Nylon Salt Solution Production via Eutectic Mixture Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for manufacturing nylon salt solutions require significant energy exchange for dissolving adipic acid, removing reaction heat, and evaporating water, making them inefficient and incompatible with storage and transport at high concentrations.
Innovation Solution
A process that produces an aqueous solution of diamine and diacid salts with a concentration of 50-80% by weight, involving a first reactor where a diacid/diamine molar ratio of 1.5-5 and a water concentration of 40-75% is maintained below the boiling point, followed by a second reactor where the ratio is adjusted to 0.9-1.1, minimizing heat exchange and using an oxygen-free atmosphere to prevent oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If water is evaporated to increase nylon salt concentration above 70%, then concentration is improved, but temperature and pressure requirements increase making storage and transport incompatible
Solution Approach 1:
The invention changes the composition parameters by adding excess diacid (adipic acid) to the nylon salt solution, creating a eutectic mixture that depresses the freezing point and allows high concentration (up to 80% or more) at ambient temperatures. This compositional parameter change resolves the contradiction between high concentration and moderate temperature requirements for storage and transport
Solution Approach 2:
Excess diacid acts as an intermediary substance that mediates between the high concentration requirement and the temperature constraint. The diacid forms a eutectic system with the nylon salt, enabling the solution to remain liquid at ambient temperatures while achieving concentrations above 70%, thus facilitating storage and transport
2Ease of operation
If excess diacid is added to achieve high concentration at ambient temperature, then storage and transport compatibility is improved, but diacid/diamine ratio control becomes more difficult
Solution Approach 1:
The invention performs preliminary action by adding the exact amount of excess diacid during the neutralization process itself, rather than attempting to adjust the ratio after concentration is achieved. The process calculates and adds the precise excess diacid amount needed to achieve both the desired concentration and maintain proper stoichiometry, preventing precipitation during subsequent storage and transport
Solution Approach 2:
The invention implements feedback control by monitoring the diacid/diamine ratio throughout the neutralization process and adjusting the addition rates accordingly. The system ensures that the final mixture contains the correct excess diacid amount to maintain both high concentration and proper stoichiometry, with the understanding that some free diacid will remain to prevent precipitation
3Reliability
If traditional neutralization methods are used with heat removal, then reaction control is achieved, but energy consumption increases
Solution Approach 1:
The invention converts the harmful effect of heat generation during neutralization into a beneficial feature. Instead of removing heat as in traditional methods, the process allows the exothermic neutralization reaction to heat the mixture, which accelerates the reaction rate and improves mixing efficiency. The added excess diacid serves as a heat sink, absorbing the reaction heat and preventing runaway temperature increases, thus converting the thermal hazard into a process advantage that reduces external energy input requirements
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
This process minimizes energy exchange and prevents oxidation, allowing for the production of a stable, concentrated nylon salt solution that can be efficiently stored and transported without the need for high temperatures or pressures.
Implementation Method 1
removing the heat produced by the neutralization reaction
Implementation Method 2
circulation of the solution in a mixing zone, then in a condenser to remove the calories generated by the reaction
Implementation Method 3
the solution being brought to a temperature at most equal to the boiling point of the solution at the operating pressure
Data Source
AI summary
The invention relates more particularly to a process for producing a concentrated solution of hexamethylenediammonium adipate salt, also known as nylon salt, used as starting material for the production of polyamide, more specifically of PA66. The process for producing an aqueous solution of diamine and diacid salts, obtained by mixing a diacid and a diamine, at a concentration of salt of between 50% and 80% by weight, comprises preparing, in a first step, an aqueous solution of diacid and diamine having a diacid/diamine molar ratio of greater than 1.1 and, in a second step, adjusting the diacid/diamine molar ratio, through the addition of diamine, to a value of between 0.9 and 1.1, preferably between 0.99 and 1.01, and fixing the concentration of salt by weight through, optionally, the addition of water.