optionally from 7.0 wt% to 18 wt%, by repeat units, of) a hydrogenated polybutadiene-based (alk)acrylate ester macromonomer; (b) (optionally from 33 wt% to 64 wt%, by repeat units, of) a C3-C8 alkyl (alk)acrylate ester monomer; (c) a C12-C24 alkyl (alk)acrylate ester monomer; and (d) (optionally from 3.0 wt% to 25 wt%, by repeat units, of) H-endcapped, C1-C18 alkyl-endcapped, or C6-C20 aryl-, aralkyl-, or alkaryl- endcapped C2-C6 oxyalkyl or C2-C6 oligo(alkylene glycol)-based (alk)acrylate ester monomer, wherein repeat units based on monomer (c) and/or monomer (d) comprise at least 21.0 wt% (and optionally up to 35.0 wt%) of repeat units of the comb copolymer viscosity modifier. Lubricant compositions comprising the comb copolymer viscosity modifier, as well as uses thereof and methods for modifying viscosity and dispersancy, are also contemplated.