Current situation, development trend and technolog

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The current situation, development trend and technological innovation of China's water-based ink industry (II)

1.3 current situation of water-based ink technology

1.3.1 technological transformation of water-based ink

through nearly 10 to 15 years of technological improvement, the water-based ink system has successfully solved most of the original difficulties, such as difficult to use, ink storage, substrate limitations, corona treatment and surface tension, The new generation of ink painting has changed its initial disadvantages into advantages, and gradually grew and matured

1. Advantages of ink painting

1) ink painting has the advantages of environment and safety. In many paper products, ink printing can be designed as low VOCs or zero v0cs. The policy for external wall insulation materials has returned to the Interim Provisions on external temperature protection system and external wall decoration fire prevention of civil buildings (Gong Tong Zi [2009] No. 46;

2) jointly issued by the Ministry of public security and the Ministry of housing and urban rural development in 2009 Ink has the advantages of stability and low flammability. Ink has better viscosity stability because of the low volatility of water

3) the new generation of water-based products are easier to clean than the solvent system. The whole cleaning of printing machine components can be completed by washing with soap water or weak alkaline detergent, thus improving the production efficiency

ink manufacturers have overcome most of the difficulties that originally existed in the ink system, and are actively trying to solve the existing difficulties

2. Difficulties in the application of ink technology

1) drying time is still the most important problem in the application of ink. Unless the printing machine is equipped with sufficient drying equipment, the printing speed will be affected. This is also the most important factor affecting the speed of the process of water ink replacing solvent ink

2) due to the solubility of ink in alkaline solution, the application of ink in high magnetic environment is limited

3) the application of ink in frozen food packaging still does not have the tolerance of solvent ink, although the distance is rapidly shortening

1.3.2 technical problems of water-based inks

quick drying agent ink drying speed may be slow due to different resins selected by ink manufacturers or too fast machine speed during use. Speeding up the drying agent can adjust the drying speed of ink to meet the requirements of printing machine speed and improve production efficiency. Its use proportion is 2 ~ 3%. Slow drying agent can inhibit and slow down the drying speed of ink, play a moisturizing role, prevent the ink from drying on the printing plate or roller, and reduce the occurrence of printing failures such as blocking and pasting. The use proportion is between 1% and 2%

application scope of water-based inks after introducing the structure and types of water-based inks, let's talk about some important factors affecting the printing quality of water-based inks. In paper printing, ink transfer and ink volume control are undertaken by the embossing roller. Therefore, the embossing roller must be selected according to the requirements of the product. The number of embossing roller lines is about four times that of the number of printed lines, so as to obtain better printing clarity and resolution

fineness refers to the size of toner particles in ink, which is completed in the process of producing ink pastes. It is a key quality index. Whether the color paste production process is scientific and meticulous plays an absolute role in the quality of ink. It is better to add dispersant and wetting agent in the production of color paste. Generally, the fineness of ink is required to be 10 ~ 25 μ M is better, too fine or too large will affect the fluidity and rheology of ink

viscosity refers to the consistency of ink and is an indicator of ink flow. Viscosity is too large, resulting in poor liquidity and slow drying; Low viscosity ink has good fluidity, fast drying, thin ink layer and less ink consumption. Generally, the viscosity of ordinary ink is 50 ~ 65/25 ℃ (coated with 4 # cup), and the viscosity of high-grade ink is controlled at 25 ~ 35/25 ℃ (coated with 4 # cup). If the viscosity of ink is low, the toner content is required to be high; On the contrary, the toner content is low. Because the 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, low viscosity will cause light color, and high viscosity will cause dirty version, paste version and other phenomena, so please add transfer agent when it is difficult to control, which can improve the transfer effect and increase the bright color and three-dimensional sense

1.3.3 additives of water-based inks

additives commonly used in water-based inks. It mainly includes pH stabilizer, defoamer, fast drying agent and slow drying agent

1. PH stabilizer

pH stabilizer is mainly used to adjust the pH value of ink. The pH value of ink should be updated in time. It is often mentioned that ink products are promoted to printing enterprises by ink manufacturers. Low pH value is easy to cause ink caking, while high pH value is relatively low viscosity. Generally, the pH value change of ink should be detected during the printing process. When the pH value is lower than 8, an appropriate amount of pH stabilizer should be added to keep the ink in a good printing state. The pH value of ink in European countries is based on neutrality. When the pH value is adjusted to 8.5, its fluidity and gloss reach the best state. However, during the printing process (within one hour) due to the volatilization of amine solvents, the viscosity of ink will increase rapidly, the gloss will decrease, and the fluidity will become poor, resulting in a large number of unqualified products. If the pH value is adjusted, amine solvents need to be added, In addition, during the printing process (within an hour), continuous detection (using an acidimeter) should be carried out. If you are not careful, waste products will appear, and the whole workshop is full of unpleasant smell. Such products are considered bad in the printability. For example, the pH value of ink is between 7 and 8, and the stability of ink is the best. Users can add purified water as a solvent to reduce the viscosity, which will not increase the cost, but also reduce the resin taste of ink

