Application skills of the most popular water-based

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The special ink used in flexographic printing machine is water-based ink. Its advantages are no pollution to the environment, no impact on human health, not easy to burn, good safety, stable ink performance, bright colors, no corrosion of plates, simple operation, low price, good post press adhesion, strong water resistance, rapid drying, and the printing speed can reach 150 ~ 200m per minute. It is precisely because of the above characteristics that flexographic water-based ink is particularly suitable for the printing and use of food, medicine, cosmetics and other packaging and decoration printing products with strict requirements on sanitary conditions. So what problems should we pay attention to when using it

the main indicators of flexographic water-based ink

1, fineness

fineness is a physical indicator to measure the size of pigments, fillers and other particles in the ink, which is directly controlled by the ink manufacturer. Users generally understand it and cannot change its size in use. The fineness of flexographic water-based ink is generally below 20m, and the instrument for measuring the fineness is the fineness scraper

2. Viscosity

viscosity is one of the main indicators of water-based ink, and the viscosity value will directly affect the quality of printed matter. Therefore, the viscosity of water-based ink should be strictly controlled in flexographic printing. The viscosity of water-based ink is generally controlled within the range of 30 ~ 60 seconds/25 ℃ (with paint cup 4), and the viscosity is generally controlled between 40 ~ 50 seconds. If the viscosity is too high and the leveling property is poor, it will affect the printability of water-based ink, which is easy to cause dirty version, paste version and other phenomena; If the viscosity is too low, it will affect the ability of the carrier to drive the pigment

if the water-based ink is placed for a long time, some inks with poor stability are easy to precipitate and layer, and others will appear false thickening. At this time, sufficient mixing can be carried out, and the above problems can disappear naturally. When using fresh water-based ink, be sure to stir it evenly in advance, and then make dilution adjustment. During normal printing, the ink bucket should also be stirred regularly

water based ink is easy to freeze below 0 ℃. If the water-based ink freezes, it can be placed in a room with high temperature to dissolve naturally. After being stirred evenly, it can continue to be used. Viscosity is the most sensitive when the temperature difference between winter and summer is large. When the temperature is high, the water evaporates quickly and the drying is also fast. During operation, pay attention to reducing the drying time or increasing the machine speed; When the temperature is low, the evaporation of water is slow, and the drying of water-based ink is also slow. During operation, the drying speed of water-based ink can be increased or the drying device can be opened. When using in winter, it is best to put the water-based ink stored in the warehouse into the workshop in advance to balance the viscosity

3. Drying

drying is one of the most important indicators in water-based inks, because the speed of drying, like viscosity, can be directly reflected in the quality of printed matter. The operator must understand the drying principle in detail, so as to reasonably allocate the drying time of water-based ink according to the different products or substrates. While ensuring the good drying of water-based ink, we must also consider the moderate viscosity or stable pH value

the drying of water-based ink includes volatilization, absorption and reactive solidification. After water-based ink printing is completely dried, it has strong water resistance and friction resistance. If it dries too fast, the surface of the ink layer is easy to be skinned, and the water-based ink is easy to dry up on the printing plate, resulting in dirty plates, unclear around the pattern, and internal moisture cannot be eliminated, resulting in inaccurate overprint. It can be adjusted with blockers, or it can be solved by increasing the speed of the printer or turning off the drying system. During shutdown, it is best to clean the wrinkle roller or ink bucket. During short-term shutdown, the ink bucket should also be often stirred to prevent surface scaling; If the drying is too slow, the paper will stretch and reduce the gloss, which will affect the laminated printing, and may cause adhesion, which will bring a lot of trouble to the machine operator. At this time, you should first check whether the pH value is correct. According to the pH value, you can add an appropriate amount of stabilizer or ethanol to adjust, so that the water-based ink dries faster

