Dragging ink refers to the process of laminating, where the glue pulls down the ink layer on the printing surface of the printing substrate, causing the ink to adhere to the upper rubber roller or mesh roller. The result is incomplete text or color, resulting in the product being scrapped. Moreover, the ink attached to the top glue roller is transferred to the next pattern, causing waste. The colorless part has ink spots and a serious decrease in transparency, which affects product quality.
1. It is related to the amount of glue applied and the operating concentration
The probability of one component hot melt adhesive dragging ink is higher than that of two component adhesive, which is inseparable from the main adhesive type and diluent.
Due to the small amount of glue applied, the amount of ink dragged down is in the form of fine threads, like marks caused by meteors. These fine dots are most noticeable in the blank area of the plastic film, and in the patterned part, careful observation is necessary to discover them. The gluing amount of the scraper type dry laminating machine is determined by the number of lines and depth of the anilox roller. Excessive pressure on the scraper during actual operation will also reduce the amount of glue applied. If the amount of glue applied is small, the phenomenon of dragging ink is severe, while if the amount of glue applied is large, the phenomenon of dragging ink is reduced.
The concentration of homework is closely related to the phenomenon of ink dragging. If the concentration of a single component adhesive is less than 35%, the solid content of the main adhesive is less than 3g/㎡, or the concentration of a two component reactive adhesive is less than 20%, and the solid content of the main adhesive is less than 3.2g/㎡, it is easy to occur ink drawing phenomenon, which is also related to the actual operating process. If the operating concentration is low and ink dragging occurs, it is necessary to increase the operating concentration to solve it, which actually means increasing the amount of main agent or reducing the amount of diluent used. Usually, the working concentration of a single component is controlled at around 40%, and it is best to control the concentration of two components at around 25-30%, so that the ink dragging phenomenon can be solved.
2. Related to the pressure of the glue roller
In the dry composite process, a gluing pressure roller is usually used, which is used to make the gluing coating more uniform and reduce the generation of bubbles. When ink dragging occurs, in addition to considering the amount of glue applied and the concentration of the operation, it is the pressure of the rubber roller.
Usually, when the pressure exceeds 4MPa, there is a possibility of ink dragging. The solution is to reduce pressure, and at the same time, a skilled operator should use a cloth to stick a diluent to wipe the ink area of the running anilox roller. If it is too severe, the anilox roller should be stopped for cleaning.
3. Related to the quality of the glue roller
The rubber roller is not smooth or delicate, and may drag ink, which is most easily reflected on single component hot melt adhesives.
Due to the unevenness and roughness of the resin, the ink pulled off is irregular and unevenly distributed, leaving ink spots in the blank space, resulting in a decrease in transparency, ink loss in color, and incomplete text. To change this phenomenon, it is necessary to replace the smooth and delicate gluing roller.
4. Related to machine speed and drying temperature
The speed of the machine indicates that the interface between the ink layer and the adhesive on the film layer undergoes a change in wetting time.
Often, due to slow machine speed, there is a phenomenon of ink dragging, which is solved by increasing the speed and reducing the dwell time between the ink layer and the adhesive interface. In theory, if the machine speed is increased, the drying temperature should also be relatively increased. At the same time, if the machine speed is increased during actual operation, it should be observed whether there are other faults, such as material displacement, and corresponding adjustments need to be made.
5. Related to the adhesion of printing substrate or ink
If different types of ink are used for gravure printing, the occurrence of faults is most easily reflected during lamination.
Ink can be divided into surface printing ink and inner printing ink. Due to different types of ink, their adhesion may be different or incompatible, and weak adhesion can lead to weak adhesion. When dry lamination is used, it is easy to cause ink dragging. When the surface tension of the printing substrate is poor, it is more prone to ink dragging.
The pulled down ink layer appears as a whole, and the ink adheres to the glue basin, causing turbidity and dirt. If it has already been printed, in order to avoid waste, the machine speed can be increased, the glue amount can be increased, and the glue concentration can be increased at the same time. Reduce the pressure on the rubber roller while reducing the unwinding tension.
6. Related to mechanical factors
During operation, if mechanical failure occurs, resulting in uneven gluing or poor coating, it can also cause ink dragging.
The synchronization of the upper rubber roller and the anilox roller is completed by two matching gears. If there is ink dragging phenomenon, careful observation should be made. It will be found that the ink dragging occurs due to the shaking of the upper rubber roller and poor coating. The reason for the shaking is due to severe wear and asynchronous gear teeth.
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Post time: Oct-13-2023
