Multi-layer film with HDPE outer layers for heat sealing
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Solution Overview
Problem
Multi-layer films used in packaging often lack improved heat sealing and hot tack properties, which are crucial for efficient film joining techniques.
Innovation Solution
A 5-layer film structure comprising linear low density polyethylene as outer layers, low density polyethylene as the core layer, and high density polyethylene as intermediate layers, with specific density and melt flow index ranges, enhances heat sealing and hot tack properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If multi-layer films are used to reduce film thickness and material usage, then sustainability is improved, but heat sealing and hot tack properties are insufficient
Solution Approach 1:
The patent applies local quality by assigning different polymer densities to different layers of the multi-layer film. The outer layers use high density polyethylene (HDPE) with density ≥0.940 g/cm³ to provide excellent heat sealing and hot tack properties, while the core layer uses low density polyethylene (LDPE) with density ≤0.930 g/cm³ to maintain flexibility and reduce overall film thickness. This localized differentiation of material properties allows the film to achieve both reduced material usage and improved sealing performance.
Solution Approach 2:
The patent employs composite materials by combining multiple polymer types with different densities in a multi-layer structure. The specific combination of HDPE outer layers (≥0.940 g/cm³), intermediate layers (0.925-0.935 g/cm³), and LDPE core layer (≤0.930 g/cm³) creates a composite film structure that leverages the advantages of each material: HDPE provides superior heat sealing, while LDPE contributes to film flexibility and reduced thickness, achieving both sustainability goals and functional performance.
2Loss of substance
If film thickness is reduced to use less material, then sustainability is improved, but mechanical strength and sealing performance deteriorate
Solution Approach 1:
The patent applies local quality by concentrating high density polyethylene (HDPE) with density ≥0.940 g/cm³ in the outer layers specifically where heat sealing and mechanical strength are most critical. The core layer uses lower density LDPE (≤0.930 g/cm³) to minimize thickness while maintaining flexibility. This localized optimization allows the film to achieve reduced overall thickness without compromising the mechanical strength and sealing performance at critical interfaces.
Solution Approach 2:
The patent segments the film into distinct functional layers with specific density requirements: outer layers (HDPE, ≥0.940 g/cm³) for strength and sealing, intermediate layers (0.925-0.935 g/cm³) for transition, and core layer (LDPE, ≤0.930 g/cm³) for thickness reduction. This segmentation allows each layer to be optimized for its specific function, enabling the overall film to be thinner while maintaining necessary mechanical properties through the high-density outer layers.
Data Source
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AI summary
The present invention concerns a multi-layer film comprising at least five layers, comprising two outer layers, at least one core layer and at least one intermediate layer located between each outer layer and the core layer, wherein both outer layers comprise linear low density polyethylene substantially free of long chain branching and having a density above 915 kg/m3, wherein the amount of linear low density polyethylene in at least one or in both outer layers is preferably at least 60% by weight based on the total weight of the respective layer and at least one of either the core layer or at least one intermediate located between each outer layer and the core layer consists essentially of polyolefins and comprises high density polyethylene.