Overview of the application of the hottest water-b

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Overview of the application of water-based inks

I. what is water-based inks? The so-called water-based inks are mainly scientifically processed with water as the solvent. Compared with other printing inks, water-based inks do not contain volatile toxic organic solvents, so they have no adverse impact on the health of printer operators, no pollution to the atmospheric environment, and no pollution to the print itself in the printing process. As the ink is non flammable, it can also eliminate the hidden dangers of flammability and explosion in the printing workshop, which is conducive to safe production. Of course, the application scope of ink and ink is different now. Ink is mainly offset printing, while ink is mainly flexo printing and gravure printing. In developed countries such as Europe, America and Japan, ink has gradually replaced ink as a special ink for other printing methods except offset printing. Take the United States as an example, 95% of flexographic printing materials use ink, and 80% of gravure printing materials use ink

in addition to environmental protection, ink widely used abroad also has excellent performance: stable ink color, high brightness, strong coloring power, non-corrosive plate, strong adhesion after printing, adjustable drying speed, strong water resistance, four-color overprint and spot color printing, etc. The development and application of ink painting in China started late, but it has developed rapidly, especially in recent years. With the increasing demand for ink, the quality of domestic ink has also been improved. In the traditional sense, the shortcomings of ink painting, such as slow drying, poor gloss, water intolerance, and false printing, have been significantly improved. Under the condition that the price of imported ink is generally high, domestic ink with low price and good quality has gradually occupied the market

II. Composition and characteristics of water-based inks

water based inks are made of water-soluble resins, advanced pigments, solvents and additives through scientific compound processing and grinding. Water soluble resin mainly plays the role of connecting material in the ink, which is to make the pigment particles evenly dispersed, make the ink have a certain fluidity, and provide the adhesion with the substrate material, so that the ink can form a uniform film after printing. The hue in the ink mainly depends on the pigment. The pigment is evenly distributed in the connecting material in the state of particles. The pigment particles can absorb, reflect, refract and transmit light, so they can show a certain color. Generally, pigments are required to have bright color, appropriate coloring power and hiding power, and high dispersion. In addition, it can also have different wear resistance according to different purposes of use. The function of solvent is to dissolve the resin, make the ink have a certain fluidity, transfer smoothly in the printing process, and adjust the viscosity and drying performance of the ink. The solvent of water-based ink is mainly water and a small amount of ethanol

the commonly used additives in water-based ink mainly include: pH stabilizer, slow drying agent, defoamer, diluent, etc

(1) pH stabilizer. PH stabilizer is mainly used to adjust and control the pH value of water-based ink to make it stable at 8 At the same time, it can also adjust the viscosity of water-based ink and dilute the ink. Generally speaking, an appropriate amount of pH stabilizer should be added every certain time in the printing process to keep the water-based ink in good printing condition

(2) slow drying agent. Slow drying agent can inhibit and slow down the drying speed of water-based ink, prevent the ink from drying on the printing plate or roller, and reduce the incidence of printing failures such as blocking and pasting. Control the amount of slow drying agent, which should generally be controlled between 1% and 2% of the total ink volume. If the amount is too much and the ink is not completely dried, the printed matter will stick dirty or produce peculiar smell

(3) defoamer. The function of defoamer is to inhibit and eliminate the generation of bubbles. Generally speaking, when the viscosity of water-based ink is too high, the pH value is too low, or when the printing machine runs faster, it is easy to produce bubbles. If the amount of bubbles is relatively large, there will be white leakage and uneven ink color, which will inevitably affect the quality of printed matter

water based inks comply with the requirements of environmental protection. The products are non-toxic, non corrosive, non irritating odor, non combustible, non explosive, good safety, convenient transportation, high concentration, low dosage, low viscosity, good printing adaptability, stable performance, good adhesion fastness, fast drying, excellent water, alkali and abrasion resistance after drying; It is easy to adjust the operation before and after printing and during the printing process. The biggest advantage of printed matter is its strong power. After printing, it appears full impression, bright colors, high gloss, gorgeous and rich. The printing of complex patterns can also reach a rich level, and can print bright and high gloss colors

