Viscosity Index Improver Polymer Shear Stability
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Solution Overview
Problem
Conventional viscosity index improvers with low molecular weight compromise viscosity index performance and require higher concentrations, increasing costs, while those with star structures of divinylbenzene core still lack optimal balance between viscosity index and shear stability.
Innovation Solution
A viscosity index improver with a polymer having a weight-average molecular weight of 200,000 to 600,000, number-average molecular weight of 90,000 or more, molecular weight distribution of 4.0 or less, and branching degree of 1.0 or more, obtained by polymerizing monomers in the presence of tri- or higher functional mercaptan and/or initiators, specifically using maleimide and alkyl (meth)acrylate monomers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low molecular weight polymer is used as viscosity index improver, then shear stability is improved, but viscosity index improving effect deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the molecular weight parameters (Mw: 200,000-600,000, Mn: 90,000 or more, Mw/Mn ≤ 4.0) and branching degree (≥1.0) of the polymer to achieve the optimal balance between shear stability and viscosity index improvement. This quantitative parameter optimization resolves the contradiction by finding the specific molecular weight range that simultaneously provides both properties.
Solution Approach 2:
The patent uses composite materials by incorporating polymers with specific molecular weight distributions and branching structures into lubricating oil compositions. The polymer structure combines linear and branched components to achieve both shear stability (from the structured morphology) and effective viscosity index improvement (from the molecular weight characteristics).
2Reliability
If low molecular weight polymer is used to improve shear stability, then amount of viscosity index improver must be increased, but cost increases
Solution Approach 1:
The patent resolves this contradiction through parameter changes by optimizing the polymer's molecular weight and branching degree to achieve high efficiency. The specific parameters (Mw: 200,000-600,000, branching degree ≥1.0) enable the polymer to provide both shear stability and viscosity index improvement at lower concentrations, reducing the amount of additive needed and thereby lowering cost.
3Reliability
If polymer with star structure of divinylbenzene core is used, then shear stability is improved, but compatibility between viscosity index and shear stability is insufficient
Solution Approach 1:
The patent applies parameter changes by transitioning from a qualitative structural description (star structure of divinylbenzene core) to quantitative parameters (Mw: 200,000-600,000, Mn: 90,000 or more, Mw/Mn ≤ 4.0, branching degree ≥1.0). This quantitative approach enables precise control over the polymer's molecular architecture to achieve optimal compatibility between viscosity index improvement and shear stability.
Solution Approach 2:
The patent uses composite materials by creating polymers with complex molecular architectures that combine multiple structural features. The polymer structure integrates branched and linear components with specific molecular weight characteristics to achieve both shear stability and effective viscosity index improvement, resolving the compatibility issue.
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 solution provides a high viscosity index and improved shear stability while ensuring sufficient solubility in lubricating base oils, enhancing the performance of lubricating oil compositions.
Implementation Method 1
a viscosity index improver comprising a polymer which satisfies the following (1) to (4)... obtained by polymerizing a monomer component in the presence of a tri- or higher functional mercaptan and/or a tri- or higher functional initiator
Data Source
AI summary
A viscosity index improver comprising a polymer which has a high viscosity index and good shear stability and which exhibits sufficient solubility in a lubricating base oil, a process for producing the same, and a lubricating oil composition containing the viscosity index improver are provided, wherein the viscosity index improver comprising a polymer satisfying the following (1) to (4): (1) weight-average molecular weight (Mw) of 200,000 or more and 600,000 or less; (2) number-average molecular weight (Mn) of 90,000 or more; (3) molecular weight distribution (Mw/Mn) of 4.0 or less; and (4) branching degree of 1.0 or more.