Precautions for water-based inks in screen printing

[China Glass Network] 1. In screen printing, attention should be paid to controlling the parameters of water-based inks, including ink viscosity, fluidity, thixotropy and plasticity;

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

3. Since the water-based ink is a pure aqueous system, care should be taken not to mix the aqueous ink with the alcohol ink and the solvent-based ink or to add an organic solvent to the ink to avoid printing quality problems;

4. When using water-based ink, it should be stirred evenly. After measuring the viscosity, pour it into the ink tank. If the viscosity is not suitable, adjust it with thinner or thickener, and pay attention to controlling the pH value 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 will drop. Therefore, the use of the ink should be observed frequently. If the viscosity of the ink is increased or the pH is outside the control range, the diluent and pH stabilizer should be used in time. Adjust to ensure viscosity and pH stability;

5. Under normal circumstances, the ink is very suitable for high-speed printing. If the drying speed is too fast or the printing effect is not good during low-speed printing, a certain proportion of slow-drying agent can be added;

6. After printing, the remaining ink should be taken back to the corresponding original barrel or the lid of the ink tank should be tightly closed for future use. Prevent conjunctiva, thickening or even drying due to the ink surface. The water-based ink should be stored in a cool and ventilated room, and the room temperature is controlled at 5 to 45 °C;

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

8. The printing suitability of ink is affected by the objective conditions such as printing conditions, surface characteristics of the substrate, ambient temperature and humidity, and storage time. Therefore, some additives are needed to finely adjust the ink to obtain better printing. effect. The commonly used additives in water-based inks are color materials, pH stabilizers, slow-drying agents, defoamers, thinners, etc., and the characteristics and methods of use of the additives should be familiar with the printing;

1) The colorant is used to deepen the color, and the amount thereof should generally be controlled at 0 to 30%. If the content exceeds 30%, the content of the binder in the ink will be too low, resulting in a decrease in adhesion and wear resistance;

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

3) The slow drying agent is used to reduce the drying degree of the ink. The slow drying agent can suppress and slow the drying speed of the water-based ink, prevent the ink from drying on the printing plate, and reduce the occurrence of printing failures such as blocking and paste. The amount of slow-drying agent should generally be controlled to 0-10% of the total ink volume. If the amount of the slow-acting agent is too much, the ink is not dried thoroughly, and the printed matter will be dirty or odor-producing;

4) Dilution agent is mainly used to reduce the depth of color, and the amount is not limited. However, the addition of a large amount of thinner may cause a slight increase in the viscosity of the ink, and a small amount of diluent may be added at the same time for adjustment;

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

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

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