Cellulosic Textile Recycling via Reducing Swelling and pH-Controlled Bleaching
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Solution Overview
Problem
Current methods for recycling cellulose from textiles are inefficient, particularly in terms of yield and de-colorization, and can cause clogging issues in viscose production processes.
Innovation Solution
A method involving sequential steps: providing textile materials, swelling cellulose under reducing conditions with a reducing agent, and bleaching with oxygen at alkaline conditions or ozone at acid conditions to improve yield, de-colorization, and control viscosity, preventing nozzle clogging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional recycling methods are used to process cellulose from textiles, then the process can be performed with standard equipment, but the yield is low and de-colorization is ineffective
Solution Approach 1:
The patent applies preliminary action by performing a swelling step under reducing conditions before the main bleaching process. This pre-treatment modifies the cellulose structure to make it more accessible to subsequent bleaching agents, thereby improving de-colorization efficiency and recycling yield without requiring complex equipment changes
Solution Approach 2:
The patent employs parameter changes by systematically varying pH levels, temperature, and chemical concentrations across different process stages. The swelling step uses specific pH and reducing agent concentrations, followed by controlled bleaching at different pH conditions, optimizing both yield and de-colorization while maintaining process feasibility
2Ease of manufacture
If strong bleaching agents are used to improve de-colorization, then color removal is enhanced, but the cellulose viscosity decreases and causes nozzle clogging in viscose production
Solution Approach 1:
The patent carefully controls pH parameters throughout the process. The swelling step uses alkaline conditions with reducing agents, followed by bleaching at controlled pH levels. This parameter control achieves effective de-colorization while preserving cellulose viscosity by avoiding excessive degradation, thus preventing nozzle clogging in subsequent viscose production
Solution Approach 2:
The patent uses reducing agents as intermediaries during the swelling step before bleaching. These reducing agents protect the cellulose structure from excessive degradation during the subsequent bleaching process, enabling effective color removal while maintaining sufficient viscosity for viscose production without causing nozzle clogging
3Ease of manufacture
If the cellulose is heavily processed to improve recycling quality, then the de-colorization is enhanced, but the polymerization degree decreases and yield is reduced
Solution Approach 1:
The swelling step under reducing conditions serves as a preliminary action that prepares the cellulose for bleaching without causing significant polymerization degradation. This pre-treatment makes the cellulose more accessible to bleaching agents while preserving the polymer structure, thereby achieving good de-colorization with minimal yield loss
Solution Approach 2:
Reducing agents act as intermediaries that protect the cellulose polymer chains during the bleaching process. By applying reducing conditions before bleaching, the patent prevents excessive chain scission and polymerization degree reduction, maintaining both recycled cellulose quality and acceptable yield
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
Enhances cellulose recycling yield, effectively de-colorizes materials, and prevents nozzle clogging in viscose production, allowing for the production of high-quality recycled cellulose suitable for use in viscose processes.
Implementation Method 1
treating the material to swell the cellulose under reducing conditions, wherein at least one reducing agent is present at least during a part of the swelling
Implementation Method 2
bleaching the material with oxygen at alkaline conditions pH 9-13.5
Implementation Method 3
bleaching the material with ozone at acid conditions below pH 6
Data Source
AI summary
A method for recycling textiles comprising cellulose with the following steps of: optionally disintegrating the textile, swelling the cellulose, under reducing conditions, wherein at least one reducing agent is present at least during a part of the swelling, and then performing at least one of the following two bleaching steps in any order: i) bleaching the material with oxygen at alkaline conditions with a pH in the range 9-13.5, and ii) bleaching the material with ozone at acid conditions below pH 6. An advantage is that the yield is improved at the same time as excellent decolourization is achieved. If the recycled material is used in viscose manufacture, the risk of clogging nozzles and so on is reduced.