Polyester Waste Purification Using DCM for Cleaner Recycling Feedstock
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Solution Overview
Problem
Current recycling processes for polyester waste are inefficient due to the presence of impurities, which require costly and energy-intensive purification methods, and mechanical recycling has low recovery rates due to stringent cleanliness requirements.
Innovation Solution
Purify polyester waste with dichloromethane (DCM) to separate impurities, allowing for efficient recycling by density differences and reducing the need for post-reaction purification procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If current purification methods (activated carbon, ion exchange resins) are used to remove impurities from polyester waste, then product purity is improved, but energy consumption and processing costs increase significantly
Solution Approach 1:
The patent extracts and removes impurities (dyes, pigments, dirt, foreign polymers) from polyester waste feedstock through pre-treatment processes before recycling. This extraction of harmful components at the beginning of the process eliminates the need for energy-intensive post-reaction purification methods like activated carbon treatment and ion exchange resin regeneration, thereby reducing overall energy consumption while maintaining high product purity
Solution Approach 2:
The patent applies preliminary purification actions (sorting, cleaning, pre-treatment) to the polyester waste feedstock before the main recycling process. By performing these purification steps in advance, the process avoids the need for costly and energy-intensive post-reaction purification procedures, including the regeneration of spent activated carbon through pyrolysis at 600-900°C and ion exchange bed regeneration with acid or base backflow washing
2Manufacturing precision
If mechanical recycling uses stringent cleanliness requirements, then product quality is maintained, but recovery rate decreases due to rejection of contaminated materials
Solution Approach 1:
The patent implements preliminary sorting and cleaning actions on polyester waste feedstock before the main recycling process. This pre-treatment removes contaminants such as polyolefins, dyes, and other foreign matter, enabling mechanically recycled products to meet quality standards while significantly increasing the recovery rate of otherwise rejectable materials
Solution Approach 2:
The patent extracts and removes foreign matter and contaminants from polyester waste streams through pre-treatment processes. By taking out impurities such as polyolefins, dyes, pigments, and dirt before recycling, the process expands the acceptable feedstock range while maintaining product quality, thereby increasing overall recovery rates
3Manufacturing precision
If ion exchange resins are used for deionization, then product purity is improved, but environmental waste and additional processing requirements increase
Solution Approach 1:
The patent extracts and removes ionic impurities from polyester waste feedstock through pre-treatment processes before the main recycling reaction. By removing these impurities in advance, the process eliminates or reduces the need for ion exchange resin treatment, thereby preventing the generation of acidic or basic waste streams associated with resin regeneration and reducing environmental harm
Solution Approach 2:
The patent converts the potentially harmful process of ion exchange resin regeneration (which generates acidic or basic waste) into a beneficial pre-treatment step. By performing deionization as an initial cleaning operation rather than a post-reaction purification step, the process achieves the same purity goal without generating harmful waste streams
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 enhances recycling efficiency, reduces processing costs and waste generation, and improves product purity by minimizing the need for labor-intensive and energy-consuming purification steps.
Implementation Method 1
separate impurities, allowing for efficient recycling by density differences
Data Source
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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.