Glycolide Depolymerization Impurity Control
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Solution Overview
Problem
The production of high-molecular weight polyglycolic acid from glycolide is hindered by impurities in commercially produced glycolic acid oligomers, including nitrogen-containing substances that slow down the depolymerization reaction and increase viscosity, making it difficult to achieve stable and efficient glycolide production.
Innovation Solution
A process involving repetitive or continuous feeding of glycolic acid oligomer into a depolymerization system with an organic solvent, where the concentration of depolymerization-obstructing substances, such as diglycolic acid and nitrogen-containing compounds, is controlled to no more than 15 wt.% to suppress adverse effects, and the use of a polar organic solvent with specific boiling and molecular weight ranges for efficient glycolide formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If commercially produced glycolic acid oligomer is used as starting material for glycolide production, then the process can be economically viable, but impurities including nitrogen-containing substances and hydroxyl group-free carboxylic acids adversely affect the depolymerization reaction
Solution Approach 1:
The patent applies preliminary action by purifying the glycolic acid oligomer before using it in the depolymerization process. Specifically, the oligomer is treated to remove hydroxyl group-free carboxylic acids and nitrogen-containing substances in advance, so that the depolymerization reaction can proceed efficiently without interference from these impurities. This preliminary purification step enables the use of commercially produced oligomer while mitigating the harmful effects of impurities.
Solution Approach 2:
The patent extracts and removes specific impurities from the glycolic acid oligomer mixture. Hydroxyl group-free carboxylic acids and nitrogen-containing substances are selectively extracted or removed through purification processes, leaving behind the desired glycolic acid oligomer that can undergo efficient depolymerization. This extraction approach directly addresses the harmful effects of impurities while maintaining the economic viability of using commercial starting materials.
2Adaptability or versatility
If impurity carboxylic acids are present in the depolymerization system, then the process can proceed with commercially available oligomer, but the reaction velocity decreases and viscosity increases
Solution Approach 1:
The patent applies parameter changes by controlling the concentration of impurities in the depolymerization system. Through purification treatments, the levels of hydroxyl group-free carboxylic acids and nitrogen-containing substances are reduced to specific ranges that allow efficient depolymerization. This parameter control enables the use of commercially available oligomer while maintaining optimal reaction velocity and viscosity characteristics throughout the process.
3Ease of manufacture
If nitrogen-containing substances are present in the oligomer, then the production process can utilize common glycolic acid synthesis methods, but the depolymerization is obstructed and viscosity increases
Solution Approach 1:
The patent applies preliminary action by removing nitrogen-containing substances from the glycolic acid oligomer before the depolymerization process. Common glycolic acid synthesis methods that may introduce nitrogen-containing impurities are used to produce the oligomer, followed by a purification step that specifically removes these nitrogen-containing substances. This ensures that the depolymerization can proceed reliably without obstruction from nitrogen-containing contaminants.
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 approach stabilizes the depolymerization process, allowing for the effective and prolonged production of glycolide by reducing the impact of impurities, thereby improving the efficiency and yield of the glycolide production process.
Implementation Method 1
depolymerizing the glycolic acid oligomer under heating to produce glycolide
Implementation Method 2
a depolymerization system containing an organic solvent
Data Source
AI summary
Glycolide production through depolymerization of glycolic acid oligomer is stabilized by controlling impurities in the glycolic acid oligomer to allow economical and effective production of glycolide. More specifically, the depolymerization system is controlled to suppress an effective concentration (x+100y wt. %) of depolymerization-obstructing substances calculated as a total of a concentration calculated as diglycolic acid (of x wt. %) of hydroxyl group-free impurity carboxylic acids (A) and 100 times a concentration calculated as ammonia (of y wt. %) of nitrogen-containing substances (B), respectively with respect to the starting glycolic acid oligomer in the depolymerization system, to at most 15 wt. %.