Recycled Polyester Purification via Dissolution and Reprecipitation
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Solution Overview
Problem
Existing methods for recycling polyesters from composite materials face challenges in achieving high-quality recycled polyesters with desirable color tone and mechanical strength while minimizing environmental impact and production costs, particularly due to the use of harsh solvents and high energy requirements.
Innovation Solution
A method involving specific solvent washing, filtration, and reprecipitation processes using phenolic and chlorine-based solvents, along with aggregating agents, to separate and purify polyesters from composite materials, avoiding decomposition into monomers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical recycling is used to remove impurities and obtain high-quality recycled polyester, then the quality of recycled polyester is improved, but the environmental load and production cost increase due to multiple processes and large heat energy requirements
Solution Approach 1:
The invention changes the fundamental parameter of the recycling approach from chemical decomposition (depolymerization to monomers) to physical dissolution and reprecipitation. This maintains polymer molecular weight and structure while achieving impurity removal, thereby reducing energy consumption and environmental load while preserving polyester quality
Solution Approach 2:
The invention extracts and removes impurities (dyes, other resins, additives) from the polyester composite material through selective dissolution and filtration, separating the desired polyester component from contaminants without decomposing the polymer structure, thus achieving both quality and energy efficiency
2Ease of manufacture
If material recycling is used to recycle at low cost, then production cost is reduced, but the quality deteriorates due to impurities remaining in the recycled polyester
Solution Approach 1:
The invention uses a solvent as an intermediary medium to selectively dissolve the polyester from the composite material, allowing impurities to be separated through filtration. The solvent acts as a mediator that enables both cost-effective processing and high-quality output by facilitating impurity removal without requiring expensive chemical depolymerization processes
Solution Approach 2:
The invention utilizes phase transition of the polyester through dissolution in solvent followed by reprecipitation. This phase change process enables separation of polyester from impurities during the dissolved state, with subsequent reprecipitation yielding high-quality recycled polyester at lower cost than chemical recycling
3Ease of manufacture
If HFIP is used as a dissolving solvent to dissolve polyester, then the polyester can be dissolved and processed, but the solvent is corrosive, toxic, and unsuitable for industrialization
Solution Approach 1:
The invention replaces the hazardous HFIP solvent with safer, more environmentally friendly solvents that can be used in industrial settings. The new solvent system prioritizes worker safety and environmental protection while maintaining the necessary dissolution capability for polyester processing
Solution Approach 2:
The invention changes the chemical parameters of the dissolving solvent from highly reactive and toxic HFIP to safer alternatives with appropriate solubility characteristics. This parameter change maintains the functional capability of dissolving polyester while eliminating the harmful corrosive and toxic properties
4Manufacturing precision
If high temperature distillation is used to remove solvent from recycled polyester, then the solvent can be removed, but the polyester may depolymerize and the process requires large amount of energy
Solution Approach 1:
The invention utilizes the phase transition of the solvent from dissolved state to vapor state through evaporation or low-temperature distillation, enabling solvent removal without subjecting the polyester to high temperatures that would cause depolymerization. This maintains polymer integrity while achieving effective solvent removal at lower energy consumption
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 enables the production of recycled polyesters with excellent color tone and mechanical strength at a lower environmental cost and energy consumption, effectively removing impurities and maintaining molecular integrity.
Implementation Method 1
a step of washing a polyester composite material using a washing solvent obtained by mixing a solvent (X1) composed of a phenolic solvent and/or a chlorine-based organic solvent
Implementation Method 2
a step of mixing the washed polyester composite material and a dissolving solvent containing a solvent (X2) composed of a phenolic solvent and/or a chlorine-based organic solvent to obtain a solution containing a polyester in the polyester composite material dissolved therein
Implementation Method 3
a step of mixing the liquid component (L) and a poor solvent (PS) having a boiling point of 130°C or lower to precipitate the polyester, thereby obtaining a slurry
Data Source
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AI summary
Provided is a production method that makes it possible to produce a recycled polyester having excellent color tone and mechanical strength by a method with a small environmental load. A method for producing a recycled polyester including a step (A) of washing a polyester (PEs) composite material using a washing solvent obtained by mixing a solvent (X1) composed of a phenolic solvent and/or a chlorine-based organic solvent and one or more solvents (Y1) selected from the group consisting of an aromatic hydrocarbon-based solvent, an aliphatic hydrocarbon-based solvent, a ketone-based solvent, an aldehyde-based solvent, an alcohol-based solvent, an ether-based solvent, and water, a step (B) of dissolving PEs in the washed PEs composite material in a dissolving solvent containing a solvent (X2) composed of a phenolic solvent and/or a chlorine-based organic solvent, subjecting the solution to solid-liquid separation to obtain a liquid component (L), a step (C) of obtaining PEs from the liquid component (L) using a poor solvent (PS) having a boiling point of 130°C or lower, and a step (D) of drying PEs.