Solvent Extraction Process for Dye Removal from Polyester Textiles
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Solution Overview
Problem
Existing methods for recycling polyester-containing textiles face challenges in effectively removing dyes without degrading the polyester or cotton fibers, often resulting in partial degradation and contamination from polyurethane materials like elastane filaments.
Innovation Solution
A process involving a solvent extraction method where textiles are held in a static condition, using solvents like DMF or DMAC, with optional alkali water, and centrifugation to separate the dye solution, allowing for multiple extractions and solvent recovery, minimizing degradation and achieving high dye removal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dye removal methods (dichloromethane, hydrothermal treatment) are used, then dyes can be removed from textiles, but polyester and cotton fibers undergo degradation and mechanical properties deteriorate
Solution Approach 1:
The patent changes the chemical parameters by using dimethyl carbonate (DMC) as a novel solvent instead of conventional harsh chemicals like dichloromethane. DMC operates under milder conditions (60-100°C, atmospheric pressure) compared to hydrothermal methods (100-170°C, autogenic pressure), thereby removing dyes effectively while preserving fiber strength and avoiding degradation
Solution Approach 2:
The patent employs a soluble polyester powder as a sacrificial additive that dissolves during the treatment process. This disposable material serves to protect the valuable textile fibers by creating a protective matrix during dye removal, allowing the fibers to be recovered intact while the sacrificial polyester is consumed in the process
2Manufacturing precision
If harsh chemical treatments are applied to remove dyes, then dye removal is achieved, but polyurethane materials (elastane filaments) contaminate the recovered polyester
Solution Approach 1:
The patent uses dimethyl carbonate with specific operational parameters (60-100°C, atmospheric pressure) that create selective solubility conditions. Under these milder parameters, polyester dissolves effectively while polyurethane materials remain insoluble and can be easily separated, preventing contamination of the recovered polyester stream
Solution Approach 2:
The patent exploits the different chemical properties of various textile components under the same treatment conditions. The soluble polyester powder and target polyester fibers exhibit local solubility to DMC, while polyurethane elastane filaments maintain their structural integrity and can be separated, achieving selective processing of different material types within the same fabric
3Manufacturing precision
If extended treatment times are used to ensure complete dye removal, then dye extraction improves, but fiber degradation increases
Solution Approach 1:
The patent achieves rapid dye removal (complete extraction within minutes) by using dimethyl carbonate as a highly effective solvent that penetrates fiber structures quickly. The combination of DMC's chemical properties and moderate heating (60-100°C) accelerates the extraction kinetics, achieving complete dye removal in significantly shorter times than conventional methods while preventing fiber degradation through the short exposure duration
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
The process effectively removes dyes from polyester and cotton fibers with minimal degradation, enabling efficient recycling of polyester and cotton materials while recovering most of the solvent, with a solvent recovery ratio of up to 99.9% and a total process time of about 25-30 minutes.
Implementation Method 1
extracting said batch of said textile with a solvent to provide a solution comprising solvent and extracted material, said extracted material including at least a dye
Implementation Method 2
using solvents like DMF or DMAC, with optional alkali water, and centrifugation to separate the dye solution
Implementation Method 3
centrifugation to separate the dye solution
Data Source
AI summary
In a process for removing dyes from a waste textile material, including at least 50% by weight of polyester fibers, a batch of said textile material in an extraction chamber is extracted with a solvent that is circulated through the textile and the extraction chamber; said solution comprising solvent and extracted material is used as a solvent to extract dye from another batch of textile material, and in that said steps of extraction are repeated, until the amount of extracted material in said solution comprising solvent and extracted material reach a concentration whereby further dye extraction is impaired.