Process and plant for recycling fabrics
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Solution Overview
Problem
Existing methods for recycling elastomeric fibers from waste fabrics often result in partial degradation of the material, making it unsuitable for reuse with the required mechanical characteristics.
Innovation Solution
A process involving the use of a solvent recirculation system where elastomeric fibers are extracted from waste textiles in a static extraction chamber, with the solvent being repeatedly circulated to increase contact time and concentration, and then evaporated under reduced pressure to minimize degradation, using a solvent like dimethylacetamide (DMAC) at controlled temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrothermal reactors with superheated reaction solution and organic acids are used to hydrolyze fabric, then the elastomeric fibers can be recovered, but the elastomeric material undergoes partial degradation that compromises its mechanical characteristics
Solution Approach 1:
The patent changes the chemical parameters of the extraction process by using supercritical carbon dioxide instead of organic acids and superheated water. This alternative parameter set achieves elastomeric fiber recovery without the degradation caused by acid hydrolysis, thereby maintaining mechanical characteristics while enabling recycling.
Solution Approach 2:
The patent employs carbon dioxide in its supercritical state as an inert solvent environment for extracting elastomeric materials. This inert atmosphere prevents the chemical degradation that occurs with acid-based hydrolysis, allowing recovery of elastomeric fibers that retain their original mechanical properties and can be reused effectively.
2Ease of manufacture
If controlled thermal degradation is used to separate spandex PU fibers from yarns, then separation can be achieved, but the elastomeric material is degraded and requires additional processing for reuse
Solution Approach 1:
The patent replaces thermal degradation mechanisms with a solvent extraction mechanism using supercritical carbon dioxide. This substitution achieves separation of elastomeric fibers from the fabric matrix without applying degrading thermal stress, thereby maintaining material quality while simplifying the recovery process.
Solution Approach 2:
The patent utilizes the phase transition properties of carbon dioxide between supercritical and gaseous states to control the extraction process. By adjusting pressure and temperature to achieve supercritical conditions, the CO2 effectively dissolves and extracts elastomeric materials, then returns to gaseous state for easy separation, leaving recovered fibers undegraded and ready for reuse.
3Productivity
If polar solvents like DMAC or DMF are used to remove polyurethane fibers from fabric, then fiber removal is effective, but the process complexity increases and environmental concerns arise
Solution Approach 1:
The patent employs carbon dioxide as a solvent that can be easily separated from the extracted elastomeric material through pressure reduction. The CO2 then returns to gaseous state and can be readily condensed and reused, eliminating the need for complex solvent recovery systems required by traditional polar solvents like DMAC or DMF, thereby reducing overall process complexity.
Solution Approach 2:
The patent uses carbon dioxide as an environmentally benign, inert solvent alternative to polar solvents like DMAC and DMF. This eliminates environmental concerns associated with toxic polar solvents while maintaining effective extraction capability. The inert nature of CO2 also simplifies safety handling and reduces the complexity of solvent management infrastructure.
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 effectively recovers elastomeric material with minimal degradation, achieving a yield of 90-99% and maintaining the material's physical and chemical properties, allowing for its reuse with minimal post-treatment.
Implementation Method 1
circulating a solvent through said extraction chamber and said waste textile to dissolve and remove the elastomeric material from the waste textile
Implementation Method 2
evaporating at least part of the solvent obtained in step c) in an evaporation chamber to increase the amount of elastomeric material in the solvent
Implementation Method 3
condensing the evaporated solvent in at least one condensation chamber
Data Source
Figure 1
Figure 2
AI summary
In a process for recycling waste fabric comprising elastomeric material a polar solvent is flowed through the waste fabric in an extraction chamber to dissolve and remove the elastomeric material; the solvent is evaporated in an evaporation chamber and condensed to be sent to a solvent collection tank or back to the extraction chamber; the dissolved elastomeric material is eventually recovered from the concentrated polar solvent.