1. The layout and characteristics of tinplate
1). The layout of tinplate
Tin Plate, also called tin plate, is made by plating tin on a thin steel plate substrate. It is composed of oil film, iron oxide, tin layer, alloy layer, and substrate. It combines the strength and formability of steel with that of tin. Corrosion resistance, solderability and beautiful surface are connected in one material, which has the characteristics of corrosion resistance, non-toxicity, high strength and good ductility.
2). The characteristics of tinplate
①Opacity: Tinplate has good opacity, can effectively prevent visible light and ultraviolet radiation, can protect food from corrosion and deterioration, and extend the shelf life.
②Good airtightness: The good airtightness of tinplate makes it a benefit for canned products, especially food security, to isolate air and other gases when making packaging containers.
③Good environmental protection: Tinplate is a material that can be completely acquired, which is beneficial to protect our livelihood environment. In addition, tinplate can be naturally dissociated in the environment, and will not be left behind to cause environmental pollution.
④Power saving: using tinplate scraps to make steel is less power than using iron ore to make steel, and each ton of scrap iron scraps can save 230m3 of natural gas.
2. Tinplate surface properties and printing fastness
1). Tinplate surface properties
The surface performance of the tinplate is the difference between the surface condition and the surface quality. The surface of the tinplate may have defects such as scars, pits, wrinkles, dust, rust, etc. From the perspective of the layout of the tinplate, there is often a very thin oil film on the surface of the tinplate. And it is usually electroplated, so the surface is relatively smooth. Judging from the relationship between the specific surface area of the solid surface and the adsorption force, the adsorption force of tinplate is not very good.
2). Surface properties affect printing fastness
The tinplate printing is mainly offset printing, and its process is as follows:
The surface roughness of tinplate is one of the tense components that affect printing fastness. The surface of the tinplate substrate is relatively smooth, although some organic coatings also have strong adhesion on the smooth surface, but the overall absorption is poor and the adhesion is small, which makes the adhesion fastness and drying performance of the coating layer and the ink layer affected.
3). The influence of oil film
In the tinplate layout, the surface layer is an oil film. This oil film is to prevent the tinplate from rusting during storage and conflicting with each other during transportation, which will greatly reduce the adhesion fastness of coating and ink. Therefore, the amount of oil film is very tight, and the tinplate made in the world does not have an inevitable standard for the thickness of the oil film. Generally, the oil amount is controlled at 2 to 4mg/m2, but some are above 6mg/m2. If the amount of oil applied is too much, it will affect the printing quality of the tinplate, so that the coating and ink layer can not completely wet the surface of the tinplate, and the adhesion performance is poor. The "pinhole" will cause the drop of the adhesive force between the ink layer and the tinplate. Therefore, when the amount of oil applied to the surface of the tinplate is relatively high, that is, above 6mg/m2, the tinplate should be pre-baked once before printing to evaporate the excess oil film.
In addition, the slippery tinplate surface will not only cause the ink adsorption force to drop and the printing fastness, because of the poor adsorption performance, the ink drying rate is slow, and the conjunctivity is poor, which affects the adhesion fastness and abrasion resistance of the ink layer. As a metal material, tinplate will form a lot of fine water droplets on the surface of the tinplate when the air humidity is relatively large and the temperature difference is relatively large, which will also reduce its adsorption force and affect the printing fastness.
4). The influence of oxide layer
In addition to the oil film on the surface of the tinplate that will affect the adsorption, the second oxide film in the tinplate layout will also affect the adhesion of the ink. There is a very thin oxide film on the surface of the tin layer of tinplate. The layout of this oxide film is unstable and will continue to oxidize and thicken, and even cause the ink layer on the oxide film to fall off, dissipating ink adhesion. Therefore, the tinplate must be passivated after tinning to improve the stability of the oxide layer, block the increase of the oxide film, and maintain the stability of ink adsorption.
Therefore, the surface properties of the tinplate will have a greater impact on the printing fastness of the ink. In addition to good quality tinplate, good coatings and inks are required, and the surface of the tinplate can be best treated and improved. Good surface adsorption.