Tinplate printing ink has special requirements:
(1) requires the ink has good adhesion and mechanical properties
As the tinplate print eventually made into canned food, toys, metal frames and chemical products barrel, cans, subject to cutting, bending and stretching process, which requires printing ink on the tin has good adhesion and the corresponding mechanical performance. In order to improve ink adhesion, the first need to print tinplate white primer. White is the basic color of all the pictures, with high brightness. After adding other high-energy hue, can increase the brightness of the various colors and the formation of color levels.
(2) white ink requirements
Tinplate surface is silver white (or yellow), metallic luster, in the printing of color graphics, you need to paint the surface white or white, limited by the ink coverage, monochrome machines often need to print twice, the whiteness Up to 75%. Whiteness as an important indicator of tinplate printing product quality, requiring white ink with a good combination of primer, after repeated high-temperature baking is not yellowing, high temperature steaming do not go color. Priming the tinplate increases the adhesion to the tinplate and gives good adhesion to the white ink. Commonly used primer is epoxy amine type, with a light color, after repeated baking is not yellowing, not aging characteristics and good flexibility, impact resistance of the process performance.
(3) Color ink requirements
Tinplate printing color ink, in addition to having a certain degree of water resistance, but also need to have its special requirements. Because the tin does not penetrate the surface of water and solvents, need to go through baking drying, so the ink should be thermosetting type. Pigments on the coloring and durability of the higher requirements. In addition to printing ink should have the basic properties of general offset printing ink, but also according to the characteristics of Indian iron should have heat resistance, ink film adhesion, impact resistance, hard, resistant to cooking and light characteristics.
(4) ink drying process
In tinplate printing production, ink drying is a complex physical and chemical reaction process. To properly control the ink drying speed, ink drying in the grasp of the physical and chemical mechanisms in order to effectively carry out fast printing operations to ensure product quality. Drying ink too fast will reduce the normal transfer performance of the ink, affecting the normal production; resulting in India made hair, pale ink, printing plate, roller surface ink drying, so that the transfer of the ink blocked; make plate graphic dry Layer outward expansion; excessive use of desiccant caused by increased ink adsorption, the blank part of the dirty from the phenomenon. The ink is too slow and can cause overprint drying difficulties, adhesion, adhesion, etc., lower firmness; easily lead to scratches and other transmission process. Therefore, the ink drying speed should be appropriate too fast too slow are unfavorable.
(5) special structure of printing equipment
Due to the different substrates, tinplate printing press ancillary agencies are different from the printing press. Tin does not dissolve in water, do not adsorb solvent, so the printing ink to be high temperature baking to solvent evaporation conjunctival curing. Therefore, the printing process equipment generally need to be equipped with drying room. The entire tinplate automatic printing line is generally about 50 meters in length, with a large and sophisticated features. In addition, the tinplate printing machine is the use of magnet sub-Zhang and double-sheet control, tinplate material also determines the high hardness of the printing process can not be advanced continuous iron structure, thrusting, quasi-level and stacking parts of the structure are different Offset printing machine.