Recyclable Multilayer Polyethylene Films via Homogeneity
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Solution Overview
Problem
Current plastic packaging materials that combine multiple polymer types for desirable properties are difficult to recycle, as they complicate the recycling process and limit the range of available properties.
Innovation Solution
Development of mechanically recyclable multilayer polymer films comprising specific layers of single-site catalysed linear low density polyethylene, random propylene-ethylene copolymer, and polypropylene homopolymer, which can be recycled and reused to form new films with suitable properties for packaging applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple polymer types are combined in multilayer films to achieve desired properties (stiffness, toughness, sealing behavior, optical properties), then the range of available properties is improved, but the complexity of recycling the plastic packaging worsens
Solution Approach 1:
The patent applies homogeneity by ensuring all layers in the multilayer film are made from the same polyethylene polymer type (either all LLDPE or all LDPE). This allows the different layers to maintain different functional properties through compositional variations (additives, crosslinking, crystallinity) rather than through polymer type differentiation, thereby enabling recycling as a single polymer stream while still achieving the desired range of properties through controlled variations in layer composition and structure.
2Ease of operation
If a single material solution is used to simplify recycling, then the ease of recycling is improved, but the range of available properties worsens
Solution Approach 1:
The patent applies local quality by creating layers with different local properties (stiffness, toughness, sealing behavior, optical properties) within each layer through variations in composition, additives, crosslinking degree, and crystallinity, while maintaining the overall homogeneity of using a single polymer type throughout the multilayer structure. This allows the film to exhibit diverse properties in different regions/layers without requiring multiple polymer types, thus simplifying recycling while maintaining property diversity.
Solution Approach 2:
The patent applies parameter changes by varying physical and chemical parameters (compositional ratios, additive concentrations, crosslinking levels, crystallinity) within the same polymer type to achieve different layer properties. For example, adjusting the density of polyethylene from 0.910 to 0.940 g/cm³ or varying the melt flow rate creates layers with different mechanical and processing properties, enabling a single polymer material to deliver the property range traditionally requiring multiple polymers.
Data Source
AI summary
Provided are multilayer polymer films comprising LLDPE, LDPE and a random propylene-ethylene copolymer which films suitable for packaging applications and are mechanically recyclable, and to recycled polymer compositions formed by mechanically recycling such films. The recycled polymer compositions may be combined with a polypropylene random copolymer and used to form further polymer films suitable for packaging applications applications.