Multilayer Polyethylene Film for Low SIT and High Hot Tack
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Solution Overview
Problem
Existing multilayer films in the packaging industry face challenges in achieving a balance of mechanical properties, such as stiffness and toughness, while maintaining low sealing initiation temperature (SIT) and high hot tack force, and often require multiple materials that complicate recycling.
Innovation Solution
A multilayer polyethylene film comprising a sealing layer with specific compositions of multimodal metallocene catalysed linear low density polyethylene (mLLDPE) and optional ethylene-1-octene or ethylene-1-butene plastomer, and a core layer with Ziegler-Natta catalysed linear low density polyethylene (znLLDPE) and metallocene catalysed LLDPE, optimized for low SIT and high hot tack force without compromising optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multilayer structure with different materials is used to achieve good mechanical properties and sealing behavior, then the packaging performance is improved, but the recycling complexity increases
Solution Approach 1:
The film is divided into distinct functional layers: a sealing layer (A) with specific composition for low SIT and high hot tack force, and a core layer (B) with different composition for mechanical properties. This segmentation allows each layer to be optimized for its specific function while maintaining overall packaging performance.
Solution Approach 2:
The patent changes the compositional parameters of the polyethylene layers, specifically using multimodal metallocene catalysed LLDPE with controlled density (0.918-0.930 g/cm³) and molecular weight distribution (Mw/Mn ≥ 8) in the sealing layer, and multimodal Ziegler-Natta catalysed LLDPE with density (0.920-0.945 g/cm³) in the core layer. These parameter changes optimize both performance and recyclability.
2Strength
If polyethylene with higher density is used to improve mechanical properties, then stiffness and toughness are enhanced, but optical properties deteriorate
Solution Approach 1:
Different density ranges are assigned to different layers: the sealing layer uses lower density (0.918-0.930 g/cm³) to preserve optical properties, while the core layer uses higher density (0.920-0.945 g/cm³) to provide mechanical strength. This local differentiation resolves the contradiction between optical and mechanical properties.
3Reliability
If sealing layer composition is optimized for low SIT and high hot tack force, then sealing performance is improved, but mechanical properties may be compromised
Solution Approach 1:
The film structure is segmented into a sealing layer (A) optimized for sealing performance with multimodal metallocene catalysed LLDPE (density 0.918-0.930 g/cm³, Mw/Mn ≥ 8) and a core layer (B) optimized for mechanical properties with multimodal Ziegler-Natta catalysed LLDPE (density 0.920-0.945 g/cm³). This segmentation allows each layer to fulfill its specific function without compromising the other.
Data Source
AI summary
Multilayer films including at least one layer, being a sealing layer, and one layer, with beneficial heat sealing and hot tack properties. A multilayer packaging film includes a sealing layer based on a specific multimodal metallocene catalysed LLDPE.