Dope-Dyed Polyester Fabric Recycling With Activated Carbon Separation
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Solution Overview
Problem
Current polyester fabric recycling technologies struggle to effectively separate pigments with small particle sizes from the resin in dope-dyed fabrics, leading to low yield and poor hue due to difficulties in filtration and adherence during crystallization processes.
Innovation Solution
A manufacturing method involving a pre-depolymerization step that aggregates and agglomerates pigments with small particle sizes using activated carbon, followed by filtration, to enhance separation efficiency and improve yield and hue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If solvent extraction is used for decolorization to separate dye from fabric fibers, then the fabric can be recycled, but the method cannot effectively separate pigment with small particle size dispersed in resin, resulting in low yield
Solution Approach 1:
The patent applies preliminary action by performing a pre-depolymerization step before the main depolymerization process. The dope-dyed fabric is first depolymerized at lower temperature (180-220°C) for shorter time (5-120 minutes) to break down the resin matrix and release pigments, making them accessible for subsequent filtration. This preliminary breakdown enables effective separation that would be impossible in the intact fabric structure.
Solution Approach 2:
The patent uses activated carbon as an intermediary substance to facilitate pigment separation. The activated carbon particles (with size larger than pigment particles) act as a mediator that adsorbs and aggregates the fine pigment particles dispersed in the depolymerized resin, enabling their removal through filtration. This intermediary approach solves the problem of separating sub-micrometer pigments that cannot be directly filtered.
2Ease of manufacture
If conventional filtration is used to separate pigment from resin, then the process is simple, but filtration is more difficult and pigment may easily adhere during subsequent crystallization process
Solution Approach 1:
The patent applies parameter changes by controlling the particle size relationship between activated carbon and pigment. The activated carbon is selected with particle size larger than the pigment particles (first particle size < 1 micrometer, second particle size > 1 micrometer). This parameter difference enables the activated carbon to aggregate the fine pigments while allowing the mixture to pass through filtration, achieving both ease of filtration and complete separation.
Solution Approach 2:
The patent replaces direct mechanical filtration of fine pigments with a chemical-physical approach using activated carbon adsorption. Instead of attempting to mechanically filter sub-micrometer pigment particles directly, the method uses activated carbon to chemically adsorb and physically aggregate these particles, transforming the separation mechanism from direct mechanical filtration to adsorption-based separation followed by filtration.
3Manufacturing precision
If activated carbon with large particle size is used to aggregate pigment with small particle size, then separation efficiency is improved, but the mixing and filtration process becomes more complex
Solution Approach 1:
The patent applies segmentation by dividing the overall recycling process into distinct stages: pre-depolymerization, mixing with activated carbon, filtration, and post-processing. Each stage has a specific function and can be independently optimized and controlled. This segmentation allows the complex task of pigment separation to be broken down into manageable steps, reducing overall process complexity while maintaining high separation efficiency.
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 method effectively separates pigments from resin, resulting in recycled polyester fabrics with improved yield and hue, while also allowing for waste disposal and energy recovery through activated carbon utilization.
Implementation Method 1
adding the oligomer to an activated carbon to perform a mixing procedure; and performing a filtration procedure to separate the oligomer from the activated carbon
Data Source
AI summary
A manufacturing method of a recycled polyester fabric includes: providing a dope-dyed fabric; performing a pre-depolymerization step on the dope-dyed fabric; and performing a post-processing step on a pre-depolymer to obtain the recycled polyester fabric. The dope-dyed fabric includes a pigment and a polyethylene terephthalate resin, and a first particle size of the pigment is less than 1 micrometer. The pre-depolymerization step includes performing a first depolymerization procedure on the dope-dyed fabric to form an oligomer; adding the oligomer to an activated carbon to perform a mixing procedure; and performing a filtration procedure to separate the oligomer from the activated carbon and obtain the pre-depolymer. A second particle size of the activated carbon is larger than the first particle size of the pigment. The post-processing step includes a second depolymerization procedure, a monomer purification procedure, a polymerization procedure, or a combination thereof.