In the flexible packaging technology, the foil seal is welded on the filling machines immediately after filling sealed. Depending on the shape and weight of the filling, the not yet solidified welding seam is may be partially or completely opened by the tension applied to it. Therefore, in most cases, in multilayer films a weld layer must be used in which, after the opening of the welding jaws, the not yet not yet solidified has a sufficiently high hot adhesion (which is not the same as the hot adhesion of the weld). strength of the weld) and is resistant to opening. Good hot adhesion has its own tricks. This is the subject of the following text.