Diblock Polymer Viscosity Modifiers for Engine Oil Fuel Economy

Solution Overview

Problem

Existing viscosity index modifiers for lubricating oils face challenges in achieving optimal fuel economy across a broad temperature range due to issues with shear stability and thickening efficiency, leading to inadequate performance at both high and low temperatures.

Innovation Solution

A diblock polymer with a specific block structure, comprising a polyethylene-rich A block and an ethylene-alpha-olefin B block, is developed, which provides improved shear stability and thickening efficiency by forming reversible associations that break under high shear conditions, optimizing viscosity characteristics across a broader temperature range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If Viscosity Index Improver polymer with good shear stability is used at higher concentrations, then shear stability is improved, but thickening at low temperatures becomes unacceptable

Engineering Contradiction:

Improveshear stabilityVSAvoidlow temperature thickening

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The polymer is divided into two distinct blocks: Block A (70-85 wt%) with high ethylene content providing shear stability, and Block B (15-30 wt%) with lower ethylene content controlling low-temperature thickening. This segmentation allows each block to independently contribute its specific functionality, resolving the contradiction between shear stability and low-temperature performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the polymer molecule are given different properties: Block A has high ethylene content (85-95%) for shear stability while Block B has lower ethylene content (65-85%) for low-temperature behavior. This local differentiation of properties within the single polymer molecule enables simultaneous optimization of both contradictory requirements.

Inventive Principle:

Principle #3Local quality

2Ease of operation

If lower concentrations of reduced shear stability VI-improving polymers are used, then low temperature performance is improved, but high temperature viscosity decreases significantly with use

Engineering Contradiction:

Improvelow temperature performanceVSAvoidhigh temperature viscosity

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The polymer is divided into two distinct blocks: Block A (70-85 wt%) with high ethylene content providing shear stability, and Block B (15-30 wt%) with lower ethylene content controlling low-temperature thickening. This segmentation allows each block to independently contribute its specific functionality, resolving the contradiction between shear stability and low-temperature performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the polymer molecule are given different properties: Block A has high ethylene content (85-95%) for shear stability while Block B has lower ethylene content (65-85%) for low-temperature behavior. This local differentiation of properties within the single polymer molecule enables simultaneous optimization of both contradictory requirements.

Inventive Principle:

Principle #3Local quality

3Loss of energy

If lowering the viscosity of engine oil is done to reduce internal friction, then fuel economy is improved, but oil film thickness decreases leading to increased wear

Engineering Contradiction:

Improveinternal frictionVSAvoidwear

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The polymer provides dynamic viscosity modification where the polymer coils remain compact at high temperatures (reducing viscosity and friction) but expand and associate at lower temperatures (increasing viscosity and film thickness). This dynamic adaptation to temperature conditions allows the oil to simultaneously achieve low friction at operating temperature and adequate film thickness for wear protection.

Inventive Principle:

Principle #15Dynamics

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 diblock polymer achieves enhanced fuel economy by maintaining low HTHS viscosity at elevated temperatures, reducing engine wear, and promoting fuel efficiency through reduced friction, as demonstrated by improved Fuel Economy Index values compared to reference polymers.

Implementation Method 1

provides improved shear stability and thickening efficiency by forming reversible associations that break under high shear conditions

Methodology Applied

Scientific EffectReversible associations:

Implementation Method 2

impart a non-Newtonian fluid property to the oil composition since the viscosity varies with the shear rate

Methodology Applied

Scientific EffectShear thinning: Shear Thinning

Implementation Method 3

maintaining low HTHS viscosity at elevated temperatures, reducing engine wear, and promoting fuel efficiency through reduced friction

Methodology Applied

Scientific EffectHigh Temperature High Shear viscosity control:

Data Source

PatentUS8105992B2Viscosity index modifiers and lubricant compositions containing such viscosity index modifiers

Publication Date: 2012.01.31 EXXONMOBIL CHEMICAL PATENTS INC

AI summary

The invention relates to viscosity modifier polymers, concentrate and lubricant formulations utilizing a diblock polymer having one block A and one block B, block A contributing from 15 to 30% of the total chain length and block B from 70 to 85% of the total chain length, wherein block A comprises at least 93 wt % of ethylene and at least one other alpha-olefin and block B comprises an ethylene content between 40 and 75 wt % and at least one other alpha-olefin and wherein the resulting block copolymer has an average ethylene content of between about 60 wt % to 80 wt % ethylene, a fast Gaussian NMR relaxation signal between 17 and 22% and a slow exponential NMR relaxation signal between 58 and 68% of the total NMR relaxation signal, a SSI of at least 35% and a TE of at least 3.5 in order to obtain improvements in fuel economy.