A part of the color packaging film method is the use of biaxially oriented polypropylene film, and the product after the film coating will appear dark or blistering. This issue was studied and analyzed and the following points were summarized.
1, inappropriate temperature control
When laminating different substrates, the temperature of the electrically heated steel drum must be adjusted according to the product covered. If the film substrate is gold paper, the pressure of the steel cylinder should be controlled at 70-80°C. If the gray paper is covered with 250g/m2 or 300g/m2, the temperature should be adjusted to 80-90°C. Whiteboard paper absorbs much more moisture than gold paper during placement. Especially on rainy days and in winter, if the temperature is not adjusted properly, the film products will not shine. During coating, it is sometimes found that there are noticeable droplets or vapors on the silicon-germanium roller. This is due to the fact that the paper absorbs a lot of moisture. The film temperature of such a product must be further increased. For a product, the drying tunnel temperature can be controlled at 50 ~ 60 °C. To glue the film at the outlet of the baking lane with a finger stick to test no trace of obvious marks, a little sticky. If the film temperature is too high, it will blistering. Therefore, the temperature of the heated steel drum must be controlled according to the characteristics of the product during lamination.
2, under pressure
According to the customer's needs, the thickness of the substrate material is often inconsistent. When laminating, the pressure between the silicone drum and the steel drum should be adjusted according to the thickness of the sheet. If the pressure is too small, the film of the film product is not firm, bright, and prone to wrinkles: if the pressure is too high, film wrinkles and paper deformation may occur.
3, the amount of rubber
When using stretched polypropylene film coating. Must be glued on the film. The amount of glue is controlled by a rotating steel roller installed in a plastic box and coated with glue on the moving film. The control of the amount of glue is controlled by a steel blade that falls on the steel roller. The pressure light glue is large: the pressure heavy glue amount is small. The amount of glue must be mastered, and it can be evenly covered without producing crystal spots. If the amount of glue is too large, the overlaid product will have no gloss.
During the gluing process, special attention should be paid to the fact that it is necessary to prevent the tiny particles and foreign substances from remaining in the rubber disc after the gel has solidified. If there is retention, it will be lifted by the rubber roller during rotation, and it will stick on the plastic blade. There will be a glueless white mark here. Therefore, after the laminator has been shut down for a long period of time, the laminating water or high-boiling point kerosene cleaning glue pump and the rubber container are used to ensure that the glue on the rubber roller is normally applied to the film without generating Traces.
4 Keep the roller clean
After a long period of overpressure, the steel drum is in direct contact with the membrane, and with the effect of temperature, some residues remain on the steel drum. The contact between the silicone roller and the back side of the paper covered by the product, coupled with the separation of the paper feed distance, causes many glues to be hot pressed directly onto the glue roller and cause stacking, which will affect the brightness of the products covered. In severe cases, wrinkles may also occur on the covered products. Therefore, we must keep the drum clean, stop cleaning at any time to ensure the quality of the film product.