Reasons for bubbles appearing after recombination or after some time
1. The surface wettability of the substrate film is poor. Due to poor surface treatment or precipitation of additives, poor wettability and uneven coating of the adhesive result in small bubbles. Before composite, the surface tension of the substrate film should be tested.
2. Insufficient glue application. It is mainly because the ink surface is uneven and porous, so that Adhesive is absorbed. The actual Adhesive coating amount on the ink surface is less, and the amount of glue applied on the printing film with large ink surface and thick ink should be increased.
3. The Adhesive is poor in fluidity and dryness, or the temperature at the operation site is too low. The transfer of Adhesive and poor wettability are prone to bubbles. Adhesive should be selected well, and Adhesive should be preheated if necessary.
4. When Adhesive is mixed with water, high solvent water content, high air humidity and high substrate moisture absorption can make Adhesive react to produce CO2 trapped in the composite membrane and cause bubbles. Therefore, Adhesive and solvent should be well managed, and nylon, Cellophane and Vinylon with high moisture absorption should be sealed tightly.
5. The drying temperature is too high and the drying is too fast, resulting in blistering or surface filmization of Adhesive. When the temperature of the third section of the drying tunnel is too high, the solvent on the surface of the Adhesive layer evaporates rapidly, resulting in a local increase in the concentration of the surface glue solution and surface crusting. When the subsequent heat penetrates into the interior of the adhesive, the solvent underneath the film vaporizes, breaking through the film and forming a crater like ring, also causing the adhesive layer to be uneven. Opaque.
6. The composite roller is pressed with air, causing bubbles to be present in the composite film. The film has high hardness and is easier to enter when the thickness is large. Firstly, adjust the wrap angle between the composite roller and the film. If the wrap angle is too large, it is easy to trap air, and try to enter the composite roller in the tangent direction as much as possible; Secondly, the flatness of the second anti roll substrate is good, such as loose edges and shaking of the film. After entering the composite roller, a large amount of air will inevitably be trapped, causing bubbles.
7. The residual solvent is too high, and the solvent vaporizes to form bubbles sandwiched in the film. Regularly check the air volume of the drying duct.
Post time: Jul-20-2023
