Need to pay attention to water-based ink in screen printing

1. In screen printing, pay attention to control the parameters of water-based inks, including the viscosity, fluidity, thixotropy and plasticity of inks;

2. Pay attention to the control index of water-based ink. The control indicators of water-based ink mainly include fineness, viscosity, pH value and drying speed, etc., which play a decisive role in the application effect of the ink;

3. As the water-based ink is a pure water-based system, care must be taken not to mix water-based inks with alcohol-based inks and solvent-based inks or add organic solvents to the ink to avoid printing quality problems;

4. When using water-based ink, stir it evenly and pour it into the ink tank after measuring the viscosity. If the viscosity is not suitable, adjust it with a diluent or thickener and pay attention to controlling the pH of the ink. Generally, it is controlled at 8.5 ~ 9.5. During the printing process, due to the volatilization of water, the viscosity of the ink will increase and the pH value will decrease. Therefore, it is necessary to constantly observe the use of the ink. When the ink viscosity is increased or the pH exceeds the control range, the diluent and pH stabilizer should be used in time Adjust to ensure the stability of viscosity and pH;

5. In general, ink is very suitable for high-speed printing. If low-speed printing encounters a situation where the drying speed is too fast or the printing effect is not good, a certain percentage of slow-drying agent can be added;

6. After printing, the remaining ink should be returned to the corresponding original bucket or the lid of the ink tank should be tightly closed for future use. Prevent from condensing, thickening or even drying due to the ink surface. Water-based inks should be stored in a cool and ventilated room, and the room temperature should be controlled at 5 ~ 45 ℃;

7.The ink remaining on the printing equipment after printing can be washed with water when it is not completely dry, and the ink that cannot be washed with water can be washed with a cleaning agent;

8. The printing suitability of ink is affected by the objective conditions such as printing conditions, substrate surface characteristics, environmental temperature and humidity, and storage time. Therefore, when using it, some auxiliary agents need to be used to fine-tune the ink to obtain the best printing. effect. Common additives in water-based inks are colorants, pH stabilizers, slow-drying agents, defoamers, diluents, etc. You must be familiar with the characteristics and use of additives in printing;

1) The colorant is used to deepen the color, and its amount should generally be controlled at 0-30%, and more than 30% will make the content of the binder in ink and ink too low, resulting in a decrease in its adhesion and abrasion resistance;

2) pH stabilizer is used to adjust and control the pH value of water-based ink to stabilize it at 8.0 to 9.5 to ensure the printing state of water-based ink. At the same time, it can also adjust the viscosity of water-based inks and dilute the inks;

3) Slow-drying agent is used to reduce the drying degree of water ink. Slow-drying agent can suppress and slow down the drying speed of water-based ink, prevent the ink from drying on the printing plate, and reduce the occurrence of printing failures such as blocking and paste printing. The amount of slow-drying agent should generally be controlled at 0 to 10% of the total ink amount. If the amount is too large, the ink will not dry completely, and the print will become dirty or produce an odor;

4) The diluent is mainly used to reduce the depth of the color, and the amount is not limited. However, adding a large amount of diluent may cause a slight increase in the viscosity of the ink. At this time, a small amount of diluent can be added to adjust it;

5) The dilution benefit is mainly used to reduce the viscosity of ink and wash, and the amount should be controlled within 3%, so as not to reduce the color depth of ink and wash, and keep the pH of ink and wash unchanged. The diluent should be added slowly while stirring to prevent the viscosity from becoming too low. If more diluent is added or diluted with tap water with high hardness, air bubbles will be generated. At this time, defoamer should be added;

6) The main reason for the foam problem in the use of water-based inks is that it uses water as a diluent. During emulsion polymerization, a certain amount of emulsifier must be used to greatly reduce the surface tension of the emulsion system.