There are three common problems со стоячими пакетами: bag leakage during use, uneven bag shape и asymmetric bottom seal during bag making.

The leakage of стоячий bag is mainly caused by the selection of composite materials и heat sealing strength.

(1) Selection of materials

The material selection of стоячий bag is very important to prevent leakage. The purpose is to increase the peel strength between the outer layer и the middle barrier layer, between the barrier layer и the heat sealing layer и the heat sealing strength of the bag. Therefore, the surface tension of the composite surface of the film is required to be greater than 38 dyn / cm; The low-temperature heat sealing performance of the inner heat sealing film is better, и the surface tension of the heat sealing surface is less than 34dyn / cm; In addition, we should choose the ink с good connection performance и the adhesive с high solid content и low viscosity.

(2) Heat sealing strength

Low heat sealing strength is also one of the important factors affecting the leakage of стоячий bags. During heat sealing, the matching relationship between heat sealing temperature, heat sealing pressure и heat sealing time shall be adjusted. It is mainly necessary to explore the heat sealing temperature of bags с different structures. Due to the different melting points of different kinds of plastic films, the heat sealing temperature is also different; The heat sealing pressure should not be too large, и the heat sealing time should not be too long to avoid macromolecular degradation. The heat sealing layer is cut by the heat sealing knife in the state of high-temperature melting, so as to reduce the sealing strength. In addition, the four-layer sealing part at the bottom of the стоячий bag is the key part. The heat sealing temperature, heat sealing pressure и heat sealing time can be determined only after full test и verification.

In the actual production process, the стоячий bag shall be tested для leakage according to the different requirements of its contents. The simple и practical method is to fill some air into the bag, heat seal the bag mouth, put it into the basin containing water, и squeeze different parts of the bag by hand. If no bubbles escape, it indicates that the sealing tightness of the bag is good; Otherwise, the heat sealing temperature и pressure of the air leakage part shall be adjusted in time. The стоячий bag containing liquid should be treated с caution. The method of extrusion и drop can be used to detect whether it leaks liquid. для example, fill some amount of water in the bag и seal the mouth.

1. The стоячий bag shape is uneven

Flatness is one of the indicators to measure the appearance quality of packaging bags. In addition to material factors, the flatness of стоячий bags is also related to heat sealing temperature, heat sealing pressure, heat sealing time и cooling effect. High heat sealing temperature, high heat sealing pressure и long heat sealing time will cause shrinkage и deformation of composite film. Insufficient cooling will result in insufficient setting after heat sealing, which can not eliminate the internal stress и wrinkle the bag. Therefore, the process parameters should be adjusted и the cooling water circulation system should work normally.

2. Poor symmetry of стоячий bag

Symmetry not only affects the appearance of стоячий bags, but also affects their sealing performance. The common asymmetry of стоячий bags is often reflected in the bottom material. Due to the improper control of the bottom material tension, the round hole on the bottom surface will be deformed or wrinkled due to the mismatch с the main material tension, и the heat sealing strength will be reduced. When the round hole of the bottom material is deformed, the discharge tension shall be properly reduced, и the waiting time shall be increased для correction during heat sealing, so as to fully heat seal the intersection of the four layers at the bottom of the bag. In addition, the asymmetry of bag shape is also related to photoelectric tracking, feeding, cursor design, rubber roller balance, stepping motor or servo motor synchronization и other factors. This problem should be solved in specific operation according to different products и different bag making equipment.