Part of the color packaging film method is to use biaxially oriented polypropylene film, the product after the film will appear dull or blistering. The author conducted research and analysis on this issue and summarized the following points.
        1. Unsuitable temperature control
         When laminating different substrates, the temperature of the electrically heated steel drum must be adjusted according to the coated product. If the coated substrate is gold cardboard, the temperature of the laminated steel cylinder should be controlled at 70℃～80℃: if it is coated with 250g/m2 or 300g/m2 gray whiteboard paper, the temperature should be adjusted to 80℃～90℃. During the placement of whiteboard paper, the moisture absorbed by it far exceeds that of gold cardboard. Especially in rainy days and winters, if the temperature is not adjusted properly, the film-covered products will not shine. When laminating, sometimes there are obvious water droplets or steam on the silicon roller, which is caused by the paper absorbing a lot of moisture. The film laminating temperature of such products must be raised a little bit more. For the product received, the drying tunnel temperature can be controlled at 50 ℃ ~ 60 ℃. Use the glued film to stick the finger at the exit of the drying tunnel and test it without traces, just a little sticky. If the film temperature is too high, it will foam. Therefore, the temperature of the heating steel drum must be controlled according to the characteristics of the product when laminating.
         2. Keep the roller clean
         After a long period of pressure, the steel drum is in direct contact with the membrane. With the effect of temperature, some residues will be left on the steel drum. The silicone roller is in direct contact with the back of the coated product paper, plus the separation of the paper spacing, many glues are directly pressed onto the rubber roller to cause accumulation, which will affect the brightness of the coated product. In severe cases, the covered product may wrinkle. Therefore, the drum must be kept clean and shut down at any time to ensure the quality of the film-covered product.
        3. Insufficient pressure
        According to customer needs, the thickness of the substrate material is mostly inconsistent. When laminating, the pressure between the silicone roller and the steel roller should be adjusted according to the thickness of the substrate paper. If the pressure is too low, the film of the film-covered product is not strong, bright, and wrinkle-prone: too much pressure will cause film wrinkle and paper deformation.
        4. The amount of glue
        When using stretched polypropylene film. The film must be glued. The amount of glue is applied to a moving film by a transmission steel roller installed in a plastic box through a rotating belt. The amount of glue is controlled by a steel blade that falls on the steel roller. Large amount of pressure light glue: small amount of pressure heavy glue. The amount of glue should be well controlled, so that it can be covered evenly, and no crystal points can be generated. If the amount of glue is too large, the covered product will be dull.
       Special attention should be paid to the process of gluing, it is necessary to prevent the tiny particles and foreign objects after the gel is solidified from remaining in the rubber tray. If left, it will be picked up by the rubber roller during rotation and stuck on the rubber blade, and there will be a rubber-free white mark here. Therefore, after the laminator is shut down for a long time, before the laminator is turned on, the glue pump and the hopper box should be cleaned with laminating water or high-boiling kerosene to ensure that the glue of the upper roller is normally coated on the film without being produced. Trace.