1. Stand up pouch doypack bag leaks
The leakage of stand up pouch (doypack bag) is mainly caused by the selection of composite materials and heat sealing strength.
First of all, the material selection of the stand up pouch bag is very important to prevent leakage. The purpose is to improve the peeling strength between the outer layer and the middle barrier layer, between the barrier layer and the heat-sealing layer and the heat-sealing strength of the bag. Therefore, the surface tension of the composite surface of the film must be greater than 38dyn/cm; The low temperature heat sealing performance of the inner heat-sealing film is better, and the surface tension of the heat-sealing surface must be less than 34 dyn/cm; In addition, it is necessary to select inks with good connectivity, adhesives with high solid content and low viscosity, and organic solvents with high purity.
Secondly, the low heat-sealing strength is also one of the important factors affecting the leakage of the stand up pouch bag. During heat sealing, the matching relationship between heat sealing temperature, heat sealing pressure and heat-sealing time shall be adjusted. In particular, we should pay attention to the heat-sealing temperature of bags with different structures. Because the melting points of different types of plastic films are different, the heat-sealing temperature is also different; The heat-sealing pressure should not be too high, and the heat-sealing time should not be too long, so as to avoid the degradation of macromolecules. The heat-sealing layer is cut by the heat-sealing knife in the high temperature melting state, which will reduce the sealing strength. In addition, the four-layer seal at the bottom of the stand up pouch doypack bag is the most critical part. The heat-sealing temperature, pressure and time can be determined only after full test verification. In the actual production process, the leakage test shall be conducted for the stand up pouch bag according to the different requirements of the contents. The simplest and practical method is to fill the bag with a certain amount of air, heat-sealing the bag mouth, putting it into the basin containing water, and squeezing different parts of the bag with your hand. If no bubbles escape, it means that the bag is sealed well. Otherwise, the heat-sealing temperature and pressure of the leaking part shall be adjusted in time. Stand up pouches doypack bags containing liquid should be treated with more caution. Extrusion and drop methods can be used to detect whether there is liquid leakage. If a certain amount of water is filled in the bag, the mouth should be sealed, and the test should be conducted according to GB/T1005-1998 pressure test method. The drop test method can also refer to the above standards.
2. Uneven bag type
Flatness is one of the indicators to measure the appearance quality of packaging bags. In addition to the material factor, the flatness of the self-supporting bag is also related to the heat-sealing temperature, heat sealing pressure, heat sealing time, cooling effect and other factors. If the heat-sealing temperature is too high, or the heat-sealing pressure is too high, or the heat-sealing time is too long, the composite film will shrink and deform. Insufficient cooling will lead to insufficient shaping after heat sealing, which cannot eliminate internal stress and wrinkle the bag. Therefore, adjust the process parameters and ensure that the cooling water circulating system works normally.
3. Poor symmetry
Symmetry not only affects the appearance of the stand up pouch bag, but also affects its sealing performance. The most common asymmetry of the stand up bag is often reflected in the bottom material. Due to improper control of the bottom material tension, it will cause deformation of the bottom hole or wrinkles due to mismatching with the tension of the main material, reducing the heat-sealing strength. When the bottom material round hole is deformed, the discharge tension shall be appropriately reduced, and the waiting time shall be increased during heat sealing for correction, so as to fully heat seal the intersection of the four layers at the bottom of the bag. In addition, bag asymmetry is also related to photoelectric tracking, feeding, cursor design, rubber roller balance, synchronization of stepping motor or servo motor and other factors.
Post time: Nov-25-2022