Special requirements for printing ink:
(1) Has good adhesion and mechanical properties
Because tinplate printing products are eventually made into food cans, toys, metal photo frames, and barrels and cans of chemical products, they need to be cut, bent, and stretched. Therefore, printing inks are required to have good adhesion to tinplate and corresponding machinery performance. In order to improve the adhesion of the printing ink, the tinplate needs to be white-primed before printing. White is the base color of all pictures and has a very high brightness. After adding other high-energy hue, the brightness of each hue can be increased to form a Color scale.
(2) Requirements for white ink
The tinplate surface is silver-white (or yellow) with metallic luster. Before printing the color graphics, the surface needs to be printed white. Due to the limitation of the ink covering ability, it usually takes 2-3 times to print white, and its whiteness can reach 75%. Whiteness is an important indicator of the quality of printed tinplate products. Printed white ink has a good binding force with the primer, does not turn yellow after high temperature baking, and does not discolor after high temperature resistance. Applying a primer to tinplate can increase the adhesion to tinplate and have a good combination with white ink. force. The commonly used primer is epoxy-amine based, with light color, no yellowing and aging after repeated baking, good flexibility and impact resistance.
(3) Requirements for color ink
Tinplate printing color inks, in addition to having a certain degree of water resistance, also need their special requirements. As the tinplate surface does not penetrate water and solvents, it needs to be baked and dried, so its ink should be heat-curable. The pigment is required to have higher tinting strength and durability. In addition to the basic properties of general offset printing inks, iron printing inks should also have the characteristics of heat resistance, strong ink film adhesion, impact resistance, good rigidity, cooking resistance and light resistance according to the characteristics of printing iron.
(4) Drying process of ink
In the production of printing iron, the drying of the ink is a complicated physical and chemical reaction process. There are many factors that affect drying, so to control the drying speed of the ink and ensure the quality of the product, the physical and chemical mechanism in the ink drying, that is, the factors that affect the drying speed, must be mastered in order to effectively perform the fast iron printing operation. The drying speed of the ink has become the main content of the ink drying. Then, what harm is the ink drying too fast? It can reduce the normal transfer performance of the ink and affect the normal production process; it can cause the print to be dim, the ink color to be faded, and the ink to dry on the surface of the printing plate and the ink roller, which will hinder the lower ink in the transfer; Outer expansion; it can make the ink absorbent increase due to excessive amount of desiccant, and the dirty part will cause dirt. So what harm is the ink drying too slowly? Can cause overprinting difficulties and cause adhesions; can cause poor adhesion and reduced firmness; and can easily cause scratches during transport. Therefore, the drying speed of the ink should be appropriate. Too fast or too slow is disadvantageous.