Plastic Film Deinking Before Sorting for Higher-Purity Recycling
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Solution Overview
Problem
The recycling of post-consumer plastic films is hindered by the presence of printing inks, which lead to poor quality recycled plastics and limited applications due to visible imperfections and potential health hazards, and existing processes require separate washing and sorting steps that reduce efficiency and purity.
Innovation Solution
A method involving deinking plastic films with an aqueous solution containing a surfactant and a base, followed by sorting, to enhance the accuracy of film classification and increase the purity of recycled plastics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sorting is performed prior to deinking, then the sorting process can be simplified, but the sorting accuracy deteriorates due to ink interference with film analysis
Solution Approach 1:
The patent applies preliminary action by performing deinking before sorting. The deinking process removes printing inks and contaminants from the plastic film surfaces beforehand, creating a cleaner state that enables accurate sorting. This reverses the conventional sequence and resolves the contradiction by preparing the material in advance to eliminate interference during sorting.
2Measurement precision
If separate washing and sorting steps are used, then the sorting process can be more accurate, but the overall process efficiency deteriorates
Solution Approach 1:
The patent merges the washing and deinking operations into a single integrated step. By combining these functions, the process eliminates redundant operations while maintaining sorting accuracy, as the merged step achieves both cleaning and ink removal simultaneously before sorting occurs.
Solution Approach 2:
The deinking solution serves multiple functions: it removes printing inks, cleans contaminants, and prepares the film for accurate sorting. This multi-functional approach increases process efficiency by consolidating multiple objectives into one operation while maintaining the accuracy needed for effective sorting.
3Ease of operation
If printing inks are present on plastic film, then the film can be identified and sorted, but the recycled plastic quality deteriorates due to visible imperfections and health hazards
Solution Approach 1:
The patent extracts and removes printing inks from the plastic film through the deinking process before recycling. By taking out the harmful ink components, the process eliminates visible imperfections and health hazards while preserving the base plastic material for high-quality recycled products.
Solution Approach 2:
The patent converts the harmful presence of printing inks into a beneficial sorting mechanism. The inks initially aid in film identification and sorting, but the process then removes them completely, transforming the temporary useful function of ink-based identification into a permanent benefit of ink-free, high-quality recycled plastic.
4Measurement precision
If multiple concurrent processing streams are used for each sorted product class, then the sorting can be more precise, but the equipment requirements and processing space increase
Solution Approach 1:
The patent applies preliminary deinking to all film before sorting begins. This preliminary action uniformizes the material state across all product classes, eliminating the need for separate processing streams for each class. The single deinking stream prepares all material for subsequent sorting, reducing equipment requirements while maintaining sorting precision.
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 method improves the sorting efficiency, increases the amount of usable plastic film, and allows for higher-quality recycled plastics suitable for applications like food packaging, while reducing equipment needs and streamlining the recycling process.
Implementation Method 1
exposing pieces of plastic film to an aqueous deinking solution comprising a surfactant and a base
Implementation Method 2
The inks, as well as post-consumer contamination such as food waste, makes the plastic films difficult to sort
Implementation Method 3
By first deinking the plastic film, inks and/or other contaminants are less able to interfere with any analysis of the film
Implementation Method 4
The presence of printing inks in the final recycled plastic is undesirable, as the inks and their degradation products can damage the quality
Data Source
AI summary
This invention relates to a method for recycling plastics, e.g. plastic films.