Multilayer Polyethylene Films for Recyclable Packaging
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Solution Overview
Problem
Existing multilayer films used in packaging, composed of different polymeric materials, face challenges in recyclability due to material dissimilarity, and often compromise on mechanical and barrier properties when trying to improve recyclability.
Innovation Solution
Development of multilayer films comprising specific combinations of polyethylene compositions, including a first polyethylene composition with a high density and low branching, and a second polyethylene composition with a narrower peak width and higher molecular weight distribution, to enhance dart performance, modulus, and gas barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different polymeric materials are combined to achieve a balance of properties, then mechanical properties and barrier properties are improved, but recyclability deteriorates
Solution Approach 1:
The patent applies homogeneity by using multiple polyethylene compositions (all polyethylene structures) instead of combining dissimilar polymeric materials. This maintains material uniformity which improves recyclability while still achieving the desired balance of mechanical properties and barrier properties through careful selection of polyethylene densities and molecular weights.
Solution Approach 2:
The patent employs parameter changes by varying the density, molecular weight, and composition ratios of polyethylene fractions within the multilayer film structure. By adjusting parameters such as the ratio of first to second polyethylene fractions and their respective density ranges, the invention optimizes both performance properties and recyclability without introducing materially dissimilar components.
2Strength
If polyethylenes having lower densities are used, then mechanical properties such as dart impact resistance are improved, but other properties such as secant modulus and gas barrier properties deteriorate
Solution Approach 1:
The patent applies composite materials by combining multiple polyethylene fractions with different density ranges and molecular weight characteristics within the same layer or across different layers. The first polyethylene fraction (0.935-0.947 g/cm³) provides impact resistance while the second polyethylene fraction (0.965-0.976 g/cm³) provides modulus and barrier properties, creating a composite structure that achieves all desired properties simultaneously.
Solution Approach 2:
The patent employs local quality by assigning different polyethylene fractions to specific layers or regions within the multilayer film structure. Different regions can be optimized for specific functions: lower density fractions in layers requiring impact resistance and higher density fractions in layers requiring barrier properties and structural stiffness, allowing each local region to have the optimal material properties for its function.
Data Source
AI summary
The present invention relates to multilayer films. In one aspect, a multilayer film comprises a first polyethylene composition having a density of at least 0.965 g/cm3 and as further described herein and a second polyethylene composition having a density of 0.924 g/cm3 to 0.936 g/cm3 and as further described herein, wherein the multilayer film comprises 40 weight percent or less of the first polyethylene composition based on the total weight of the multilayer film.