Maintaining the same print quality as solvent-based inks, a good water-based gravure printing ink must achieve zero emission of VOCs; must have good printability; be able to print on the surface of various types of substrate materials; and It is hoped that the cost of this type of printing ink will be relatively low.
The use of aqueous gravure printing inks can create problems such as changing the engraving of gravure printing cylinders, changing the operation of the printing press, maintenance of the printing press, replacement of the dryer, and the like. Similarly, the substrate material will also strongly influence the printing effect of the ink, especially for the printing of low surface tension substrates such as plastic film materials and coated paper surfaces. For non-coated paper, the ink may even cause deformation and curling of the paper. These problems do not exist for solvent-based gravure printing inks.
The importance of PH value of water-based gravure printing ink:
Comparing water-based and solvent-based gravure printing inks, the gravure printing process using solvent-based inks minimizes solvent evaporation during imprinting as the squeegee scrapes excess ink from the gravure printing ink holes. After the process is completed, the ink is transferred to the substrate material, and then the ink film is slowly formed. In this process, the solvent in the ink must complete the volatilization process before the ink film is adhered and quickly reach the drying of the ink film. In water-based inks, organic solvents are replaced by a certain percentage of water, cosolvents, and volatile amines that are necessary to neutralize acidic resins. Since the water is relatively slow in volatility, there is no problem in that the ink is volatilized and dried in the printing ink in the printing plate, but there is a problem of drying after printing. Therefore, the choice of the amines in the ink, the adjustment of the pH, and the control of the viscosity of the ink As important. Because the premature release of the amine solvent prior to the completion of the imprinting process results in a decrease in the pH, the resin dries in the ink refill in the intaglio printing cylinder. In addition, water and cosolvent systems are unable to redissolve the resin, unlike solvent inks. Therefore, it is impossible to re-dissolve any possible drop in pH. In the gravure printing, it is necessary to carefully control the PH value, because the drop of PH value of the ink causes the ink hole to be slowly blocked until it is completely blocked, which is a very serious problem and will cause the printing job to be unable to continue.
The importance of the surface tension of water-based gravure printing inks:
At the same time, the surface tension of ink is also an unavoidable factor, which is also completely different from solvent inks. Compared with solvent inks, the surface tension of inks is much higher; and too high a surface tension will cause inks to not wet the surface of the substrate material and ink in the gravure printing cylinders. This will cause the ink film Uniform; due to the surface tension of the ink, the ink film will form a contracted state on the surface of the substrate, causing the ink film to show a clear mesh, which can also cause the ink to be uniformly transferred from the ink hole to the surface of the substrate.
However, the surface tension can be reduced, which requires careful selection of the appropriate surfactant or a small amount of alcohol. Despite the enormous amount of labor involved in developing printing inks, it is still a difficult challenge to completely reduce the VOC emissions of gravure printing while maintaining the printing quality of printing inks (as with the printing quality of solvent-based inks).
The use of aqueous gravure printing inks can create problems such as changing the engraving of gravure printing cylinders, changing the operation of the printing press, maintenance of the printing press, replacement of the dryer, and the like. Similarly, the substrate material will also strongly influence the printing effect of the ink, especially for the printing of low surface tension substrates such as plastic film materials and coated paper surfaces. For non-coated paper, the ink may even cause deformation and curling of the paper. These problems do not exist for solvent-based gravure printing inks.
The importance of PH value of water-based gravure printing ink:
Comparing water-based and solvent-based gravure printing inks, the gravure printing process using solvent-based inks minimizes solvent evaporation during imprinting as the squeegee scrapes excess ink from the gravure printing ink holes. After the process is completed, the ink is transferred to the substrate material, and then the ink film is slowly formed. In this process, the solvent in the ink must complete the volatilization process before the ink film is adhered and quickly reach the drying of the ink film. In water-based inks, organic solvents are replaced by a certain percentage of water, cosolvents, and volatile amines that are necessary to neutralize acidic resins. Since the water is relatively slow in volatility, there is no problem in that the ink is volatilized and dried in the printing ink in the printing plate, but there is a problem of drying after printing. Therefore, the choice of the amines in the ink, the adjustment of the pH, and the control of the viscosity of the ink As important. Because the premature release of the amine solvent prior to the completion of the imprinting process results in a decrease in the pH, the resin dries in the ink refill in the intaglio printing cylinder. In addition, water and cosolvent systems are unable to redissolve the resin, unlike solvent inks. Therefore, it is impossible to re-dissolve any possible drop in pH. In the gravure printing, it is necessary to carefully control the PH value, because the drop of PH value of the ink causes the ink hole to be slowly blocked until it is completely blocked, which is a very serious problem and will cause the printing job to be unable to continue.
The importance of the surface tension of water-based gravure printing inks:
At the same time, the surface tension of ink is also an unavoidable factor, which is also completely different from solvent inks. Compared with solvent inks, the surface tension of inks is much higher; and too high a surface tension will cause inks to not wet the surface of the substrate material and ink in the gravure printing cylinders. This will cause the ink film Uniform; due to the surface tension of the ink, the ink film will form a contracted state on the surface of the substrate, causing the ink film to show a clear mesh, which can also cause the ink to be uniformly transferred from the ink hole to the surface of the substrate.
However, the surface tension can be reduced, which requires careful selection of the appropriate surfactant or a small amount of alcohol. Despite the enormous amount of labor involved in developing printing inks, it is still a difficult challenge to completely reduce the VOC emissions of gravure printing while maintaining the printing quality of printing inks (as with the printing quality of solvent-based inks).
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