Several considerations for the use of water-based inks in flexo printing

The special ink used in flexo printing machine is water-based ink, which has the advantages of no pollution, no impact on human health, easy to burn, good safety, stable ink performance, colorful, anti-corrosive materials, simple operation, cheap, attached after printing Good focus, strong water resistance, fast drying, printing speed up to 150-200 meters per minute. Because of the above characteristics, water-based flexographic ink is especially suitable for the printing use of strict food hygiene, medicine, cosmetics other packaging decoration printing products. So do you know what you should pay attention to when using it?

Key indicators of water-based flexo ink

1. Fineness

Fineness is a physical indicator for measuring the particle size of ink pigments fillers, is directly controlled by the ink manufacturer. Users generally understand that it can change its size during use. The fineness of water-based flexographic ink is generally 20 microns, the instrument measures the fineness fineness of the doctor device.

2. Viscosity

It is the viscosity of one of the main stock index aqueous inks. The viscosity value will directly affect the quality of the printed matter. Therefore, the viscosity of the aqueous ink is strictly controlled in flexographic printing. The viscosity of water-based ink is generally controlled at 30-60 seconds/25°C (4 cups of paint), it is generally better to control the viscosity at 40 to 50 seconds. If the viscosity is too high the flow performance is poor, it will affect the printing suitability of the water-based ink, it is easy to cause dirty plates other phenomena. If the viscosity is too low, it will affect the driving pigment of the vehicle.

If the water-based ink is left for a period of time, some inks with poor stability are easy to precipitate delaminate, which will cause a thick phenomenon. At this time, it can be completely mixed, these problems will disappear naturally. When using fresh water-based ink, be sure to stir well in advance adjust for dilution. During normal printing, it also takes time to stir the ink fountain.

Water-based ink freezes at 0°C. If the water-based ink freezes, it can be placed at a high temperature in the room to allow it to dissolve naturally, stir evenly, may continue to be used. When the temperature difference between winter summer, viscosity is the most sensitive performance. At high temperature, the water evaporates quickly the drying is fast. The operation will pay attention to reduce the drying time increase the speed of the machine; at low temperatures, the water evaporates slowly the water-based ink drying speed is slow. When the operation can be faster, the water-based ink drying speed additional drying equipment. For winter use, it is best to store the water-based ink in the warehouse in advance to the workshop in order to balance the viscosity.

3. Dry

Drying is one of the main indicators of water-based inks. Due to the drying speed viscosity, it can be directly reflected in the quality of the printed matter. The operator must have detailed information on the principle of drying, which can be based on different products substrates, the reasonable deployment of water-based ink drying time. While ensuring good water-based ink drying, it must also consider moderate viscosity stable pH.

Water-based ink drying includes three methods: volatility, absorption reaction curing. The water-based ink is completely dried after printing, the flushing resistance the friction resistance. Drying too fast, the ink layer surface is easy to peel, the water-based ink is easily depleted, resulting in dirty plates, unclear patterns, internal water cannot be excluded, resulting in inaccurate recording, can be adjusted with a retarder, the printer can be increased shut down by speed Drying system to solve. When stopping, it is best to clean the anilox roller ink fountain. When stopping for a short time, it is also necessary to frequently stir the ink fountain to prevent the surface crust; too slow drying, paper expansion, reduce gloss, affect the color printing stack, possible adhesion , The machine operator caused a lot of trouble. At this time, you should check that the pH value is correct. You can add stabilizer ethanol in an appropriate amount according to the high low pH value, the water-based ink dries faster.

4. pH value

The water-based ink contains a certain amount of ammonium solution, which is used to improve its stability increase the water resistance after printing. Therefore, it is an important indicator of pH.

The pH value of water-based ink factory is generally controlled at around 9. The machine uses pH value, which can be adjusted controlled between 7.8~9.3 according to different flexible substrate temperature control. At the same time, the relationship between drying viscosity should be considered, various additives should be added in an appropriate amount. The pH value of golden ink should be too high, it can be controlled between 8 8.5, make it slightly alkaline. Generally testing for 2~3 hours, SuiDiao tries to control the best printability in the pH range.