Problems with the Use of Water-based Ink in Food Packaging

With the enhancement of people’s awareness of environmental protection, various countries have put forward many requirements for hygiene and environmental protection in terms of packaging and printing. Especially for the printing of food packaging, the use of water-based ink with low pollution, pollution, and pollution-free has become a green packaging. The inevitable requirements of development.

Water-based ink refers to an ink prepared from a combination of a specific aqueous polymer resin, a pigment, water, and a cosolvent added by a combination of physical and chemical processes, and is simply referred to as ink.

Water-based ink as a new type of packaging printing material, its biggest advantage is that it does not contain volatile organic solvents, its use reduces the amount of organic volatiles (VOC), will not harm the health of ink manufacturers and printing operators, improve The environmental quality, so it is known as environmentally friendly ink. The biggest feature of water-based ink is no pollution to the environment, no impact on human health, not easy to burn, and good safety. It can not only reduce the residual toxicity on the printed surface, make the printing equipment clear and convenient, but also reduce the risk of fire due to static electricity and flammable solvents.

In addition to environmental features, water-based inks also have better printing characteristics. Water-based ink and ink stability, does not corrode plate, simple operation, low price, good adhesion after printing, strong water resistance, drying faster (printing speed up to 150-200 meters / minute). In addition to gravure inks, water-based inks are also suitable for flexographic and screen printing applications with great development potential.

When using water-based inks on food packaging, attention should be paid to the following issues:

One is to pay attention to pH control. The pH should be controlled between 8.0-9.5. If the pH of the water-based ink is too high, too strong alkaline will affect the drying speed of the ink, the back of the ink will appear dirty and the water resistance will be poor; if the pH is too low, the alkali is too low. Weakness will increase the viscosity of the ink, the drying speed will increase, and it will easily cause defects such as dirty plate, paste plate, and bubbles. The pH value of water-based inks is mainly maintained by amines. During the printing process, due to the constant volatilization of the amines in the binders, the pH value will drop, affecting the printing quality. In actual control, on the one hand, it is necessary to avoid leakage of amines as much as possible, such as covering the upper cover of the ink tank; on the other hand, it is necessary to add stabilizers to the ink tank regularly and quantitatively. When the pH is low, a pH stabilizer or a small amount of a basic substance may be added. When the pH is high, a solvent or thinner may be added to be diluted.

The second is the control of temperature and humidity. The temperature and humidity of the printing shop are closely related to the drying and color of water-based ink printing products. Relative humidity of 95% compared with 65%, drying time is almost 2 times more than the difference. 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 printing methods stacked. Since oxygen or blowing is a factor that promotes the oxidative polymerization and volatilization of water-based inks and solidifies the formation of ink film, the degree of ventilation in the printing room and the stacking method of the prints also affect the drying speed of the ink.

Fourth, printing materials. The pH of the substrate also affects the drying and gloss of aqueous inks. Water-based inks are affected by the pH value of the printing paper when it is printed on the surface of the paper. When the acidity of the paper is high, the coupling agent acting as a driers in the water-based ink does not work, the alkali in the water-based ink is neutralized, and the dryness is advanced; when the paper alkali is high, the water-based ink dries slowly, sometimes limiting the water-based properties. The ink reaches full resistance to water.

Due to the excellent environmental characteristics of water-based inks, developed countries and regions are currently working hard to develop and use aqueous inks to gradually replace solvent-based inks. The packaging printing with water-based printing as the main development object has become a trend in the world. From the point of view of the development trend of international packaging printing, water-based ink has developed from a single carton ink to various substrates and multi-color overprints.

Source: China Food News