1. Different appearance problems
1. White spots appear in areas with white ink or light-colored ink;
2. Regular small bubbles or dots appear throughout the page;
3. Snowflake-like spots appear;
4. Small, shiny glue dots appear on the PET surface.
2. Corresponding solutions
1. White spots appearing in white ink or light-colored ink areas
If the problem of white spots occurs, we must first analyze and determine whether the amount of glue applied is enough? How is the leveling of the chosen glue? Whether the particle size of the white ink is too coarse, etc., the white spots can be easily solved by making appropriate adjustments according to different reasons.
2. Regular small bubbles or dots appear on the entire page.
Regular small bubbles appear all over the page: There may be two situations for small bubbles. One is irregular small bubbles formed by tiny dirt inside. If you look carefully or use a magnifying glass, you can clearly see that there is a tiny particle inside. of dirty things. The other is regular air bubbles or small dots.
The most important thing for composite aluminum foil products is to keep the equipment hygienic. Each guide roller must be cleaned very clean, otherwise it is easy to have appearance defects, such as small bubbles.
Regarding the problem of bubbles or dots during lamination, one possibility is that the glue reacts with the ink or solvent to generate small bubbles. Due to the characteristics of the material, the air bubbles cannot be released, and small bubbles are formed.
Another possibility is that the glue slowly shrinks to form small dots due to lack of initial tack when applied, and gradually bulges to form small dots.
In these cases, we must first choose the appropriate glue to match the ink, and at the same time keep the composite roller operating at a lower temperature. After getting off the machine, place the material in an environment of 15~20℃ for 2~5 hours, perform secondary leveling, and then proceed to the next step. Process compounding. The winding tension should be as high as possible, and it would be better to wrap several turns of stretch film on the surface of the film roll. During the composite process, try to reduce the speed as much as possible and keep it at 120~150m/min. The composite aluminum plating or AL//PA layer can increase the speed appropriately according to the situation.
Another situation where bubbles appear is due to the influence of the printing layout. When the printing layout is uneven, the winding cannot be tightened, resulting in loose areas that cannot be leveled for a second time, and glue spots or bubbles will occur. So try not to choose hollow layout lamination.
Composite these structures must ensure the environmental conditions of the workshop, and the corresponding temperature and humidity are very important for the composite effect.
3. Snowflake-like spots
This problem is basically caused by the mismatch between ink and glue, which is what everyone usually calls dissolved ink. This problem can be solved by adjusting the glue or adjusting the ink.
4. Shiny glue spots appear on the surface of PET
Some careful people will find that when we laminate PET//AL, we will find that there are scattered small shiny glue dots on the surface of PET. In fact, this is because there is a certain amount of aluminum foil when we laminate. Because solvent-free glue has no initial viscosity, after compounding, the glue will seep back along the pinholes of the aluminum foil to the surface of PET, and such glue spots will appear after solidification.
