Why Is Water-based Ink An Environmentally Friendly Ink?

With the increase of people's environmental awareness, countries have put forward many requirements and constraints on hygiene and environmental protection in packaging and printing. Especially for the printing of food packaging, the use of water-based inks with little pollution, less pollution or even no pollution has become an inevitable requirement for the development of green packaging. Water-based ink refers to ink prepared by combining specific water-based polymer resins, pigments, water, and adding co-solvents through physical and chemical processes, referred to as water-based ink. As a new type of packaging and printing material, the biggest advantage of water-based ink is that it does not contain volatile organic solvents.

Its use reduces the amount of volatile organic compounds (VOCs), does not harm the health of ink manufacturers and printing operators, and improves the quality of the environment. Therefore, it is known as environmentally friendly ink. The biggest feature of water-based ink is that it does not pollute the environment, has no effect on human health, is not easy to burn, and has good safety. It can not only reduce the toxicity of the residual on the surface of the printed matter, making the printing equipment clear and convenient, but also reduce the risk of fire caused by static electricity and flammable solvents. In addition to its environmental protection characteristics, water-based ink also has good printing properties. Water-based ink is stable, does not corrode the plate, is easy to operate, cheap, has good adhesion after printing, strong water resistance, and dries quickly (printing speed can reach 150-200 m/min). In addition to being used in gravure printing, water-based ink is also suitable for flexographic printing and screen printing, which have great development potential.

When using water-based ink on food packaging, attention should be paid to the following issues: First, attention should be paid to the control of pH value. The pH value should be controlled between 8.0 and 9.5. If the pH value of water-based ink is too high, the alkalinity will be too strong, which will affect the drying speed of the ink, resulting in sticky dirt on the back and poor water resistance; if the pH value is too low, the alkalinity will be too weak, which will increase the viscosity of the ink, speed up the drying speed, and easily cause defects such as dirty plates, paste plates and bubbles. The pH value of water-based ink is mainly maintained by amine compounds. During the printing process, due to the continuous volatilization of amines in the binder, the pH value will decrease, affecting the printing quality. In actual control, on the one hand, amine substances should be avoided as much as possible, such as covering the upper cover of the ink tank; on the other hand, stabilizers should be added to the ink tank regularly and quantitatively.

When the pH value is low, pH stabilizers or a small amount of alkaline substances can be added; when the pH value is high, solvents or diluents can be added for polar dilution. Second, the control of temperature and humidity. The temperature and humidity of the printing workshop are closely related to the drying and color of water-based ink printing products. Compared with 65% relative humidity, the drying time is almost twice as long when the relative humidity reaches 95%. At the same time, the dryness and humidity of the substrate itself will also directly affect the drying time of the printed product. Third, the degree of ventilation and the stacking method of printed materials. Since oxygen or blowing is a factor that promotes the oxidation polymerization and volatilization of water-based ink and the formation of a solid ink film, the degree of ventilation in the printing workshop and the stacking method of printed materials will also affect the drying speed of the ink. Fourth, the printing material. The pH value of the printing material also affects the drying and gloss of water-based ink. When water-based ink is printed on the surface of paper, it will be affected by the pH value of the printing paper.

When the acidity of paper is high, the coupling agent used as a drying agent in water-based ink does not work, and the alkali in water-based ink is neutralized, which makes the drying process come early; when the alkalinity of paper is high, water-based ink dries slowly, which sometimes limits the water-based ink from being completely water-resistant. Due to the excellent environmental protection characteristics of water-based ink, developed countries and regions are currently working hard to develop and use water-based ink to gradually replace solvent-based ink. Packaging printing with water-based printing as the main development target has become a trend internationally. From the development trend of international packaging printing, water-based ink has developed from a single carton ink to various substrates and multi-color overprinting.