After being familiar with and mastering the solubility, volatilization speed and surface tension of solvent, how to choose and quantify the mixed solvent in gravure ink?
First, the solvent can be dissolved or mixed by selecting the solvent.
According to the mechanism of action, solvents can be divided into true solvent, false solvent and cosolvent. In gravure ink solvent, the solvent that can dissolve gravure ink alone is called true solvent; the solvent that can't dissolve gravure ink is called false solvent; the solvent that can't dissolve gravure ink only by mixing with other solvents is called cosolvent. Adjust the balance between true solvent, false solvent and cosolvent to achieve the expected solubility, evaporation rate, viscosity and other requirements. The solubility of mixed solvents should not be too large or too small. Because it is too large, the solvent is slow to dilute; if it is too small, the resin can not be fully dissolved, affecting the quality of gravure printing ink.
The volatilization of mixed solvents generally belongs to the volatilization behavior of non ideal liquid. If the proportion of the true solvent to the residual solvent is reduced, the solubility will be weakened, and the wet film will be in a bad dissolution state or even insoluble, resulting in phase separation phenomenon, which makes the ink film appear white. Therefore, the amount of fast, medium and slow volatile components in the mixed solvent formula should be balanced, the distillation curve equation of mixed solvent should be in the shape of equilibrium rising, and try to keep the composition of vapor phase and liquid phase of mixed solvent consistent in the process of volatilization at ambient temperature, so that the mixed solvent has good solubility.
Second, establish the volatile profile of solvent or mixed solvent. If the volatilization diagram of solvent or mixed solvent with time and temperature is not known, it is usually necessary to select several mixed solvents with different volatile properties to test, so as to establish the volatile profile of these mixed solvents and provide reference for the selection of solvent or mixed solvent.
Third, experiments confirm the selected solvent or mixed solvent. Once several candidate solvents or mixed solvents are selected through the above steps, the next step is to determine which solvent or mixed solvent can meet the requirements of gravure ink formula through experiments. Sometimes, it may be necessary to adjust the composition and amount of mixed solvent in a small range to improve a certain aspect of gravure ink The properties of gravure ink, such as viscosity, leveling, volatilization and so on, can finally meet the requirements of gravure ink performance of mixed solvents.
Fourth, optimize the solvent or mixed solvent to meet the solubility of resin and other properties of gravure ink. Under the premise of ensuring that the mixed solvent has sufficient dissolving power, suitable volatilization speed, proper viscosity and surface tension, according to the above performance data, effective, inexpensive and low toxic solvent is selected, which can effectively dissolve resin and disperse pigment, meet the performance requirements of ink film, and reduce the cost of solvent as much as possible.
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