How to reduce the impact of the composite process on solvent residues?
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The most important factor causing odor in composite flexible packaging materials comes from solvent residues of inks and adhesives, especially in dry recombination where solvent residue is unavoidable. To this end, soft pack factories can usually take the following measures to avoid or reduce dissimilarity.
1. Select a two-component adhesive that is compatible with the ink. The thinner should also meet the requirements of no odor.
2. Control the amount of glue applied, the amount of glue applied is too large or the glue layer is too thick, which is not conducive to solvent evaporation, resulting in an increase in solvent residue.
3. According to the speed of the compound machine, the viscosity of the adhesive is adjusted, so that the solvent can dissolve the adhesive well, and the coating roller can not use the corrosion plate. The laser roller, the electric engraving roller or the knurling roller should be used to make the rubber coating layer. Uniform, solvent evaporation is consistent. It has been found through testing that a larger coating roll is used in combination with a lower working viscosity, and the total amount of solvent remaining in the composite while ensuring the coating amount is smaller than the total amount of solvent remaining in the high-viscosity glue mixed with the small-sized coating roller. It reminds us that we can not only consider the cost of the solvent that is volatilized, but ignore the difficulty of solvent evaporation in the glue. The excessively high working viscosity deteriorates the solvent release property of the adhesive layer, and the adhesive layer just applied to the film encounters the high temperature of the oven and the surface layer of the hot air blown film 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 °C in Zone 1, 60-75 °C in Zone 2, 70-85 °C in Zone 3, and the speed is usually 100-150 m / min, and some manufacturers compound speed is 180--250 m / min. In fact, the design of the internal air outlet of the dry composite machine produced by many machinery factories, the air supply volume and the wind speed design are not completely scientific and reasonable, or the drying tunnel length is insufficient, and cannot match the actual running speed of the machine. If the drying capacity and the discharge capacity are insufficient and the length of the drying tunnel is insufficient, the excessive composite speed is undoubtedly prone to the occurrence of odor in the residual semi-finished residual solvent. The reasonable compound speed should be tested by gas chromatograph to test the minimum speed of the total residual solvent residue of the composite semi-finished product. The speed of the machine under the drying condition of the coating amount is not suitable for the pursuit of production capacity. It is considered how many meters the speed of a machine is designed to leave the factory and set the running speed of the machine.
5. After curing, the curing time should be controlled. The curing time and temperature should be controlled. The curing time is generally 36 to 48 hours, and the temperature is about 45-50 °C. Incomplete curing will not only produce odor, but also seriously affect the peel strength. At the same time, the air inlet and exhaust ducts of the curing chamber should be smooth. The finished semi-finished product is reversely re-rolled under the condition of permission and assists in the cooling of the blower, which is also very helpful for reducing the odor of the final product.