Thermoformed Polyester Dome Cap for PET Recycling Compatibility
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Solution Overview
Problem
Conventional container closures made from HDPE and PP are not recyclable with PET containers, leading to contamination and inefficiencies in recycling streams due to incompatibility, and injection molding limits the thinness of these closures.
Innovation Solution
Developing closures from thermoformed polyester resin, particularly polyethylene furandicarboxylate (PEF), which can be recycled in the same stream as PET containers, with features like interference fits and thermoforming processes to ensure compatibility and effective sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If closures are made from HDPE or PP through injection molding, then the closures have sufficient strength and structural integrity, but the closures are incompatible with PET recycling streams causing contamination and loss
Solution Approach 1:
The closure is made from polyester resin (PET or PEF), the same material family as the container, ensuring homogeneity throughout the recycling stream. This eliminates material incompatibility and contamination issues that arise from mixing different plastic types in recycling facilities.
Solution Approach 2:
The invention changes the material parameter of the closure from conventional HDPE/PP to polyester resin, and changes the manufacturing process parameter from injection molding to thermoforming. This allows the closure to be compatible with PET recycling streams while achieving the desired structural properties through controlled thermal and mechanical processing.
2Strength
If injection molding is used to manufacture closures, then the closures have adequate thickness for strength, but the manufacturing process limits how thin the parts can be made
Solution Approach 1:
The invention replaces the injection molding mechanical process with thermoforming, which uses thermal energy and controlled mechanical deformation. This substitution allows for greater flexibility in achieving thin-walled structures with adequate strength, as thermoforming can produce uniform thin walls that are then strengthened through controlled crystallization and interference fit mechanisms.
Solution Approach 2:
The manufacturing process parameters are changed from injection molding (high pressure, molten state) to thermoforming (controlled heating, forming, and cooling). This enables production of thinner-walled closures that maintain sufficient strength through the interference fit sealing mechanism and controlled material orientation during forming.
3Reliability
If conventional closures are used, then the sealing function is provided, but oxygen and carbon dioxide barriers are insufficient reducing shelf-life
Solution Approach 1:
The invention uses PEF (polyethylene furandicarboxylate) as the polyester resin, which has superior barrier properties compared to conventional PET and traditional closure materials. The molecular structure of PEF provides enhanced resistance to oxygen and carbon dioxide permeation, extending shelf-life while maintaining the sealing function through the interference fit mechanism.
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 polyester resin closures maintain recyclability, reduce contamination, enhance oxygen and carbon dioxide barriers, and provide better sealing properties, improving the shelf-life and environmental impact of containers.
Implementation Method 1
an inner cylindrical wall that extends downwardly from the annular wall, the inner cylindrical wall configured such that an outwardly facing surface of the inner cylindrical wall has an interference fit with an inwardly facing surface of the finish of the container for sealing against the inwardly facing surface of the finish
Implementation Method 2
a thermoformed polyester resin closure for closing a container including a polyester
Data Source
AI summary
Thermoformed polyester resin closures for closing containers, the polyester resins including polyethylene terephthalate (“PET”), polyethylene furandicarboxylate (“PEF”), or a copolymer including PET and PEF, are provided herein. Methods of making the thermoformed closures are further provided. Methods of sterilizing the thermoformed closures are further provided.