Water-Soluble PVOH Interlayer for Multilayer Packaging Recycling
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Solution Overview
Problem
Existing multilayer composite materials face challenges in complete separation of layers during recycling, leading to contamination and reduced recyclability, particularly due to non-removable barrier coatings, and insufficient oxygen barrier properties in packaging applications.
Innovation Solution
Incorporating a polyvinyl alcohol (PVOH) intermediate layer with at least 98 wt.% solubility in water at 40°C, which allows complete detachment of layers during cold washing, maintaining gas barrier functionality and enabling high purity recyclates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If barrier coatings are applied to achieve high oxygen transmission resistance, then oxygen barrier properties are improved, but complete removal during recycling becomes difficult
Solution Approach 1:
The packaging structure is divided into distinct layers with specific functions: a carrier material layer, a PVOH intermediate layer, and a barrier coating layer. This segmentation allows the barrier coating to be applied only where needed while maintaining the ability to separate layers during recycling through the soluble PVOH intermediate layer.
Solution Approach 2:
A PVOH intermediate layer is introduced between the carrier material and the barrier coating. This intermediate layer serves as a mediator that can be completely removed during recycling through cold water washing, enabling complete separation of the barrier coating from the carrier material while maintaining the barrier coating's functionality during use.
2Reliability
If multiple layers are combined to achieve necessary barriers, then protection against water/vapor and gases is improved, but complete separation during recycling becomes difficult
Solution Approach 1:
The PVOH intermediate layer acts as a removable intermediary between different functional layers (carrier material and barrier coating). During use, it maintains the integrity of the multilayer structure providing necessary barriers. During recycling, it dissolves in cold water, enabling complete separation of adjacent layers without contamination.
Solution Approach 2:
The PVOH intermediate layer undergoes a parameter change from a solid adhesive state during use to a dissolved state during recycling. Its water solubility at ambient temperatures allows it to transition from maintaining layer integrity to enabling complete layer separation, achieving both protection and recyclability.
3Strength
If adhesives are used to hold layers together, then layer bonding is improved, but complete detachment during recycling is difficult
Solution Approach 1:
The PVOH intermediate layer functions as a disposable bonding element that is intentionally designed to be temporary. During use, it provides sufficient adhesion to hold layers together. During recycling, it is completely dissolved and removed, allowing complete detachment of layers without leaving residues that would contaminate recyclates.
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
Enables efficient separation of layers without contamination, achieving high purity recyclates and maintaining oxygen barrier properties, suitable for food packaging applications.
Implementation Method 1
the intermediate layer contains at least 98 wt.％ polyvinyl alcohol and is soluble in water at a maximum temperature of 40°C
Data Source
AI summary
The invention relates to the use of a polyvinyl acetate intermediate layer for the production of a multilayer composite material and the multilayer material containing such an intermediate layer for improved separation of two adjacent layers in recycling processes.