EVA-LLDPE Seal Layer for PET Adhesion and Wide Sealing Window
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Solution Overview
Problem
Heat-sealable films used in packaging, particularly for food, face challenges with limited adhesion to polar substrates like PET and a narrow sealing temperature window, making them difficult to open and seal effectively.
Innovation Solution
A multi-layer film composition comprising 25-80 wt.% EVA and 20-75 wt.% LLDPE, with specific density and melt flow index ranges, enhances adhesion to polar substrates and provides a wide sealing temperature window, allowing for easy opening and strong sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If heat-sealable films of polyolefin materials are used, then the films are easy to open along the seal, but the adhesion to polar substrates such as PET is insufficient
Solution Approach 1:
The patent applies composite materials by creating a seal layer that combines EVA and LLDPE polymers in specific proportions (25-80 wt% EVA and 20-75 wt% LLDPE). This composite composition leverages the polar character of EVA for adhesion to PET substrates while incorporating LLDPE to maintain easy opening properties, thus resolving the contradiction between adhesion and ease of opening.
Solution Approach 2:
The patent applies parameter changes by precisely controlling the compositional parameters (weight percentages of EVA and LLDPE) and physical parameters (density between 0.915-0.927 g/cm³, melt flow index between 2.5-3.5 g/10min) of the seal layer. These parameter optimizations enable the film to achieve both strong adhesion to polar substrates and easy opening characteristics simultaneously.
2Device complexity
If conventional polyolefin seal layers are used, then the film structure is simple, but the sealing temperature window is narrow
Solution Approach 1:
The patent uses composite materials (EVA-LLDPE blend) to broaden the sealing temperature window while keeping the film structure relatively simple. The synergistic effect of the two polymers creates a wider processing window compared to single-polymer systems, achieving versatility without excessive structural complexity.
Solution Approach 2:
The patent applies parameter changes by optimizing the density (0.915-0.927 g/cm³) and melt flow index (2.5-3.5 g/10min) of the seal layer to achieve a broad sealing temperature window of 80-150°C. These controlled parameter variations enable the film to adapt to different sealing conditions while maintaining a straightforward film structure.
3Reliability
If high adhesion to polar substrates is achieved, then the peel strength increases, but the sealing temperature range becomes limited
Solution Approach 1:
The patent resolves this contradiction through parameter changes by controlling the density (0.915-0.927 g/cm³) and melt flow index (2.5-3.5 g/10min) of the seal layer, along with the specific composition ratio of EVA to LLDPE. These optimized parameters enable the film to achieve high adhesion strength (peel strength 1-20 N/15mm) while simultaneously maintaining a broad sealing temperature range of 80-150°C.
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 film achieves improved adhesion to PET substrates and a broad sealing temperature range, ensuring easy opening and strong sealing, with peel strengths between 1-20 N/15 mm at temperatures from 80°C to 150°C, enhancing consumer-friendly packaging solutions.
Implementation Method 1
This may contribute to a good adhesion on polar substrates, such as for example PET substrates
Implementation Method 2
Heat-sealable films are heat sealable-films, which may be heat sealed to themselves or to a substrate
Implementation Method 3
the seal layer comprises or consists of between 25 and 80 wt. % of EVA and between 20 and 75 wt. % of LLDPE
Data Source
AI summary
A multi-layer film for seal-peel applications, an article comprising said film and the use of said film a disclosed. The multi-layer film for seal-peel application comprising at least two layers, namely a cover layer and a seal layer, whereby the seal layer comprises between 25 and 80 wt. % of EVA and between 20 and 75 wt. % of LLDPE based on the total weight of the layer.