Waste Polyester Dissolution and Filtration for Purified Recycling Feedstock
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Solution Overview
Problem
Current recycling methods for waste polyester face challenges in efficiently purifying low-quality feedstock due to the presence of impurities, which leads to degradation in the quality of reformed polymers and incurs high energy costs and environmental waste.
Innovation Solution
A method involving the use of a dissolution solution comprising hexafluoroisopropyl alcohol (HFIPA) and dichloromethane (DCM) to treat waste polyester, followed by purification and solidification, effectively separates impurities and produces high-quality solid polyester for reuse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If activated carbon and ion exchange resins are used for purification, then impurity removal effectiveness is improved, but energy consumption and process complexity increase
Solution Approach 1:
The patent extracts and removes impurities (dyes, pigments, dirt, foreign polymers) from the polyester feedstock using a dissolution-filtration-precipitation process. The dissolution solution selectively dissolves the polyester while leaving impurities behind, which are then removed by filtration, achieving effective purification without requiring activated carbon or ion exchange resins.
Solution Approach 2:
The patent changes the physical and chemical parameters of the purification process by using a specific dissolution solution (comprising dichloromethane and hexafluoroisopropyl alcohol) at controlled temperatures and concentrations. This allows selective dissolution of polyester at optimized conditions, enabling effective impurity removal with reduced energy input compared to high-temperature pyrolytic regeneration or chemical regeneration methods.
2Reliability
If activated carbon is regenerated through pyrolysis, then purification media effectiveness is restored, but energy cost increases significantly
Solution Approach 1:
The patent replaces expensive, energy-intensive purification media (activated carbon requiring pyrolytic regeneration at 600-900°C) with a disposable or easily regenerable filtration system using the dissolution solution. The dissolution solution can be filtered and reused multiple times without requiring high-energy regeneration, effectively eliminating the need for costly pyrolytic regeneration.
Solution Approach 2:
The patent replaces the thermal/chemical regeneration system (pyrolysis at high temperatures) with a mechanical filtration system. The dissolution solution is filtered through a filter to remove impurities and then reused, substituting high-energy thermal processing with low-energy mechanical separation.
3Reliability
If ion exchange beds are regenerated with acid or base, then purification capacity is restored, but environmental waste and processing complexity increase
Solution Approach 1:
The dissolution solution performs self-regeneration through filtration. After dissolving polyester and separating impurities via filtration, the solution can be reused multiple times without requiring external acid or base treatments. The system is self-sustaining, eliminating the need for harmful chemical regeneration processes that generate environmental waste.
4Ease of manufacture
If mechanical recycling is applied to contaminated plastic waste, then processing simplicity is maintained, but recovery rate decreases due to rejection of impure materials
Solution Approach 1:
The patent applies preliminary purification action by dissolving the polyester in the dissolution solution before recycling processing. This pre-treatment step removes impurities (dyes, pigments, dirt, foreign polymers) that would otherwise cause rejection in mechanical recycling, allowing contaminated waste materials to proceed through the recycling process without being discarded.
Solution Approach 2:
The patent changes the state of the polyester from solid contaminated material to dissolved state in the dissolution solution. This parameter change enables selective separation of impurities through filtration, converting materials that would be rejected in mechanical recycling into purifiable feedstock suitable for high-quality recycling applications.
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 method significantly improves the purity and quality of recycled polyester, reduces processing costs and complexity, and enables the recycling of previously rejected materials, thereby enhancing the efficiency of chemical and mechanical recycling processes.
Implementation Method 1
treating a waste material comprising a polyester with a dissolution solution comprising hexafluoroisopropyl alcohol and a chlorinated hydrocarbon and/or an aromatic hydrocarbon to form dissolved polyester
Implementation Method 2
purifying the dissolved polyester
Implementation Method 3
treating the dissolved polyester with a technique to produce solid polyester
Data Source
AI summary
A waste polyester material is prepared for recycling by dissolving the material in a solution comprising hexafluoroisopropyl (HFIPA) and a chlorinated hydrocarbon, such as dichloromethane (DCM) and/or an aromatic hydrocarbon, such as toluene or xylene, to form a dissolved polyester sample. The dissolved polyester may be prepared for recycling by evaporation, spray drying, and/or precipitation, which produces a purified solid polyester product. The dissolution solution, which is separated from the purified solid polyester product, is also recycled through distillation with purification.