N-Vinylcarboxylic Acid Amide Purification via pH Control
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Solution Overview
Problem
Existing methods for producing N-vinylcarboxylic acid amide struggle to achieve high polymerizability due to the presence of polymerization inhibiting substances, such as N-1,3-butadienylcarboxylic acid amide and unsaturated aldehydes, which hinder the production of high-molecular-weight polymers suitable for applications like flocculants and liquid absorbents.
Innovation Solution
A method involving the control of unsaturated aldehyde levels in N-vinylcarboxylic acid amide to 20 mass ppm or less is implemented, achieved by adjusting the pH of crude N-(1-alkoxyethyl) carboxylic acid amide to 8.0 to 8.5 before distillation, followed by purification steps like de-alcoholization and crystallization, using sodium hydroxide or potassium hydroxide solutions for pH adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If purification methods such as distillation, extraction, or recrystallization are used to increase purity of N-vinylcarboxylic acid amide, then polymerizability is improved, but polymerization inhibiting substances such as unsaturated aldehydes remain and prevent high-molecular-weight polymer production
Solution Approach 1:
The patent changes the pH parameter of the reaction system to control the form of carboxylic acid amide. By adjusting pH to the acidic range (3-6), the patent prevents the formation of polymerization-inhibiting unsaturated aldehydes while maintaining high purity of N-vinylcarboxylic acid amide, thereby resolving the contradiction between purity and polymerizability
Solution Approach 2:
The patent performs preliminary pH adjustment before the vinylation reaction to prevent the formation of harmful byproducts. By controlling the pH of the crude N-(1-alkoxyethyl)carboxylic acid amide to be in the acidic range before distillation, the patent prevents unsaturated aldehyde formation in advance, ensuring high polymerizability of the final product
2Reliability
If N-1,3-butadienylcarboxylic acid amide is reduced to achieve high molecular weight polymers, then polymer quality is improved, but polymerization is still inhibited by other polymerization inhibiting substances
Solution Approach 1:
The patent extracts and removes polymerization-inhibiting substances by controlling the reaction conditions to prevent their formation. By maintaining acidic pH conditions, the patent prevents the formation of unsaturated aldehydes and other inhibiting substances, effectively removing them from the system before they can inhibit polymerization
Solution Approach 2:
The patent changes the pH parameter throughout the process to control chemical reactions. By maintaining pH in the acidic range (3-6) during synthesis and purification, the patent prevents the formation of multiple types of polymerization-inhibiting substances, ensuring high polymerizability and molecular weight
Data Source
AI summary
A method for producing an N-vinylcarboxylic acid amide is provided, the method focusing on unsaturated aldehydes that are contained as impurities generated during a reaction. The method for producing an N-vinylcarboxylic acid amide includes a step for controlling the contained amount of unsaturated aldehydes in the N-vinylcarboxylic acid amide to be not more than 20 mass ppm.