The main cause of odor in composite flexible packaging materials comes from the solvent residues of inks and adhesives, especially the solvent residues in dry composites cannot be avoided. For this reason, soft package factories can usually take the following measures to avoid or reduce ambiguity.
1. Choose a two-component adhesive that is compatible with the ink, and the thinner should also meet the requirement of no odor.
2. Control the amount of glue, if the amount of glue is too large or the layer of glue is too thick, it is not conducive to volatilization of the solvent, resulting in an increase in the amount of residual solvent.
3. The viscosity of the adhesive is adjusted according to the speed of the compound machine, so that the solvent can dissolve the adhesive well, and the coating roller cannot use the corroded version. Use a laser roller, an electric engraving roller or a knurling roller to apply the glue layer Uniform, consistent solvent evaporation. Through the test, it is found that using a larger coating roller with a lower operating viscosity, while ensuring the coating amount, the total amount of solvent residue compounded is smaller than that of a small-size coating roller with high viscosity glue. It reminds us that we can not only consider the cost of volatile solvent and ignore the difficulty of evaporating the solvent in the glue. Too high operating viscosity makes the solvent release of the adhesive layer worse. The adhesive layer just applied to the film encounters the high temperature of the oven and the surface layer of the blown layer of hot air, so that the solvent inside the adhesive layer cannot be completely volatilized.
4. In dry compounding, the drying tunnel is usually divided into three sections. The temperature setting is usually: 50-65 ℃ in zone 1, 60-75 ℃ in zone 2, and 70-85 ℃ in zone 3. The speed is usually 100-150 meters / minute, and some manufacturers have a compound speed of 180-250 meters / minute. In fact, the design of the internal air outlet, the supply and exhaust air volume and the air speed of the dry compound machine produced by many machinery factories are not completely scientific and reasonable, or the length of the drying tunnel is insufficient, and it cannot match the actual speed of the machine. In the case of insufficient drying capacity and discharge capacity and insufficient length of the drying tunnel, the excessively high compounding speed is undoubtedly prone to the phenomenon that the residual solvent of the compound semi-finished product exceeds the standard and produces odors. The reasonable compound speed should be the speed when the gas chromatograph is used to test the minimum value of the total residual solvent of the compound semi-finished product as the appropriate speed of the machine under the coating amount and drying conditions. The operating speed of the machine is set based on how many meters the designed vehicle speed was when the machine was shipped from the factory.
5. Curing should be carried out after compounding. The curing time and temperature should be well controlled. The curing time is generally 36 to 48 hours, and the temperature is around 45-50 ℃. Incomplete curing will not only produce odor, but also seriously affect the peel strength. At the same time, the inlet and exhaust ducts of the curing chamber should be smooth. The semi-finished product after aging is reversed and rewinded under the conditions permitting and assisted with air cooling, which is also very helpful to reduce the odor of the final product.
Fresnel Screen Ust,Fresnel Screen,Fixed Frame Projector Screen,Alr Projector Screen Ust
Dongguan Aoxing Audio Visual Equipment CO.,Ltd , https://www.aoxing-whiteboard.com