Container Seal Laminate for PET Recycling Integrity
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Solution Overview
Problem
Recycling processes for polyethylene terephthalate (PET) bottles face challenges in separating and cleaning metal foil layers from adhesive residues, as aluminum degrades in caustic baths, leading to undesirable contamination of PET during recycling.
Innovation Solution
A laminate seal structure comprising a plastics top layer, a plastic foam adhesive layer, a foam layer, a foam/foil adhesive layer, and a metal foil with a heat seal layer, where the foam/foil adhesive bond strength is enhanced to prevent metal foil separation and maintain integrity during recycling processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum foil is used in the seal, then induction heat sealing is enabled, but the aluminum degrades in caustic recycling baths, causing contamination of PET and reducing bath life
Solution Approach 1:
The patent extracts the aluminum foil from direct contact with the caustic recycling bath by positioning it within the seal structure that is removed with PET. The aluminum is protected by being encapsulated in the seal laminate, preventing its degradation while maintaining heat sealing functionality. This extraction isolates the harmful effect (aluminum degradation) from the recycling process.
Solution Approach 2:
The patent uses a composite seal structure comprising multiple layers including aluminum foil, foam layer, adhesive layers, and plastics layers. This composite construction protects the aluminum foil from direct exposure to caustic environments while maintaining its heat sealing properties. The composite structure ensures the aluminum remains adhered and does not degrade during recycling.
2Reliability
If the seal is designed with multiple layers for heat sealing, then sealing performance is improved, but the complexity of the seal structure increases
Solution Approach 1:
The patent merges multiple functional layers (aluminum foil for heat sealing, foam layer for cushioning and adhesion, adhesive layers for bonding, and plastics layers for protection) into a single integrated seal structure. This consolidation achieves reliable sealing performance while managing structural complexity through functional integration rather than separate components.
Solution Approach 2:
The seal structure is designed as a multi-functional component where each layer serves multiple purposes: the foam layer provides both cushioning and adhesion surfaces, the adhesive layers bond multiple materials together, and the aluminum foil provides both heat sealing and induction heating capabilities. This multi-functionality reduces the need for additional separate components.
3Stability of the object's composition
If adhesive layers are used to bond the seal layers, then the seal integrity is maintained, but the adhesive residues contaminate PET during recycling
Solution Approach 1:
The patent uses disposable adhesive layers that are designed to be removed with the PET bottle during recycling. These adhesive layers are temporary in nature, serving their bonding function during the seal's service life and then being discarded along with the PET, preventing any residual contamination. The adhesive layers are optimized for their specific bonding function and then discarded.
Solution Approach 2:
The seal structure is designed so that all adhesive layers and non-PET materials are discarded with the PET during the recycling process. The adhesive layers are positioned and formulated to be completely removed in the recycling bath, ensuring no residues remain to contaminate the recovered PET. This discarding approach eliminates adhesive contamination while maintaining seal integrity during use.
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 enhanced bond strength between the foam and foil layers ensures that the metal foil remains adhered to the foam, preventing contamination of PET during recycling and extending the life of recycling baths by resisting degradation in caustic conditions.
Implementation Method 1
a foam/foil adhesive layer which adheres the foam to the foil over substantially the entire area of their mutually facing surfaces with a bond strength of at least 8N/12.5 mm
Implementation Method 2
heat seal layer... for adhering to the mouth of the container... upon melting of the heat sealable layer
Implementation Method 3
a resonance tower extending from the container body away from the seal, the resonance tower having a resonance frequency which isolates the seal from the container body
Data Source
AI summary
A seal for a container for comestibles, especially potable liquids, and in particular for use for sealing polyester containers such as bottles, which is suitable for passage through a PET recycling process, comprises a metal foil layer, a foam layer and a plastics film layer as well as a heat sealable layer below the foil. The foam is selected for its density and thickness so is to confer upon the seal a high buoyancy. The adhesion a between the foam and the foil is increased compared to currently available products, in order to prevent de-lamination between the foil and the foam during the recycling process.