Multilayer Film Segmentation for Extrusion Stability
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Solution Overview
Problem
Existing stretch films require blends of polymers for optimal properties, leading to unstable extrusion, inhomogeneities, and quality issues, complicating the production process and increasing the risk of defects.
Innovation Solution
A multilayer film structure comprising a first outer layer of at least 98 wt% linear low density polyethylene, a first inner layer of at least 98 wt% propylene homopolymer or copolymer, and a second outer layer with a combination of linear low density and very low density polyethylene, eliminating the need for polymer blends while maintaining desired mechanical and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polymer blends are used in the inner layers to achieve optimal mechanical properties, then the holding force and tear resistance are improved, but the extrusion stability deteriorates and inhomogeneities and defects increase
Solution Approach 1:
The film is divided into multiple layers with distinct polymer compositions. The inner layers use pure propylene homopolymer or copolymer instead of blends, while outer layers provide adhesion. This segmentation allows each layer to perform its specific function optimally without the instability caused by blends.
Solution Approach 2:
Different layers are assigned different polymer types based on their specific functional requirements. The inner layers focus on mechanical strength and stretchability using pure propylene, while outer layers provide adhesion and surface properties. This local optimization resolves the contradiction by placing the right material in the right location.
2Strength
If polymer blends are used to achieve desired mechanical properties, then the film performance is improved, but the production process complexity increases
Solution Approach 1:
The multilayer structure segments the film into distinct layers, each extruded from separate dies. This allows pure polymers to be used in each layer without blending, simplifying the production process while maintaining high tear resistance through the layered architecture.
Solution Approach 2:
The invention uses a composite multilayer structure where different pure polymers are combined in specific layers. This achieves the benefits of material optimization and simplified processing by eliminating blends while maintaining the protective and mechanical functions through the composite layer structure.
3Strength
If polymer blends are used in inner layers, then the mechanical properties are optimized, but the film quality and consistency deteriorate
Solution Approach 1:
By segmenting the film into layers with pure polymers, the invention eliminates the quality issues associated with blends. Each layer can be precisely controlled during extrusion, ensuring consistent film quality while maintaining impact resistance through the layered composite structure.
Solution Approach 2:
The invention changes the material parameter from blended compositions to pure polymers in specific layers. This parameter change improves manufacturing precision and film quality by eliminating the variability and defects associated with blends, while maintaining mechanical properties through the layered architecture.
4Force
If blends are used to achieve desired properties, then the holding force is improved, but the risk of defects and inhomogeneities increases
Solution Approach 1:
The multilayer structure segments the film to use pure propylene in inner layers for holding force and pure polyethylene in outer layers for adhesion. This segmentation eliminates the defect risks of blends while maintaining high holding force through the optimized layer configuration.
Solution Approach 2:
The invention uses straightforward extrusion of pure polymers without complex blending processes, reducing the risk of defects. The simple, clean material inputs lead to more reliable production with fewer inhomogeneities and defects.
Data Source
AI summary
The invention relates to a stretchable multilayer film comprising in the following order a. a first outer layer comprising at least 98 wt% of a linear low density polyethylene, b. a first inner layer, c. a second inner layer, d. a third inner layer and e a second outer layer comprising 70% to 30wt% of a linear low density polyethylene and 30 to 70wt% very low density polyethylene (VLDPE), wherein at least one of the inner layers comprises at least 98wt% of a propylene homopolymer or 98wt% of a propylene ethylene copolymer and wherein the other inner layer(s) comprise(s) at least 98wt% of a linear low density polyethylene.