Tear-open bag and three-layer coextrusion film for making the bag

Abstract

A tear-open packaging is formed by a pair of plastic film panels having inner faces joined together by a weld. One of the film panels is formed by a two- or three-layer coextrusion having a nonsticky foam core layer and a weldable inner layer that is secured by the weld directly to the inner face of the other film panel. The strength of the core layer and of the bond between the core layer and inner and outer layers are such that, when the two panels are pulled away from each other, the core layer or an interface between the core layer and the weldable inner layer will tear along the weld. If the weld does not extend directly to an edge of the film tear-open packaging, the weldable layer breaks on both sides of the weld.

We claim: 
     
         1 . In a tear-open packaging formed by a pair of plastic film panels having inner faces joined together by a weld, the improvement wherein:
 one of the film panels is formed by a three-layer coextrusion having a nonsticky foam core layer sandwiched between an outer layer and a weldable inner layer, the weldable inner layer being turned toward the other film and secured by the weld directly to the inner face of the other film panel, the strength of the core layer and of the bond between the core layer and inner and outer layers being such that, when the two panels are pulled away from each other, the core layer or an interface between the core layer and the weldable inner layer will tear.   
     
     
         2 . The tear-open packaging defined in  claim 1 , wherein the inner layer is of low-density polyethylene. 
     
     
         3 . The tear-open packaging defined in  claim 1 , wherein the inner layer has a thickness between 3 μm and 10 μm. 
     
     
         4 . The tear-open packaging defined in  claim 1 , wherein the other film panel is a foam tray. 
     
     
         5 . In a tear-open packaging formed by a pair of plastic film panels having inner faces joined together by a weld, the improvement wherein:
 one of the film panels is formed by a two-layer coextrusion having a nonsticky foam layer laminated to an outer cover layer, the foam layer the inner face of the respective panel that is turned toward the other film and secured by the weld directly to the inner face of the other film panel, the strength of the foam layer and of the bond between the foam layer and the outer cover layer and the weld being such that, when the two panels are pulled away from each other, the foam layer or an interface between the foam layer and the weld will tear.   
     
     
         6 . The tear-open packaging defined in  claim 5 , wherein the other film layer is also formed by a nonsticky foam layer laminated to an outer cover layer and the weld lies between the foam layers. 
     
     
         7 . The tear-open packaging defined in  claim 5 , further comprising:
 an outer cover layer on an outer face of the foam layer.   
     
     
         8 . The tear-open packaging defined in  claim 5 , wherein the coextrusion is at least 50% by weight of polyolefin. 
     
     
         9 . The tear-open packaging defined in  claim 8 , wherein the polyolefin is polyethylene. 
     
     
         10 . The tear-open packaging defined in  claim 5 , wherein the outer cover layer is of low-density polyethylene. 
     
     
         11 . The tear-open packaging defined in  claim 5 , wherein the foam layer is at least 50% by weight polyolefin. 
     
     
         12 . The tear-open packaging defined in  claim 5 , wherein the foam layer has a density between 0.1 g/cm 3  and 0.8 g/cm 3 . 
     
     
         13 . The tear-open packaging defined in  claim 5 , wherein the foam layer has cells filled with nitrogen. 
     
     
         14 . The tear-open packaging defined in  claim 5 , wherein the foam layer includes between 10% by weight and 30% by weight particles. 
     
     
         15 . The tear-open packaging defined in claim wherein the coextrusion has a thickness between 20 μm and 250 μm.