EVOH Resin Pellet Surface Polyene Treatment for Fish Eye Defects

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Solution Overview

Problem

Existing EVOH resin pellets exhibit fish eyes defects during molding due to oxidation and crosslinking, which are not adequately addressed by existing methods, and there is a need for improved gas-barrier performance and appearance in wrapping films.

Innovation Solution

The EVOH resin pellets are treated with a conjugated polyene to achieve a surface concentration of 30ppb or more, which suppresses the occurrence of fish eyes by trapping radicals during the molding process, using a method involving agitation in a water-methanol solution to determine the polyene concentration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If EVOH resin is molded at high temperatures to achieve good gas-barrier performance, then the gas-barrier performance is improved, but oxidation and crosslinking occur causing fish eyes and defects

Engineering Contradiction:

Improvegas-barrier performanceVSAvoidoxidation and crosslinking

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by adding a polymerization inhibitor during the polymerization step before saponification. This inhibitor remains in the final EVOH resin product and acts preemptively to prevent oxidation and crosslinking during subsequent high-temperature molding processes, thereby eliminating fish eyes and defects without compromising gas-barrier performance

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the potentially harmful residual polymerization inhibitor into a beneficial antioxidant that protects the EVOH resin during molding. The inhibitor, which would normally be considered waste or impurity, is instead utilized to trap radicals and prevent harmful oxidation reactions, transforming a negative factor into a protective mechanism

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Object-affected harmful factors

If a polymerization inhibitor is added during polymerization to suppress fish eyes, then the occurrence of fish eyes is reduced, but residual inhibitor may cause odor or exudation in the final product

Engineering Contradiction:

Improvefish eyesVSAvoidodor and exudation

Core Design Contradiction:

Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The patent applies parameter changes by carefully controlling the type and concentration of polymerization inhibitor, as well as the polymerization and saponification conditions. These parameter optimizations ensure sufficient inhibitor remains to prevent fish eyes during molding, while minimizing residual amounts that could cause odor or exudation in the final product

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies local quality by ensuring the inhibitor is distributed throughout the resin matrix at appropriate concentrations. This localized presence of inhibitor provides targeted protection against oxidation at critical points during molding, while the overall distribution and concentration are controlled to prevent excessive residuals that would cause odor or exudation

Inventive Principle:

Principle #3Local quality

3Manufacturing precision

If conjugated polyene is added to suppress fish eyes, then the appearance quality is improved, but the complexity of the production process increases

Engineering Contradiction:

Improveappearance qualityVSAvoidproduction process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent merges the function of polymerization inhibitor and fish-eye suppression agent into a single substance - the conjugated polyene. This compound performs dual functions: inhibiting polymerization during production and suppressing fish eyes during molding. By combining these functions, the patent eliminates the need for separate inhibitor addition steps and complex post-processing, thereby improving appearance quality without significantly increasing production process complexity

Inventive Principle:

Principle #5Merging (Combining)

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 treated EVOH resin pellets significantly reduce the occurrence of fish eyes, meeting strict appearance requirements for wrapping films and maintaining gas-barrier performance, and can be produced using existing manufacturing equipment with minimal process changes.

Implementation Method 1

achieve a surface concentration of 30ppb or more, which suppresses the occurrence of fish eyes by trapping radicals during the molding process

Methodology Applied

Scientific EffectRadical trapping: Absorption (physical)

Implementation Method 2

hydrogen bond is formed between hydroxyl groups in the molecular chain of the EVOH resin to form a crystal part which can prevent oxygen from intruding

Methodology Applied

Scientific EffectHydrogen bonding: Chemical Bonding

Implementation Method 3

saponified ethylene-vinyl ester-based copolymer

Methodology Applied

Scientific EffectSaponification: Hydrolysis

Data Source

PatentEP3375818B1Saponified ethylene-vinyl ester-based copolymer pellet and method for producing same

Publication Date: 2021.06.02 MITSUBISHI CHEM CORP

AI summary

Provided is an EVOH resin pellet which is capable of reducing the occurrence of fish eyes in a melt molded article of an EVOH resin. The occurrence of fish eyes in a melt molded article such as a film that is produced by melt molding using pellets is able to be suppressed by setting the abundance of a conjugated polyene in a surface portion of the pellet to an intended amount or more.