Method for producing decolored polyester, decolored polyester, and decoloring agent
Find Innovative SolutionsGenerate Solutions
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 decolorize polyester fibers at temperatures below their melting point, effectively removing colorants without substantial weight loss, allowing for chemical recycling and closed-loop reuse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If heated monoethylene glycol is used as a dye extraction solvent, then the dye can be extracted from colored polyester, but the solubility of dye into the solvent is low requiring large amounts of repeated contact, and the polyester dissolves into the solvent causing 10-15% weight loss
Solution Approach 1:
The invention changes the chemical parameter of the extraction solvent from monoethylene glycol to a carboxylic acid solvent (formic acid, acetic acid, or propionic acid). This parameter change fundamentally alters the solvent's interaction with both the dye and polyester, achieving high dye extraction efficiency while preventing polyester dissolution and weight loss.
Solution Approach 2:
The carboxylic acid solvent acts as an intermediary substance that selectively interacts with the dye molecules through chemical affinity, extracting them from the polyester matrix without causing the polyester to dissolve. The solvent mediates the separation between dye and polyester effectively.
2Quantity of substance
If a large amount of heated monoethylene glycol is repeatedly brought into contact with fibrous polyester for dye extraction, then more dye can be removed, but the process becomes time-consuming and complex
Solution Approach 1:
Changing the solvent type to carboxylic acid fundamentally improves extraction efficiency, allowing complete dye removal in a single contact rather than requiring repeated contacts with monoethylene glycol. This parameter change transforms a multi-step lengthy process into a single efficient step.
3Device complexity
If the polyester is incinerated or landfilled instead of recycled, then the complex recycling process is avoided, but material loss occurs and environmental protection is compromised
Solution Approach 1:
The invention extracts and removes the dye substance from the polyester using carboxylic acid solvent. By taking out the harmful dye component, the polyester is restored to a usable state suitable for recycling, transforming waste material into reusable resource and avoiding incineration or landfilling.
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 efficiently decolorizes polyester fibers, reducing nitrogen atom residues to 30 ppm or less, enabling high-quality recycling and reducing environmental impact by preventing material incineration and landfilling, thus contributing to resource conservation and environmental protection.
Implementation Method 1
solubility of the dye into the monoethylene glycol is low
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.