With the wide application of flexible packaging composite bags, packaging companies have higher and higher requirements for the quality of flexible packaging composite bags, so the quality inspection of flexible packaging composite bags is more important, so what about the quality of composite bags?

Two detection methods for composite bags:

1. Sealing tightness There are some slender seams at the seal, and slight neglect in visual inspection will bury the danger of food leakage in the future, so it is necessary to check the sealing tightness of the composite bag. The commonly used method is: spray a surface active agent with dye into the seal, and check whether it penetrates or not. If the color of the dye passes through the seal, it means that the sealing function is not good, and on the contrary, it means that it meets the requirements of sealing quality. In actual work, we often use a smooth, burr-free small iron ruler with a length of 20cm, a width of 5cm and a thickness of 0.8mm to push the seal tightly. If there is a drop, perforation, etc., it means that the sealing performance is poor; if the seal still adheres to the proper sealing size, it means that the sealing performance is good. The factors that lead to the poor sealing performance are: the pressure of the sealing knife is not good or uneven, which can be solved by adjusting the spring pressure of the sealing knife; the low temperature will also make the sealing of the composite bag worse. We noticed that when the total thickness of the composite material exceeds 80 μm, the problem of poor adhesion is easy to occur during bag making processing, especially the structure of BOPP/OPP. To ensure the tightness of the product, there is a uniform and stable sealing pressure and a suitable temperature.

2. Appearance visual Appearance visual inspection includes items such as the inspection of the flatness and transparency of the composite bag. It is mainly used to check whether there are obvious scratches and pinholes on the surface of the composite bag, and there is wu pollution at the seal. Our company has a complete set of appearance inspection methods, the details are as follows.

(1) Place the composite bag in your hand, sway it gently at the 40W fluorescent lamp, and through the reflected light on the surface of the composite bag, you can clearly find out whether the composite bag has scratches or marks on the surface, which is often called "bag surface drawing" in the industry. . If the wire drawing is severe, the fault location should be found according to the actual situation, and the impact should be reduced to a low point to ensure the quality of the product. Most of the wire drawing scenes we found through investigation are caused by the uncleanness of the guide rollers drawn by the bag making machine, so we must ensure that the guide rollers are clean. In addition, the non-rolling of the guide roller will also cause the drawing problem of the composite bag. The factor that the guide roller does not roll is mostly caused by the lack of oil in the bearing, so excellent smoothness is the basic condition for the bearing to roll.

(2) Check the flatness of the composite bag. The detailed method is: take several samples of the product bag for "air-to-ground" drop, let it touch the ground naturally (the landing place should be clean), and investigate the condition of the composite bag after it touches the ground. If the composite bag is bent, warped outwards or inwardly arched when it hits the ground, it means that the flatness of the composite bag is poor; otherwise, it means that the flatness is good. The factors that cause the difference in flatness are generally as follows: the bag making temperature is too high, the stress stiffness of the inner layer of the composite bag has been damaged; the structural composition is unreasonable; the thickness of the material itself is unequal. We noticed that when the total thickness of the composite materials of PET/PE and BOPP/PET/PE structures does not exceed 80 μm, the flatness is likely to deteriorate.

(3) The visual inspection of appearance also includes the inspection of transparency. Transparency is particularly important for some products because there is no pattern in a large area. The way to check the transparency is: take a product bag and check it through the indoor indirect light source. If there are "pockmarks", "rings", "fog" and other phenomena in the blank, it means that the transparency is poor, otherwise it means that the transparency is good. . There are many factors that cause poor transparency. For example, when compounding, because the color of the compound glue itself is yellowish or reddish, when it is transferred to the compound bag, a corresponding color shift will occur, which will affect its transparency; if the material itself has poor transparency , there is "fog", which will also affect its transparency, so when the materials are put into the warehouse, the quality should be strictly controlled, so that the unqualified raw materials will not be put into the warehouse. In addition, the transparency of different composite raw materials is also different. For example, the transparency of cast CPP is much higher than that of blow-molded co-extruded CPP.