Analysis of Application of Metal Printing Alcohol Wetting (II)

2 tinplate performance analysis

2.1 Features of Tinplate Printing

The principle of tinplate printing is similar to that of lithographic offset printing, but due to the special nature of its materials, the structure of the equipment during printing should also have a special structure to suit the needs of tinplate printing.

Tinplate printing has the following features:

1) Because the surface of tin-plated steel plate is tin-plated, with a flashing color effect, and then through the background color printing, the printed graphic has the characteristics of bright colors, rich layers, and good visual effects.

2) The tinplate has good mechanical properties and processing and forming properties. Its printed products can realize novel and unique design and can be used to manufacture various shaped containers, cans, boxes and other packaging containers.

3) The good performance of tinplate and the good abrasion resistance and durability of its printing ink are conducive to achieving the unity of use value and artistry of the goods.

3 The application of alcohol dampening system in tinplate printing

Alcohol wetting liquid is usually prepared by adding ethanol or isopropyl alcohol in common wetting fluid. The effect of isopropanol is similar to that of ethanol, but its rate of volatilization is slower than that of ethanol. Ethanol improves the spreading performance of the wetting fluid on the printing plate, greatly reducing the amount of wetting fluid, so it also reduces the water and the severe emulsification of the ink. Since ethanol has a large latent heat of evaporation, it can carry a lot of heat when volatilized, so that the layout temperature is reduced, the dot increase value decreases, non-graphical parts are not easy to stain dirty. Therefore, the use of alcohol wetting fluid can print high-quality fine offset products, which have been highly praised by people in the printing industry in recent years.

However, the volatilization rate of ethanol is faster, and if it is not controlled, the wetting liquid will decrease due to the concentration of ethanol. As the surface tension rises and the wettability decreases, it is necessary to replenish the consumed ethanol in time. At the same time, in order to reduce the volatilization of ethanol, the temperature of the wetting fluid should be controlled to be below IO[deg.] C. (preferably 4 to 9[deg.] C.). Therefore, an offset press using an alcohol wetting liquid generally employs an alcohol wetting device as shown in FIG. 3 to continuously supply the wetting liquid to the printing plate, and is equipped with a wetting liquid circulating cooling and auxiliary equipment for automatically adding ethanol. . The fountain roller and the metering roller are independently driven by the DC speed-regulating motor, while the water roller and the axially-synchronized bridge roller are driven by the plate cylinder gear.

3.1 Alcohol Wetting Water Supply Device

1) Fountain solution pre-mixing device: Mix isopropyl alcohol, water and additives;

2) damper coating circulator: the fountain solution is delivered to the freezing fountain device;

3) Low-temperature freezing equipment: The temperature of the fountain solution is kept at about 5°C. The main purpose is to prevent the isopropyl alcohol from evaporating and the ink emulsifying and other failures.

4) Bucket: A good insulation layer is needed to keep the fountain solution at about 5°C.

3.2 Method of Controlling Water Quantity

The water volume control of this system is adjusted by three aspects of pressure, inclination and rotation speed to achieve ink-water balance.

3.3 Advantages of Alcohol Wetting System

Due to the small amount of fountain solution used in the alcohol dampening system. The low working temperature of the layout, the constant concentration and the improved printing quality, and the following features in tinplate printing:

1) The proportion of rotation of each water roller in the alcohol dampening system is different (when the transmission ratio between the roller and the dampening roller is 1:0.8), the amount of flow of dampening fluid does not change with the line speed at this time. All of them are kept even and uniform so that the ink and ink balance reaches the print quality requirements. In addition, the combination of these ratios also has the effect of protecting the surface of the PS plate.

2) Swing roller w, which can be swung and twisted between the dampening roller and the ink roller, adjust it to make the dampening on the dampening roller more uniform, and can also remove the water line and printing ghosts and ink on the printing surface. Chips and other product defects.

3) When the fan is working, it can reduce the operating temperature of the ink system. Can also take away the moisture in the ink path, to maintain the printability of ink, reduce ink emulsification play a certain role.

4) The continuous supply of water by the alcohol dampening system can avoid the uneven distribution of dampening fluid and the water-bar failure that is easily caused by intermittent water discharge.

4 Conclusion

It can be seen that alcohol wetting plays an important role in metal printing. Controlling the amount of alcohol and improving the effect of alcohol dampening can greatly improve the quality of metal prints. Therefore, alcohol dampening has a wide range of application prospects in the packaging and printing industry.

Authors / Li Xiaodong, Zhu Xinlian, Gong Huiqing, Yu Juan

Source: Packaging Project