On the advantages and disadvantages of ink emulsif

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Advantages and disadvantages of ink emulsification

in the process of offset printing, ink emulsification often occurs. The so-called emulsification refers to the phenomenon that a liquid is dispersed into another liquid with a different phase. Ink emulsification refers to the dispersion of ink into the fountain solution. If the ink is over emulsified, it will bring great harm to printing. When we shut down, we saw a thick layer of rugged flocculent ink on the surface of the creative ink roller using ultra light earth as the medium, which is the phenomenon of ink over emulsification that we can observe. So what harm does excessive emulsification of ink bring to printing

first of all, the color of the printed matter is light, the color is not bright, lusterless, the point is seriously deformed, the surrounding is not bright and clean, the imprint is weak, and the drying speed is slow, resulting in the back of the printed matter is sticky and dirty, the penetration printing is serious, the ink color of the printed matter is shallow, it is easy to achieve the scope of industrial production, the thickness is inconsistent, there are problems such as embossed version, blind version, unclear text, and the printing plate does not hang ink. The main factors causing excessive emulsification of ink in the printing process are as follows:

(1) paper. Offset paper and coated paper for printing will contain certain surfactants, adhesives and fillers. In the process of printing the operating system of the four ball friction and wear tester, these free substances are rolled and stripped by the rubber blanket, and then transferred to the ink roller through the printing plate. They are mixed with oil and ink in the ink bucket, which reduces the water resistance of the ink and intensifies the emulsification of the ink. Offset paper has a greater impact, especially for those papers with poor sizing, poor hole sealing, loose paper and easy to lose powder and wool, which are more likely to cause ink emulsification

(2) ink. Ink viscosity, strong water resistance, not easy to emulsify; On the contrary, the ink viscosity is small, the fluidity is strong, the cohesion between molecules is reduced, and emulsification is easy to occur. Another example is that the pigments in the ink have different properties, which can be divided into hydrophilicity and water resistance, and the hydrophilic ones are easy to emulsify

(3) fountain solution. Fountain solution includes ordinary fountain solution, non-ionic surfactant fountain solution and alcohol fountain solution. Alcohol fountain solution is an electrolyte free solution, which contains alcohol and volatilizes quickly, thus greatly reducing the emulsification value of ink. During the use of ordinary fountain solution, the pH value of fountain solution must be detected with test paper, and it should be controlled within 3 ~ 4.5, which is weakly acidic and keeps the ink moderately emulsified. However, no matter what kind of fountain solution you want to control the amount, the larger the amount, the easier it is to cause the emulsification of ink

(4) auxiliary materials for inking. For example, 6# inking oil or viscosity remover can reduce the viscosity of the ink and increase the fluidity of the ink, but at the same time, it also reduces the water resistance of the ink, which is easy to cause the emulsification of the ink. Therefore, we must control the amount of auxiliary materials during printing, and try to control it at about 2% - 3%. In addition, diluents, raw materials and additives, whether gb9685 or resin white oil, Weili oil, white ink and other auxiliary materials, are very easy to cause the emulsification of ink, especially white oil and Weili oil

(5) workshop temperature, humidity and machine speed have a considerable impact on ink emulsification. The higher the temperature in the workshop, the thinner the ink, the greater the fluidity, the smaller the viscosity, and the weaker the water resistance, which will aggravate the emulsification. In addition, when the machine is running at high speed, the interaction between the rollers increases, and the surface temperature of the ink roller increases. These factors are very easy to cause excessive emulsification of the ink. The greater the humidity in the workshop, the easier it is to emulsify the ink. Therefore, the temperature of the workshop must be controlled at about 20 ℃ and the humidity between 55% and 65%

after fully understanding the various factors that cause ink emulsification, as long as we have a targeted grasp of the degree of ink emulsification, we can print prints with clear points, clear gradation and bright colors. (Li Fengjin, Taiyuan Xinhua Printing Factory) ("printing technology")

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