Printing of tin cans

tin can printing has special requirements for ink:

Require printing ink to have good adhesion and mechanical properties

Because most of the printed products on tin cans are made into food cans, tea cans, biscuit cans, etc., and tin cans need to go through more than ten processes such as cutting, bending, stamping, and stretching, it is required that the printing ink has good adhesion and corresponding mechanical properties to the iron plate tin cans. To improve ink adhesion, a white ink base should be printed on the tin can before printing. White ink is the basic color tone for all printed patterns and has high brightness. After adding other high-energy inks, the brightness of all colors can be increased, thereby forming a color scale.

Requirements for Printing White Ink in Iron Can Printing

The surface of the tin can is silver white (or yellow) with a metallic luster. It needs to be painted white or printed white before printing colored graphics and text. Due to the limited ink coverage ability, monochrome machines often need to go through two rounds of white printing, and its whiteness can reach 85%. White is an important standard for the printing quality of tin cans, which requires good adhesion between white ink and primer, no yellowing after multiple high-temperature baking, and resistance to high-temperature evaporation without fading. Applying primer can improve the adhesion of tin cans and provide good adhesion to white ink. The commonly used primer is epoxy amine based, with a light color that does not turn yellow after multiple baking cycles, does not age, has good elasticity, and is impact resistant.

Requirements for color ink in iron can printing

The colored ink printed on tin cans not only has certain water resistance, but also has special requirements for it. Due to the absence of solvent on the surface of the tin can, it needs to be dried and dried, so its ink should be thermosetting. There are high requirements for the coloring ability and durability of pigments. In addition to the basic properties required for general offset printing ink, according to the characteristics of the printing iron, it should also have characteristics such as heat resistance, strong ink film adhesion, impact resistance, good hardness, resistance to steaming and cooking, and light resistance.

Drying process of printing ink for iron cans

In the production of tinplate can printing, the drying of ink is a complex physical and chemical reaction process. To effectively carry out rapid printing operations and ensure product quality, it is necessary to control the drying speed of ink reasonably and master the physical and chemical mechanisms of ink drying. Drying ink too quickly can reduce its normal transfer performance and affect normal production; Causing the surface imprint of the printing plate and ink roller to weaken, the ink color to fade, the ink to dry, and hindering the transfer of ink; Expand the dry layer of the printing plate outward; Excessive desiccant can lead to increased ink adsorption, causing the blank area to become dirty. However, ink drying too slowly can cause difficulties in overprinting, adhesion, and sticking. Reduced hardness; Scratches are easily caused during transmission. So the drying speed of ink should be appropriate, not too fast or too slow.

Special structure of iron can printing equipment

Because the substrate is tinplate, the auxiliary mechanism of a printing press is different from that of a paper offset press. Tinplate is insoluble in water and does not adsorb solvents, so the ink on tinplate cans needs to be baked at high temperatures to solidify the film after the solvent evaporates. Therefore, a drying chamber is usually required during the printing process. The fully automatic printing line for tinplate cans is usually around 40-55 meters long, with sophisticated and large equipment. In addition, the tinplate printing machine is controlled by separate and double magnets, and the high hardness of the tinplate material also determines that advanced continuous iron transport structures cannot be used in the printing process, which is different from the structure of the offset printing machine in pushing, positioning, and stacking parts.