The vertical bag is more eye-catching and faster to convey product information, so it stands out from many packaging forms. So, there are two kinds of films most commonly used for high-temperature sterilization vertical bags – PET film and NY. What’s the ingenuity of the printing process of the two materials? PET film is thin and easy to wrinkle. PET film is easy to generate large static electricity, which may lead to quality problems such as blocking, ink spots, knife lines, etc. during printing. In addition to conventional electrostatic removal methods, it is an effective way to strengthen the temperature and humidity control in the workshop. During printing, a large tension is required, and a special ink resistant to high temperature cooking shall be selected, and attention shall be paid to whether the film is static at all times. NY is prone to moisture absorption and deformation, and its packaging film cannot be damaged when the tension is extremely unstable and not printed; Before printing, pay attention to testing the ambient humidity, and it is better to take dehumidification measures; Print immediately after opening the packaging film. At the same time, one process cannot be ignored – preheating. The preheating temperature is controlled at 50~80 ℃. Without preheating equipment, printing equipment and devices can be flexibly used. The first color group can be vacated as a preheating device; The tension should be properly reduced during printing; After printing, it must be sealed and packed, and put into the curing room for curing for 2 to 3 days, and then compounded as soon as possible. The key point of control is the ink, whether it is printing PET or printing NY. It mainly includes the following two aspects. 1. Adjustment of ink printability. Including the adjustment of viscosity and color concentration. The automatic viscosity regulator can be selected to improve the working efficiency. The regulator can add solvent according to the preset value to keep the viscosity of the ink unchanged. But the color concentration of the ink must not be diluted with solvent, and special diluent should be used to adjust it. 2. The influence of active particles shall be closely monitored. After printing for a certain period of time, the ink will produce many active groups, which will combine with the chromium ion of the gravure cylinder. When these compounds appear in the shallow screen part of the gradient version, their binding force will hinder the transfer of the ink, resulting in blocking and graining. Therefore, the manufacturer should not worry about the cost at this time, but can add an appropriate amount of CHY-1 auxiliary agent, an active retarder.