What are the processes for printing iron?

The general process of metal plate printing is shown in figure 1- 1.

Metal plate pretreatment → coating and drying → primer coating and drying → coating background color → offset printing.

(or degreasing) color separation → plate making

Stamping and post-treatment/film protection/drying and forming/polishing

Figure 1- 1 General process of metal plate printing process

The difference between metal printing and paper printing is that a layer of paint is needed before printing. Coatings play an important role in metal printing. Metal printing is not the ultimate goal, but the beautification means of metal packaging, aiming at making all kinds of metal containers, such as tin cans, cosmetic cans and boxes, various bottles and cans, toys and so on. To make the pictures and texts printed on the metal plate bright and eye-catching, it is inseparable from the special role of coatings. Its function can be summarized as follows:

① Increase the adhesion between metal and ink film. Previous experiments have verified that the ink is printed directly on the metal plate, and the adhesion, wear resistance and firmness between the ink and the metal are very poor. First, the primer coating is printed on the metal plate, and then the ink is printed, which improves the wear resistance and firmness of the ink film and lays a good foundation for the product molding and processing in the future. This is because a layer of paint with special properties is printed on the metal plate, which not only has strong adhesion to metal, but also enhances the affinity with ink.

(2) The ink film layer on the metal printed matter can be protected, and at the same time, the brightness of the pattern on the metal plate can be increased, so that the color will not change and the paint will not fall off during the can making process.

Indian iron coating can be divided into three categories: primer coating, white coating and glazing coating:

Low temperature primer (alkyd type)

primer

High temperature primer (epoxy amino type)

Alkyd resin type

Printed iron pigment white pigment printed polyester type

Acrylic acid type

Low temperature varnish: ester glue, epoxy ester, semi-drying oil alkyd amino.

Oil polishing agent

High temperature varnish: coconut oil alkyd amino, oil-free alkyd amino, epoxy amino, acrylate.