Fishing-Net Nylon 6 Depolymerization for High-Purity Caprolactam
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Solution Overview
Problem
Existing processes for recovering epsilon-caprolactam from nylon 6 comprising fishing nets produce low-quality monomers unsuitable for high-demanding applications, generate significant waste, and have a high carbon footprint, lacking efficient, economically viable methods to purify and recycle these materials on an industrial scale.
Innovation Solution
A process involving depolymerization, recovery, and purification steps, including temperature-controlled depolymerization at 180°C to 400°C, solvent extraction, and crystallization, which effectively separates epsilon-caprolactam from impurities, producing high-purity epsilon-caprolactam suitable for high-speed melt spinning and reducing carbon footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical recycling (re-granulation and compounding) is used to process wasted fishing nets, then processing simplicity is maintained, but the quality of recycled material deteriorates resulting in downcycling
Solution Approach 1:
The patent applies chemical recycling through depolymerization at controlled temperatures (180-400°C) to convert nylon 6 back to epsilon-caprolactam monomers, fundamentally changing the processing parameters from simple mechanical operations to controlled chemical reactions. This enables high-purity recovery suitable for high-speed melt spinning applications while maintaining economic viability through optimized process conditions
2Quantity of substance
If conventional depolymerization processes are used to recover epsilon-caprolactam from nylon 6, then monomer recovery is achieved, but purification efficiency deteriorates resulting in low-quality monomers
Solution Approach 1:
The patent employs a multi-stage purification process that extracts impurities from the depolymerization product stream. This includes filtration to remove solid particles, distillation to separate epsilon-caprolactam from volatile impurities, and crystallization to achieve high-purity monomer suitable for demanding applications like high-speed melt spinning
Solution Approach 2:
The purification process utilizes phase transitions including condensation of vaporized epsilon-caprolactam, crystallization from solution or melt, and filtration of solid impurities. These phase changes enable effective separation of the monomer from various impurities generated during depolymerization of fishing nets
3Quantity of substance
If conventional depolymerization and purification processes are used, then epsilon-caprolactam is recovered, but environmental impact worsens due to high carbon footprint and significant waste generation
Solution Approach 1:
The patent implements comprehensive waste recovery and resource utilization. Solid impurities from filtration are minimized through optimized depolymerization conditions, and the process is designed to recover epsilon-caprolactam with high efficiency. The purified monomer can be reused to produce new nylon 6, creating a circular economy approach that reduces the need for virgin petrochemical feedstock and lowers overall carbon footprint
Solution Approach 2:
The patent optimizes depolymerization parameters including temperature (180-400°C), residence time, and catalyst selection to maximize epsilon-caprolactam yield while minimizing byproduct formation and waste generation. These parameter optimizations enable efficient monomer recovery with reduced environmental impact compared to conventional processes
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-purity epsilon-caprolactam suitable for high-speed melt spinning, reduces environmental impact, and operates economically, with a carbon footprint lower than virgin synthesis methods, enabling large-scale recycling of fishing nets.
Implementation Method 1
depolymerizing the material derived from nylon 6 comprising fishing net material in the depolymerization section (B) at a temperature ranging from 180° C. to 400° C.
Implementation Method 2
extracting the crude epsilon-caprolactam with an organic solvent, whereby an organic phase is obtained, and wherein the organic phase comprises the organic solvent, epsilon-caprolactam and impurities
Implementation Method 3
obtaining purified epsilon-caprolactam by crystallization of epsilon-caprolactam from a solution comprising epsilon-caprolactam and impurities at a temperature of 10 to 95° C.
Data Source
AI summary
The present invention provides a process and a plant for recovering purified F-caprolactam from nylon 6 comprising fishing nets, wherein the plant comprises a depolymerization section [B], a recovery section [C], and a purification section [D]. The present invention also provides purified ε-caprolactam that has a particularly low product carbon footprint and is obtained via depolymerization of nylon 6 from fishing nets. In a second preferred embodiment, the purification of the distilled caprolactam is achieved by crystallization in a process of concentrating. The crystallized caprolactam resulting from concentrating is generally sufficiently pure to be used directly. After crystallization, it may be necessary to purify the mother liquor by, for example, recycling it to the aqueous solution before the extraction with the alkyl phenol. The mother liquor can be purified for example by means of distillation.