Nylon 6 and Polyether Polyurethane Recovery via Selective Dissolution
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Solution Overview
Problem
Current processes fail to recover high-purity ε-caprolactam and polyether polyurethane from nylon 6 and polyether polyurethane comprising materials on an industrial scale due to high temperatures causing degradation and solvent formation, resulting in inferior quality products and environmental concerns.
Innovation Solution
A process involving a separation, depolymerization, and purification sequence using selective dissolution below 100°C, followed by depolymerization at 180°C-400°C and solvent-based purification to obtain high-purity ε-caprolactam and polyether polyurethane, minimizing solvent use and environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high temperature depolymerization is used to recover ε-caprolactam from nylon 6, then depolymerization efficiency is improved, but product degradation and solvent formation occur resulting in inferior quality
Solution Approach 1:
The process is divided into multiple sequential stages: pretreatment, depolymerization, filtration, and purification. Each stage addresses specific requirements - the depolymerization stage operates at high temperature for efficiency, while the purification stage removes degradation products to ensure purity. This segmentation allows optimization of each stage independently.
Solution Approach 2:
Water is introduced as an intermediary substance during depolymerization to facilitate the breakdown of nylon 6 into ε-caprolactam. The water acts as a medium that enables the hydrolysis reaction, and subsequent removal of water through evaporation and purification steps leaves high-purity ε-caprolactam without the harmful effects of high temperature direct heating.
2Speed
If conventional high temperature processing is used, then processing speed is improved, but environmental harm increases due to solvent formation and degradation
Solution Approach 1:
The process carefully controls temperature parameters at different stages. During depolymerization, temperature is maintained at 180-400°C to ensure complete breakdown. During evaporation and purification, temperature is reduced to 60-100°C to prevent degradation and solvent formation. This dynamic parameter adjustment maintains processing speed while eliminating environmental harm.
Solution Approach 2:
The process uses a combination of multiple treatment methods - hydrolysis, filtration, evaporation, and crystallization - rather than relying on a single high-temperature step. This composite approach achieves complete depolymerization and purification without the need for prolonged high-temperature exposure that would generate harmful solvents.
3Manufacturing precision
If selective dissolution at low temperature is used to separate polyether polyurethane, then product quality is improved, but processing time increases
Solution Approach 1:
The dissolution temperature is optimized to 60-100°C, which is low enough to prevent degradation of polyether polyurethane and ensure high separation quality, yet high enough to maintain adequate dissolution rate. This parameter optimization balances processing time and product quality.
Solution Approach 2:
The dissolution process is conducted continuously with adequate mixing and agitation to maximize the dissolution rate at the moderate temperature. The filtered solution is then immediately processed through evaporation and recovery steps without interruption, minimizing total processing time while maintaining separation 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
The process achieves high yields of high-purity ε-caprolactam and polyether polyurethane, reducing carbon footprint and production costs, suitable for industrial-scale recycling of nylon 6 and polyether polyurethane comprising materials.
Implementation Method 1
separating the nylon 6 and polyether polyurethane comprising material in a nylon 6 rich stream and a polyether polyurethane rich stream by selective dissolution of the polyether polyurethane in an organic solvent at a temperature below 100° C.
Implementation Method 2
depolymerizing the nylon 6 in the nylon 6 rich stream in the depolymerization section (C) at a temperature ranging from 180° C. to 400° C.
Implementation Method 3
extracting the crude ε-caprolactam with an organic solvent so that an aqueous phase and an organic phase are obtained
Implementation Method 4
obtaining purified ε-caprolactam by crystallization of ε-caprolactam from a solution comprising ε-caprolactam and impurities at a temperature of 10° C. to 95° C.
Data Source
AI summary
The present invention provides a process for recovering ε-caprolactam and polyether polyurethane from nylon 6 and polyether polyurethane comprising material in a plant, wherein the plant comprises a separation section [B], a depolymerization section [C], a recovery section [D], and a purification section [E].