Distillative Ketazine Removal from Polyurethane Dispersions
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Solution Overview
Problem
The existing processes for producing aqueous polyurethane dispersions result in the formation of ketazine as a by-product, which has a high boiling point and can hydrolyze back to carcinogenic hydrazine, posing a significant environmental and health risk, and there is a need for a method to remove ketazine without impairing the quality of the dispersion.
Innovation Solution
A process involving distillation where the vapour temperature is controlled to exceed the boiling point of acetone by no more than 10%, allowing for the removal of acetone and subsequently ketazine without reaching the boiling point of ketazine, thereby reducing its concentration to less than 100 ppm, while maintaining the quality of the polyurethane dispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If distillation is performed to remove ketazine by heating to its boiling point, then ketazine removal efficiency is improved, but the polyurethane dispersion quality deteriorates due to thermal degradation
Solution Approach 1:
The patent changes the temperature parameter during distillation by operating below the boiling point of ketazine (134°C at standard pressure). Specifically, the distillation is performed at reduced pressure where ketazine boils at lower temperatures, allowing removal of ketazine while preventing thermal degradation of the polyurethane dispersion. This parameter change resolves the contradiction between removal efficiency and product quality.
Solution Approach 2:
The patent utilizes phase transition (evaporation) of ketazine at temperatures below its standard boiling point by applying reduced pressure. This allows ketazine to be removed from the liquid dispersion through vaporization without heating the entire mixture to high temperatures that would degrade the polyurethane matrix, thus resolving the contradiction between effective removal and quality preservation.
2Manufacturing precision
If distillation temperature is increased to remove ketazine, then ketazine concentration is reduced, but energy consumption increases
Solution Approach 1:
The patent applies reduced pressure to the distillation system, which changes the boiling point parameter of ketazine to a lower temperature. This allows ketazine to be removed at lower temperatures than its standard boiling point, significantly reducing the energy input required for heating while achieving the same concentration reduction goal.
3Manufacturing precision
If acetone is completely removed from the dispersion, then dispersion purity is improved, but ketazine formation increases due to hydrazine reaction
Solution Approach 1:
The patent performs preliminary removal of acetone from the dispersion before the chain extension step. By eliminating acetone beforehand, the subsequent reaction between hydrazine and the prepolymer cannot form ketazine, thus preventing the harmful by-product while maintaining dispersion purity. This sequential approach resolves the contradiction between purity and harmful factor formation.
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 method effectively removes over 90% of ketazine from the polyurethane dispersion without increasing the temperature to the boiling point of ketazine, ensuring the dispersion is free from harmful residues and maintaining its quality.
Implementation Method 1
a process for removing ketazine from polyurethane dispersions by means of distillation below the boiling point of ketazine
Implementation Method 2
the vapour temperature constantly exceeds the temperature at which removal of acetone is achieved by at maximum 10%
Data Source
AI summary
The present invention relates to a process for removing ketazine from polyurethane dispersions by means of distillation below the boiling point of ketazine.