Water-based ink in screen printing problems

1. In screen printing, it is necessary to control the parameters of the aqueous ink, including the viscosity, fluidity, thixotropy, and plasticity of the ink.
2. Note the control index of water-based ink. The control indexes of water-based inks mainly include fineness, viscosity, pH value, and drying speed. They play a decisive role in the application of inks.
3. Because water-based inks are pure water-based systems, care should be taken not to mix water-based inks with alcoholic inks and solvent-based inks or to add organic solvents to inks in order to avoid print quality problems.
4. When using water-based ink, it should be evenly stirred, and after measuring the viscosity, pour into the ink tank. If the viscosity is not suitable, adjust with diluent or thickener, and pay attention to control 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, the usage of the ink must be observed frequently. When the viscosity of the ink is increased or the pH exceeds the control range, the diluent and pH stabilizer should be used in time. Adjustment 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 low or the printing effect is not good during low-speed printing, a certain proportion of slow-drying agent can be added.
6. After the printing is finished, the remaining ink should be taken back to the corresponding original bucket or the lid of the ink tank should be tightly closed for the next use. Prevents filming, thickening or even drying out of the ink surface. Water-based ink should be stored in a cool, ventilated room with room temperature controlled at 5 to 45°C.
7. The ink remaining on the printing device after printing can be washed with fresh water when it is not completely dry, and the ink that cannot be washed with fresh water can be cleaned with a cleaning agent.
8. The printability of ink is affected by objective conditions such as printing conditions, substrate surface characteristics, ambient temperature and humidity, and the length of storage, so when using it, some additives are needed to make fine adjustments to the ink to obtain the best printing effect. Commonly used additives in water-based ink color materials, pH stabilizers, slow drying agents, defoamers, dilutants, etc., should be familiar with the characteristics and use of additives in printing.
1) The coloring material is used to deepen the color, and its amount should generally be controlled at 0 to 30%. More than 30% will cause the content of the binder in the ink to be too low, resulting in a decrease in adhesion and wear resistance.
2) pH stabilizer is used to adjust and control the pH value of water-based ink, making it stable at 8.0-9.5, ensuring the printing state of water-based ink. At the same time, it can also adjust the viscosity of 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 stencil printing. The amount of slow-drying agent should generally be controlled at 0 to 10% of the total amount of ink. If the amount of slow-drying agent is too much, the ink will not dry completely and the printed matter will become dirty or have an odor.
4) Diluter is mainly used to reduce the depth of color, and the amount is not limited. However, the addition of a large amount of diluting agent may cause the ink viscosity to slightly increase. At this time, a small amount of diluent may be added at the same time to adjust.
5) Dilution is mainly used to reduce the viscosity of ink, the amount should be controlled within 3%, it will not reduce the color depth of ink, and can maintain the pH of ink. The thinner 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, air bubbles will be generated, and defoamer should be added at this time.
6) The main reason for foaming problems in the use of water-based inks is that water is used as a diluent. In emulsion polymerization, a certain amount of emulsifier must be used to greatly reduce the surface tension of the emulsion system. Defoamer's role is to suppress and eliminate the generation of air bubbles, to avoid the appearance of pinholes, white leaks, uneven ink and other print quality problems caused by bubbles, but the amount of general defoamers should be controlled at 0.1% to 0.2%.
7) The thickener is mainly used to increase the viscosity of the ink, while also giving the ink excellent mechanical and physicochemical stability, to control the rheological effect during printing, but the amount can not be too much, if used in water-based ink too More thickeners will increase the thickness of the bubble's membrane wall and increase its elasticity so that the foam is not easily eliminated. Generally, it is controlled at 0.5% to 1%.
8) The quick drying agent is mainly used to accelerate the drying speed of the ink, and the amount is 0 to 30%.
9) The anti-settling agent can make the pigment particles in the ink suspended and dispersed evenly and not easily aggregated and settled to avoid floating phenomenon.