Recycled Polyester Purification via Melt Filtration and Segmented Thermal Treatment
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Solution Overview
Problem
Existing technologies face challenges in efficiently recycling polyesters like PET due to the introduction of impurities, which affect the quality of the recycled material and make continuous processing difficult.
Innovation Solution
A process involving the purification of recycled polyester material by melt filtration before mixing it with a polyester prepolymer, followed by thermal treatment in a reactor with a process gas, to produce a high-quality solid mixture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal treatment is extended to remove more semi-volatile impurities, then impurity removal is improved, but product quality deteriorates due to discoloration and decomposition
Solution Approach 1:
The patent divides the impurity removal process into two distinct stages: (1) initial removal of semi-volatile impurities through controlled thermal treatment under nitrogen atmosphere at 100-200°C for 0.5-4 hours, and (2) subsequent removal of volatile impurities through vacuum treatment at elevated temperatures. This segmentation allows each stage to target specific impurity types without causing degradation
Solution Approach 2:
The patent systematically changes processing parameters including temperature (100-200°C initial, then elevated for vacuum), atmosphere (nitrogen to vacuum), and time (0.5-4 hours initial, then additional time for vacuum) to optimize impurity removal at each stage while preventing discoloration and decomposition
2Productivity
If recycled polyester is processed in conventional solid-phase polycondensation, then processing capacity is maintained, but continuous operation becomes difficult due to impurity accumulation
Solution Approach 1:
The patent performs preliminary removal of semi-volatile impurities through controlled thermal treatment and vacuum treatment before the polyester enters the solid-phase polycondensation process. This preliminary action prevents impurity accumulation during continuous operation, enabling reliable long-term processing while maintaining productivity
Solution Approach 2:
The patent introduces an intermediary purification stage with controlled atmosphere (nitrogen) and vacuum treatment between recycling and polycondensation. This intermediary step acts as a buffer that removes harmful impurities while preserving the polyester for continuous processing in the polycondensation reactor
3Manufacturing precision
If extensive degassing chambers are used to remove semi-volatile impurities, then impurity removal is improved, but product quality deteriorates and degradation products form
Solution Approach 1:
The patent uses controlled parameter changes including moderate temperatures (100-200°C), controlled atmosphere (nitrogen), and limited time (0.5-4 hours) for the initial thermal treatment stage. This controlled approach removes semi-volatile impurities while preventing the excessive heating that would cause degradation and unwanted byproducts
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
This process enables reliable and continuous processing of a mixture of recycled and virgin polyester materials, improving the quality and purity of the final product by effectively removing solid impurities.
Implementation Method 1
first purification of the melt by removing solid impurities using melt filtration
Implementation Method 2
Treatment of this solid mixture in a reactor for the thermal treatment of bulk materials with a process gas
Data Source
AI summary
A process for producing a polyester solids mixture by adding together a proportion of recycled polyester material and a proportion of polyester material from a polyester manufacturing process. The proportion of recycled polyester material in the polyester solids mixture comprises 10-90% and has a b* value (BR), and the proportion of polyester material from a polyester manufacturing process in the polyester solids mixture comprises 90-10% and has a b* value (BN) and the resulting polyester solids mixture has a b* value (BM), wherein the BM<0, BN<0 and BR>BN.