Reasons for wrinkles in high-temperature cooking bags after sterilization.aluminum foil bags for cooking

If wrinkling is found on the surface of the packaging bag during high-temperature cooking, careful observation and accurate analysis should be made. If there are longitudinal, transverse, or irregular wrinkles on the printing substrate. The analysis is mainly based on three considerations: a. During printing, the temperature of the drying oven is too high, the constant tension between winding and unwinding is inconsistent, and the unwinding tension is too high, resulting in deformation of the PET film. b. The paper core of the winding material roller is not smooth. As the volume of the winding product continues to increase, longitudinal or transverse wrinkles will occur at the bottom of the winding, making the originally flat printing substrate uneven. This wrinkling phenomenon is not easy to eliminate during the composite process. c. The printing traction roller has foreign objects or is too dirty. When the printing substrate passes through foreign objects, it slides laterally. When the sliding substrate passes through the imprinting rubber roller, wrinkles are generated, and these wrinkles are regular, with one section having one section without another.

Solution: a. Adjust the drying temperature based on workshop temperature and humidity, machine speed, and actual printing effect pattern depth. 15 for printing nylon on most high-temperature cooking bags μ m. PET is 12 μ m. Therefore, it is recommended that the drying temperature be between 40-60 ℃. If the drying temperature is too high, the film cannot withstand the high temperature and undergoes deformation, elongation, and softening. Adjusting the constant tension of winding and unwinding, there are now high-speed gravure printing machines that have produced automatic tension controllers. When the limit or set value is exceeded, an automatic alarm will be triggered, and automatic adjustment is very convenient. b. Exchange the paper tube with a smooth center and pay attention to flatness when winding. At the beginning, the winding tension should be small. When reaching a certain thickness, gradually increase the tension value, so that the winding material will not wrinkle. c. Wipe the traction roller that has foreign objects clean.

When the surface of the substrate and composite substrate is wrinkled together, the flatness is extremely poor, and the factors include: a. the printing substrate itself is wrinkled or cannot be eliminated due to wrinkling during printing; b. When the pressure at both ends of the hot steel roller is inconsistent or the thickness deviation of the composite substrate PE and CPP is large, when the deviation is 10 μ This wrinkling phenomenon is highly likely to occur at m; c. A phenomenon that occurs when the bottom tension is too low and the top tension is too high during the winding of composite products, resulting in compression.

Solution: a. Strictly control printing quality; b. Adjust the pressure of the steel roller to a balanced state, and ensure that the composite substrate does not deviate as much as possible. When the middle of the composite is aluminum foil, try to wear less traction rollers to prevent fracture; c. Adjust the winding tension to achieve consistency as much as possible.

When the substrate shows wrinkles and bubbles in the middle, it is mostly due to poor tension control during dry lamination, resulting in excessive tension and tension. It is most likely to occur in NY/PE or NY/aluminum foil/CPP, especially in nylon substrates. If the unwinding tension is too high, thermal shrinkage and deformation occur during the drying process, and this phenomenon occurs after the finished product cools down; The influence of glue solution, when coating high-temperature cooking bags, the dry solid content must reach 4.5g/m2, and the mesh roller is generally selected as 80 μ M deep is sufficient. If uneven coating occurs or the adhesive itself has poor quality and cannot withstand high temperature boiling, it is easy for the adhesive to separate from the substrate after boiling, greatly reducing its fastness.

Solution: a. Adjust the unwinding tension and try not to dry at high temperature as much as possible when the solvent evaporates completely to avoid deformation and cooling shrinkage; b. Increase the concentration of the operation and choose a glue solution with a large dry solid content. Generally, when the solid content is 75% and the operation concentration is 30%, it is good; c. Choose professional adhesives that are resistant to high temperatures, and it is strictly prohibited to apply general adhesives.

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