| 摘要 |
In the packaging of a wide variety of products in flexible film bags, problems with edge tear and incomplete bag cut-off have been encountered. The edge tear and incomplete cut-off are worse for films containing low melting polymers, such as metallocene-catalyzed ethylene/alpha-olefin copolymers. These problems can be solved using a clamp-cut-seal process, as opposed to a clamp-seal-cut process. By cutting before sealing, the film is still cool, and the strain on the film due to the cutting does not pull on the seal area enough to cause edge tearing (i.e., tearing at the seal). The higher resistance to elongation of the cool, clamped film also serves to reduce or prevent incomplete bag tail cutoff. Also, by providing a means for sealing which clamps the film before it is cut, defective seals from bag "pull back" can be avoided. |
