Dimensionally Stable Recyclable Multi-Layer Plastic Packaging
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Solution Overview
Problem
Flexible packaging materials, such as toothpaste tubes, are not recyclable due to their composition of multiple plastics and poor dimensional stability, which causes them to curl and become unsuitable for reuse.
Innovation Solution
A multi-layer sheet structure is developed, comprising layers with non-zero and different stress values, where the net stress value is less than the greatest individual layer stress, ensuring dimensional stability and recyclability, formed through blown-film or cast film processes and laminated with polyolefin and barrier layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If flexible packaging is made from multiple different plastics to achieve flexibility, then flexibility is improved, but recyclability deteriorates because mixed plastics are not recyclable
Solution Approach 1:
The packaging is divided into multiple functional layers, each made from a specific plastic material with distinct properties. The structure segments the functions of flexibility, barrier protection, and sealability into separate layers, allowing each layer to be optimized for its specific function while maintaining overall recyclability through the use of compatible polymers throughout the structure.
Solution Approach 2:
The invention uses composite material structure where multiple plastic layers are laminated together to create a flexible packaging material that combines the advantages of different plastics. The composite structure provides both flexibility and recyclability by using compatible polymer combinations that can be processed together in recycling streams.
2Object-affected harmful factors
If flexible material is used to achieve flexibility, then flexibility is improved, but dimensional stability deteriorates causing the material to curl onto itself
Solution Approach 1:
Different layers in the flexible packaging structure have different local qualities tailored to specific functions. The molecular orientation and stress characteristics are locally optimized in each layer to provide the necessary flexibility while maintaining overall dimensional stability. This local quality differentiation allows the packaging to be flexible where needed while resisting curling through the balanced stress distribution across layers.
Solution Approach 2:
The multi-layer structure uses layers with different stress values that counterbalance each other. The stress from molecular orientation in one layer is compensated by the opposing stress in another layer, preventing the material from curling onto itself while maintaining flexibility. This stress counterbalancing mechanism resolves the dimensional stability issue inherent in flexible materials.
3Object-affected harmful factors
If layers with non-zero and different stress values are used to achieve flexibility, then flexibility is improved, but net stress control deteriorates causing excessive curling
Solution Approach 1:
The invention controls the stress parameters of each layer by adjusting molecular orientation during manufacturing. By changing the stress parameters (stress values) of individual layers within specific ranges, the overall net stress of the multi-layer structure is controlled to prevent excessive curling while maintaining the flexibility provided by non-zero stress values in each layer.
Data Source
AI summary
Described herein is a sheet comprising: a multi-layer structure comprising: a plurality of layers including an uppermost layer and a lowermost layer, each of the plurality of layers having a molecular orientation that results in a stress value for each layer; wherein the stress value of at least two of the plurality of layers are non-zero and different from one another; and wherein the multi-layer structure has a net stress value that is less than the greater stress value of the plurality of layers.