Environmental temperature and humidity control requirements in the workshop of packaging manufacturers

January 22, 2023

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Due to the moisture absorption of nylon film and a series of adverse consequences caused by moisture absorption, there are certain requirements for the environment of paper-plastic packaging manufacturers. should generally be stored intwenty three℃,± 3℃, the dry humidity difference is 60%RH±5%RHIt is ideal within the range, and the nylon membrane cannot be placed directly on the floor or in the open air to avoid moisture absorption. The difference between dryness and humidity in the production environment is generally not more than75%RH, Rhoda80%RHproduction should be stopped(especially composite production)in order to avoid bad causes. If you must put into production in a hurry, you can add exhaust fans and dehumidifiers in the production site to enhance indoor air circulation and reduce the humidity of the production environment to a minimum.70%RHreproduced below. In short, at humidity over70%RHWhen using it with caution, when the temperature is low or the humidity is high, you must turn on the preheating equipment of the printing and laminating machine, preheat the nylon film first, and dry the moisture attached to the surface of the nylon film, so as to facilitate printing and compounding. The production is going on smoothly; at the turn of winter and spring, due to the large temperature changes, the use of mixed solvents should be adjusted effectively with changes in temperature to prevent quality accidents caused by too fast solvent volatilization or too much residual solvent.Workshop environmental controls maintain humidity at50%~60%RH, the summer temperature is20~twenty two℃ is the best, because the printing workshop will generate a lot of heat energy release during the production process, and controlling the temperature and humidity is the first condition to ensure the printing quality.In dry and solvent-free lamination processes, different types of two-component polyurethane adhesives have different sensitivities to water and alcohols. Exceeding the range may cause failure. If the sensitivity is out of range ,(higher )the less flexible ,The compounded product is sometimes hard and brittle. Therefore, the composite effect will be seriously affected, because the solvent-free polyurethane adhesive containsNCOThese groups can react with active hydrogen atoms. These reactions will consume isocyanate, reduce the amount of it participating in the glue reaction, and release carbon dioxide at the same time, making the glue layer contain bubbles, which is extremely unfavorable for compounding and will also cause the surface to dry or sticky. Combined strength decreased. For materials with strong moisture absorption such as nylon film and cellophane, the residual solvent after printing and the humidity in the air must be strictly managed and controlled.In the nylon membrane family,PA6The water absorption rate of the membrane is the largest, and the saturated water absorption rate can reach9%Left and right, the biaxially oriented nylon film will not only wrinkle after being damp and absorb moisture, but will also elongate in the transverse direction and shorten in the longitudinal direction, and the elongation will increase with the increase of humidity, and the elongation can reach up to1.5%. If the humidity is75%RH, lateral elongation0.37%left and right, and vertically—0.28%; if the humidity rises to85%RH, the lateral elongation0.5%, portrait—0.38%. The stress of nylon membrane after moisture absorption–The strain curve changes significantly. After the nylon film absorbs moisture, it will not have a great influence on the corona effect, but it will have a great influence on the adhesion of ink and adhesive. Generally, the moisture content of nylon membrane exceeds3%It will not only affect the adhesion of ink and adhesive, but also make the film feel hard, and the surface will turn yellow, which will affect the appearance. Therefore, special attention should be paid to the flexible packaging color printing factory to prevent the nylon film from being damp and absorbing moisture.

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