In the offset printing process, 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 means that the ink is dispersed into the fountain solution. If the ink is over-emulsified, it will bring great harm to the printing. At the time of shut-down, we saw a thick layer of mesh-like bumpy floc accumulating on the surface of the roller. This is the phenomenon that we can observe that the ink is over-emulsified. So what kind of harm is caused by printing ink over emulsification?
The first is that the printed product has a dark picture, and the colors are not bright and dull. The dots are severely deformed, the surrounding area is not clean, the imprinting is imaginary, and the drying speed is slow, causing the back of the printed matter to become dirty, and the printing is serious. The ink is dark and light, and the shades are inconsistent. The appearance of the flower version and the version, the text is unclear, and the printing plate does not hang ink. The main factors that cause ink emulsification in the printing process are the following:
(1) Paper. Offset paper and coated paper for printing will contain certain surface active substances, adhesives and fillers. During the printing process, these disperse materials are rolled off by a rubber blanket and then transferred to the ink roller through the printing plate. The mixing with the ink reduces the water resistance of the ink and makes the ink more emulsified. Among them, offset paper has a greater impact, especially for those papers with poor sizing, poor sealing, loose paper, and easy powder dropping and lint-free, which are more likely to cause ink emulsification.
(2) Ink. The ink has large viscosity, strong water resistance, and is not easy to emulsify. On the contrary, the ink has small viscosity, strong fluidity, reduced cohesion between molecules, and is prone to emulsification. Another example is the nature of pigments in inks, which are hydrophilic and water-resistant. Hydrophilic are easily emulsified.
(3) fountain solution. The fountain solution includes ordinary fountain solution, non-ionic surfactant fountain solution, and alcohol fountain solution. Alcohol fountain solution is a non-electrolyte solution containing alcohol, fast evaporation, which greatly reduces the emulsification value of the ink. The ordinary fountain solution in the use process must use a test paper to measure the pH of the fountain solution, it is controlled within 3 to 4.5, was weakly acidic, and maintain the proper emulsification of the ink. However, no matter what kind of fountain solution should be used to control the amount, the greater the amount, the easier the emulsification of the ink.
(4) Auxiliary materials for ink transfer. Such as 6 # varnish oil or relieving agent can reduce the viscosity of the ink, increase the ink's fluidity, but it also reduces the ink's water resistance, it is easy to cause the emulsification of the ink. Therefore, the amount of auxiliary materials must be controlled during printing, and it should be controlled as much as 2% to 3%. In addition there are diluents, white oil, maintenance oil, white ink and other accessories are very easy to cause the emulsification of ink, especially white oil and Weili oil.
(5) The temperature of the workshop, the humidity and the speed of the machine all have a considerable influence on the ink emulsification. The higher the temperature of the shop, the thinner the ink, the greater the fluidity, the smaller the viscosity, and the weakened water resistance, which will intensify the emulsification. When the machine is operated at a high speed, the interaction force between the rollers is increased, and the surface temperature of the ink roller is increased. These factors easily cause over-emulsification of the ink. The higher the humidity in the workshop, the more easily the ink is emulsified. Therefore, the workshop temperature must be controlled at about 20°C and the humidity should be between 55% and 65%.
After fully understanding the various factors that cause ink emulsification, as long as there is a targeted grasp of the degree of ink emulsification, it will be able to print clear, clear-keyed, colorful prints. (Taiyuan Xinhua Printing Factory Lifen Jin) ("Printing Technology")
The first is that the printed product has a dark picture, and the colors are not bright and dull. The dots are severely deformed, the surrounding area is not clean, the imprinting is imaginary, and the drying speed is slow, causing the back of the printed matter to become dirty, and the printing is serious. The ink is dark and light, and the shades are inconsistent. The appearance of the flower version and the version, the text is unclear, and the printing plate does not hang ink. The main factors that cause ink emulsification in the printing process are the following:
(1) Paper. Offset paper and coated paper for printing will contain certain surface active substances, adhesives and fillers. During the printing process, these disperse materials are rolled off by a rubber blanket and then transferred to the ink roller through the printing plate. The mixing with the ink reduces the water resistance of the ink and makes the ink more emulsified. Among them, offset paper has a greater impact, especially for those papers with poor sizing, poor sealing, loose paper, and easy powder dropping and lint-free, which are more likely to cause ink emulsification.
(2) Ink. The ink has large viscosity, strong water resistance, and is not easy to emulsify. On the contrary, the ink has small viscosity, strong fluidity, reduced cohesion between molecules, and is prone to emulsification. Another example is the nature of pigments in inks, which are hydrophilic and water-resistant. Hydrophilic are easily emulsified.
(3) fountain solution. The fountain solution includes ordinary fountain solution, non-ionic surfactant fountain solution, and alcohol fountain solution. Alcohol fountain solution is a non-electrolyte solution containing alcohol, fast evaporation, which greatly reduces the emulsification value of the ink. The ordinary fountain solution in the use process must use a test paper to measure the pH of the fountain solution, it is controlled within 3 to 4.5, was weakly acidic, and maintain the proper emulsification of the ink. However, no matter what kind of fountain solution should be used to control the amount, the greater the amount, the easier the emulsification of the ink.
(4) Auxiliary materials for ink transfer. Such as 6 # varnish oil or relieving agent can reduce the viscosity of the ink, increase the ink's fluidity, but it also reduces the ink's water resistance, it is easy to cause the emulsification of the ink. Therefore, the amount of auxiliary materials must be controlled during printing, and it should be controlled as much as 2% to 3%. In addition there are diluents, white oil, maintenance oil, white ink and other accessories are very easy to cause the emulsification of ink, especially white oil and Weili oil.
(5) The temperature of the workshop, the humidity and the speed of the machine all have a considerable influence on the ink emulsification. The higher the temperature of the shop, the thinner the ink, the greater the fluidity, the smaller the viscosity, and the weakened water resistance, which will intensify the emulsification. When the machine is operated at a high speed, the interaction force between the rollers is increased, and the surface temperature of the ink roller is increased. These factors easily cause over-emulsification of the ink. The higher the humidity in the workshop, the more easily the ink is emulsified. Therefore, the workshop temperature must be controlled at about 20°C and the humidity should be between 55% and 65%.
After fully understanding the various factors that cause ink emulsification, as long as there is a targeted grasp of the degree of ink emulsification, it will be able to print clear, clear-keyed, colorful prints. (Taiyuan Xinhua Printing Factory Lifen Jin) ("Printing Technology")
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