III. application of water-based inks

the biggest feature of water-based inks is to reduce the emission of VOC (organic volatile matter) into the atmosphere, so as to prevent air pollution, improve the printing environment, and significantly reduce fire hazards. It can completely eliminate the harm of some toxic substances in solvent based ink to human body and the pollution of packaged goods, and improve the overall environmental quality. It is especially suitable for packaging and printing products with strict hygienic conditions such as food and drugs

the main application fields of water-based printing inks are flexible printing and gravure printing. According to the information, 95% of narrow flexographic paper prints in the United States use water-based microcomputer controlled electronic universal experimental machine, which is your better choice for ink printing, and 80% of gravure paper prints use water-based ink. In recent years, China has also developed rapidly, but there is still a large gap between the application amount and that of foreign countries

whether the application of water-based ink is appropriate is an important factor affecting its printing quality. The control indicators of water-based ink include fineness, viscosity, drying speed and pH value

in the technical problem brush of the flexographic printing digital display pipe static pressure testing machine, the transmission of water-based ink and the control of ink volume are undertaken by the wrinkle roller, so the fineness of the wrinkle roller must be selected according to the situation of the product. For field printing, the wrinkle roller of about 300 lines is generally selected, and the ink layer is relatively thick, while for printing 150 lines of fine-level version, the wrinkle roller of 600 lines needs to be selected, and the number of lines of the wrinkle roller is generally four times the number of print lines, In order to obtain better printing clarity and resolution

viscosity is the most important control index in the application of water-based ink, and it is a property that prevents fluid flow. Because viscosity directly affects the transferability of ink and the quality of printed matter, it is very important to control the viscosity of ink. In the printing process, the low viscosity of water-based ink will cause the disadvantages of light color, dot expansion, uneven ink transfer and so on; On the contrary, if the viscosity of water-based ink is too high, the transfer performance of ink is relatively poor, prone to dirty version, paste version and other disadvantages

flexible water-based ink is generally used directly without dilution, and its viscosity range can be 30 ″ -45 ″/25 ℃ (coated with 4 # cups). The viscosity of flexible water-based ink for cartons can be lower. As long as water stabilizer is added regularly, its viscosity change can be basically controlled. Gravure water-based ink is usually diluted with ethanol and water 1:1 diluent according to the traditional custom, and the viscosity is generally controlled at 15 ″ -25 ″/25 ℃

water based inks are usually alkaline (mainly maintained by amines). Generally, the pH value of water-based inks should be controlled at 8 5. If the pH value of water-based ink is too high, it will affect the drying speed of the ink; If the pH value is too low, the viscosity of the ink increases and the drying speed becomes faster, which is easy to cause the blocking of the printing plate and the wrinkle roller, causing the dirty on the plate

1. The drying of ink is mainly volatile drying and osmotic drying. The drying performance of ink refers to the time required for the ink to dry after being transferred to the substrate, which is also one of the important indicators to measure the quality and performance of ink. Therefore, controlling the drying performance of ink is an important means to achieve good printing effect

the drying speed of flexo water-based ink depends on the printing speed of the printing machine, the drying capacity of the drying equipment, the performance of the substrate material and the composition of the ink itself. The general principle of selecting the ink drying speed is that under the existing conditions of the printing machine, the ink should be able to be fully dried before the next printing color deck and before rewinding or stacking, but it cannot be dried on the printing plate. If the ink dries too fast, it will dry and gradually accumulate on the printing plate and the embossing roller, and may block the embossing roller, resulting in the loss or damage of halftone points, and white leakage in the field part; If the drying speed of the ink is too slow, there will be a printing smell, or in the case of multi-color overprint, it will cause the back to stick dirty

2. Diluent: it is used to reduce the depth of color, and the dosage is unlimited. Adding a large amount of diluent may cause the viscosity of ink to rise slightly. At this time, a small amount of diluent can be added at the same time for adjustment

3. Diluent: used to reduce the viscosity of ink. If the dosage is less than 3%, the color depth of the ink will not be reduced, and the pH value of the ink will remain unchanged. Adding more diluents or diluting with high hardness tap water will lead to bubbles. Defoaming agent can be added at the same time. Diluent should be added slowly while stirring to prevent low viscosity

4. Slow drying agent: used to reduce the drying speed of ink, the dosage is%

5. Quick drying agent: used to speed up the drying speed of ink, the dosage is%

6. Defoamer: used to eliminate bubbles, the dosage is 1 ‰ -2 ‰

7. PH stabilizer: it is used to maintain the pH value of ink, and the amount is used to maintain the pH value of ink at 8 5 is appropriate

8. Thickener: used to increase the viscosity of ink, the dosage is 0.5% - 1%

v. conclusion

in China, with the rapid promotion and use of high-strength corrugated boxes in the packaging industry, the printing of corrugated boxes has been paid more and more attention. People have also paid considerable attention to the quality of water-based ink, an important printing material. In the production of cartons, although the ink accounts for a small proportion of the cost, once it affects the printing quality, it will cause the return and scrap of the whole batch of cartons. Therefore, it is very important to produce excellent quality water-based ink products and adjust its performance reasonably in printing. In recent years, with the continuous improvement of environmental protection requirements, many health and environmental protection requirements and constraints have been gradually increased in packaging printing and commercial printing. In this general trend, efforts to develop pollution-free "green" printing materials, water-based inks, will achieve good economic results. Check whether the joints of the oil system are tightening benefits and social benefits

source: Chemical Industry Forum

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