Aramid Polymerization With Carbon Dioxide Solvent Recovery
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Solution Overview
Problem
Current aramid polymerization methods face challenges in controlling product quality and solvent recovery, particularly due to the use of solvents like NMP, which are difficult to recover and require stringent moisture control, leading to unstable product quality and environmental concerns.
Innovation Solution
Employing carbon dioxide in its liquid or supercritical state as a solvent for aramid polymerization, maintaining specific temperature and pressure conditions to stabilize the reaction, and using a mixture of organic and inorganic acid-binding agents to enhance molecular weight and solubility, followed by recycling the carbon dioxide through changes in temperature and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If NMP is used as solvent for aramid polymerization, then good dissolving capacity is achieved, but solvent recovery becomes difficult and product quality becomes unstable
Solution Approach 1:
The patent changes the physical and chemical parameters of the solvent system by using supercritical carbon dioxide instead of conventional NMP solvent. This parameter change resolves the contradiction by providing both adequate dissolving capacity through CO2's unique supercritical state properties and complete solvent recovery through its gaseous transition after reaction, eliminating product quality instability caused by moisture in NMP systems.
Solution Approach 2:
The patent utilizes the phase transition properties of carbon dioxide between supercritical and gaseous states. During polymerization, CO2 is maintained in supercritical state for dissolving monomers and polymers, then after reaction it transitions to gaseous state for easy separation and recovery. This phase transition mechanism simultaneously achieves good dissolving capacity and complete solvent recovery, resolving the quality stability issue.
2Quantity of substance
If NMP is used as solvent, then dissolving capacity is improved, but solvent recovery and sewage treatment become difficult
Solution Approach 1:
The patent exploits the phase transition of carbon dioxide from supercritical to gaseous state after the polymerization reaction. This phase change enables automatic solvent-product separation without complex recovery processes, making solvent recovery extremely easy while maintaining good dissolving capacity during the reaction phase.
Solution Approach 2:
The patent extracts the solvent recovery problem by using carbon dioxide's unique property of transitioning to gas phase after reaction. The CO2 solvent naturally separates from the polymer product through phase change and can be directly recovered by compression, eliminating the need for energy-intensive distillation or chemical treatment required for NMP recovery.
3Reliability
If moisture control is maintained in NMP system, then product quality is improved, but dehydration control becomes difficult
Solution Approach 1:
The patent creates an inert environment using supercritical carbon dioxide as the reaction medium. CO2's inherent low moisture content and inert properties eliminate the need for complex dehydration control systems. The supercritical CO2 environment naturally prevents moisture-related quality issues while simplifying the overall process control.
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
Achieves stable product quality with controllable molecular weight and high yield, while ensuring environmentally friendly and cost-effective solvent recovery, suitable for industrial applications.
Implementation Method 1
employs liquid carbon dioxide or supercritical carbon dioxide fluid as a solvent for polymerization reaction
Implementation Method 2
The use of liquid carbon dioxide and supercritical carbon dioxide as solvents... Separation of the product from the solvent can be achieved only by changing the temperature and/or pressure
Data Source
AI summary
Disclosed herein is a method for aramid polymerization using carbon dioxide as a solvent, comprising reacting phenylenediamine with benzenedicarbonyl dichloride, wherein an acid-binding agent is added to the reaction system, and liquid carbon dioxide and/or a supercritical carbon dioxide fluid is used as a reaction solvent. The method of the present application is environmentally friendly, saves resources, has low cost, and is safe for production and suitable for industrial production. The polycondensate obtained in the present application has a controllable molecular weight, a good product quality, and an intrinsic viscosity ηinh of 8-9 dl/g. The yield in the aramid condensation stage can reach 98%, and the recovery rate of the aramid condensation solvent is higher than 90%.