Foamable Ink Coating for PET Label Recycling Separation
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Solution Overview
Problem
The separation of polyethylene terephthalate (PET) containers from heat-shrink labels during recycling is challenging due to the labels' density matching that of PET, leading to contamination and the need for disposing of PET flake rather than recycling it, as existing methods either render labels opaque or are difficult to print on.
Innovation Solution
A film with a polymeric base layer and a chemical blowing agent-based ink or coating that sinks in a liquid until activated during the recycling process, allowing it to float and be separated without affecting the label's aesthetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sink-float separation is used with heat-shrink labels, then PET containers can be separated from labels, but the labels sink with PET flake causing contamination and requiring disposal of PET flake
Solution Approach 1:
The patent applies parameter changes by modifying the density of the label through the application of a foamable coating. The coating contains a blowing agent that changes the physical state and density of the label surface, making it less dense than PET flake so that it floats during sink-float separation while maintaining the label's functional properties
Solution Approach 2:
The patent uses composite materials by combining the original label material with a foamable coating layer. This composite structure allows the label to have different density characteristics from the base material, enabling it to float during separation while the coating provides the necessary buoyancy without compromising label integrity
2Reliability
If pre-foamed labels are used to reduce density for separation, then labels can float and be separated from PET flake, but the labels become opaque and difficult to print on
Solution Approach 1:
The patent applies preliminary action by applying the foamable coating to the label during the manufacturing process, before the label is put on the container. This allows the coating to be applied to a smooth, printable surface, and the foaming occurs later during the recycling process, preserving printing capability while enabling separation
Solution Approach 2:
The patent uses dynamics by making the coating foamable rather than pre-foamed. The coating remains in a non-foamed state during manufacturing and application, allowing normal printing and labeling processes, then transitions to a foamed state during recycling to provide buoyancy for separation
3Adaptability or versatility
If shrink labels with density greater than 1.0 g/cm³ are used, then labels can be made from various materials like copolyester, polystyrene, PLA, or PVC, but they sink with PET flake causing contamination and corrosion issues
Solution Approach 1:
The patent applies universality by creating a universal solution that works with all types of shrink labels (copolyester, polystyrene, PLA, PVC) regardless of their base material. The foamable coating provides a consistent density modification that enables separation for all label types, making the recycling process universally applicable
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
Enables efficient separation of PET containers from heat-shrink labels without opacity or printing issues, ensuring high-quality PET flake recycling by ensuring the labels float during the recycling process, thus preventing contamination and enhancing recycling efficiency.
Implementation Method 1
The ink or coating composition comprises at least one chemical blowing agent. The blowing agent and coating are designed so that foaming does not substantially occur until the label reaches the recycle process
Implementation Method 2
the ink or coating composition is present in an amount sufficient to make the film, which would sink in a liquid in which it is submerged in the absence of the ink or coating composition, float in the liquid when the chemical blowing agent is activated
Implementation Method 3
the ink or coating composition is present in an amount sufficient to make the film, which would sink in a liquid in which it is submerged in the absence of the ink or coating composition, float in the liquid when the chemical blowing agent is activated
Data Source
AI summary
The present invention is directed to films that are deposited with foamable inks or coatings. One purpose is to facilitate their separation for recycling purposes. The films are particularly useful as packaging labels. The inks/coatings are designed so that foaming is activated when the film is in the hot-wash stage of a typical recycle process. This provides added buoyancy to the film allowing it to float to the surface and be removed, thereby significantly improving the efficiency of the recycle process. A feature of the invention is that, prior to this hot wash, the inks/coatings remain substantially unfoamed and thereby do not negatively affect the aesthetics of labeled package. The foamable inks/coatings can be used with any type of film.