Uniaxially Stretched EVOH Multilayer for Oxygen Barrier Films
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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, exhibit insufficient barrier properties when vapor-deposited films are formed on biaxially stretched substrates or when using EVOH resins with different ethylene unit contents.
Innovation Solution
A multilayer structure is developed with an extrusion molded and uniaxially stretched EVOH resin layer containing a single ethylene unit, laminated 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 film can be formed, but the barrier properties become insufficient
Solution Approach 1:
The patent changes the stretching parameters from biaxial to uniaxial direction, which fundamentally alters the molecular orientation and crystalline structure of the EVOH resin. This parameter change creates a more favorable substrate for vapor-deposited films, resulting in improved barrier properties while maintaining manufacturability through the uniaxial stretching process
Solution Approach 2:
The patent creates a composite structure combining uniaxially stretched EVOH resin with inorganic vapor-deposited layers (such as silicon oxide, aluminum oxide, or their combinations). This composite approach leverages the advantages of both materials: the EVOH provides mechanical strength and processability, while the inorganic layer provides enhanced barrier properties against gases and moisture
2Reliability
If two types of EVOH resins having different ethylene unit contents are used, then the film can be formed, but the barrier properties become insufficient
Solution Approach 1:
The patent focuses on optimizing the EVOH resin with a specific ethylene unit content (30-70 mol%) rather than using multiple resin types. This local optimization of a single material's composition creates uniform molecular structure and crystalline morphology, which provides consistent and superior barrier properties compared to composite resin systems
Solution Approach 2:
The patent employs a single EVOH resin type with uniform ethylene unit content throughout the film, ensuring homogeneous molecular structure and consistent barrier properties. This homogeneity eliminates the variability and potential interface defects that arise from using multiple resin types with different crystalline structures
3Reliability
If uniaxially stretched EVOH resin with single ethylene content is used, then excellent barrier properties are achieved, but the manufacturing process becomes more specific
Solution Approach 1:
The patent incorporates the vapor-deposited layer formation into the extrusion molding process itself, where the EVOH resin is extruded and uniaxially stretched to the desired dimensions before the inorganic layer is deposited. This preliminary action of forming the substrate in the correct configuration ensures optimal barrier properties while streamlining the overall manufacturing process
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 structure achieves excellent oxygen barrier properties with improved gas barrier performance, particularly when the EVOH resin layer is uniaxially stretched and combined with an inorganic vapor-deposited layer, reducing oxygen permeability.
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
Implementation Method 3
an EVOH resin exhibits a very strong intermolecular force due to hydrogen bonding between hydroxyl groups present in the polymer side chains
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.