Multilayer Stretch Film Composition for Material Savings
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Solution Overview
Problem
Current multilayer stretch film production methods face challenges in achieving optimal performance properties such as stretchability, adhesion, and dart impact resistance while maintaining a small thickness, which requires precise control over layer composition, sequence, and thickness to achieve material savings.
Innovation Solution
A multilayer stretch film composition consisting of at least 7 layers, including a central layer, 2 outer layers, 2 blocks of microlayers, and intermediate layers, with specific polymer compositions and densities, where the main component is linear low-density polyethylene, and incorporating polypropylene and elastomers, with the option of using recycled materials, to achieve enhanced performance and reduced thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the number of layers is increased to improve performance properties (strength, impact resistance, stretchability), then the film thickness can be reduced, but the manufacturing complexity increases
Solution Approach 1:
The film is divided into multiple functional layers (5-2000 layers) with specific compositions - inner layers containing adhesive promoters for substrate bonding, outer layers providing protective and aesthetic properties, and intermediate layers offering mechanical strength. This segmentation allows each layer to be optimized for its specific function, achieving high performance while managing manufacturing complexity through standardized layer types.
Solution Approach 2:
The patent employs composite material structures where different polymer materials are combined in specific layers - including polyolefins, polyesters, polyamides, and adhesive-containing layers. Each material is selected for its specific properties (adhesion, strength, flexibility), and their combination creates a multifunctional film that achieves superior performance characteristics while maintaining manageable manufacturing processes.
2Loss of substance
If the film thickness is reduced to achieve material savings, then the performance properties (adhesion, stretchability, dart impact resistance) deteriorate, but increasing thickness consumes more material
Solution Approach 1:
Different regions of the film (inner layers vs. outer layers) are assigned different material compositions and thicknesses based on their specific functional requirements. Inner layers closer to the substrate receive higher concentrations of adhesive promoters and specific polymers optimized for bonding, while outer layers use materials optimized for protection and aesthetics. This local optimization allows the film to achieve high performance in critical areas while minimizing material usage overall.
Solution Approach 2:
The patent systematically varies material composition parameters, layer thickness parameters, and adhesive promoter concentration parameters across different layers to optimize performance. By adjusting these parameters locally rather than uniformly throughout the film, the invention achieves high adhesion, stretchability, and dart impact resistance with reduced overall material consumption.
3Ease of operation
If multiple layers with different compositions are used to improve performance, then the adhesion and stretchability are enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent develops standardized layer types that can serve multiple functions - for example, intermediate layers that provide both mechanical strength and contribute to overall film flexibility, or outer layers that simultaneously provide protection, aesthetics, and environmental resistance. This multi-functionality reduces the total number of distinct layer types needed, simplifying the manufacturing process while maintaining enhanced adhesion and stretchability 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
The described film composition results in films with excellent performance properties, including improved adhesion and stretchability, while maintaining a small thickness, leading to significant material savings and effective use in various industries.
Implementation Method 1
heating and mixing the materials in the extruder
Implementation Method 2
melts and mixes polymer materials
Implementation Method 3
extruded by flat and narrow slit or slits
Implementation Method 4
having left the slits the film is stretched and cooled down on rotating rollers
Data Source
AI summary
Multilayer film consisting of at least 5 layers with 50-95 % content of linear low-density polyethylene (LLDPE) from synthesis on Ziegler-Natta-type catalyst, metallocene catalyst or post-metallocene catalyst with specific density ranging from 0.910 to 0.935 g/cm3 and mass flow rate ranging from 0.5 to 10 g/10 min (190 °C, 2.16 kg) is characterised by at least one of the layers containing 50-99 % of the copolymer of propylene with ethylene with the ethylene content of 1-10 % mixed with 1-50 % of other copolymer of propylene with ethylene with the ethylene content ranging from 3 to 20 % or with elastomer. At least one of the layers contains the linear low-density polyethylene (LLDPE) with specific density ranging from 0.910 to 0.935 g/cm3 and mass flow rate ranging from 0.5 to 10 g / 10 min (190 °C, 2.16 kg) and 1-10 % of copolymer of propylene or elastomer. At least 1 layer may contain the mixture of the copolymer of polypropylene with ethylene and the copolymer of polypropylene with α-olefin such as butene, hexene or octene, with the propylene content ranging from 50 to 99 %. At least 1 layer may contain the mixture of the copolymer of polypropylene with ethylene and the terpolymer of propylene with ethylene and butene with the propylene content ranging from 50 to 99 %. The total percentage of intermediate layers (between the most middle and the outer layers) compared to the entire film volume ranges from 50 to 80 %. In the film there might be two blocks of thin layers and each of them consists of at least 10 alternate thin layers with the thickness of less than 0.5 µm. In the method for producing the multilayer film, the above-mentioned components undergo extrusion, and they are extruded through the slit head at the temperature ranging from 260 to 300 °C and stretched by simultaneously cooling down the extruded film so that the film crystallization and solidification takes place after 0.05-1 second.