The printing of tinplate cans is to process the text, pictures, photos, anti-counterfeiting, etc. in the design manuscript through the production processes of plate making, ink application, and pressure, so that the ink is printed on the surface of the tinplate can in the form of patterns. The principle is to use the mutually exclusive nature of water and ink, and then use the pressure of the printing press to print the printing plate graphics on the tinplate can. What are the technical requirements for printing tinplate cans and special requirements for printing inks? The details will be described below.

Printing principle of tinplate cans:

Tinplate can printing also uses the mutually exclusive nature of water and ink, and uses printing pressure to print the printing plate graphics on the tinplate can. This process belongs to tinplate offset printing. Because tinplate has special physical and chemical properties, its printing process is quite different from ordinary paper offset printing.

Tinplate can printing has special requirements for ink:

(1) The printing ink is required to have good adhesion and mechanical properties

Since most of the printed materials of tinplate cans are made into food tin cans, tea tin cans, biscuit tins, etc., the production of tinplate cans requires more than a dozen processes such as cutting, bending, stamping and stretching. Therefore, the printing ink is required to be applied to the iron plate. Tinplate cans have better adhesion and corresponding mechanical properties. In order to improve the ink adhesion, the tinplate cans must be printed with white ink before printing. White ink is the basic hue of all printed patterns, and it has a high brightness. After adding other high-energy inks, the brightness of each color can be improved to form a color gradation.

(2) Requirements of tinplate can printing for printing white ink

The surface of tinplate cans is silvery white (or yellow) with metallic luster. Before printing color graphics and texts, it is necessary to paint or print white on the surface of tinplate cans. Due to the limitation of ink coverage, monochromatic machines often need to print twice. White, its whiteness can reach 85%. Whiteness is an important standard for the printing quality of tinplate cans. The white ink is required to have a good bonding force with the primer. After repeated high-temperature baking, it will not yellow and resist high-temperature steaming. Priming tinplate can increase the adhesion to the tinplate can and has a good adhesion to the white ink. Commonly used primers are epoxy amine-based, with light color, no yellowing, no aging after repeated baking, good flexibility, and impact resistance.

(3) Requirements of tinplate can printing for color ink

In addition to a certain degree of water resistance, the color inks printed on tinplate cans also need special requirements. Since the surface of tinplate cans is impermeable to moisture and solvents and needs to be baked and dried, the ink should be heat-curable. High requirements for pigments’ tinting strength and durability. 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 printing ink for tinplate cans

In tinplate can printing production, the drying of ink is a complicated physical and chemical reaction process. It is necessary to reasonably control the ink drying speed and master the physical and chemical mechanism of ink drying in order to effectively carry out fast printing operations and ensure product quality. Drying the ink too quickly will reduce the normal transfer performance of the ink and affect the normal production; it will cause the imprint to be weak, the ink color will fade, and the ink drying on the surface of the printing plate and ink roller will hinder the ink during the transfer; dry the printing plate graphics and text The layer expands outward; the excessive amount of desiccant will increase the ink absorption and the blank part will become dirty. The ink drying too slowly can cause overprinting difficulties, adhesion, adhesion, etc., and the firmness will be reduced; it is easy to cause scratches during the conveying process. Therefore, the drying speed of the ink should be appropriate, too fast or too slow is unfavorable.

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