What is the problem with the heat sealing time of soft bag composite bag?

1. The heat sealing time of the composite bag is mainly determined by the speed of the bag making machine.

High speed, short heat sealing time; slow speed, long heat sealing time. The heat sealing time is also a key factor affecting the strength and appearance of the weld seal. Under the same heat sealing temperature and pressure, the longer the heat sealing time, the more fully the melting of the heat sealing layer and the stronger the bonding; however, if the heat sealing time is too long, it is easy to cause wrinkling and deformation of the weld, affecting the flatness and appearance. If the weld after heat sealing is not cooled well, it will not only affect the appearance flatness of the weld, but also have a certain impact on the heat seal strength. The cooling process is to form a weld after melting and heat sealing at a lower temperature under a certain pressure. Therefore, insufficient pressure, poor cooling and circulation, poor circulation, high water temperature or untimely cooling will lead to poor cooling and reduced heat seal strength.

2. The more times of heat sealing, the higher the heat sealing strength. The number of longitudinal heat seals depends on the ratio of the effective length of the longitudinal electrode to the length of the bag.

The number of transverse heat seals depends on the number of sets of machine transverse heat seal devices. A good heat seal requires at least two heat seals. For composite films with the same structure and thickness, the higher the degree of interlaminar peeling, the greater the heat sealing strength. For products with lower composite peeling strength, the weld damage is often the primary interlayer peeling of the composite film at the weld, resulting in independent failure tensile force borne by the internal heat sealing layer, while the surface material loses its reinforcement effect, resulting in greatly reduced heat sealing strength of the weld. If the degree of peeling between composite layers is very strong, the layer on the edge of the weld will not peel off, and the actual heat seal strength measured will be much greater; when the heat seal inner layer is PE or OPP, the heat seal strength is significantly better than BOPP of the same thickness.

3. The influence of the contents of the composite bag.

Some products are packaged with powder, which can easily contaminate the seal during the filling process. For example, when LDPE is used as the inner layer, it is found that the seal is prone to cracking. This is because the heat sealing property of LDPE to inclusions is not very good. At this time, it is necessary to replace the inner film material or increase the material thickness to improve the heat sealing strength.

4. The role of composite additives.

In the production process of composite polyethylene film, polyethylene will be precipitated after extrusion by hot roll. A layer of white like broken powder. This phenomenon is that a certain amount of lubricant, that is, some low melting point wax, is added to polyethylene during the production process, which is easy to precipitate on the surface of the film. After the precipitation of this layer of low melting point wax, the direct harm is that the composite strength and heat sealing strength are greatly weakened, especially in the edge sealing position, which is easy to open and separate.

The solutions are as follows: 1) Pretreatment of polyethylene to achieve the ideal surface tension; 2) Select a suitable adhesive to improve its composite fastness; 3) Reduce the curing temperature and try not to precipitate substances to improve the fastness of the composite bag And heat seal strength.

5. The delamination of the flexible packaging composite bag after heat sealing is related to the quality of the ink layer and the corona surface.

In the actual production process, in order to achieve the true reproduction of color, it is inevitable to mix the internal printing ink with the surface printing ink. Theoretically, the internal ink is not compatible with the surface ink.