The hottest green packaging water-based ink and it

2022-08-07
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Water based ink for green packaging and analysis of problems (Part 2)

IV. problems in the use of water-based ink

in the use of water-based ink, there are usually problems in the protection of experimental machine products, such as inaccurate color, unstable viscosity, drying too fast or too slow, blurred outline, difficult to register, ink bubbles, sticky version, imprint falling off, etc. in general, the main reasons are as follows:

1 PH value control

ph value is the key to the success or failure of water-based ink manufacturing and printability technology. When using water-based inks, it is necessary to accurately control their viscosity and pH value to successfully pass the expert review in the application for "the capital of new plastic materials in China". Its 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, resulting in dirty back and poor water resistance; If the pH value is too low and the alkalinity is too weak, the viscosity of the ink will increase, the drying speed will become faster, and it is easy to cause defects such as dirty version, paste version 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 amine in the binder, the pH value will decrease, affecting the printing quality. In the actual control, on the one hand, the leakage of amine substances should be avoided as much as possible, such as covering the upper cover of the ink tank; On the other hand, the stabilizer should be added to the ink tank regularly and quantitatively. 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 dilution

2. 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

3. Ventilation degree and printing stacking method

as oxygen or blowing is a factor to promote the oxidative polymerization of water-based ink and the formation of volatile solid ink film, the ventilation degree and printing stacking method of the printing workshop will also affect the drying speed of ink

4. Once such a detailed problem occurs in the substrate, the pH value of the substrate also affects 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 water-based ink dries slowly, which sometimes limits the water-based ink to achieve complete water resistance

v. development of water-based inks

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 with water-based printing as its main development object has become a trend in the world. From the development trend of international packaging printing, water-based ink has developed from a single carton ink to a variety of substrates and multi-color overprint

solvent based inks containing benzene have been banned in the United States and some European countries and replaced by green environmental friendly inks. At present, 40% of plastic printing in the United States uses water-based ink. Other developed countries, such as Japan, Germany and France, are also increasingly using water-based inks in plastic film printing. The United Kingdom has legislated to prohibit the use of solvent based inks to print films for food packaging

in recent years, China has also made some regulations on food packaging, and the status of water-based printing is being continuously improved in China. At present, the water-based printing ink for soft packaging in China ranks first among other printing inks with 35% consumption due to the suitable degradability, good initial mechanical properties and bioactive packaging of PGA

source: PRINT world

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