2. Defoamer

defoamer ink viscosity is too high, pH value is low, printing speed is fast, and printing technicians add too much water, which are easy to produce bubbles. When the bubble is relatively large, there will be white printing, less ink, and other phenomena, which will seriously affect the printing quality. It is generally recommended to add foam inhibitor and surface defoamer to the ink to solve the foaming phenomenon. The proportion of use is 1 ~ 2%

3. Quick drying agent

during the use of quick drying agent ink, due to the different resins selected by the ink manufacturer or the machine speed is too fast, the drying speed of ink may be slow. Speeding up the drying agent can adjust the drying speed of ink to meet the requirements of printing machine speed and improve production efficiency. Its use proportion is 2 ~ 3%

4. Slow drying agent

slow drying agent can inhibit and slow down the drying speed of ink, play a moisturizing role, prevent the ink from drying on the printing plate or roller, and reduce the occurrence of printing faults such as blocking and pasting. The use proportion is between 1% and 2%

1.3.4 water based ink usage matters

1 Do not mix water ink with solvent ink. In the process of use, add water appropriately. When it is really necessary to adjust the viscosity or drying speed, add an appropriate amount of alcohol or ester and other additives

2. Before use, it should be stirred evenly, then poured into the ink tank, and the viscosity can be adjusted appropriately with water before use. If it is not used, the packaging barrel should be covered, and the ink cannot volatilize in nature

3. Before use, you should check all technical indicators, especially whether the hue meets your own requirements. If the hue deviation is large, please inform the ink manufacturer to make appropriate allocation, so as to avoid disputes between both parties due to hue error

4. During the printing process, due to the volatilization of water, the original viscosity and pH value of ink will be affected. It is necessary to often detect the viscosity and pH value. When necessary, pure tap water or pH stabilizer should be added appropriately

5. The ink left on the printing equipment after printing should be washed with clean water, and the ink on the printing roller of the printing machine should be cleaned with cleaning agent to serve the next printing

1.3.5 get out of the misunderstanding of using water-based inks

not all users of water-based inks understand the principle of viscosity. Many people will have such a misunderstanding that a high viscosity of ink is a good ink. You can add a lot of water and print more cartons to reduce costs and improve efficiency. In fact, it is very impractical and unscientific to blindly buy high-grade ink without considering the performance of production equipment, and think that with high-grade ink, you can print high-quality prints

the simplest test standard for high-grade ink is whether there is color loss, but it is not particularly accurate to think that the ink that does not lose color is high-grade, or that high-grade ink does not lose color. Because the problem of color loss is still a problem all over the world so far, no ink factory has been able to make ink without color loss. If the ink is required not to lose color, the only way is to use offset ink printing method, either a layer of varnish or a layer of PVC

the printing effect of a printed matter is affected by many factors, such as printing press, ink, cardboard, technical operators and climate change. However, once the end customer reports that there is a problem with the carton, the carton factory usually talks with the ink factory at the first time. In fact, we should find reasons in many aspects when encountering this kind of problem. It is really the quality problem of ink itself that should be punished by economic means

at present, if the sheet metal is scratched carelessly, the ink price is low, and the profit margin is relatively small. However, the carton printing factory controls the cost tightly and tries hard to lower the ink price. Generally, the ink factory is unable to cope with and reduce the cost. There is no time and sufficient funds to develop products, improve product quality and better serve the carton factory. In fact, the cost of paper is the key point. Most of the production costs of carton factories are on paper or paperboard. Ink and wash accounts for less than 0.01% of the cost of a carton product. It is not worth spending so much time and energy dealing with the price of ink and wash. In addition, in order to promote the service brand, some ink factories send computer color matching machines to the carton factory. The carton factory thinks it is a treasure, which actually increases the production cost of the carton factory invisibly

because it is not omnipotent color matching, at present, except for the paint baking in the automotive high consumption industry equipped with computer color matching machines, other industries rarely buy it. As a low-value consumables, whether the carton industry must be equipped with computer color matching machines and increase costs and expenses, it is worth considering

1.4 production status of water-based ink

in recent years, flexographic printing has developed rapidly all over the world and is considered as "the best and most promising printing method on the earth" in developed countries in Europe and the United States. In the United States, 95% of flexographic printing and 80% of gravure printing use ink. Flexographic printing is still in its infancy in China, accounting for only about 3% of the printing field at present. However, with the gradual popularity of environmentally friendly packaging, many cigarette factories, distilleries, pharmaceutical factories, cosmetics factories and children's toy enterprises are preparing to use flexographic printing product packaging, and the proportion of flexographic printing in the printing field will gradually increase, especially in the field of packaging printing. In flexographic packaging and printing, water-based inks are mostly used at home and abroad. From 1995 to the end of 1998, China has introduced more than 130 combined flexographic printing production lines in just a few years, which are distributed in more than 20 provinces and cities across the country. At present, there are nearly 200 narrow width flexographic printing production lines in China. Now the number is increasing by about 30 every year, and there are many imported high-end three-color and four-color water-based ink printing slotting machines for corrugated paper color printing

on average, there are more than 1000 large and small carton factories in each province in China. If 10% of high-grade cartons are printed with water-based ink, and each household uses 10 tons of ink, each province needs about 1000 tons of water-based ink every year. By 2010, the share of flexographic printing in the printing field will reach about 15%, with annual water demand

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