Merocyanine Crystallization pH Control for Impurity Removal
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Solution Overview
Problem
Merocyanine compounds used as UV absorbers often contain colored impurities that cause unwanted discoloration in final products, such as sunscreen creams or packaging, leading to reduced effectiveness and aesthetic issues.
Innovation Solution
A crystallization process for merocyanine compounds involving dissolution in an organic, polar solvent at a pH below 7, followed by crystallization and isolation, which minimizes residual colored impurities and improves color properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If merocyanine compounds are produced via multi-step sequence, then the compound can be synthesized, but colored by-products are formed causing unwanted discoloration
Solution Approach 1:
The patent extracts and removes colored impurities from the merocyanine compound through crystallization processes. The purification steps separate the desired product from harmful by-products, achieving both synthesis capability and removal of discoloration causes.
Solution Approach 2:
The patent changes physical and chemical parameters during crystallization, including pH control (maintaining pH below 7), temperature variations, and solvent selection, to optimize the separation of merocyanine from colored impurities and minimize discoloration.
2Device complexity
If conventional crystallization is performed without pH control, then the process is simpler, but the Gardner Index is higher indicating more discoloration
Solution Approach 1:
The patent introduces pH control as a critical parameter in the crystallization process. By maintaining pH below 7 through acid addition, the process achieves lower Gardner Index values and reduced discoloration, demonstrating that this parameter change significantly improves product quality.
3Manufacturing precision
If purification steps are increased to reduce colored impurities, then purity improves, but the process becomes more complex
Solution Approach 1:
The patent utilizes phase transitions during crystallization to achieve purification. The merocyanine compound transitions from dissolved state to crystalline form, naturally separating from impurities that remain in solution, thereby achieving high purity through a relatively simple process.
Solution Approach 2:
The crystallization process extracts the pure merocyanine compound from the reaction mixture, separating it from colored impurities that remain in the mother liquor. This single extraction step achieves significant purification without requiring multiple complex treatment stages.
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
The process achieves merocyanine crystals with a Gardner Index of less than 5 and a transmission value at 460 nm higher than 90%, indicating superior purity and reduced discoloration in final applications.
Implementation Method 1
dissolving a merocyanine compound in an organic, polar solvent
Implementation Method 2
causing crystallization of the merocyanine compound from the solution obtained in step (a)
Data Source
AI summary
The present invention relates to a process for preparing a crystalline merocyanine compound, comprising the step of dissolving a merocyanine compound in an organic, polar solvent, wherein the process is performed at a pH below than 7 in the presence of an acid, wherein residual levels of colored impurities are eliminated.