Uniaxially Stretched EVOH Multilayer Barrier Structure
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Solution Overview
Problem
Existing multilayer structures using EVOH resins for gas barrier properties, such as those described in JP 2022-009162 A and WO 2021/210606 A1, suffer from insufficient barrier properties when carbon-containing silicon oxide vapor-deposited films are formed on biaxially stretched substrates or when using two types of EVOH resins with different ethylene unit contents.
Innovation Solution
A multilayer structure is developed with an extrusion molded and uniaxially stretched EVOH resin layer having a single ethylene unit content, combined with an inorganic vapor-deposited layer, such as alumina or silica, to enhance barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a carbon-containing silicon oxide vapor-deposited film is formed on a biaxially stretched multilayer substrate, then the substrate provides structural stability, but the barrier properties are insufficient
Solution Approach 1:
The patent changes the stretching parameters from biaxial stretching to uniaxial stretching with a stretching ratio of 3 or more times. This parameter change in the processing method creates a molecular orientation that significantly improves oxygen barrier properties while maintaining manufacturability through a modified but still feasible stretching process
Solution Approach 2:
The patent creates a composite structure by laminating an inorganic vapor-deposited layer (silicon oxide or aluminum) on the uniaxially stretched EVOH resin layer. This composite material approach combines the excellent oxygen barrier properties of the stretched EVOH layer with the protective and barrier-enhancing properties of the inorganic vapor-deposited layer
2Reliability
If two types of EVOH resins having different ethylene unit contents are used, then the resin composition can be optimized, but the barrier properties of the vapor-deposited film are likely to be insufficient
Solution Approach 1:
The patent simplifies the resin composition by using a single type of EVOH resin with a specific ethylene unit content (20-40 mol%), rather than mixing two types with different ethylene contents. This parameter specification approach ensures optimal barrier properties while reducing compositional complexity and processing difficulties
Solution Approach 2:
The patent uses a homogeneous EVOH resin composition with a single ethylene unit content range, ensuring uniform molecular structure and consistent barrier properties throughout the layer. This homogeneity improves the effectiveness of the vapor-deposited layer formation and overall 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 proposed multilayer structure achieves excellent barrier properties, particularly in oxygen barrier, by laminating an inorganic vapor-deposited layer on a uniaxially stretched EVOH resin layer, resulting in improved gas barrier performance.
Implementation Method 1
an inorganic vapor-deposited layer (B) adjacent to the layer (A)
Implementation Method 2
the layer (A) is extrusion molded and uniaxially stretched
Data Source
AI summary
A multilayer structure has excellent barrier properties and including: a layer (A) comprising an ethylene-vinyl alcohol copolymer; and an inorganic vapor-deposited layer (B) adjacent to the layer (A). The layer (A) is extrusion molded and uniaxially stretched, and the ethylene-vinyl alcohol copolymer has a single ethylene unit content.