1. Printability of aluminum foil paper
Aluminum foil paper is a non-absorbent paper. It is made by attaching aluminum foil to the surface of cardboard. Due to the non-absorptive nature of the aluminum foil surface, it directly affects the dry form of the ink layer.
We know that the penetration, solidification and polymerization of ink on ordinary paper, and oxidized conjunctiva are the main forms of ink layer drying. But after the ink layer is printed on the paper, the drying effect of the ink layer permeating on the paper is quick and obvious in terms of the drying time, and after the dry vegetable oil in the ink layer comes into contact with oxygen, It is a very slow process to dry the film in the form of oxidation and polymerization. It takes a while to complete the entire process of its chemical and physical reactions. It can be seen that the joint effect of these two forms the final result of complete and dry printing. When printing on aluminum foil, the situation is different. This is mainly due to the significant change in its dried form. Because aluminum foil paper cannot or cannot absorb the solvent in the ink, the dry vegetable oil, high boiling point kerosene and other solvents in the ink binder cannot penetrate into the paper and have to stay in the ink layer on the surface of the paper, so that the ink layer cannot be compared. It thickens and fixes quickly, so the ink layer loses its initial drying time. That is to say, the ink layer slowly polymerizes, and the drying process of the oxidized conjunctiva becomes the main dry form of the aluminum foil ink layer. The solvent remaining in the ink layer not only failed to thicken the ink quickly, but in turn hindered the polymerization and oxidation of the ink layer, making its drying speed slower. This phenomenon is often referred to as "nothing." The nature of the aluminum foil paper determines the characteristics of the ink layer can not be dried quickly.
Another characteristic of aluminum foil paper is high smoothness and poor absorption, and the printed matter is very prone to sticking after printing. Once this happens, the ink layer, which is relatively smooth and flat when printed, will instantly become fragmented or incomplete, seriously affecting the visual effect of the product, and even becoming a waste product.
The "non-drying" phenomenon mentioned earlier induces the sticky dirt phenomenon to become more prominent. Therefore, it can be said that the "non-drying" phenomenon and the "sticky dirty" phenomenon are the same as a pair of twin brothers. They affect each other and are related to each other, and have become an important content that we need to pay great attention and care throughout the aluminum foil printing process. Around these two issues, it is necessary to adopt corresponding technological measures and requirements.
2. Printing process of aluminum foil paper
1. Aluminum foil printing process
The temperature of the printing environment plays a large role in the drying speed of the ink layer. When the temperature is low, the printing speed is relatively slow, and the time required for drying increases accordingly.
In order to prevent the ink layer from "drying" not to be too serious, there is a certain temperature requirement when printing on aluminum foil. The ideal ambient temperature is above 25 ℃. Printing under such temperature conditions is conducive to the drying of the ink layer, and the operation is more convenient. If the natural temperature (such as winter) does not meet certain requirements, the necessary heating facilities can be used. Because the higher ambient temperature can accelerate the speed of the movement of material molecules in the ink layer, it is conducive to the contact between the vegetable oil and oxygen in the ink layer to produce a film layer, thereby increasing the speed of oxidation and polymerization to meet the requirements of accelerating the drying of the ink layer. On the other hand, because the drying process of the ink layer is also an exothermic reaction process, the heat generated by the reaction further promotes the drying of the ink layer, thereby forming a virtuous cycle of the ink layer to accelerate the conjunctiva. This is very advantageous for the drying of the blot and the complete transfer of the ink layer. Aluminum foil paper is best to print in a relatively dry environment, which is good for the drying of the printed matter and preventing sticking. We know that the drying of the ink layer must first evaporate the water inside, because the water has the effect of hindering and inhibiting the drying of the ink layer.
Only after the water evaporates can the ink layer be effectively oxidized and polymerized until finally dried to form a film. The rate of evaporation of water in the ink layer is directly related to the humidity of the environment. When the ambient humidity increases, that is, the air is relatively humid, the rate of evaporation of water in the ink layer appears slow, and the drying time of the ink layer increases.
Conversely, when the ambient humidity is reduced, that is, when the air is dry, the evaporation rate of the water in the ink layer is correspondingly accelerated, and the drying time of the ink layer is shortened accordingly.
On the other hand, when printing in a humid environment, the activity of oxygen in the air becomes less active, which will directly affect the inhalation of oxygen by the ink layer, resulting in a slow drying process of the oxidative conjunctiva, which is the effect of the ambient temperature on the ink Another reason for the dry layer.
2. Take anti-sticking measures
â‘ Increase the amount of dry oil. When we print aluminum foil paper, the amount of dry oil should be appropriately increased in the ink, and the drying effect of the ink should be used to accelerate the oxidation and polymerization of the ink layer to promote the drying and solidification of the ink layer to prevent the occurrence of sticky faults.
â‘¡ Master the stacking volume of printed products. Because aluminum foil paper prints are very easy to stick and dirty, the ink layer wetted by the prints is more prone to such failures under the effect of the paper's own gravity, so it is an important link to master the stacking amount of prints. Generally speaking, all Take plywood measures to minimize the pressure on the ink layer caused by the gravity of each paper, to prevent the surface of the paper from sticking to the back. Under normal circumstances, it is appropriate to control the stacking volume of a knife of paper at about 30 sheets each time.
â‘¢ The layout keeps a minimum amount of moisture. The absorption of moisture by paper is the main method of moisture consumption on offset printing plates. Aluminum foil paper does not seem to absorb ink at the same time as it does not absorb ink.
Therefore, when we print aluminum foil paper, the amount of water consumed in the bucket is very small. For this reason, we can keep the minimum amount of moisture on the layout without scumming, so as not to dilute the ink color and the printed ink layer is "dry" and sticky and dirty. At the same time, less moisture on the layout is also very beneficial to keep the ink color bright and improve product quality.
3. Printing ink should not be too thick
Compared with ordinary paper, the surface of aluminum foil paper is much smoother, and its ink absorption performance is also significantly worse than ordinary paper. Therefore, when the ink on the printing plate is finally transferred to the aluminum foil through the blanket, if the ink used is thick, the phenomenon that the ink will not print on the aluminum foil paper or "underprint" will often occur, which mainly It is because the adsorption force of ink and blanket is much greater than that of ink and aluminum foil. In this case, we can use the ink to properly dilute the ink, and increase the fluidity of the ink to reduce the adsorption force between the blanket and the ink, so that it can be smoothly transferred to aluminum foil under the pressure on.
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