EVOH Resin Composition for Flexible Gas Barrier Packaging
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Solution Overview
Problem
Existing resin compositions for packaging materials, medical infusion bags, and tire tubes face challenges in achieving a balance between gas barrier properties and flexibility, and often require additional adhesive layers when integrated with polyolefin layers, which complicates the molding process.
Innovation Solution
A resin composition comprising an ethylene-vinyl alcohol copolymer and a block copolymer with a vinyl aromatic monomer unit and an isobutylene unit, forming a co-continuous phase structure, which exhibits superior gas barrier properties, flexibility, and adhesiveness to polyolefin layers without the need for additional adhesives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ethylene-vinyl alcohol copolymer is used as a gas barrier layer, then gas barrier properties are improved, but flexibility is insufficient and adhesive layers are required when combined with polyolefin
Solution Approach 1:
The patent uses a composite material system consisting of ethylene-vinyl alcohol copolymer (EVOH) as the gas barrier layer and polyolefin as the flexible outer layer. This composite structure allows each layer to contribute its superior properties: EVOH provides excellent gas barrier properties while polyolefin provides flexibility and processability. The combination resolves the contradiction by distributing functions across different materials rather than requiring a single material to excel at both properties simultaneously.
Solution Approach 2:
The patent introduces an adhesive layer as an intermediary between the EVOH gas barrier layer and the polyolefin flexible layer. This adhesive mediator enables proper bonding between the two layers, allowing the gas barrier layer to maintain its integrity and performance while being integrated with the flexible polyolefin layer. The adhesive resolves the adhesion problem that would otherwise prevent effective combination of these two materials.
2Ease of operation
If NR or IIR is used for packing material, then flexibility is improved, but gas barrier properties are insufficient for long term storability
Solution Approach 1:
The patent creates a composite structure where polyolefin (NR or IIR) provides the flexible matrix and EVOH provides the gas barrier function. This composite approach allows the material to exhibit both the flexibility needed for processing and handling, and the gas barrier properties required for long-term storability. The multi-layer composite resolves the contradiction by assigning different functional requirements to different materials within the same product.
3Ease of operation
If vinyl chloride is used for medical infusion bags, then flexibility and gas barrier properties are improved, but environmental harm increases due to chlorine content
Solution Approach 1:
The patent extracts the harmful chlorine element from the material composition by replacing vinyl chloride with polyolefin and EVOH. This substitution removes the source of environmental harm (chlorine atoms that generate hydrogen chloride during incineration) while maintaining the desired functional properties of flexibility and gas barrier performance through the composite material system.
Solution Approach 2:
The patent adopts polyolefin and EVOH materials that are environmentally friendly and suitable for disposable applications. These materials can be safely incinerated without generating harmful chlorine-based emissions, making them appropriate for single-use medical products like infusion bags where sterilization and disposal are critical concerns.
4Ease of operation
If thermoplastic elastomers SEBS or SEPS are used, then flexibility is improved and vulcanizing step is eliminated, but gas barrier properties become insufficient
Solution Approach 1:
The patent combines thermoplastic elastomer (SEBS or SEPS) as the flexible matrix with EVOH as the gas barrier layer. This composite structure allows the thermoplastic elastomer to provide ease of processing and flexibility without requiring vulcanization, while the EVOH layer simultaneously provides the necessary gas barrier properties. The composite approach resolves the contradiction by distributing functional requirements across multiple materials.
Data Source
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AI summary
A resin composition according to an aspect of the present invention comprises: an ethylene-vinyl alcohol copolymer (A); and a block copolymer (B) having a block (b1) that includes a vinyl aromatic monomer unit, and a block (b2) that includes an isobutylene unit, wherein the ethylene-vinyl alcohol copolymer (A) and the block copolymer (B) form a co-continuous phase structure; and a DSC curve obtained following heating the resin composition up to a melting point and cooling at a rate of 50 °C/min in a differential scanning calorimetry analysis shows two peaks, with a higher peak top temperature falling within a range of 130 °C or greater and 170 °C or less, and a lower peak top temperature falling within a range of 100 °C or greater and less than 130 °C. A resin composition may thus be obtained that is able to give a molded article that is superior in balance between gas barrier properties and flexibility.