1. Low strength of packaging bags
Peel off the two layers of film and wipe them with your fingers on the PE film. The friction between the two fingers feels smooth. There is a significant amount of lubricant precipitation in the film.
The adhesive used in this product is PU-1850, which has a certain resistance to slippery agents.
The temperature thermocouple in the ripening room of the factory is parallel to the heating source and only 30 to 40 centimeters away from the heat source. Under this control, the heat source remains in a state of stopping heating for a long time, and the actual ripening temperature cannot reach 50 ℃. And the heating time for turning on the power supply is less than 16 hours.
Adjust the position of the thermocouple, extend the curing time, and achieve the required peel strength.
When using PE film with a high content of composite lubricant, it is necessary to choose an adhesive that has a certain resistance to the lubricant. After the film is rolled off the machine, enter the curing room as soon as possible and increase the curing temperature appropriately. The general ester soluble two component polyurethane adhesive has poor natural aging and anti slip properties.
2. Increased friction coefficient
The roll film of BOPP/VM PET/PE structure has been produced without any problems in winter. Produced in June, the friction coefficient increased and the packaging machine cannot be used normally. Change to natural aging, and the film roll cannot be used.
This product uses 30 μ The thick PE film has good smoothness before lamination. When laminating, the cooling roller does not receive cold water, and the surface of the cooling roller is warm. The heat brought by the film from the oven is still present before winding, and the film is also warm during winding. Although it is naturally aged in the workshop, the temperature is high in summer (30 ℃ in the workshop at 10 am), and the heat carried by the membrane is not easily dissipated, it is actually in a hot state.
Take the composite film from the machine on site and place it in two environments: 27 ℃ and 45 ℃ for about 20 hours. The composite film placed at 27 ℃ has good smoothness, while the composite film placed at 45 ℃ has astringency and a significant decrease in smoothness. The temperature has a significant impact on the product's smoothness.
Similar to some thin transparent CPPs that are sensitive to temperature, the friction coefficient of CPP before composite is less than 0.1, but it can only naturally mature after composite.
3. Cooking delamination
Soy egg packaging bags were sterilized at 115 ℃ for 30 minutes in the food factory. The bags on the top of the sterilization pot had layers of BOPA, and Huai ink was transferred to CPP.
Technicians believe that the quality and amount of adhesive can meet the product requirements, and the curing time of 48 hours at 50 ℃ to 55 ℃ is also satisfactory. The problem is likely to be caused by the ink.
Mature the sample bag at 55 ℃ again for 24 hours, and cook at 121 ℃ for 30 minutes without delamination; And all the samples that were cooked together but not matured again showed delamination.
The direct manifestation of this problem is ink transfer, and the reason for this phenomenon is insufficient maturation.