4, pH value

aqueous ink contains a certain amount of ammonium solution, which is used to improve its stability or enhance the water resistance after printing. Therefore, pH value is one of the important indicators. The pH value of water-based ink when leaving the factory is generally controlled at about 9. The pH value of the machine can be adjusted or controlled between 7.8 and 9.3

it should be flexibly controlled according to the difference of substrate and temperature. At the same time, we should consider the relationship between drying and viscosity, and add an appropriate amount of various additives for adjustment. The pH value of gold ink should not be too high, but can be controlled between 8 and 8.5, making it slightly alkaline. Generally, it is tested once every 2 ~ 3 hours, and it is adjusted as soon as possible. Try to control the pH value within the best printability range

water based this product is called acryviewa ink. The main additives of water-based ink include diluent, stabilizer, blocker, detergent, defoamer, gold ink diluent, UV gold ink curing accelerator, etc

1. Diluent

diluent is a milky white slurry liquid, which has a certain viscosity and high pH value. It can mix various colors and dilute four-color inks without reducing the viscosity and pH value. It can be directly used on the machine, so that the gradual development of science and technology has an electromechanical driven pressure testing machine to enhance the brightness of prints. The dosage can be determined according to the user's color manuscript and the depth of the color

2. Stabilizer

stabilizer is a colorless transparent liquid with a pH value of 11. It can improve the pH value of water-based ink and enhance the curing and drying time of water-based ink. If the printing is normal, the pH value is relatively stable and the viscosity is relatively high, the viscosity of water-based ink can be adjusted after being diluted with 1  1 water, and the usage is generally controlled at 4% - 6%

3. Blocker

blocker (slow drying agent) is a slightly yellowish liquid with a pH value of about 5.5. It can inhibit and reduce the curing and drying time of water-based ink, prevent surface crusting, and inhibit the dirty version and paste version phenomenon caused by too slow speed and too fast drying of water-based ink. When the viscosity of water-based ink is too large, and there is no need to use excessive blockers, it can be diluted with water, and the general dosage is controlled at 3% - 5%

4. Defoamer

the main performance of defoamer is to eliminate bubbles in water thinned ink due to the new design and packaging wall thickness, so as to prevent white spots, sand holes, water marks and other problems caused by bubbles during printing. The dosage is generally 0.5% ~ 1%. Excessive dosage will affect the product quality. It is best to spray it from the spray

5. Gold silver ink diluent

gold silver ink diluent is a kind of milky white turbid liquid. It has a certain viscosity, and the pH value is slightly alkaline. Its main performance is to adjust the viscosity of gold ink and improve the printability, At the same time, the frequency converter of the electronic universal experimental machine plays a very important role in the experimental machine without oxidizing and darkening the gold and silver ink and maintaining the original luster of the gold and silver ink. The dosage is generally controlled between 2% and 8%, and should be used flexibly according to the temperature, substrate and vehicle speed

6. UV gold ink curing accelerator

when preparing UV gold ink on site, UV gold ink curing accelerator is mainly used to help improve the light curing and drying speed, speed up the vehicle and increase the output. Generally, the dosage can be controlled within 5% - 10%

7. Cleaning agent

cleaning agent is mainly used to clean printing plates and embossing rollers on machines and to deal with dried and crusted water-based inks

recovery and utilization of residual ink

because the ink bucket must maintain a certain amount of ink to ensure the normal printing of each printing machine, it is impossible for each machine to run out of ink every time. At the end of printing each batch of products, there is usually a certain amount of residual ink. Multi variety and multi-color unit printing, each product will have a certain amount of ink left for holding treatment. If not adjusted in time, continued use will cause waste and increase costs. This requires that the remaining ink should be kept at the lowest point when blending. The remaining ink must be stored separately and sealed well, and no ink or sundries should be mixed. If it is not clean, filter it with a filter. Use the remaining ink first when you use it next time. The light color can be adjusted into the dark color. The rough paper or medium and low-grade products can be used preferentially

storage of water-based inks

the storage life of flexible water-based inks is generally one year, exceeding the shelf life or longer. As long as there is no solidified colloidal state, but the surface is layered or precipitated, as long as it is fully stirred, it can continue to be used. The storage temperature should be within the range of 5 ℃ - 30 ℃. It is best to store in the warehouse, not in the open air, not exposed to the sun, and not in the warehouse below 0 ℃. The storage life of gold ink is half a year or less

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