Multilayer Film Structure for Produce Packaging Gas Selectivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current multilayer films used for produce packaging face challenges in maintaining desired CO2 and O2 transmission rates while ensuring mechanical strength, particularly when additional layers are incorporated, which affects the desired CO2/O2 selectivity ratio necessary for optimal produce preservation.
Innovation Solution
A multilayer film structure comprising at least three layers (A/B/C) with high-density polyethylene and a gas permeation layer, oriented in the machine direction, achieving a normalized CO2 transmission rate of at least 3000 cm3·mil/100 in2/day and a CO2/O2 transmission rate ratio of at least 4.0, along with a manufacturing method involving cold and hot stretching to enhance mechanical strength and gas permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If polymers with high CO2/O2 selectivity ratio (e.g., EVA, polyether block amide) are used to achieve desired transmission rates, then CO2/O2 selectivity ratio is improved, but mechanical strength deteriorates
Solution Approach 1:
The film is divided into multiple functional layers: Layer A (HDPE) provides mechanical strength and structural support, Layer B (gas permeation layer) provides CO2/O2 selectivity, and Layer C (HDPE) provides additional mechanical strength. This segmentation allows each layer to specialize in one function, resolving the contradiction between strength and selectivity.
Solution Approach 2:
The invention uses a composite multilayer structure combining HDPE and gas permeation layer materials. The HDPE layers contribute mechanical properties while the gas permeation layer contributes selective gas transmission, creating a composite material system that achieves both high CO2/O2 selectivity ratio and adequate mechanical strength simultaneously.
2Strength
If additional layers are incorporated into multilayer films to maintain mechanical strength, then mechanical strength is improved, but CO2/O2 selectivity ratio deteriorates
Solution Approach 1:
Each layer is designed with specific local quality: Layer A and Layer C are optimized for mechanical strength with high HDPE content (at least 90%), while Layer B is optimized for gas permeability with specific gas transmission rates. This local quality differentiation ensures that strength-providing layers do not compromise selectivity, as each layer performs its designated function optimally.
3Strength
If film is oriented in machine direction to enhance mechanical strength, then mechanical strength is improved, but gas permeability deteriorates
Solution Approach 1:
The invention specifies precise parameter ranges for the HDPE layers (Mw,cc/Mn,cc of at least 6.0, Mz,abs of at least 500,000 grams/mol, density of 0.957-0.970 g/cm3) and layer configuration that optimize both mechanical strength and gas permeability. By controlling molecular weight distribution and density parameters, the film achieves adequate mechanical strength when oriented while maintaining sufficient gas transmission rates through the structured multilayer design.
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 film provides desirable CO2 and O2 transmission rates, maintaining mechanical strength, and achieving the desired CO2/O2 selectivity ratio, effectively extending the shelf life of produce by creating a suitable atmosphere for packaging applications.
Implementation Method 1
Layer B comprises a gas permeation layer, wherein a top facial surface of Layer B is in adhering contact with a bottom facial surface of Layer A
Implementation Method 2
a multilayer film that comprises at least 3 layers, each layer having opposing facial surfaces and arranged in the order A/B/C
Data Source
AI summary
The present invention provides multilayer films, packages formed from such films, and methods of making multilayer films. In one aspect, a multilayer film comprises multilayer film comprising at least 3 layers, each layer having opposing facial surfaces and arranged in the order A/B/C, wherein a top facial surface of Layer B is in adhering contact with a bottom facial surface of Layer A; wherein a top facial surface of Layer C is in adhering contact with a bottom facial surface of Layer B, wherein the film is oriented in the machine direction and wherein the film exhibits a normalized carbon dioxide transmission rate of at least 3000 cm3·mil/100 in2/day, and wherein the film exhibits a ratio of the carbon dioxide transmission rate to an oxygen transmission rate of at least 4.0.