PET-Flake Decolorization via Hot Ethylene Glycol Extraction
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Solution Overview
Problem
Current PET recycling methods require color sorting to produce high-quality recycling products, which is inefficient and not feasible for mixed-color PET-flake recycling.
Innovation Solution
A method involving pre-treatment of PET-flake in a hot organic liquid, followed by extraction with hot ethylene glycol to remove organic colorants and embrittle the PET-flake without depolymerization, using a counter-current flow process at specific temperature and pressure conditions to achieve decolorization without significant softening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If color sorting is performed to obtain high quality recycling products, then product quality is improved, but process complexity and cost increase
Solution Approach 1:
The patent extracts and removes colorants from PET-flake through chemical treatment with glycol, transforming the colored PET into colorless PET monomers. This extraction of the harmful colorant component eliminates the need for physical color sorting while maintaining high product quality in the recycling process.
Solution Approach 2:
The patent changes the chemical state of PET from polymer to monomer through glycolysis reaction, and simultaneously changes the color from colored to colorless. This parameter change in chemical structure and color allows mixed-color PET-flake to be processed into high-quality colorless recycling products without sorting.
2Productivity
If chemical recycling techniques are used to process PET-flake, then recycling efficiency is improved, but color removal capability is insufficient
Solution Approach 1:
The patent optimizes the glycolysis reaction parameters (temperature, pressure, glycol to PET ratio) to simultaneously achieve efficient recycling and complete color removal. By controlling these parameters, the process transforms colored PET-flake into colorless PET monomers with high efficiency.
Solution Approach 2:
The patent utilizes the phase transition and solubility changes of PET in glycol during heating to enable colorant removal. The PET-flake undergoes swelling and dissolution in hot glycol, allowing colorants to be extracted while maintaining recycling efficiency.
3Object-generated harmful factors
If PET-flake are treated at high temperature to remove colorants, then color removal effectiveness is improved, but PET structural integrity deteriorates
Solution Approach 1:
The patent carefully controls the temperature and pressure parameters during glycolysis to achieve color removal while preventing excessive degradation of PET structure. The optimized conditions allow colorant extraction without compromising the structural integrity of the resulting PET monomers.
Solution Approach 2:
The patent uses glycol as an intermediary substance that facilitates color removal through chemical reaction while protecting PET structure. Glycol acts as a mediator that extracts colorants through glycolysis without causing direct damage to the PET polymer chains, maintaining structural integrity.
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 the recycling of PET-flake without color sorting, effectively removing organic colorants and embrittling the PET-flake, while maintaining its structural integrity for further processing, thus facilitating the production of high-quality recycling products.
Implementation Method 1
Organic colorants are extracted from the PET-flake and the PET-flake are simultaneously embrittled using hot ethylene glycol
Implementation Method 2
PET-flake are pre-treated in a hot organic liquid
Data Source
AI summary
Organic colorants incorporated in colored PET-flake, as being obtained by shredding PET bottles, can be extracted from the PET-flake by extracting the PET-flake with ethylene glycol (EG) at ambient pressure and at the boiling temperature of EG. Pre-treating of PET-flake in EG or other suitable organic compounds prior to extraction enhances the discoloration.