Specializing in the research, development, and production of eco-friendly water-based inks
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Today, the editor will discuss the characteristics of water-based inks.
Similar to general printing inks, water-based inks typically consist of colorants, binders, additives, and other components. Colorants are the coloring substances in water-based inks, giving the ink a specific color. In flexographic printing, to achieve vibrant colors, the colorants are usually selected for their good chemical stability and high coloring strength; the binder is composed of water, resins, amine compounds, and other organic solvents.
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Like general printing inks, water-based inks typically consist of colorants, binders, additives, and other components. Colorants are the coloring substances in water-based inks, giving the ink a specific color. In flexography, to achieve vibrant colors, colorants are usually selected for their good chemical stability and high coloring power; the binder is composed of water, resins, amine compounds, and other organic solvents. Resins are an important component in water-based inks, typically using water-soluble acrylic resins. The binder components directly affect the ink's adhesion properties, drying speed, anti-blocking performance, and also influence the ink's gloss and transferability. Amine compounds mainly maintain the alkaline pH of the water-based ink, allowing the acrylic resin to provide better printing results. Water or other organic solvents primarily dissolve the resin and adjust the ink's viscosity and drying speed; additives mainly include defoamers, retarders, stabilizers, and diluents.
Since water-based ink is a soap composition, it is prone to foaming during use, so silicone oil is added as a defoamer to suppress and eliminate bubbles while improving the ink's transfer performance. Retarders are used to slow down the drying speed of water-based inks, preventing the ink from drying on the anilox roller and reducing plate sticking. Stabilizers can adjust the ink's pH and can also act as diluents to reduce the ink's viscosity. Dilutents are used to lighten the color of water-based inks and can also serve as a gloss agent to enhance the brightness of the water-based ink. Additionally, some waxes are added to water-based inks to increase their abrasion resistance.
II. pH Value of Water-Based Ink
The pH value of water-based ink directly relates to its viscosity, drying properties, and other printing suitability. Experiments show that the viscosity of water-based ink increases linearly with a decrease in pH, while its drying properties decrease linearly with a gradual increase in pH. The pH of water-based ink is mainly maintained by amine compounds. During the printing process, the volatilization of amine substances causes the pH to drop, leading to an increase in ink viscosity, poor transferability, accelerated drying, clogging of the anilox roller, and plate sticking issues. Therefore, to maintain a stable pH in water-based ink, it is essential to avoid the leakage of amine substances, such as by properly covering the ink tank. Additionally, stabilizers should be added in a timely and quantitative manner. Typically, the pH of water-based ink should be maintained between 8.0 and 9.5; both excessively high and low pH values can affect print quality. A pH that is too low can impair the printing performance of acrylic resins, while a pH that is too high can slow down ink drying, leading to issues such as dirty backs of printed products and poor water resistance.
III. Issues in the Use of Water-Based Ink
Water-based ink can be mixed with water before drying, but once the ink has dried, it will no longer dissolve in water or ink. Therefore, water-based ink must be thoroughly stirred before use to ensure uniformity of the ink components. When adding ink, any residual ink in the ink tank that contains impurities should be filtered out before mixing with new ink. During printing, do not allow the ink to dry on the anilox roller to avoid clogging the ink transfer holes, which can hinder the stable transfer of ink and cause printing instability. Throughout the printing process, the flexographic plate must always remain wet with ink to prevent the ink from drying and clogging the text and patterns on the plate. Additionally, if the viscosity of the water-based ink is found to be slightly high, it should not be casually added to.
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