Application of the most environmentally friendly w

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The application of environmental friendly water-based ink and the problems that should be paid attention to

in the printing process, the low viscosity of water-based ink will cause light color and dot expansion. If the viscosity of water-based ink is too high, the transfer performance of ink is relatively poor, and it is prone to dirty version, paste version and other ills. Flexo water-based ink is generally used directly without dilution, and its viscosity range can be 30-25 seconds/25 ℃ (4 cups). The viscosity of flexible water-based ink for cartons can be lower. As long as the water stabilizer is added regularly, the viscosity change can be basically controlled. Gravure printing water-based ink is generally carried out with a diluent of ethanol: water = 1:1. The viscosity is generally controlled at 15-23 seconds. The price will be a factor that needs to be considered, 25 ℃. Water based inks are usually alkaline (mainly maintained by amines)

generally, the pH value of water-based ink should be controlled between 8.0-95. If the pH value of water-based ink is too high, it will affect the drying speed of ink; If the pH value is too low, the viscosity of the ink increases, the drying speed becomes faster, and it is easy to cause the blocking of the printing plate and the corrugated roller, causing the dirty on the plate. The drying performance of ink refers to the time required for the ink to dry after being transferred to the substrate, which is also one of the important indicators to measure the quality and performance of ink. Therefore, controlling the drying performance of ink is an important means to achieve good printing effect. The drying speed of flexo water-based ink depends on the printing speed of the printing machine, the drying capacity of the drying equipment, the performance of the substrate material and the composition of the ink itself. The general principle of choosing the ink drying speed is that under the existing conditions of the printing machine, the ink should be fully dried before the next color group and before rewinding or stacking, but it cannot be dried on the printing plate. If the ink drying speed is too fast, it will dry and gradually accumulate on the printing plate and the embossing roller, and may block the embossing roller, causing the loss or damage of halftone points, and the white part of the field will appear. On the contrary, there will be printing odor problems, and even adhesion failures. In fact, the viscosity and pH value of the ink will also have a certain impact on the drying performance of the ink. For example, if the viscosity is too high, the drying speed of the ink will be reduced, and if the pH value is too low, the drying speed of the ink will be too fast. Therefore, the viscosity and pH value of water-based ink should be controlled first, and then an appropriate amount of fast drying agent or slow drying agent should be added to the ink according to the actual printing speed to adjust the drying speed of water-based ink. Fineness in water-based ink refers to the size of pigment particles in the ink and the uniformity of their dispersion in the binder. The fineness of the ink not only has a certain impact on the coloring power and color equality of the ink, but also reduces the fluidity of the ink. If the ink particles are too fine, there will be a point of expansion failure. Generally, the fineness of water-based ink should be 12-15 μ m。 How to use water-based inks

1. Since water-based inks are pure water-based systems, do not mix water-based inks with alcohol based inks or solvent based inks

2. Water based inks are suitable for indoor storage, and the room temperature should be about 5 ℃ ~ 50 ℃

3. When in use, the water-based ink should be stirred evenly in the barrel with a stirring rod, and then poured into the ink tank after measuring its viscosity. If the viscosity is too high or too low, it can be adjusted by diluting and culturing Yuyao intelligent photoelectric reagent or thickener

4. During the printing process, due to the volatilization of water, the viscosity of water-based ink will increase and the pH value will decrease. The pH value should be controlled between 8.5 and 9.5. If it exceeds this range, it can be adjusted with pH stabilizer to maintain the stability of viscosity and pH value

5. Generally, water-based inks are more suitable for high-speed printing. If the drying speed is too fast or the printing effect is poor during low-speed printing, a certain proportion of slow drying agent can be added

6. After printing, the remaining water-based ink should be collected into the corresponding original barrel, and the cover of the ink tank should be covered for next use. Be careful not to skin, thicken or even dry the ink surface due to the volatilization of water

7. The ink remaining on the printing equipment after printing can be washed with clean water before it is completely dried. The ink that cannot be washed with clean water can be washed with detergent. The printability of water-based ink is affected by objective conditions such as printing conditions, surface characteristics of substrate, ambient temperature and humidity, storage time of water-based ink, etc. Therefore, when using water-based ink, some additives need to be used to make subtle adjustments to the water-based ink to obtain the best printing effect. The following is a brief description of the problems in printing:

A: the reason for blocking the plate: ① the printing plate is too shallow; ② Printing pressure is too high; ③ Too much ink supply; ④ Water based ink viscosity is too high; ⑤ The drying speed of water ink is too fast. The solution is: ① deepen the printing plate; ② Adjust the printing pressure; ③ Reduce ink supply; ④ Reduce the viscosity of water-based ink; ⑤ Reduce the drying speed

b: the reason why the printed matter has spots: ① the water-based ink is too diluted; ② Water based ink has high viscosity; ③ Uneven inking of printing plate. The solution is: ① add new water-based ink; ② Increase the viscosity of ink; ③ Check and adjust the causes of uneven ink transfer from two aspects of water-based ink and ink supply

c: causes of color instability: ① viscosity or pH value changes; ② Error in operation; ③ There was an error in the ink dispensing process. The solution is: ① check whether the viscosity and pH value have changed from the last printing; ② Check the operation procedure; ③ Use spot color ink for blending

d: the reason why the drying speed is too fast:

① the printing speed is too slow

② the drying speed of water-based ink is too fast

③ the temperature of the drying system is too high. The solution is:

① improve the printing speed

② add diluent and slow drying agent for adjustment

③ reduce the drying temperature or do not use the drying system. Water based ink is mainly made by scientific processing with water as solvent. Because it does not contain volatile toxic organic solvent, it has no adverse effect on the health of printer operators, no pollution to the atmosphere, and no pollution to the print itself in the printing process. Because the water-based ink is non flammable, it can also eliminate the hidden dangers of flammability and explosion in the printing workshop, which is conducive to safe production. However, the application scope of ink and ink is different. Ink is mainly offset printing, while ink is mainly flexo printing and gravure printing. In developed countries such as Europe, America and Japan, ink has gradually replaced ink and become a special ink for other printing methods except offset printing. In addition to environmental protection, water-based inks widely used abroad also have excellent performance:

① stable ink color, high brightness and strong coloring power

② it does not corrode the plate, has strong printing adhesion, and the drying speed can be adjusted at will

③ strong water resistance, four-color overprint and spot color printing can be used, etc. As long as you pay attention to the above problems, you will be able to use water-based ink well

source: fine chemicals in the 21st century

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