Multilayer Peelable Film Structure for Flexible Packaging
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Solution Overview
Problem
Current peelable films for flexible packaging face challenges such as high resin prices, processing complexities, and optical issues due to tackiness and stickiness, especially when sealing non-polyolefinic substrates like PET, which affects the transparency and operational efficiency of packaging, particularly in bulk fresh-food and medical device markets.
Innovation Solution
A multilayer peelable film structure comprising a rupturable polyester-based inner sealant layer, an adhesive layer with specific polymers like ionomers or maleic anhydride grafted polyolefin, a gas-barrier layer, and an outer sealant layer, designed to achieve a controlled peel strength and delamination for easy opening without compromising transparency or operational performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If functionalized polymers (ionomers, grafted polymers) are used to seal onto non-polyolefinic substrates like PET, then adhesion to the substrate is improved, but the film becomes sticky and soft, causing processing difficulties and blocking issues
Solution Approach 1:
The patent divides the sealing system into two separate layers: a polyolefinic sealant layer for easy processing and a functionalized polymer layer for substrate adhesion. This segmentation allows each layer to perform its specific function without the drawbacks of combining both properties in a single material.
Solution Approach 2:
The patent applies different material properties to different layers of the packaging structure. The outer sealant layer uses polyolefin for processing ease, while the inner adhesive layer uses functionalized polymer for substrate bonding. This local differentiation of material qualities resolves the contradiction between adhesion and processability.
2Reliability
If high co-monomer content polymers are used to increase adhesion, then sealing performance on non-polyolefinic substrates is improved, but the film becomes excessively sticky, requiring anti-blocking agents that compromise transparency
Solution Approach 1:
The patent separates the sealing and adhesive functions into different layers, allowing the use of polyolefin (which maintains transparency) for sealing while using functionalized polymer for adhesion. This avoids the need for anti-blocking agents that would compromise optical properties.
Solution Approach 2:
The patent uses a thin layer of functionalized polymer specifically for its adhesive function, accepting that this layer will be consumed during the peeling process. This allows the use of materials optimized for adhesion without concern for their long-term optical properties, as the functionalized layer is designed to delaminate cleanly.
3Ease of operation
If polyolefinic incompatible blends are used to achieve peelable seals, then easy opening is obtained with cohesive failure, but a visible peel trace remains on both separated films
Solution Approach 1:
Instead of achieving peelability through cohesive failure within a single layer (which leaves traces), the patent inverts the approach by designing for adhesive failure at the interface between layers. The functionalized polymer layer is intentionally designed to delaminate from the polyolefinic sealant layer, transferring the peel trace to the functionalized layer rather than the visible polyolefinic layer.
4Ease of manufacture
If the peelable film structure is simplified to reduce costs, then manufacturing cost is reduced, but the ability to seal onto non-polyolefinic substrates like PET is compromised
Solution Approach 1:
The patent creates a multi-functional film structure where the polyolefinic sealant layer provides universal processing compatibility and ease of manufacture, while the functionalized polymer layer provides universal substrate adhesion capability. This combination allows the packaging to work with various substrates (polyolefinic and non-polyolefinic) without requiring completely different material systems.
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 solution provides a cost-effective, efficient, and transparent peelable film that maintains high clarity and operational efficiency, reducing the risk of product sticking and improving packaging quality by controlling peel strength and delamination, thus addressing the limitations of existing technologies.
Implementation Method 1
an adhesive layer in contact with said rupturable layer
Data Source
Figure 1~2
Figure 3
AI summary
The present invention is related to a flow pack comprising a peelable film, said film comprising a coextruded multilayer structure, said structure comprising: - a rupturable polyester-based inner sealant layer (1); - an adhesive layer (2) in contact with said rupturable layer, comprising a polymer selected from the group consisting of ionomers, maleic anhydride grafted polyolefin, EVA, EBA, EMA and EAA; - a gas-barrier layer (3) in contact with said adhesive layer (2), comprising a gas-barrier polymer selected from the group consisting of polyester, EVOH and polyamide, - an outer sealant layer comprising a polymer selected from the group consisting of amorphous polyester, copolymer of PET, and polyvinyl chloride, characterised in that the average peel strength (10) between the adhesive layer (2) and the inner sealant layer(1) is lower than 15N/15mm, preferably lower than 13N/15mm as measured in a 180° peel geometry.