Polyethylene Resin Composition for Moldability and Impact Strength

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Solution Overview

Problem

Conventional ethylene-based resin compositions face challenges in achieving a balance between impact strength, stiffness, and transparency, particularly in molded products with reduced wall thickness, due to limitations in moldability and long-chain branched structure development.

Innovation Solution

A specific polyethylene-based resin composition is developed by blending ethylene-based polymers with specific long-chain branched structures and melt flow rates, optimized using a transition metal-containing catalyst to enhance elongational viscosity and molecular weight distribution, resulting in improved moldability and mechanical properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If high-pressure polyethylene (HPLD) is blended to improve moldability, then flowability is improved, but impact strength is reduced

Engineering Contradiction:

ImprovemoldabilityVSAvoidimpact strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The invention changes the molecular weight distribution parameters of the polyethylene blend, specifically using a narrow MWD component with Mw/Mn ≤ 2.5 and a broad MWD component with Mw/Mn ≥ 3.0, to achieve optimal balance between moldability and impact strength without relying on HPLD

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite resin composition by blending polyethylene resins with different molecular weight distributions (narrow MWD and broad MWD) to achieve synergistic effects that improve both moldability and impact strength, avoiding the use of HPLD

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If ethylene-based polymers with different molecular weights are blended to improve melting characteristics, then moldability is improved, but transparency is worsened

Engineering Contradiction:

ImprovemoldabilityVSAvoidtransparency

Core Design Contradiction:

Ease of manufactureVSIllumination intensity

Solution Approach 1:

The invention optimizes the molecular weight distribution parameters by controlling Mw/Mn ratios and blending ratios to achieve a balance where moldability is improved while transparency is maintained, avoiding excessive broadening of the overall molecular weight distribution

Inventive Principle:

Principle #35Parameter changes

3Strength

If density is reduced to improve impact strength, then impact strength is improved, but stiffness is reduced

Engineering Contradiction:

Improveimpact strengthVSAvoidstiffness

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The invention uses a composite approach by blending resins with different molecular weight distributions to achieve improved impact strength through optimized molecular structure rather than density reduction, thereby maintaining stiffness

Inventive Principle:

Principle #40Composite materials

4Loss of substance

If wall thickness is reduced to save material, then resource usage is improved, but stiffness and impact strength are worsened

Engineering Contradiction:

Improveraw material usageVSAvoidstiffness and impact strength

Core Design Contradiction:

Loss of substanceVSStrength

Solution Approach 1:

The invention changes the molecular weight distribution parameters of the resin composition to achieve better mechanical properties at reduced wall thickness, allowing material savings while maintaining or improving stiffness and impact strength

Inventive Principle:

Principle #35Parameter changes

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 composition achieves excellent molding characteristics, impact strength, and transparency, enabling the production of molded products with reduced wall thickness while maintaining mechanical integrity and optical clarity.

Implementation Method 1

ethylene-based polymer produced by an ethylene polymerization reaction using a transition metal-containing catalyst

Methodology Applied

Scientific EffectCoordination polymerization: Catalysis

Data Source

PatentUS11643485B2Ethylene-based polymer, polyethylene-based resin composition and use thereof, catalyst component for olefin polymerization, olefin polymerization catalyst containing the component, and method for producing ethylene-based polymer by using the catalyst

Publication Date: 2023.05.09 JAPAN POLYETHYLENE CORP

AI summary

An object of the present invention is to provide a polyethylene-based resin composition excellent in the moldability and at the same time, excellent in the balance between impact strength and stiffness as well as in the transparency, and a molded product and a film, which are obtained by the molding of the polyethylene-based resin composition. The polyethylene-based resin composition of the present invention comprises from 41 to 99 wt % of (A) an ethylene-based polymer satisfying specific conditions and from 1 to 59 wt % of (B) an ethylene-based polymer satisfying specific conditions, wherein MFR of the composition as a whole is from 0.05 to 50 g/10 min and the density is from 0.910 to 0.960 g/cm3.