Multilayer Polymer Film Segmentation for Melt Processing and Optical Clarity
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Solution Overview
Problem
Unimodal polyethylene polymers used in film applications face challenges with melt processing, leading to quality issues such as inhomogeneous products and high gel content, while multimodal polymers improve processability but may result in inhomogeneous final products due to melt homogenization problems.
Innovation Solution
A multilayer film structure comprising an outer layer with a multimodal polymer of ethylene having two different comonomers and a core layer with a multimodal ethylene copolymer or terpolymer, achieving a balance of processability, stiffness, toughness, and sealing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If unimodal polyethylene polymers are used in film applications, then good optical properties are achieved, but melt processing is not satisfactory leading to quality problems
Solution Approach 1:
The patent divides the film into multiple layers, each containing specific polyethylene components with different molecular weight distributions. The unimodal PE layer provides optical properties while the multimodal PE layer provides processability, resolving the contradiction between optical quality and manufacturing ease through structural segmentation.
Solution Approach 2:
The patent uses composite multilayer structures combining unimodal and multimodal polyethylene materials. Each layer contributes specific properties: unimodal PE for optical clarity and multimodal PE for melt processing, creating a composite film that achieves both good optical properties and satisfactory manufacturability.
2Ease of manufacture
If multimodal polymers are used to improve processability, then easier processing is achieved, but melt homogenisation becomes problematic resulting in inhomogeneous final product
Solution Approach 1:
The patent segments the multimodal polymer into separate layers rather than attempting to homogenize it within a single layer. This allows each layer to maintain its specific polymer composition and molecular weight distribution characteristics, achieving processability benefits while avoiding homogenization problems that would create inhomogeneity.
Solution Approach 2:
Different layers are assigned different polymer compositions and molecular weight distributions tailored to specific functional requirements. The multimodal PE layer provides local processability enhancement where needed, while unimodal PE layers maintain local homogeneity and optical quality, avoiding the need for problematic melt homogenization across the entire film.
3Ease of manufacture
If multimodal polymer with broad molecular weight distribution is used, then processability and toughness are improved, but sealing properties deteriorate
Solution Approach 1:
The patent separates the functions of processability/toughness and sealing by placing them in different layers. The multimodal PE layer with broad molecular weight distribution provides processability and toughness, while the unimodal PE layer provides reliable sealing properties, eliminating the trade-off between these properties.
Solution Approach 2:
Specific layers are optimized for specific functions: the multimodal PE layer is designed locally for processability and toughness enhancement, while the unimodal PE layer is designed locally for sealing reliability. This local optimization allows each layer to excel at its designated function without compromising the other properties.
Data Source
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AI summary
A multilayer film comprising at least two layers, a layer (B) and an outer layer (A), wherein outer layer (A) comprises a multimodal polymer of ethylene with at least two different comonomers selected from alpha-olefins having from 4 to 10 carbon atoms, which multimodal polymer of ethylene has a density of 910 to 935 kg/m3, and a Mw/Mn of 2 to 8; and said layer (B) comprising a multimodal ethylene copolymer of ethylene and one C4-10 comonomer or a multimodal ethylene terpolymer of ethylene and at least two C4-10 comonomers, or a mixture thereof, wherein said multimodal ethylene copolymer or terpolymer has a density of 910 to 940 kg/m3 and an Mw/Mn of 9 or more.