Oriented Multilayer Polyethylene Films for Recyclable Packaging
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Solution Overview
Problem
Current multilayer films and laminates used in packaging face challenges in achieving desired physical and optical properties while being fully recyclable, as they often require multiple resin types, leading to recycling complexities and increased costs due to the need for multiple collection streams.
Innovation Solution
The development of oriented multilayer films comprising layers of polyethylene with specific density ranges and ethylene:C4-C12 alpha-olefin copolymers, which are recyclable in a single collection stream, maintains optical and mechanical properties by adjusting layer distribution and density, reducing blocking issues during the directional orientation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multilayer films are made with multiple resin types to achieve desired physical and optical properties, then film performance is improved, but recyclability deteriorates due to requiring multiple collection streams
Solution Approach 1:
The patent applies homogeneity by making all layers of the multilayer film from polyethylene resin, creating a homogeneous material composition throughout the film structure. This allows the entire film to be recycled through a single collection stream while maintaining the multilayer structure needed for desired physical and optical properties.
2Quantity of substance
If film thickness is reduced to decrease cost and material usage, then cost is reduced, but stiffness and utility are lost
Solution Approach 1:
The patent uses composite materials by combining multiple polyethylene layers with different densities (HDPE, MDPE, LDPE) to create a multilayer film structure. This composite approach allows thinning of the overall film while maintaining stiffness through the strategic placement of higher density layers that provide structural support.
Solution Approach 2:
The patent applies local quality by assigning different resin densities to different layers based on their functional requirements. The HDPE layer provides stiffness and structural support where needed, while LDPE layers provide flexibility and sealability in other regions, allowing the film to be thinner overall while maintaining necessary mechanical properties.
3Strength
If directional orientation process is used to improve film properties including modulus and tensile strength, then mechanical properties are improved, but blocking occurs during the process
Solution Approach 1:
The patent applies parameter changes by carefully controlling the density parameters of the polyethylene resins used in each layer. The specific density ranges (HDPE: 0.94-0.97 g/cm³, MDPE: 0.926-0.94 g/cm³, LDPE: 0.91-0.925 g/cm³) are selected to optimize the film's resistance to blocking during directional orientation while achieving the desired mechanical properties.
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
This approach enables the production of films with enhanced mechanical and optical properties, improved recyclability, and cost-effectiveness by using a single type of resin, addressing the limitations of existing multilayer films and laminates.
Implementation Method 1
The directional orientation process in which an extruded film is heated to a temperature below the melting point (Tm) and stretched in a particular direction
Implementation Method 2
stretched in a particular direction. Generally this is in the machine direction (MD) or perpendicular to the machine direction, the transverse direction (TD)
Data Source
AI summary
The present disclosure provides oriented multilayer films including a first layer, a second layer disposed on the first layer and a third layer disposed on the second layer, where the first layer and the third layer include a polyethylene independently selected from (i) a polyethylene having a density of about 0.94 g/cc or greater; (ii) a polyethylene copolymer including ethylene and a C4-C12 alpha-olefin and having a density 7 from about 0.927 g/cc to about 0.95 g/cc; or (iii) a mixture thereof, and at least one of the first layer or the third layer includes the polyethylene copolymer, the second layer includes a polyethylene composition having a density of about 0.91 g/cc or greater and the oriented multilayer film has a haze of about 10% or less and a 1% secant modulus in the direction of stretching of about 500 MPa or greater.