Application and Misunderstanding of Waterborne Ink in Carton Printing

The main difference between water-based inks and oil-based inks is the difference in solvents. Water-based inks use water (45% to 50%) as the solvent; oil-based inks use organic solvents (toluene, xylene, industrial alcohol, etc.) as the solvent. From the solvent used, it is easy to understand that the water-based ink is more environmentally friendly and non-flammable than the oil-based ink. This article will focus on the water-based inks used in the carton packaging industry.

China's carton water-based inks were the first to introduce water-based furnish from Singapore, and the Gangu ink factory copied the first-generation water-based furnish. After many years of use, it developed the second-generation water-based ink. Third-generation water-based inks are imported directly into China. The high-grade ink we use nowadays can be said to be the fourth generation product, which is characterized by self-developed resin or directly using imported resin. At present, China's water-based ink technology has matured much more than before. The current production of four-color ink, dot, overprint and high-speed printing carton water-based inks has basically met the requirements of most carton factories. The fourth-generation water-based ink products have low cost, quality is not inferior to imported ink, and are trusted by customers. According to the author's understanding, in addition to the use of high-speed four-color printing presses in coastal cities, large and medium-sized inland cities are rapidly popularizing the use of high-speed printing presses. It can be believed that in the future, higher and higher requirements for carton printing are an inevitable trend in the carton industry. This will surely require higher and higher requirements for water-based ink quality technology.

The main components of the carton ink structure consist of inorganic (organic) toner, rosin (acrylic acid) acid, additives (defoamers, dispersants, leveling agents, stabilizers) and water. The structure is relatively simple and the investment equipment is not large. The profit rate is relatively high, so currently there are many domestic manufacturers, but the quality of products is uneven. There are only 50 manufacturers producing carton ink and ink on a certain scale across the country. Carton ink type includes common ink (rosin resin), high-grade ink (acrylic resin) and mid-range ink (part of rosin resin and some acrylic resin). Because the resins used in high-grade inks are all acrylic resins, high-grade inks have the fastest drying speed, highest water resistance, best abrasion resistance, highest ink stability, high brightness, strong coloring power, and no corrosion of the plate material, but their cost. And the technical content is high. Many ink-and-wash factories use high-grade ink and ink as the economic pillar. For this reason, the author suggests that carton customers should purchase water-based ink according to their own printing equipment and printing requirements. If the printing requirement is not high or the equipment is poor, it is better to use ordinary-type or mid-range ink. This will not only satisfy the requirements of the end customers, but also reduce the cost. Do not think that as long as the high-priced ink is used, it can be printed. Good results. If the demand for printing products is high or the printing press is relatively advanced, high-grade ink shall be selected to meet the requirements. At present, in order to reduce the production cost, a small number of ink-jet factories will use some of the rosin resin to add high-grade ink. Carton manufacturers can't detect whether it is made entirely of acrylic resin. It can be said that it is purely fraudulent behavior. It reminds carton manufacturers to purchase Keep your eyes open.

Here are some commonly used additives in water-based inks. There are PH value stabilizers, defoamers, fast drying agents and slow drying agents.

The pH stabilizer is mainly used to adjust the PH value of the ink to make it stable within the range of 8.0 to 9.0. Low pH tends to cause agglomeration of the ink, and the viscosity is relatively low when the pH is high. Generally in the printing process should detect the ink PH value changes, when the PH value is lower than 8, should be properly added appropriate amount of PH stabilizer, so that the ink maintains a good printing state.

Defoamer ink viscosity is too high, PH value is low, the printing speed is faster and printing technicians add too much water, are prone to air bubbles. When the bubbles are relatively large, there will be phenomena such as whitening of the printed matter and less ink, which will seriously affect the printing quality. It is generally recommended to use a mixture of a foam suppressor and a surface defoamer in the ink to solve the blistering of the ink. The use ratio is 1 to 2%.

When the quick-drying agent ink is used, the ink used by the ink manufacturer may be different or the machine speed may be too fast, which may cause the ink drying speed to be slower. n The quick-drying agent can adjust the ink drying speed to meet the speed requirement of the printing press and improve the production efficiency. The use ratio is 2~3%.

Slow drying agent It can inhibit and slow down the drying speed of the ink, play a role in moisturizing, prevent the ink from drying on the printing plate or anilox roller, and reduce the occurrence of printing failures such as blocking plate and stencil printing. The use ratio is 1 to 2%. between.

