Modified EVOH Barrier Layer for Hot-Water Sterilized Packaging
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Solution Overview
Problem
Hot-water sterilization of ethylene-vinyl alcohol copolymer (EVOH) packaging materials leads to resin whitening and deterioration in shape retention performance due to moisture permeability, resulting in compromised gas barrier properties.
Innovation Solution
A hot-water sterilized package with a barrier layer containing 96% or more modified EVOH, formulated with specific monomer unit contents and a high degree of saponification, which maintains excellent oxygen barrier properties after sterilization by incorporating a 1,3-diol structure for improved flexibility and hydrogen bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EVOH is used for packaging containers to achieve excellent gas barrier properties, then oxygen barrier performance is improved, but moisture permeation causes resin whitening and deterioration in shape retention after hot-water sterilization
Solution Approach 1:
The invention modifies the chemical structure of EVOH by introducing a 1,3-diol structure through copolymerization, which changes the physical and chemical parameters of the resin. This structural modification reduces moisture permeation and improves shape retention after hot-water sterilization while maintaining oxygen barrier properties
Solution Approach 2:
The invention creates a composite resin system by copolymerizing EVOH with a compound containing a 1,3-diol structure. This composite material combines the excellent oxygen barrier properties of EVOH with the moisture resistance and shape retention characteristics of the 1,3-diol structure
2Strength
If polyimide is added to EVOH composition to improve heat resistance, then shape retention is improved, but moisture permeation increases causing voids and whitening
Solution Approach 1:
Instead of adding polyimide, the invention changes the chemical composition parameters of the EVOH itself by introducing a 1,3-diol structure. This internal modification achieves both improved shape retention and reduced moisture permeation without the harmful side effects of polyimide blending
3Temperature
If the resin composition contains polyimide to solve shape retention issues, then heat resistance is improved, but gas barrier properties are reduced
Solution Approach 1:
The invention modifies the EVOH structure to inherently withstand hot-water sterilization temperatures while maintaining its gas barrier properties, eliminating the need for polyimide addition which would compromise oxygen barrier performance
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 modified EVOH package retains superior oxygen barrier properties post-sterilization, inhibiting content degradation and ensuring long-term quality preservation.
Implementation Method 1
the modified EVOH has a 1,3-diol structure and exhibits excellent oxygen barrier properties by maintaining hydrogen bonding even in a hydrated state
Data Source
AI summary
A hot-water sterilized package includes a container having a barrier layer filled with contents, wherein the barrier layer contains 96 mass % or more of a modified ethylene-vinyl alcohol copolymer based on the resin total, the modified ethylene-vinyl alcohol copolymer is represented by a following formula (I), contents (mol %) of a, b, and c based on the total monomer units satisfy following formulae (1) through (3), a degree of saponification (DS) defined by a following formula (4) is 90 mol % or more, and in measurement using a differential scanning calorimeter (DSC), crystalline melting enthalpy (ΔHA: J/g) during temperature rise in a hydrated state and crystalline melting enthalpy (ΔHB: J/g) during temperature rise after drying and melting followed by rapid cooling satisfy following formulae (5) and (6). A container constituting such a package has excellent in oxygen barrier properties even after hot-water sterilization, and thus degradation of content quality is inhibited for a long period.18≤a≤55 (1)0.01≤c≤20 (2)[100−(a+c)]×0.9≤b≤[100−(a+c)] (3)DS=[(Total Number of Moles of Hydrogen Atoms in X,Y, and Z)/(Total Number of Moles of X,Y, and Z)]×100 (4)ΔHA/ΔHB≥0.5 (5)ΔHB≥70 (6).