Application of water-based ink in corrugated board printing

Water-based inks in corrugated board printing should pay attention to the following issues.

(1) Since water-based inks are pure water-based systems, it is imperative that water-based inks be mixed with alcoholic inks and solvent-based inks or that organic solvents be added to water-based inks to avoid causing print defects and affecting print quality.

(2) The water-based ink should not only be fully stirred before use to keep the ink components uniform, but also pay attention to the measurement of viscosity in use, use a stirring rod to stir the water-based ink in the barrel, measure the viscosity and pour it into the ink tank. If the viscosity is too high, an appropriate amount of diluent may be added. If the viscosity is too low, a thickener is used to adjust.

(3) Pay attention to changes in viscosity and pH during printing. Because in the printing process, due to the volatilization of water, it will cause the viscosity of the water-based ink to increase and the pu value to drop. The pH value should be controlled between 8.5-9.5. If it exceeds this range, it can be adjusted by the p-stabilizer. Keep viscosity and pH stable. In addition, if the water-based ink is found to be slightly thicker during use, an appropriate amount of water may be added for adjustment.

(4) After opening and use, the ink should be stamped and sealed immediately to prevent dust from falling and crusting. After printing, the remaining aqueous ink should be collected back to the corresponding original bucket or the lid of the ink tank should be tightly closed for the next time. Care must be taken to prevent the water-based ink surface from becoming conjunctiva, thickening or even drying out due to the volatilization of water. Yu ink, such as containing impurities should be filtered first, and then used together with new ink.

(5) Water-based inks should be stored at room temperature of 5-50°C in a cool, ventilated place. In general, aqueous inks can be stored under normal conditions for 1 year without deterioration.

(6) The residual ink remaining on the printing equipment after printing can be rinsed with fresh water when it is not completely dry, and can be cleaned with a cleaning agent if the ink cannot be washed with clean water.

(7) Reasonable use of ink additives. Since the printability of water-based inks is influenced by objective conditions such as printing conditions, surface characteristics of substrates, ambient temperature and humidity, and the length of water-based ink storage, when using aqueous inks, some additives are required to make fine adjustments to water-based inks. For the best printing results. Ink auxiliaries include colorants, eliminators, thinners, thickeners, slow drying agents, fast drying agents, defoamers, and pH stabilizers. Their use depends on many factors such as the environment, equipment, and materials. Adjust the printability of the ink to ensure stable print quality. To sum up, the use of ink additives should pay attention to the following issues: 1 color material. Mainly used to deepen the color, the amount should be controlled at 0-30%, because more than 30% will make the content of the binder in the water-based ink is too low, resulting in decreased adhesion and wear resistance; 2 withdrawal agent. Mainly used to reduce the depth of color, the amount of use. However, adding a large amount of a withdrawal agent may cause a slight increase in the viscosity of the aqueous oil. At this time, a small amount of diluent may be added at the same time to adjust; 3 dilution is beneficial. Mainly used to reduce the viscosity of water-based inks. The amount below 3% does not decrease the color depth of the water-based ink and maintain the pH of the water-based ink. The thinner should be added slowly while stirring to prevent the viscosity from being too low. Adding more diluent or diluting with tap water with high hardness will lead to the generation of bubbles. At this time, defoamer should be added to defoam; 4 thickener. Used to increase the viscosity of water-based ink, the amount of control in the 0.5% - l%, so as not to affect the printing viscosity of the ink viscosity is too high; 5 slow drying agent. For reducing the drying speed of water-based inks, the amount can be controlled at 0-10%. Under normal circumstances, water-based inks are suitable for high-speed printing. Therefore, the drying speed is required to be faster. Only when the drying speed is too low or the printing effect is poor during low-speed printing, a small amount of slow-drying agent can be added to meet the printability. ;6 Quick drying agent. It is used to accelerate the drying speed of water-based inks. The dosage is generally controlled at 0-30%; 7 defoamer. For the elimination of bubbles, the amount should be controlled at 0.1%-0.2%; 8pH stabilizer. It is mainly used to maintain the stability of water-based ink pH. Generally, the pH value of water-based inks should be kept at 8.5-9.5. If it exceeds this range or is not suitable for the printing environment and substrates, it should be applied in a timely manner. The pH is adjusted and kept stable.

Water-based ink development and application prospects

We know that printing inks consist of pigments, binders, solvents, and adjuvants. Among them, organic solvents and heavy metal elements cause serious damage to the human body. Traditional solvent-based inks are mostly based on volatile drying. The solvent has a low boiling point and is easily volatilized. Volatile gases emitted during volatilization not only pollute the surrounding environment and are harmful to the operator's body, but their surface remains after printing. The harmful substances are not suitable for printing food packaging, pharmaceutical packaging, children's toys and other packaging. The biggest difference between water-based and solvent-based inks is that water-based inks use water instead of organic solvents. Its greatest feature is the obvious reduction of organic volatiles (VOC) emissions, thus preventing air pollution, non-flammable, and good safety. It can completely eliminate the harmful effects of certain toxic and harmful substances in solvent-based inks on the human body and The pollution of packaging products has improved the quality of the printing operation environment and is conducive to the health of workers. Especially suitable for food, beverages, pharmaceuticals and other sanitary conditions require strict packaging and printing products. In addition, it not only reduces the risk of fire and hazards caused by static electricity and flammable solvents, but also reduces the residual solvent odor on the print surface. Water-based ink is a world-recognized environmentally friendly printing ink, and is the only inorganic ink approved by the US Food and Drug Association in all printing inks. Water-based ink and ink stability, colorful, non-corrosion plate, simple operation, low price, good adhesion after printing, strong water resistance, rapid drying, especially for food, medicine, cosmetics and other strict requirements on the health conditions Printing and use of packaging and decorating printing products. At present, 40% of U.S. plastic printing uses water-based ink, and other economically developed countries (such as Japan, Germany, France, etc.) use water-based ink more and more in plastic film printing. The United Kingdom has enacted legislation to prohibit the printing of food films using solvent-based inks. According to relevant data, the United States has strict restrictions on the total amount of organic volatiles (VOC) emitted from organic solvents that can produce photochemical smog, while water-based inks comply with VOC regulations. The proportion of volatile components is below 25%, and moisture is 75%. The above; the ink with less moisture in use, the non-volatile components in the above two standards of 60%. Water-based inks are generally used for the printing of paper products including paper-plastic composite products. Its characteristics are to meet the paper printing ink absorption, making the print color full, more importantly, the solvent is water and ethanol, environmental pollution, can be called green printing ink. In addition, water-based UV inks are also a new research direction in the field of UV inks. The viscosity of prepolymers in general UV inks is generally very high, requiring the addition of a reactive diluent for dilution. However, the currently used diluent acrylate compounds have different degrees of skin irritation and toxicity. Therefore, while developing low viscosity prepolymers and low toxicity reactive diluents, it is of great significance to study aqueous UV inks. Water-based UV inks are UV inks that use water and ethanol as diluents. Not only do alcohol-soluble inks have good compatibility and excellent adhesion properties, but they can also be achieved with very low VOC emissions. With lower toxicity, water-based UV inks have been successfully developed and used in some printing applications.