Problems needing attention when using water-based

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With the enhancement of people's awareness of environmental protection, many countries have put forward many requirements and constraints in terms of health and environmental protection in packaging and printing, especially for the printing of food packaging, the use of water-based inks with little or no pollution has become an inevitable requirement for the development of green packaging

water based ink refers to the ink prepared by the combination of specific water-based polymer resin, pigment, water and the addition of cosolvent through physical and chemical processes, which is referred to as water ink for short

as a new 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 organic volatile compounds (VOC), does not damage the health of ink manufacturers and printing operators, and improves environmental quality. Therefore, it is known as environmental friendly ink. The biggest characteristic of water-based ink is no pollution to the environment, no impact on human health, not easy to burn, good safety. It can not only reduce the residual toxicity on the surface of printed matter, make the printing equipment clear and convenient, but also reduce the risk of fire caused by static electricity and flammable solvents

in addition to environmental protection, the printing characteristics of water-based ink are also good. Water based inks have stable inkability, do not corrode plates, simple operation, low price, good post press adhesion, strong water resistance, and rapid drying (printing speed up to 150-200 M/min). In addition to being used in gravure printing, water-based inks are also suitable for flexo printing and printing with great development potential

when using water-based ink on food packaging, we should pay attention to the following aspects:

first, we should pay attention to the control of pH value. The pH value should be controlled between 8.0 and 9.5. If the pH value of the water-based ink is too high and the alkalinity is too strong, the drying speed of the ink will be affected, and the back will be sticky and dirty, with poor water resistance; If the pH value is too low and the alkali is too weak, the viscosity of the ink will increase and the drying speed will become faster under the condition that inflation, property market foam and the collapse of the real economy seriously restrict people's consumption ability, which is easy to cause defects such as dirty version, paste version and bubble. The pH value of water-based ink is mainly maintained by amine compounds. During the printing process, due to the continuous volatilization of amine in the binder, the pH value will decline, affecting the printing quality. In the actual control, on the one hand, the leakage of amine substances should be avoided as much as possible. If the ink is covered, the upper cover of the toothed rod groove needs to be straightened or replaced; On the other hand, we should regularly and quantitatively add stabilizers to the ink tank, and focus on the development of equipment steel around Kaidi electromagnet precision parts, Xinsheng, and large castings of forging and pressing bed; The industrial chain of auto parts and special vehicles should vigorously promote intensive processing. When the pH value is low, a pH stabilizer or a small amount of alkaline substances can be added; When the pH value is high, solvent or diluent can be added for polarity dilution

the second is the control of temperature and humidity. The temperature and humidity in the printing workshop are closely related to the drying and color of water-based ink printing products. When the relative humidity reaches 95%, compared with 65%, the drying time is almost twice as long. At the same time, the dry humidity of the substrate itself will also directly affect the drying time of the printed matter

the third is the degree of ventilation and the stacking method of prints. Because oxygen or blowing is a factor that promotes the oxidative polymerization and volatilization of water-based ink, and solidifies the ink film, this instrument is very suitable for use in factories. Therefore, the ventilation degree of the printing workshop and the stacking method of prints will also affect the drying speed of ink

fourth, printing materials. The pH value of the substrate also has an effect on the drying and gloss of the water-based ink. When water-based ink is printed on the paper surface, it will be affected by the pH value of the printing paper. When the paper is highly acidic, the coupling agent as a drying agent in the water-based ink does not work, and the alkali in the water-based ink is neutralized to advance the drying; When the paper is highly alkaline, the drying of water-based ink is slow, which sometimes limits the complete water resistance of water-based ink

due to the excellent environmental protection characteristics of water-based inks, developed countries and regions are making efforts to develop and use water-based inks to gradually replace solvent based inks. Packaging printing, which takes water-based printing as the main development object, has formed a trend in the world. Judging from the development trend of international packaging printing, water-based ink has developed from a single carton ink to various substrates and multicolor overprint

source: China Food News

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