A process for decolouring textiles
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Solution Overview
Problem
The textile industry faces challenges in recycling blended fibers like polyester/cotton due to differences in physical properties and the presence of dyes, particularly reactive dyes which form covalent bonds with fibers, making it difficult to decolorize and reuse textile waste effectively.
Innovation Solution
A process involving a two-step decolorization method using an aqueous solution of water-soluble dithionous acid salts followed by an aprotic solvent, such as dihydrolevoglucosenone and dimethyl sulfoxide, to effectively remove various types of dyes, including reactive dyes, from textile products, allowing for the recovery of decolorized solid fractions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional single-step decolorization methods are used, then the process is simple, but the decolorization efficiency is insufficient especially for reactive dyes
Solution Approach 1:
The decolorization process is divided into two sequential steps: first treating with aqueous dithionous acid salt solution to remove water-soluble dyes, then treating with aprotic solvent to remove remaining dyes including reactive dyes. This segmentation allows each step to target specific dye types, achieving comprehensive decolorization that neither method could accomplish alone.
Solution Approach 2:
The patent uses dithionous acid salt as an intermediary reducing agent in the first step to convert reactive dyes into a form that can be subsequently removed by the aprotic solvent. This intermediary step facilitates the removal of otherwise难去除 reactive dyes by transforming their chemical state.
2Reliability
If reactive dyes are used for dyeing cellulosic fabrics, then the dye fastness is improved, but the dye becomes difficult to remove during recycling
Solution Approach 1:
The patent changes the chemical parameters of the decolorization process by using a two-step approach with different chemical environments: first aqueous reducing conditions with dithionous acid salt, then organic solvent conditions. This parameter change allows the process to address both the fastness requirement (by not attacking the covalent bond directly) and the removal difficulty (by using complementary mechanisms in each step).
Solution Approach 2:
The process extracts dyes from the textile through two sequential extraction mechanisms: first water-soluble dyes are extracted by the aqueous dithionous acid salt solution, then remaining dyes including reactive dyes are extracted by the aprotic solvent. This two-stage extraction overcomes the difficulty of removing covalently bonded reactive dyes.
3Object-affected harmful factors
If textile waste blends are recycled, then the environmental impact is reduced, but the presence of dyes and fibre composition differences complicate the recycling process
Solution Approach 1:
The two-step decolorization process serves multiple functions: it removes water-soluble dyes, removes water-insoluble dyes, and prepares the textile for subsequent recycling steps. This multi-functional approach addresses the complexity of recycling dyed textile blends by providing a comprehensive decolorization solution that works across different fibre types and dye classes.
Solution Approach 2:
The patent converts the harmful effect of dye presence (which complicates recycling) into a benefit by using the dye removal process to also clean and prepare the textile fibres for high-quality recycling. The decolorization steps simultaneously remove contaminants and prepare the fibres, turning a problem into an opportunity for improved recycling quality.
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 textile products, producing high-quality solid fractions with minimal dye residue, enabling the recycling of blended fibers in an environmentally friendly, cost-effective, and reliable manner.
Implementation Method 1
adding a liquid solution of a first decolorizing agent in water to the textile product wherein the first decolorizing agent is an aqueous solution of a water-soluble salt of dithionous acid
Implementation Method 2
adding a second decolorizing agent comprising an aprotic solvent to the textile product thereby providing a second decolorized textile product
Data Source
AI summary
A process is shown for providing a solid fraction from a textile product including a natural fiber, a synthetic fiber, or both. The process involves the treatment of the textile product with a water-soluble salt of dithionous acid followed by a treatment of an aprotic solvent, such as dimethyl sulfoxide.