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The transparency of the composite packaging bag is poor, what's the matter?

by:Supouches Packaging     2022-08-29
Many packaging bags are required to have high transparency, and a large area of ​​blank base film is used for compounding, but sometimes the phenomenon of poor transparency occurs. Professional flexible packaging manufacturers think that this has a lot to do with factors such as adhesives and base films. 1. The color of the adhesive itself is too deep ​dark yellow, yellow-red, and sometimes even dark red like soy sauce soup, which is also the corresponding color when left on the film. Therefore, when high transparency is required, a yellowish or even colorless adhesive should be used. 2. The glue is mixed with dust and other particles. There is too much dust in the air in the workshop environment. There is also dust in the hot air blown into the drying tunnel after gluing. There are many small dots that make up the opaque. In this case, the glue should be filtered with a 180-mesh wire mesh to remove insoluble particles in the glue. Attention should also be paid to the cleanliness of the workshop, the ground should be bright, not dry, and there should be no floating dust. The tuyere can use a high-mesh filter or other filter material to eradicate the dust in the hot air. 3. The surface tension of the base film is not high, and the glue cannot be evenly moistened to it. It should be shortened. After monotony, the film will be uneven, and the transparency is not good. This requires a film with a surface tension greater than 38mN/m. Or deal with it from scratch and use it after passing the test. 4. The fluidity of the adhesive is lacking and the flatness is poor. At this time, it is necessary to use an adhesive with good fluidity, or use a little solvent that can be flattened beforehand, but it is necessary to avoid the problem of odor and odor caused by too much residual solvent. 5. The amount of glue is lacking and there is a blank space, and there are small air bubbles, which form mottled or opaque, and the amount of glue must be checked to make it satisfactory and uniform. 6. The adhesive glue itself is hygroscopic and has become turbid. If there is insoluble matter, please remix the glue, and use a solvent that does not contain active groups such as water, alcohol, acid, and amine. 7. The temperature at the beginning of entering the drying tunnel is too high, monotonous and too fast, so that the solvent on the surface of the glue layer is actively transpired, forming part of the glue concentration of the surface layer to travel, and the surface is crusted. Then, when the heat deepens into the glue layer, the solvent under the film evaporates, breaking the glue film and forming a ring like a volcano vent, which also makes the glue layer uneven and opaque. Therefore, the temperature of the drying tunnel should gradually travel from the inlet to the outlet, from low to high, so that the solvent can be transpired from the inside to the outside in an orderly and continuous manner. Others can be mixed with solvents of different boiling points. When heated and evaporated, the high-boiling point solvent on the surface of the adhesive layer can be stored for a long time, so that the surface conjunctiva is not crusted. However, it is also necessary to ensure that the amount of residual solvent is qualified and there is no odor and odor. 8. The rubber roller during compounding has the disadvantage that it cannot be pressed at a certain point, forming a neutral position and being opaque. Therefore, you should check it frequently, and if there are any shortcomings, even if they are small, they should be replaced.
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