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In theory: The remedial measures are to improve the flow and leveling of the wet ink film. The surface tension of the ink is not only low, but also low surface tension and wettability to the substrate material. Because of the difference in the interfacial tension between the upper wet ink film and the lower wet ink film, once the package is printed, the surface tension of the system is decreased, so that the printing ink is developed into a complete ink film. For the shrinkage failure caused by this, our specific methods are: 1 Add appropriate leveling agent to the printing ink; 2 Use a low surface tension solvent; 3 Wet the surface of the substrate (such as using a solvent before printing. Substrate material surface wetting and wiping); 4 control of the printing environment temperature and humidity; 5 select the appropriate diluent; 6 reduce the surface tension between the printing ink and printing substrate, so that the ink and the carrier has a good wettability In order to prevent it from forming a surface tension gradient with the substances that cause craters; 7 to adjust the solvent evaporation speed, reduce the viscosity, improve the flowability of the ink, and extend the leveling time; 8 to form a very thin layer on the surface of the packaging printing ink ink film Monolayers to provide a stable and uniform surface tension.
In order to properly select the anti-crater agent for printing inks, the following types of materials are described below for selection by operators.
Solvents: generally refers to high-boiling mixed solvents, it is not only a good solvent, but also a good wetting agent for the pigments (because the solvent volatilizes the ink to form a film, the solubility of the system becomes worse, resulting in shrinkage, or drying Bake marks, blisters, and other ill effects occur in baked iron offset inks.
Resins: Acetyl butyl cellulose is generally used, especially those with limited compatibility of polyacrylic vines. The dosage is: 1% to 1.5% of acrylic resin, 0.5% to 1% of epoxy resin, and 1% of polyester resin.
There are also silicone resins, which function in addition to anti-shrinkage, leveling, anti-floating, and defoaming. For example, domestic XH204 water-based silicone oil can help promote the flow, leveling, and brightening of printing inks in water-soluble acrylic inks.
In addition to the above-mentioned exemplified anti-crater agents, there are silicone-free fluorine-based surfactants that are high molecular surfactants. For preventing the shrinkage of the ink film, it is also very effective to increase the leveling and improve the glossiness of the printing ink film.
The prevention of the shrinkage of the ink film of the packaging printing ink is an important measure to improve the effect of the ink on the decoration of the packaging printing and decoration. The purpose of using different anti-shrinkage holes and leveling agents is to improve the printing quality and extend the printing (surface ink film) grade. Although its variety is of many types, its use is limited. Sometimes even improper use or improper use, not only difficult to achieve the desired effect, and sometimes will bring side effects.
Years of practice have proved that: before use, different varieties and quantities should be strictly screened and tested to find the best variety and the most appropriate amount. In addition, batch comparison tests should also be conducted on the additive process, and a more scientific process flow should be selected, and even additional application methods included in the post-printing process. Only in this way can we continuously improve the product quality of packaging and printing products in China. Only in this way can we accumulate more theoretical knowledge in practice.
Shrinkage is one of the failures of packaging ink film due to poor leveling. After the ink is printed, the wet ink film shrinks into a small circular exposed substrate material (bottom) or an ink layer during the leveling process. The main cause of the shrinkage is the printing of the upper and lower parts of the wet ink film. The surface tension is different. Some people think that: a wet ink film can be regarded as an upper and lower double liquid ink film. In the film forming process, shrinkage occurs when the surface tension of the upper wet ink film is lower than the surface tension of the lower wet ink film. Holes, this is due to the wetting of the substrate material. Sometimes when this phenomenon is about to occur, the wet ink film loses its fluidity and happens to suppress the shrinkage phenomenon. For example, in some gravure or offset printing operations, the wet film may become fluid as the temperature increases, which may cause secondary shrinkage.