Shrinkage is one of the failures of packaging ink film due to poor leveling. After the ink is printed, the wet ink film retracts in the course of leveling and becomes a small round of exposed substrate material (bottom) or an ink layer. The main cause of shrinkage is caused by different surface tensions in the upper and lower portions of the printed wet ink film. Some people think that: a wet ink film can be regarded as a double liquid ink film. In the film formation 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. 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 ink film has fluidity as the temperature increases, which may cause secondary shrinkage.
Theoretically speaking, there are many remedial measures, such as the flame method, precoating method, ion exchange method, and the addition of a crater in the ink. This article explains the changes in ink properties. Changing the properties of the ink is mainly to change the flow leveling of the wet ink film. The surface tension of the ink is not only low, but also the wettability of the substrate material. Because of the difference in the interfacial tension between the upper wet ink film and the lower wet ink film, the surface tension of the system decreases after being packaged and printed, so that the printing ink will self-release into a complete ink film. The specific methods for solving the shrinkage cavity fault are: 1) adding leveling agent to the printing ink; 2) using a low surface tension solvent; 3) wetting the surface of the substrate (such as printing with a solvent before printing (4) control the ambient temperature and humidity of the printing operation; 5) select the appropriate diluent; 6) reduce the surface tension between the printing ink and the printing substrate so that the ink and the carrier have good Wetability (makes it not to form a surface tension gradient with the substance that causes cratering); 7) Adjust solvent evaporation rate, reduce viscosity, improve ink flowability, extend flow time; 8) Ink film for packaging printing ink An extremely thin monolayer is formed on the surface to provide a stable and uniform surface tension.
In order to correctly select the anti-crater agent for printing inks, the following briefly introduces several commonly used anti-crater agents for the reference of operators.
Solvents: Generally referred to as high-boiling mixed solvent, it is not only a good solvent, but also a good wetting agent for the pigment (caused by the volatilization of the solvent, the solubility of the ink (film-forming) body is deteriorated, resulting in shrinkage, or drying. Bake marks, blisters and other ills occur in baked iron inks.
Resins: Cellulose acetate is generally used, especially polyacrylate-resistant shrink-resistance resins with limited compatibility. The dosage is: 1-1.5% of acrylic resin, 0.5-1% of epoxy resin, and 1% of polyester resin.
Silicone resin: Its function is anti-shrinkage, leveling, floating color, defoaming. For example, domestic XH204 water-based silicone oil can help promote printing ink flow, leveling, and brightening effects in water-soluble acrylic inks.
In addition to the above-mentioned examples of the anti-crater agents, there are also silicone-free fluorine-based surfactants of polymer surfactants. For the prevention of shrinkage of the ink film, it is also very effective to improve the leveling of the printing ink.
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. With different anti-shrink holes, the purpose of the leveling agent is to improve the printing quality and to extend the printing (surface ink film) grade. Although its variety is of many types, its use is limited. Sometimes even due to improper use or improper use, it is not only difficult to achieve the desired effect, but also sometimes bring about side effects.
Years of practice have proven that before use, different varieties and quantities should be screened and tested strictly to find the best variety and the most suitable amount. In addition, it is also necessary to select a simpler process flow through a batch comparison test for the process of the additive process, and even include the addition of the application method during the packaging printing process. (Liu Jiaju) ("China Packaging News and Printing Weekly")
Theoretically speaking, there are many remedial measures, such as the flame method, precoating method, ion exchange method, and the addition of a crater in the ink. This article explains the changes in ink properties. Changing the properties of the ink is mainly to change the flow leveling of the wet ink film. The surface tension of the ink is not only low, but also the wettability of the substrate material. Because of the difference in the interfacial tension between the upper wet ink film and the lower wet ink film, the surface tension of the system decreases after being packaged and printed, so that the printing ink will self-release into a complete ink film. The specific methods for solving the shrinkage cavity fault are: 1) adding leveling agent to the printing ink; 2) using a low surface tension solvent; 3) wetting the surface of the substrate (such as printing with a solvent before printing (4) control the ambient temperature and humidity of the printing operation; 5) select the appropriate diluent; 6) reduce the surface tension between the printing ink and the printing substrate so that the ink and the carrier have good Wetability (makes it not to form a surface tension gradient with the substance that causes cratering); 7) Adjust solvent evaporation rate, reduce viscosity, improve ink flowability, extend flow time; 8) Ink film for packaging printing ink An extremely thin monolayer is formed on the surface to provide a stable and uniform surface tension.
In order to correctly select the anti-crater agent for printing inks, the following briefly introduces several commonly used anti-crater agents for the reference of operators.
Solvents: Generally referred to as high-boiling mixed solvent, it is not only a good solvent, but also a good wetting agent for the pigment (caused by the volatilization of the solvent, the solubility of the ink (film-forming) body is deteriorated, resulting in shrinkage, or drying. Bake marks, blisters and other ills occur in baked iron inks.
Resins: Cellulose acetate is generally used, especially polyacrylate-resistant shrink-resistance resins with limited compatibility. The dosage is: 1-1.5% of acrylic resin, 0.5-1% of epoxy resin, and 1% of polyester resin.
Silicone resin: Its function is anti-shrinkage, leveling, floating color, defoaming. For example, domestic XH204 water-based silicone oil can help promote printing ink flow, leveling, and brightening effects in water-soluble acrylic inks.
In addition to the above-mentioned examples of the anti-crater agents, there are also silicone-free fluorine-based surfactants of polymer surfactants. For the prevention of shrinkage of the ink film, it is also very effective to improve the leveling of the printing ink.
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. With different anti-shrink holes, the purpose of the leveling agent is to improve the printing quality and to extend the printing (surface ink film) grade. Although its variety is of many types, its use is limited. Sometimes even due to improper use or improper use, it is not only difficult to achieve the desired effect, but also sometimes bring about side effects.
Years of practice have proven that before use, different varieties and quantities should be screened and tested strictly to find the best variety and the most suitable amount. In addition, it is also necessary to select a simpler process flow through a batch comparison test for the process of the additive process, and even include the addition of the application method during the packaging printing process. (Liu Jiaju) ("China Packaging News and Printing Weekly")
Ningbo Ruichang Commodity Packaging Co.,Ltd , http://www.nbrcpackaging.com