What are the ink requirements for tinplate can printing?

(1) The ink is required to have good adhesion and mechanical properties
Since tinplate printed matter will eventually be made into food cans, toys, metal photo frames, and barrels and cans of chemical products, it needs to be cut, bent, and stretched. Therefore, the printing ink is required to have good adhesion to the tinplate and the corresponding machinery. performance. In order to improve the ink adhesion, the tinplate needs to be primed with white before printing. White is the base color of all images and has high brightness. After adding other high-energy hues, the brightness of each hue can be increased to form a color scale.
(2) Requirements for white ink
The surface of tinplate is silvery white (or yellow) with metallic luster. Before printing color graphics and text, the surface needs to be painted or printed white. Due to the limitation of ink coverage, monochrome machines often need to print white twice. The whiteness Up to 75%. Whiteness is an important indicator of the quality of tinplate printing products. It requires that the white ink has good binding force with the primer, does not turn yellow after being baked at high temperatures for many times, and can withstand high temperature steaming without losing color. Applying primer to the tinplate can increase the adhesion to the tinplate and have good binding force with white ink. The commonly used primer is epoxy amine-based, which has the characteristics of light color, no yellowing and no aging after repeated baking, and good flexibility and impact resistance.
(3) Requirements for color ink
In addition to having a certain degree of water resistance, color inks for tinplate printing also need to have their own special requirements. Since the tinplate surface is impermeable to moisture and solvents and needs to be baked and dried, the ink should be heat-curing. The requirements for pigment tinting strength and durability are relatively high. In addition to the basic properties of general offset printing inks, iron printing inks should also have heat resistance, strong ink film adhesion, impact resistance, good hardness, cooking resistance and light resistance according to the characteristics of iron printing.
(4) Drying process of ink
In tinplate printing production, the drying of ink is a complex physical and chemical reaction process. It is necessary to reasonably control the drying speed of ink and master the physical and chemical mechanisms of ink drying in order to effectively carry out fast printing operations and ensure product quality. Drying the ink too fast will reduce the normal transfer performance of the ink and affect the normal production; it will cause the imprint to become blurred, the ink color will become light, and the ink will dry up on the surface of the printing plate and ink roller, which will hinder the ink transfer during transfer; it will cause the printing plate graphics and text to dry up. The layer expands outward; using too much desiccant causes the ink adsorption to increase and the blank parts to become dirty. If the ink dries too slowly, it can cause overprinting difficulties, adhesion, adhesion, etc., and reduced firmness; it can easily cause scratches during transmission, etc. Therefore, the drying speed of the ink must be appropriate. Too fast or too slow is detrimental.
(5) Special structure of printing equipment
Due to the different substrates, the auxiliary mechanisms of tinplate printing machines are also different from paper offset printing machines. Tinplate is insoluble in water and does not absorb solvents, so the printing ink needs to be baked at high temperature to evaporate the solvent and solidify the film. Therefore, printing process equipment generally needs to be equipped with a drying room. The entire tinplate printing automatic line is generally about more than 50 meters long and is sophisticated and large. In addition, the tinplate printing machine uses magnets to control sheet splitting and double sheets. The high hardness of the tinplate material also determines that the advanced continuous iron feeding structure cannot be used during the printing process. The structure of the pushing, leveling and stacking parts is different from that of the tinplate printing machine. Offset printing machine for printing paper.