Multilayer Film Outer Layer Heat Resistance Additives
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Solution Overview
Problem
Existing multilayer films with polyethylene-based outer layers face challenges in achieving desirable optical properties and enhanced temperature resistance, particularly during the form, fill, and seal packaging process, while also maintaining recyclability and avoiding additional processing steps.
Innovation Solution
Incorporating a polyethylene outer layer with a density of 0.930 g/cm³ or greater and 0.01 to 1 weight percent of additives such as sorbitol acetal derivatives or bisamides, which improve heat resistance and optical properties like gloss and haze, without compromising recyclability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an outer layer with higher melting point material (polyethylene terephthalate or oriented polypropylene) is used, then heat resistance during sealing is improved, but recyclability deteriorates and manufacturing complexity increases due to lamination requirements
Solution Approach 1:
The invention changes the chemical composition parameters of the polyethylene by incorporating specific additives (sorbitol acetal derivatives or bisamides) at controlled concentrations (0.01-5 wt%). This modifies the polymer's thermal properties to achieve higher heat resistance while maintaining the base polyethylene material's recyclability and compatibility, avoiding the need for lamination with different polymer types.
Solution Approach 2:
The invention creates a composite polyethylene material by combining base polyethylene with functional additives (sorbitol acetal derivatives or bisamides). This composite structure provides enhanced thermal properties while maintaining the fundamental polyethylene characteristics that enable recyclability and processing, effectively creating a new material class that bridges the gap between simple polyethylene and high-performance thermoplastics.
2Temperature
If a sealant resin with very low heat seal initiation temperature is incorporated, then heat resistance is improved, but thermal properties of the package deteriorate
Solution Approach 1:
The invention carefully controls the concentration of heat-resistant additives within a specific range (0.01-5 wt%) to achieve sufficient heat resistance improvement without excessively lowering the heat seal initiation temperature. This parameter optimization ensures that the package maintains appropriate thermal properties for sealing operations while gaining the necessary resistance to heat damage during the sealing process.
3Temperature
If surface lacquer is applied to polyethylene, then heat resistance is improved, but manufacturing complexity increases due to additional process steps
Solution Approach 1:
The invention merges the heat resistance function into the polyethylene material itself by incorporating functional additives during the extrusion process. This combines multiple functions (structural integrity, heat resistance, processability) into a single material layer, eliminating the need for separate lamination or coating steps and simplifying the manufacturing process while achieving the desired thermal performance.
Solution Approach 2:
The modified polyethylene material serves multiple functions simultaneously: it provides the structural base layer, delivers heat resistance through incorporated additives, maintains sealability, and preserves recyclability. This multi-functional material replaces what would traditionally require multiple separate layers or treatment steps, reducing overall package structure complexity.
4Ease of manufacture
If conventional polyethylene outer layer is used, then recyclability and optical properties are maintained, but heat resistance during sealing deteriorates
Solution Approach 1:
The invention makes targeted parameter changes to the polyethylene composition by adding small amounts (0.01-5 wt%) of heat-resistant additives. This minimal modification preserves the bulk polyethylene's desirable properties (optical clarity, recyclability, processability) while specifically enhancing the thermal stability parameter to prevent melting and sticking during sealing operations.
Data Source
AI summary
The present invention provides multilayer films and packages formed from such films. In one aspect, a multilayer film comprises an outer layer, the outer layer comprising a polyethylene having a density of 0.930 g/cm3 or greater and 0.01 to 1 weight percent of an additive, based on the total weight of the polyethylene composition, the additive comprising either a sorbitol acetal derivative or a bisamide as specified, wherein the outer layer has a 50% seal strength temperature at least 10° C greater than an outer layer in a comparative film that differs only in the absence of the additive in the outer layer, when sealed to itself at a pressure of 5 bar with a dwell time of 0.5 seconds.