DCM Polyester Waste Purification for Cleaner Recycling Feedstock
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Solution Overview
Problem
Existing recycling processes for polyester waste are hindered by the presence of impurities such as dyes, pigments, dirt, and foreign polymers, which lead to degradation of polymer quality and increased energy and waste generation due to frequent purification media regeneration.
Innovation Solution
Purify polyester waste with dichloromethane (DCM) to separate impurities based on density differences, allowing for efficient recovery of purified polyester suitable for recycling.
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 waste generation increase due to frequent regeneration
Solution Approach 1:
The patent extracts and removes impurities (dyes, pigments, dirt, foreign polymers) from the polyester feedstock using a dissolution-filtration approach before depolymerization. This pre-removal of impurities reduces the load on subsequent purification media, extending their regeneration cycles and reducing energy consumption associated with frequent regeneration.
Solution Approach 2:
The patent performs preliminary purification of the polyester feedstock by dissolving it and filtering out impurities before the main depolymerization process. This preliminary action prevents impurities from interfering with the depolymerization reaction and reduces the frequency of purification media regeneration, thereby lowering energy consumption.
2Ease of manufacture
If mechanical recycling is applied to contaminated plastic waste, then processing simplicity is improved, but recovery rate decreases due to rejection of foreign matter
Solution Approach 1:
The patent introduces a dissolution-filtration intermediary step between waste collection and mechanical recycling. This intermediary process removes foreign matter and contaminants that would otherwise cause rejection in mechanical recycling, enabling broader acceptance of mixed waste streams while maintaining processing simplicity.
Solution Approach 2:
The patent changes the physical state of the polyester waste by dissolving it in a suitable solvent, which allows for selective removal of impurities through filtration. After filtration, the polyester can be precipitated or dried to recover clean material suitable for mechanical recycling, thereby expanding the range of acceptable feedstock.
3Reliability
If post-reaction purification is performed frequently, then monomer purity is improved, but processing time and cost increase
Solution Approach 1:
The patent performs preliminary purification of the polyester feedstock by dissolving and filtering it before depolymerization. This removes impurities that would otherwise require frequent post-reaction purification, reducing both processing time and costs while maintaining monomer purity.
Solution Approach 2:
The patent skips or reduces the frequency of post-reaction purification steps by performing thorough pre-purification of the feedstock. This allows the depolymerization process to proceed more efficiently with fewer interruptions for purification, reducing overall processing time while maintaining product quality.
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
DCM purification reduces the need for costly post-reaction purification, minimizes waste, and enhances recycling efficiency by producing higher-quality polyester feedstock.
Implementation Method 1
purifying a waste material comprising a polyester by treating the waste material with dichloromethane (DCM)
Data Source
AI summary
Pre-treating a waste polyester material with dichloromethane (DCM) produce purified polyester for reuse. The purified polyester can be recycled via any chemical or mechanical recycling process. Where the waste polyester material includes non-polyester contaminants, the DCM-treated polyester material produces a slurry that includes the DCM, a solid component that includes a polyester monomer product for reuse, and a waste liquid component where the non-polyester contaminants can be filtered from the top of the liquid component.