Application of water-based ink

In principle, all printed products printed with traditional solvent-based oils can be replaced by water-based inks. Water-based inks have been widely used in the printing of coated paper, white paper, corrugated paper and plastic film, and can be printed by flexographic, gravure, and mesh printing. In the U.S. printing industry ink market, the sales of water-based inks are more than two letters of the sales of solvent-based inks, that is, water-based inks have become the main printing inks.

Water-based inks mainly use water as solvent, so they have the advantages of environmental protection and safety in the printing process. Water-based inks used in paper products can achieve low VOC non-emission or zero VOC emissions. Water-based ink has the advantages of stability and low flammability, and has the advantage of being easy to clean on the printing machine, thereby improving productivity.

Whether the application of water-based inks is correct is an important factor that affects the quality of printing.

1. Plate making

Water-based ink has a higher solid content, and the quality of the dry film of the ink layer is the highest. Therefore, for water-based inks, it is generally required to use an ink transfer roller with a high number of screen lines, so that the quality of the dry film of the lower class layer can reduce the difficulty of drying. In addition, the transfer volume of water-based inks is usually greater than 80%, so the texture should be lighter and make a shallow version.

2. Viscosity control

When in use, use a stirring rod to stir the ink evenly in the bucket, measure its viscosity and then put it into the ink tank. If the viscosity is too high or too low, it can be adjusted with a diluent or thickener.

3. Dry

The drying mechanism of water-based ink is mainly volatilization drying and reactive solidification drying. Dry water-based inks must have a higher air flow, but the temperature is not easy to be too high. If the temperature is too high, for non-absorbent materials, the surface layer of the ink layer will dry and the internal moisture will not be able to dry completely, and adhesion will occur during the color register. The drying of water-based inks is divided into two stages: a large amount of high-speed, moderate-temperature air and high-temperature, low-flow air. While paying attention to the drying speed, it is necessary to prevent drying, because once the water-based ink is dried, it is difficult to re-dissolve in water, and it will cause the ink to solidify.

4. pH value control

In the water-based ink printing process, the volatilization of water and ammonia causes the viscosity of the ink to increase and the pH value changes. Therefore, a pH stabilizer is often added to adjust the printing process.

5. Foam control

Although water-based inks contain defoamers, too fast agitation or high shear force of the pump can cause foam. Therefore, when using water-based ink, it is required that the stirring should not be too violent, and the long ink delivery pipe should be used, and it is

S-shaped. The returned ink should return to the ink tank from a position lower than the ink level.