Recycled Polyester Purification by Solvent Washing and Precipitation
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Solution Overview
Problem
Existing methods for recycling polyester composite materials face challenges in obtaining recycled polyesters with excellent color tone and mechanical strength while minimizing environmental impact and production costs, as they often require multiple processes and large amounts of heat energy, or result in impurities and degraded quality.
Innovation Solution
A method involving specific washing and dissolving steps using phenolic and chlorine-based solvents, followed by filtration and precipitation with solvents of varying boiling points, to remove impurities and separate polyester from other components without decomposing it into monomers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If chemical recycling method is used to remove impurities and obtain high quality recycled polyester, then the quality of recycled polyester is improved, but the environmental load increases and production cost increases due to multiple processes and large amount of heat energy required
Solution Approach 1:
The invention changes the fundamental parameter of the recycling approach from chemical depolymerization to physical dissolution and precipitation. By using a specific solvent system (carboxylic acid solvent) at controlled temperatures, the polyester is dissolved and then precipitated without breaking down into monomers, thereby maintaining molecular weight while removing impurities through filtration, avoiding the need for high-temperature heating processes
Solution Approach 2:
The invention extracts and removes impurities from the polyester composite material by dissolving the polyester in a carboxylic acid solvent and filtering out insoluble impurities. The soluble impurities are removed through precipitation and washing steps, effectively separating the polyester from dyes, fillers, and other contaminants without requiring extensive chemical processing
2Ease of manufacture
If material recycling method is used to reduce production cost, then the production cost is reduced, but the quality of recycled polyester deteriorates due to remaining impurities
Solution Approach 1:
The invention introduces a carboxylic acid solvent as an intermediary medium to facilitate the separation of polyester from impurities. The solvent selectively dissolves the polyester while leaving insoluble impurities behind, and subsequent precipitation and washing steps remove soluble impurities, achieving effective purification without the need for complex chemical recycling processes
Solution Approach 2:
The recycling process is segmented into distinct stages: dissolution of polyester in carboxylic acid solvent, filtration to remove insoluble impurities, precipitation of purified polyester, and washing to remove soluble impurities. This segmentation allows each step to target specific types of impurities, achieving comprehensive purification while maintaining process simplicity and cost-effectiveness
3Manufacturing precision
If chemical recycling process is used to remove dyes and impurities, then the purity of recycled polyester is improved, but the number of processes increases and production complexity increases
Solution Approach 1:
The invention merges multiple purification functions into a unified dissolution-precipitation process. The carboxylic acid solvent simultaneously dissolves the polyester and enables removal of both insoluble impurities (through filtration) and soluble impurities (through precipitation and washing), consolidating what would traditionally require multiple separate chemical treatment steps into an integrated process flow
Data Source
AI summary
Provided is a method for producing a recycled polyester including a step of washing a polyester (PEs) composite material using a washing solvent obtained by mixing a solvent composed of a phenolic solvent and/or a chlorine-based organic solvent and one or more solvents 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 of dissolving PEs in the washed PEs composite material in a dissolving solvent containing a solvent composed of a phenolic solvent and/or a chlorine-based organic solvent, subjecting the solution to solid-liquid separation to obtain a liquid component, a step of obtaining PEs from the liquid component using a poor solvent having a boiling point of 130° C. or lower, and a step of drying PEs.