1. Require ink to have good adhesion and mechanical properties
Due to the fact that tinplate printing is used to make food cans, toys, metal frames, and barrels and cans for chemical products, it requires cutting, bending, and stretching processes. Therefore, printing ink is required to have good adhesion properties to tinplate and corresponding machines. In order to improve the adhesion of ink, the tin plate needs to be coated white before printing. White is the base color of all images and has high brightness. After adding other high-energy tones, the brightness of each tone can be increased to form a color gradient.
2. Requirements for White Ink
The surface of tinplate is silver white or yellow, with a metallic luster. Before printing colored graphics, the surface needs to be painted white or white. Due to the limitation of ink coverage, monochrome printers usually need to print white twice, and the whiteness can reach 75%. Whiteness is an important indicator of the quality of tinplate printing products. The white ink is required to have good adhesion with the primer, and it should not turn yellow after repeated high-temperature baking, and it should not fade after high-temperature steaming. Primer coated tinplate can increase its adhesion to tinplate and has good adhesion to white ink. The commonly used primer is epoxy amine based, which has the characteristics of light color, no yellowing or aging after multiple baking, and good flexibility and impact resistance.