Ensure sufficient drying of food packaging bag adhesive
We usually only focus on the amount of compound glue. In fact, insufficient drying is often the most direct reason for incomplete curing of adhesive (insufficient heat resistance of adhesive layer), delamination and wrinkling during boiling. There are a small amount of water and alcohol impurities in the prepared glue solution. The good drying property can make the water and other impurities in the coating layer volatilize as much as possible, and reduce the consumption of curing agent proportion in the adhesive layer. In order to ensure that the adhesive is fully dry during dry compounding, the following points should be paid attention to:
(1) The drying performance of the equipment itself, such as the inlet and exhaust air volume of the equipment and the length of the oven.
(2) Setting of drying temperature.
① Setting of drying temperature in the first zone. The ethyl ester concentration of drying medium in the first zone is the highest, so the drying temperature of the first zone should not be set too high (generally not higher than 65 ℃). Because the temperature is too high, the solvent on the surface of the plastic layer of the food packaging bag volatilizes rapidly, and the crust inhibits the escape of the inner solvent in the drying section of the later areas.
② Drying temperature gradient setting. The oven temperature should be set according to the law of gradual increase of gradient, so as to speed up the diffusion and volatilization of the solvent in the hardening zone and the odor elimination zone, and reduce the residual solvent in the film.
(3) Adjustment of air intake and exhaust.
① In the drying process, the inlet and exhaust air valve in the evaporation area should be opened to the maximum, and the return air valve should be closed.
② However, in the dry hardening area and odor removal area, the return air volume can be appropriately increased, which can save part of energy consumption.
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Dongguan Beite packaging materials Co., Ltd
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