Flexo printing machine using special ink, water-based ink, its advantages is no pollution to the environment, there is no impact on human health, is not easy to burn, good safety, stable ink performance, bright color, corrosion plate, the operation is simple, cheap, India has the good adhesion, water resistance and strong, dry quickly and, printing speed can reach every minute 150-200m. It is because of these features, water-based flexo ink especially in the printing and use of strict demands on the health conditions of food, medicine, cosmetics and other packaging and decoration printing products. So what problems should be paid attention to in the use of it? 

The main indicators of water-based flexo ink 

1, fineness 

Fineness is a measure of the ink pigment, filler and other particle size of the physical indicators, by the ink manufacturer direct control. Users generally understand that can not be changed in the use of its size. Water-based flexo ink fineness is generally below 20 m, the instrument for measuring the fineness of scraper fineness instrument. 

2, viscosity 

Viscosity is one of the main indicators of water ink, viscosity value will directly affect the quality of printed materials, so in the flexo printing to strictly control the viscosity of water-based ink. The viscosity of water-based ink is generally controlled within the range of 30-60 seconds / 25 degrees C (with paint 4 cup), the general viscosity control in 40-50 seconds better. If the viscosity is too high, leveling, influence of water-based ink printing adaptability, easily lead to dirty version, paste version; if the viscosity is too low, it will affect the carrier to drive the pigment. 

If the water ink placed a long time, some of the stability of the ink is easy to deposit, stratification, and there will be a false thick phenomenon. At this time, can be fully stirred, the above problem can be naturally disappeared. In the use of fresh water ink, be sure to stir evenly, and then make the dilution adjustment. In the normal printing, but also regular ink mixing. 

Water based ink is easy to freeze at 0. If the water is frozen, it can be placed into the room temperature high, let it naturally dissolved, stirring evenly, can continue to use. In winter and summer, the temperature difference is large, the viscosity is the most sensitive. Temperature is high, the water evaporates quickly, dry quickly, in operation should pay attention to reduce the drying time or increase the speed of the machine; when the temperature is low, slow evaporation of water, water-based ink drying too slow, in operation can increase fast water-based ink drying rate or additional drying device. In winter, it is best to store the stored water ink in advance to the workshop, in order to balance the viscosity. 

3, dry 

Drying is one of the most important indicators of water ink, because the drying speed and viscosity, can be directly reflected in the quality of the printed matter. Operators must understand the principle of drying, in order to make a reasonable allocation of water based ink drying time according to the different product or substrate. Ensure that the water ink drying is good at the same time, must also take into account the moderate viscosity or pH value stability. 

Water based ink drying includes three ways of volatilization, absorption and reactive coagulation. After thorough drying, the water - based ink is very strong in water resistance and friction resistance. Drying too quickly, ink layer surface is easy to peel, water ink easily dried up to the plate, causing the dirty version, around the pattern is not clear, and make internal water can not be excluded, thus caused by misregister, available blockers adjustment can also be by improving the printing machine speed or closed drying system to solve. In the shutdown, the best cleaning roller or fountain, stands a short time, but also often stir ink fountain, prevent surface crust; drying too slow, paper expansion, reduce the luster, will affect the laminated color printing, and is likely to have adhesions, bring a lot of trouble to the machine operators. At this time, should first check the pH value is correct, can be based on the level of pH value, the amount of stabilizer or ethanol to adjust, so that the water ink dry faster. 

4, pH value 

Water-based ink containing a certain amount of ammonium solution for improving prepress enhanced water resistance of its stability and. Therefore, pH value is one of the important indicators. 

PH value of water ink factory, the general control in about 9. Machine use pH value, can be adjusted or controlled in 7.8 ~ 9.3 between the substrate and the temperature should be flexible and flexible. At the same time, to take into account the relationship between dry and viscosity, the amount of additives to adjust the amount of. Gold ink pH value should not be too high to control between 8.5 ~ 8, so that it is slightly alkaline. General 2 ~ 3 hours once, with the inspection with, as far as possible to control the pH value in the best printability range. 

Types, uses and dosage of main auxiliaries of water based ink 

Water based ink is the main additives, such as dilution agent, stabilizer, blocking agent, cleaning agent, anti foam agent, gold ink diluent, UV gold ink curing accelerator, etc.. 

1, dilute agent 

Dilute agent is a milk white slurry liquid, the viscosity, pH value is higher, to deploy a variety of colors and dilute the four colour printing ink without reducing the viscosity and pH value, can directly on the machine is used to enhance the brightness of the prints. Dosage can be based on the color of the user's draft and the color of the depth of the. 

2, stabilizer 

Stabilizer is a colorless transparent liquid, pH value can reach 11, it can improve the pH value of water ink, and enhance the curing and drying time of water ink. If the normal printing, pH value is stable, the viscosity is too large available 1 1 water dilution after adjusting the viscosity of water-based ink, the amount of general control in 4% ~ 6%.