Azo Pigment Production via Partial Dissolution Crystallization
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Solution Overview
Problem
Current methods for producing azo pigments face challenges such as instability of diazonium compounds, low yield, and high costs, particularly in achieving high-purity and fine particle sizes, especially when dealing with heterocyclic diazonium compounds.
Innovation Solution
A process involving an azo coupling reaction where the diazonium salt is not completely precipitated, allowing for partial dissolution in the reaction solution, followed by mixing with a poor solvent to crystallize the azo pigment, using acidic solutions with solvents like acetic acid and sulfuric acid, and controlling the solubility to achieve high-efficiency production of fine particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the diazonium compound is completely precipitated in the reaction solution, then the azo pigment can be easily separated and purified, but the particle size becomes coarse and fine dispersion is difficult to achieve
Solution Approach 1:
The patent applies partial action by allowing the azo compound to remain partially dissolved in the reaction solution rather than completely precipitating. The reaction solution is poured into a poor solvent to induce crystallization of fine particles while maintaining some compound in solution, achieving optimal particle size for fine dispersion without compromising separation ease
Solution Approach 2:
The patent changes the solvent parameters by selecting specific poor solvents (water, lower alcohols, ether, esters) and controlling the pouring conditions to adjust the degree of precipitation. This parameter control enables fine particle formation while maintaining manufacturability
2Manufacturing precision
If a large amount of solvent is used to dissolve the pigment at low concentration, then fine nanosize particles can be obtained, but the production cost increases and the process becomes unprofitable
Solution Approach 1:
The patent utilizes phase transition by pouring the reaction solution into a poor solvent, causing the azo compound to transition from dissolved state to crystalline precipitate. This phase change enables fine particle formation through controlled crystallization without requiring large amounts of solvent
Solution Approach 2:
The poor solvent acts as an intermediary medium that induces crystallization of fine particles from the reaction solution. By using this intermediary, fine particle formation is achieved without needing to dissolve the pigment in large amounts of solvent at low concentration
3Reliability
If the diazonium compound is highly unstable, then the coupling reaction becomes difficult to control, but high-purity azo pigment in high yield is required
Solution Approach 1:
The patent applies preliminary action by performing the coupling reaction immediately after generating the diazonium compound and pouring into the poor solvent. This rapid sequence prevents decomposition of the unstable diazonium compound while ensuring high-purity, high-yield azo pigment formation
Solution Approach 2:
The patent rushes through the reaction process by immediately pouring the reaction solution into the poor solvent after coupling, skipping intermediate isolation steps. This rapid processing prevents instability issues while maintaining high purity and yield
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 enables the production of azo pigments with high purity and productivity at a low cost, effectively addressing the instability and yield issues of existing methods, and achieving fine particle sizes suitable for applications like liquid crystal display color filters and inkjet inks.
Implementation Method 1
a step of performing a coupling reaction between the diazonium compound obtained in step (a) and a coupling component to obtain a mixture in which at least a part of an azo compound
Implementation Method 2
the reaction solution is poured in a poor solvent for the azo compound so as to crystallize an azo pigment
Implementation Method 3
the diazonium compound obtained in step (a) is mixed with an acidic solution containing the coupling component dissolved in an acidic solvent
Data Source
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AI summary
An object is to provide a production process of an azo pigment where an azo pigment can be produced as a fine particle with high efficiency at a low cost, an azo pigment using the production process, and a coloring composition. The process of the present invention for producing an azo pigment or its salt or hydrate includes: (a) a step of mixing a diazotizing agent and an amino compound, (b) a step of performing a reaction by mixing the reaction product obtained in the step (a) with a coupling component to obtain a solution in which at least a part of an azo compound represented by the following formula (1) produced by the reaction is dissolved, and (c) a step of mixing the solution obtained in the step (b) with a poor solvent for the azo compound to crystallize an azo pigment represented by the following formula (1): wherein G represents a heterocyclic group, each of R, X, Y, Z and Q independently represents a hydrogen atom or a substituent, n represents an integer of 1 to 4, and the formula represents a dimer through R, X, Y, Z, Q or G when n=2, represents a trimer through R, X, Y, Z, Q or G when n=3, and represents a tetramer through R, X, Y, Z, Q or G when n=4. Also, the azo pigment of the present invention or its salt or hydrate is produced by the production process above, and the coloring composition of the present invention contains at least one of the azo pigment of the present invention, its tautomer, and a salt, hydrate or solvate thereof.