Recycled PET Glycol-Modified Process for Food-Grade Production
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Solution Overview
Problem
Current recycling methods for polyethylene terephthalate (PET) struggle to produce food-grade material suitable for direct contact with food, as they require high-temperature reactors and vacuum degassing, limiting the material's reuse and increasing operational costs, while mechanical recycling generates significant waste and chemical recycling is not economically viable on a large scale.
Innovation Solution
A process involving the depolymerization of recycled PET in a mixture of monoethylene glycol and neopentyl glycol, followed by polymerization in the presence of a catalyst under high vacuum, to produce polyethylene terephthalate glycol-modified (r-PETG) with isophthalic acid insertion, which extends the PET life cycle and reduces waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical recycling is used to process PET waste, then processing cost is reduced, but the produced r-PET cannot be used for food-contact applications due to contamination
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of recycled PET through glycolysis depolymerization followed by repolymerization with controlled addition of virgin PET and specific catalysts. This transforms the material's molecular structure and purity level, enabling it to meet food-contact requirements while maintaining economic viability through optimized processing parameters
Solution Approach 2:
The patent uses an intermediary approach by introducing a blending step where mechanically recycled PET is combined with a controlled amount of virgin PET (5-50% by weight) and subjected to repolymerization. This intermediary process acts as a bridge between low-cost mechanical recycling and high-purity chemical recycling, producing food-grade material at reduced cost
2Reliability
If chemical recycling is used to produce food-grade r-PET, then material purity is improved, but operational costs and plant complexity increase significantly
Solution Approach 1:
The patent segments the recycling process into two distinct stages:第一阶段 mechanical recycling for initial processing and contamination removal, and第二阶段 controlled chemical recycling (glycolysis followed by repolymerization) for purity enhancement. This segmentation allows each stage to be optimized independently, reducing overall plant complexity while achieving food-grade quality
Solution Approach 2:
The patent applies partial chemical recycling by using glycolysis followed by repolymerization with controlled addition of virgin PET (5-50% by weight) rather than complete depolymerization to monomers. This partial action achieves sufficient purification for food-contact applications while avoiding the high costs and complexity of full chemical recycling
3Productivity
If complete mechanical recycling is used, then production volume is increased, but waste generation increases and environmental sustainability decreases
Solution Approach 1:
The patent applies discarding and recovering by diverting PET that would otherwise be discarded as waste from mechanical recycling and subjecting it to glycolysis depolymerization followed by repolymerization. This recovers valuable material that would be lost, converting it into food-grade r-PET and reducing overall waste generation while maintaining high production volumes
Solution Approach 2:
The patent creates a universal recycling system that can process both mechanically recycled PET and virgin PET feedstocks through the same glycolysis-repolymerization process. This multi-functional approach maximizes production volume by accepting various feedstock types while minimizing waste through efficient material recovery and upcycling
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 process produces r-PETG with properties similar to virgin PETG, enabling its use in food-contact applications, reducing waste disposal, and lowering raw material consumption from non-renewable sources, thus lengthening the PET life cycle and enhancing recycling efficiency.
Implementation Method 1
depolymerization of recycled PET in the presence of a mixture comprising monoethylene glycol (MEG) and neopentyl glycol (NPG)
Implementation Method 2
polymerization of the reaction mixture of step (1) in the presence of a suitable catalyst, preferably at a pressure of less than about 0.01 mmHg (about 1,33 Pa)
Data Source
Figure 1~2
AI summary
The present invention relates to a process for the production of polyethylene terephthaiate glycol-modified using recycled polyethylene terephthaiate flakes as a raw material. The process comprises two distinct steps: an initial depo!ymerization of the PET conducted in the presence of a monoethylene glycol /neopentyl glycol mixture, followed by a polymerization step.