Do you have the correct application of water-based inks?
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Whether the application of water-based ink is correct is an important factor affecting the quality of printed matter. Here is a look at the application of water-based inks and points of attention.
1 plate making
The aqueous ink has a higher solid content, and the dry weight of the ink layer is higher. Therefore, it is generally required to use an ink transfer roller having a high number of screen lines for the aqueous ink, so as to obtain a lower dry film weight of the ink layer, which can reduce drying difficulty. . In addition, the ink transfer amount of the aqueous ink is usually more than 80% and the solvent type ink is only about 65%. Therefore, the transfer roller has a lighter texture, that is, a shallow plate.
2 drying
The drying mechanism of the aqueous ink is mainly based on volatilization and drying, and at the same time, it is also coagulated and dried. Dry aqueous inks must have a high air flow rate, but not too high temperatures. If the temperature is too high, the surface of the ink layer will dry out for some non-absorbent materials, and the internal moisture cannot be dried thoroughly, and adhesion occurs during the color registration. Generally, the drying is divided into two stages: high temperature and low air flow; and a large amount of high-speed, moderate-temperature air is introduced. While paying attention to the drying speed, it is necessary to consider preventing the dry knot, because once the aqueous ink is dried, it is difficult to dissolve again in water, and it will cause the ink to solidify.
3 pH control
If the pH is too low, the viscosity of the ink is too high; if the pH is too high, the ink color depth will decrease. The pH is usually controlled at 8.5 to 9.5. Due to the volatilization of water and ammonia, the viscosity of the aqueous ink is increased and the pH is changed. Therefore, it is necessary to frequently adjust the corresponding aqueous ink additive during the printing process.
4 Eliminate foam
Avoiding aqueous ink foaming is easier than eliminating foam. Although the aqueous ink contains an antifoaming agent, the foam is caused by stirring too fast or the shearing force of the pump is too high. Therefore, when using an aqueous ink, it is required that the stirring is not too severe; a long ink delivery pipe is used, and it is in an "S" shape; the returned ink should be returned to the ink tank from a position lower than the ink level.
5 storage
The room temperature is not lower than 5 °C.
6 other
Water-based inks cannot be mixed with other alcoholic or solvent-based inks to avoid printing quality problems.