Glycol Ether Decolorization for Polyester Fiber Chemical Recycling
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Solution Overview
Problem
Current methods for recycling polyester fibers are inefficient due to low dye extraction effectiveness and significant weight loss, making it difficult to reuse colored polyester fibers as raw materials, leading to material loss and environmental concerns.
Innovation Solution
A method involving a glycol ether-type compound with a boiling point of 160° C. or higher is used to contact and heat the colored polyester, effectively removing colorants without substantial weight loss, allowing for the production of decolorized polyester suitable for chemical recycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If a large amount of heated monoethylene glycol is repeatedly brought into contact with fibrous polyester, then dye extraction can be improved, but the process becomes inefficient due to low solubility of dye into the monoethylene glycol
Solution Approach 1:
The patent changes the solvent type from monoethylene glycol to glycol ethers, which have superior dye solubility properties. This parameter change allows for efficient dye extraction with reduced solvent quantity and contact time, thereby improving processing efficiency while maintaining high dye removal effectiveness.
2Stability of the object's composition
If chemical recycling is used to convert polyester waste into raw material monomer, then quality deterioration is minimized and closed-loop recycling is achieved, but the method mainly targets resin waste and film waste rather than fiber waste
Solution Approach 1:
The patent applies preliminary decolorization treatment to colored polyester fiber waste before chemical recycling. By removing dyes in advance using glycol ethers, the fiber waste becomes suitable for subsequent chemical recycling processes, thereby expanding the adaptability of chemical recycling to include colored fiber waste while maintaining quality retention.
Solution Approach 2:
The patent introduces glycol ethers as an intermediary substance that facilitates the transition from colored fiber waste to suitable feedstock for chemical recycling. This intermediary decolorization step bridges the gap between colored fiber waste and the requirements of chemical recycling processes, enabling versatile application across different waste types.
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 efficient decolorization of polyester fibers, reducing nitrogen atom residues to 30 ppm or less, preserving material quality and enabling closed-loop recycling, thus contributing to resource conservation and environmental protection.
Implementation Method 1
a step of removing the colorant, by bringing the decolorizing agent into contact at least once with the colored polyester while heating the decolorizing agent to a temperature equal to or lower than a melting point of the polyester
Implementation Method 2
bringing the decolorizing agent into contact at least once with the colored polyester while heating the decolorizing agent to a temperature equal to or lower than a melting point of the polyester
Data Source
AI summary
A method for producing a decolorized polyester according to the present invention includes: a step of preparing a polyester colored with a colorant, and a decolorizing agent containing a glycol ether-type compound having a boiling point at atmospheric pressure of 160° C. or higher; and a step of removing the colorant, by bringing the decolorizing agent into contact at least once with the colored polyester while heating the decolorizing agent to a temperature equal to or lower than a melting point of the polyester, to thereby obtain the decolorized polyester.