EVOH Resin Composition Flexibility Gas Barrier

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Solution Overview

Problem

EVOH resin compositions used in film containers for liquids, such as bag-in-box systems, lack sufficient flexibility and durability, leading to potential pinhole formation due to fatigue accumulation from repeated deformation and poor dispersion of flexible polymers like thermoplastic elastomers and polyolefins.

Innovation Solution

A composition comprising a saponified ethylene-vinyl ester copolymer with 20-60 mol% ethylene content, a styrene-based or olefin-based thermoplastic elastomer, a polar group-modified polymer, and a hydrocarbon-based resin, which allows for fine dispersion of flexible polymers within the EVOH matrix, enhancing flexibility, gas-barrier properties, and transparency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If EVOH resin is used to provide gas-barrier properties, then gas-barrier performance is improved, but flexibility deteriorates

Engineering Contradiction:

Improvegas-barrier propertiesVSAvoidflexibility

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent uses a composite material system consisting of EVOH resin as the continuous phase and block copolymer as the dispersed phase. The EVOH resin provides the gas-barrier properties while the block copolymer domains provide flexibility. This composite structure allows both functions to coexist without compromising either property.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent creates local quality differentiation by forming discrete block copolymer domains within the EVOH matrix. The EVOH continuous phase maintains gas-barrier properties while the localized block copolymer regions provide flexibility. This spatial distribution of different material properties resolves the contradiction between overall gas-barrier performance and local flexibility.

Inventive Principle:

Principle #3Local quality

2Ease of operation

If flexible polymer is added to improve flexibility, then flexibility is improved, but dispersion uniformity deteriorates

Engineering Contradiction:

ImproveflexibilityVSAvoiddispersion uniformity

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The patent segments the flexible polymer into discrete block copolymer domains that are distributed throughout the EVOH matrix. This segmentation prevents aggregation and ensures uniform dispersion. The block copolymer structure with distinct hard and soft segments allows for controlled phase separation while maintaining overall compositional stability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent controls the dispersion uniformity by adjusting parameters such as the molecular weight of the block copolymer, the ratio of hard to soft segments, and the overall composition ratio. By optimizing these parameters, the patent achieves both improved flexibility and uniform dispersion, resolving the contradiction between these two properties.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If block copolymer is added to improve flexibility, then flexibility is improved, but gas-barrier properties may be degraded

Engineering Contradiction:

ImproveflexibilityVSAvoidgas-barrier properties

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent uses a thin-film structure where the EVOH continuous phase forms the primary barrier layer. The block copolymer is incorporated as a dispersed phase within this thin film structure, providing flexibility without creating continuous pathways that would compromise the gas-barrier properties. The thin film architecture allows the EVOH matrix to maintain its protective function while the dispersed block copolymer domains provide the necessary flexibility.

Inventive Principle:

Principle #30Flexible shells and thin films

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 film with improved flexibility, gas-barrier properties, and flex crack resistance, preventing pinhole formation and maintaining transparency even under repeated folding or deformation, while maintaining the inherent gas-barrier properties of EVOH resin.

Implementation Method 1

a polymer modified with a polar group-containing compound

Methodology Applied

Scientific EffectPolar interaction:

Implementation Method 2

acts as a dispersing assistant agent, thereby enabling the flexible polymer to be dispersed finely in the EVOH resin

Methodology Applied

Scientific EffectDispersion: Dispersion (of waves)

Data Source

PatentEP2436728B1EVOH resin composition, and molded article and multilayer structure both comprising same

Publication Date: 2018.01.03 THE NIPPON SYNTHETIC CHEM IND CO LTD

AI summary

Provided is an EVOH resin composition suitable for use as a multilayer structure serving as a material for molded articles, in particular, liquid container such as bags for bag-in-boxes. The EVOH resin composition has such flexibility that even when used in applications where the resin composition is repeatedly folded or deformed over a long period, the resin composition does not develop pinholes or the like, and further has excellent gas barrier properties and melt molding stability.