Polyethylene Melt Strength via Alkoxy Amine Free Radical Generation

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Solution Overview

Problem

Polyethylene resins, particularly Linear Low Density Polyethylene (LLDPE) and High Density Polyethylene (HDPE), lack sufficient melt strength for applications like large bubble films, blow molding, and extrusion coating, leading to compromised mechanical properties when blended with Low Density Polyethylene (LDPE).

Innovation Solution

Reacting molten polyethylene with a specific alkoxy amine derivative free radical generator during extrusion processing, which increases melt strength by at least 20% through controlled molecular weight enhancement, while maintaining processability and minimizing insoluble material formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If LLDPE or HDPE is used to achieve good mechanical properties, then mechanical strength is improved, but melt strength deteriorates

Engineering Contradiction:

Improvemechanical strengthVSAvoidmelt strength

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent changes the molecular weight distribution parameters of LLDPE by blending it with HDPE of specifically controlled molecular weight (higher than LLDPE) to achieve both good mechanical properties and sufficient melt strength. The HDPE component acts as a melt strength enhancer while the LLDPE provides mechanical strength, creating a synergistic blend.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If LDPE is added to increase melt strength, then melt strength is improved, but mechanical properties deteriorate

Engineering Contradiction:

Improvemelt strengthVSAvoidmechanical strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent replaces LDPE (which provides melt strength but degrades mechanical properties) with HDPE of controlled molecular weight. The HDPE acts as a superior alternative that provides melt strength enhancement without the detrimental effects on mechanical properties, essentially substituting a less effective additive with a more effective one.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If higher molecular weight resin is used to increase melt strength, then melt strength is improved, but processability deteriorates

Engineering Contradiction:

Improvemelt strengthVSAvoidprocessability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies local quality by using a blend of two resins with different molecular weights - LLDPE with lower molecular weight for good processability and HDPE with higher molecular weight for melt strength enhancement. Each component performs its specific function locally within the blend, achieving overall optimization of both processability and melt strength.

Inventive Principle:

Principle #3Local quality

4Strength

If LLDPE content in blend is increased to improve mechanical properties, then mechanical strength is improved, but melt strength deteriorates

Engineering Contradiction:

Improvemechanical strengthVSAvoidmelt strength

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent creates a composite material system by blending LLDPE with HDPE of controlled molecular weight. The composite structure allows the LLDPE to provide mechanical strength while the HDPE provides melt strength enhancement, achieving a synergistic effect that neither component could achieve alone.

Inventive Principle:

Principle #40Composite materials

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 process enhances melt strength and viscosity ratio of polyethylene resins, allowing for higher LLDPE usage in blends, thereby improving mechanical properties without sacrificing processability or creating unacceptable levels of insoluble material.

Implementation Method 1

reacting molten polyethylene with a free radical generator having a peak decomposition temperature within a range from about 150°C to about 280°C and a decomposition energy within a range from about -50 kJoules/mole to about -250 kJoules/mole

Methodology Applied

Scientific EffectFree radical generation through thermal decomposition: Thermolysis

Implementation Method 2

reacting molten polyethylene with a specific alkoxy amine derivative free radical generator during extrusion processing, which increases melt strength by at least 20% through controlled molecular weight enhancement

Methodology Applied

Scientific EffectFree radical reaction with polymer: Chemical Bonding

Data Source

PatentEP2523981B1Method for increasing the melt strength of a polyethylene resin

Publication Date: 2023.05.31 DOW GLOBAL TECHNOLOGIES LLC

AI summary

The present invention is a method for increasing the melt strength of a polyethylene resin comprising reacting the polyethylene resin with a free radical generator with a decomposition energy in between -50 kJoule/mole and -250 kJoules/mole and a peak decomposition temperature of less than 280 degree C. The resulting resin has increased melt strength with higher ratio of elongational viscosities at 0.1 to 100 rad/s when compared to substantially similar polyethylene resins which have not been reacted with a free radical generator such as an alkoxy amine derivative.