Multi-layer film for stretch hooding with optimized core
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Solution Overview
Problem
Current multi-layer films for stretch hood applications lack sufficient holding force and elastic recovery, especially at higher temperatures, which affects their effectiveness in securing palletized loads.
Innovation Solution
A multi-layer film structure comprising at least three layers, with two outer layers and one core layer, where the core layer contains between 25 wt.% and 50 wt.% of a specific ethylene copolymer with a density between 0.850 and 0.915 g/cm³, and optionally polyethylene, enhancing holding force and elastic recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a core layer comprises at least 50 wt.% of an ethylene copolymer having a density of less than 0.910 g/cm³, then the film achieves good elastic recovery, but the holding force deteriorates
Solution Approach 1:
The patent applies local quality by creating distinct layers with different material compositions and properties. The core layer contains ethylene copolymer for elastic recovery, while the skin layer contains polyethylene for holding force. Each layer performs its specific function locally, resolving the contradiction between elastic recovery and holding force.
Solution Approach 2:
The patent uses composite materials by combining ethylene copolymer and polyethylene in a multi-layer structure. The core layer uses ethylene copolymer (5-50 wt% polyethylene) for elasticity, while the skin layer uses polyethylene (50-95 wt%) for holding force, creating a composite structure that achieves both properties simultaneously.
2Force
If the polyethylene content in the core layer is increased to improve holding force, then the holding force improves, but the elastic recovery deteriorates
Solution Approach 1:
The patent segments the film into distinct functional layers: a core layer optimized for elastic recovery (low polyethylene content: 5-50 wt%) and a skin layer optimized for holding force (high polyethylene content: 50-95 wt%). This segmentation allows each layer to excel at its specific function without compromising the other.
Solution Approach 2:
Different polyethylene concentrations are applied locally in different layers. The core layer has low polyethylene content for elasticity, while the skin layer has high polyethylene content for holding force. This local differentiation resolves the contradiction by assigning each property to the appropriate location.
3Force
If a multi-layer structure with optimized composition is used to improve holding force and elastic recovery, then the film performance improves, but the manufacturing complexity increases
Solution Approach 1:
The patent employs a multi-layer composite structure with specific composition ranges: core layer (5-50 wt% polyethylene) and skin layer (50-95 wt% polyethylene). This composite approach achieves superior holding force and elastic recovery while using standard extrusion techniques for manufacturing.
Solution Approach 2:
The patent optimizes performance by controlling specific parameters: polyethylene content in core (5-50 wt%) and skin (50-95 wt%) layers, layer thickness ratios, and material densities. These parameter changes enable tailored performance while maintaining manufacturability through conventional processing.
Data Source
AI summary
The present invention concerns a multi-layer film for stretch hood applications comprising at least three layers, with two outer layers, at least one core layer, preferably exactly one core layer, wherein the core layer comprises between 25 wt. % and < 50 wt. % of a first ethylene copolymer having a density between 0.850 and < 0.915 g/cm3 based on the total weight of the core layer, between 25 wt. % and <50 wt.% of a second ethylene copolymer having a density between > 0.910 g/cm3 and 0.918 g/cm3 based on the total weight of the core layer and between > 0 wt. % and 50 wt.% of polyethylene based on the total weight of the core layer.