Water-based ink usage

After introducing the structure and type of water-based inks in the previous section, let's talk about some important factors affecting the printing quality of water-based inks. In carton printing, the transfer of ink and ink is controlled by the anilox roller. For this purpose, the anilox roller must be selected according to the requirements of the product. The number of lines of the anilox roller is approximately four times the number of lines of the printed matter. Get better print definition and resolution.

Fineness refers to the size of the toner particles in the ink. It is completed in the process of producing ink color paste. It is a key quality indicator. Whether or not the color paste production process is scientific and meticulous plays an absolute role in the quality of the ink. It is best to add dispersants and wetting agents during the production of pastes. The fineness of the general ink is preferably between 10 and 25 μm, and too fine or too large will affect the flow and rheological properties of the ink.

Viscosity refers to the thickness of ink and is an indicator of the flow of ink. The viscosity is too large to cause poor fluidity and slow drying; the low viscosity ink has good fluidity, fast drying, thin ink layers, and low ink consumption. Normal general ink viscosity is 50"~65"/25°C (coating 4# cups), high-grade ink ink viscosity is controlled at 25"~35"/25°C (coating 4# cups). If the viscosity of the ink is low, the toner content requirement is higher; otherwise, the toner content is low. Since the viscosity directly affects the transferability of the ink and the quality of the printed matter, the control of the viscosity of the ink is very important for this purpose. In the printing process, if the viscosity is too low, the color will be light, and the high viscosity will cause the phenomenon of dirty plate, stencil, etc. Therefore, if the transfer agent is difficult to control, the transfer agent can be added to improve the transfer effect and increase the vividness and three-dimensionality.

Water-based ink tips

â–  Do not mix ink with solvent ink. In the use of appropriate addition of water, you really need to adjust the viscosity or drying speed, the appropriate amount of additives such as alcohols or esters.

â– Before use, stir it well and pour it into the ink tank. Adjust the viscosity with water and use it. Unused containers should be covered and the ink should not be allowed to evaporate in nature.

â– Before using, check various technical indicators, especially if hue meets your own requirements. If the hue deviation is large, please inform the ink manufacturers to perform proper deployment so as to avoid disputes caused by hue errors.

â–  In the printing process, due to the volatilization of water, the original viscosity and PH value of the ink will be affected. It is necessary to constantly check the viscosity and PH value. If necessary, clean tap water or pH stabilizer should be added properly.

â–  The ink remaining on the printing equipment after printing is rinsed with clean water. The ink on the printing roller is preferably cleaned with a cleaning agent to serve the next printing.

Out of water-based ink use error

Not all water-based ink users understand the principle of viscosity, and many people will have this misconception that the viscosity of a large ink is a good ink. Can add a lot of water, printing more cardboard boxes, reduce costs and increase efficiency. In fact, we do not blindly purchase high-grade ink and ink according to the performance of production equipment. We believe that with high-grade ink, we can print good-quality prints. I think this is very impractical and unscientific.

The simplest test for high-grade ink is whether there is discoloration, but ink that does not lose color is high-end, or that high-end ink is not lost, and is not particularly accurate. Because the problem of color loss is still a problem in the world so far, there is no ink factory that can make ink that does not lose color. If the ink is not discolored, the only way to do this is to use offset ink printing, either over a layer of varnish or over a layer of PVC.

The print effect of a printed matter is affected by many factors, such as printing presses, ink, paperboard, technical operators, and climate change. However, once end-users report problems with the carton, the carton factory will often look for ink and ink manufacturers for the first time. The author believes that in the face of such problems, in fact, it should be multi-faceted to find the cause. It is indeed the quality of the ink itself that should adopt economic measures to punish the ink manufacturers.

Carton printers have tighter control over their costs and are desperately trying to lower the price of ink and wash. At present, the price of ink and wash ink is low, and the profit margin is relatively small. In general, ink-jet printers are in a poor position to cope with reducing costs. There is no time and sufficient funds to develop products and improve product quality to better serve carton factories. In fact, most of the carton plant's production costs are on paper or cardboard. The author believes that the cost of paper is the key point. The cost of ink in a carton is less than 0.01%, and spending so much time and energy to deal with ink prices is not worth it. In addition, some ink-jet factories sell computer-grade toners to carton factories in order to sell service brands. The carton factory believes that it is a treasure that actually increases the production costs of carton factories. Because it is not a universal palette, according to the author's knowledge, in addition to the automotive high-consumption industry paint computer configuration machine, other industries rarely buy, as a low-value consumables carton industry must configure the computer toning machine, If you increase the expenses and expenses, you can talk about it. It is worth considering.

Reprinted from: "Corrugated Paper Box Business" Author / Mao Shenrong