Rotatable Drum Methanolysis for Polyester Textile Recycling
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Solution Overview
Problem
Existing methods for recycling polyester textiles are inefficient in separating depolymerized polyester from other fiber types, particularly at high temperatures, leading to unwanted break-down of sensitive fibers and low yield of depolymerized polyester.
Innovation Solution
A method involving a rotatable drum reactor unit with a tilted axis less than 45°, where polyester fibers are mixed with a catalyst and methanol at controlled temperatures and pressures, followed by rinsing and spinning to separate depolymerized polyester from other fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high temperature is used for depolymerization to improve reaction efficiency, then depolymerization yield is improved, but fiber break-down increases and sensitive fibers are damaged
Solution Approach 1:
The patent changes the temperature parameter to an optimal range (80-240°C) that balances depolymerization efficiency with fiber integrity. This parameter optimization allows the process to achieve good depolymerization yield while preventing excessive fiber break-down and damage to sensitive fibers like cotton.
Solution Approach 2:
The patent introduces a catalyst (calcium oxide) as an intermediary substance that mediates the depolymerization reaction. The catalyst enables the reaction to proceed at lower temperatures with higher efficiency, thereby achieving good depolymerization yield without requiring high temperatures that would cause fiber break-down.
2Manufacturing precision
If conventional mixing methods are used to separate polyester from other fibers, then separation is achieved, but mixing efficiency is low and process time is extended
Solution Approach 1:
The patent employs a rotatable drum that dynamically tumbles the textile material during the depolymerization process. This dynamic mixing approach significantly improves contact between the polyester fibers and the catalyst-methanol suspension, enhancing separation efficiency while reducing the time required compared to conventional static mixing methods.
3Manufacturing precision
If textile material is soaked in catalyst-methanol mixture for extended time to improve depolymerization, then depolymerization completeness is improved, but fiber damage increases and productivity decreases
Solution Approach 1:
The patent optimizes the temperature parameter (80-240°C) and catalyst concentration to achieve complete depolymerization within a reasonable time frame. These parameter changes enable the process to maintain high depolymerization completeness while preventing excessive fiber damage and improving overall productivity.
Solution Approach 2:
The catalyst (calcium oxide) acts as an intermediary that accelerates the depolymerization reaction, allowing complete depolymerization to be achieved in shorter time compared to uncatalyzed processes. This reduces the soaking time required while maintaining depolymerization completeness and minimizing fiber damage.
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
Effectively separates depolymerized polyester from other fibers, maintaining their integrity, while optimizing yield and reducing unwanted fiber break-down, with efficient recovery of methanol for reuse.
Implementation Method 1
the drum is rotated during at least one of said mixing step and said depolymerization step to make the textile material tumble around inside thereof in contact with the catalyst and methanol
Implementation Method 2
providing a temperature of at least 80° C. in the reactor unit exposing the textile material to the catalyst and methanol to perform a methanolysis depolymerization reaction of the polyester portion
Implementation Method 3
the rotatable drum inside of a housing of the pressure vessel preferably is a perforated drum. This is preferable as it simplifies the separation of the methanol-monomer solution and the textile remaining in the rotatable drum after reaction, draining and spin drying
Implementation Method 4
draining and spin drying
Data Source
AI summary
The present invention describes a method of recycling at least a portion of a textile material comprising polyester fibers, the method comprisinga mixing step comprising bringing the textile material comprising polyester fibers and at least one other type of fibers into contact with a suspension comprising a catalyst and methanol in a rotatable drum of a reactor unit, the rotatable drum being arranged for rotating around an axis, said axis having an angle to the horizontal plane being less than 45°, preferable said rotatable drum being perforated;a depolymerization step comprising providing a temperature of at least 80° C. in the reactor unit and rotating the drum to make the textile material tumble around inside thereof in contact with the catalyst and methanol to perform a methanolysis depolymerization reaction of the polyester portion of the textile material, leaving said other type of fibers in a fiber state; andwithdrawing from the reactor unit a liquid solution comprising depolymerized polyester, and withdrawing from the rotatable drum a fiber material comprising said other type of fibers.