Multi-layer hermetically sealable film

Abstract

A thermoplastic multi-layer film for forming hermetic seals on packages comprising layer A comprising polyethylene, layer B comprising polypropylene, layer C comprising a copolymer, and an adhesion promoting coating applied to layer C.

What is claimed is:  
     
         1 . A thermoplastic multi-layer film for forming hermetic seals on packages comprising: 
 (a) layer A comprising polyethylene;    (b) layer B comprising polypropylene;    (c) layer C comprising a copolymer; and    (d) an adhesion promoting coating applied to layer C.    
     
     
         2 . The film of  claim 1 , wherein the copolymer of layer C is selected from the group consisting of ethylene-propylene copolymer, ethylene-propylene-butene-1 terpolymer, propylene-butene copolymer, and mixtures thereof.  
     
     
         3 . The film of  claim 1 , wherein the layer C thickness is from about 4 microns to about 10 microns.  
     
     
         4 . The film of  claim 1 , wherein the thickness of the film is from about 17 microns to about 63 microns.  
     
     
         5 . The film of  claim 1 , wherein the thickness of the film is from about 17 microns to about 63 microns; the layer C thickness is from about 4 microns to about 10 microns; the layer B thickness is from about 10 microns to about 50 microns; and the layer A thickness is from about 0.5 micron to about 3 microns.  
     
     
         6 . The film of  claim 1 , wherein the film is biaxially oriented.  
     
     
         7 . The film of  claim 1 , wherein the film is uniaxially oriented.  
     
     
         8 . The film of  claim 1 , wherein the film is hermetically sealable in a machine for making packaging bags with a combination of a fin seal and crimp seals or a combination of a lap seal and crimp seals.  
     
     
         9 . The film of  claim 1 , wherein layer A is metallized.  
     
     
         10 . The film of  claim 1 , wherein the adhesion promoting coating comprises a polyethylene acrylic acid.  
     
     
         11 . The film of  claim 10 , wherein the adhesion promoting coating has a weight from about 0.6 gms./msi to about 0.7 gms./msi.  
     
     
         12 . The film of  claim 1 , wherein the adhesion promoting coating comprises a polyvinylidene chloride.  
     
     
         13 . The film of  claim 12 , wherein the adhesion promoting coating has a weight from about 1.5 gms./msi to about 2.6 gms./msi.  
     
     
         14 . The film of  claim 1 , wherein the layer A comprises high density polyethylene.  
     
     
         15 . The film of  claim 1 , wherein the layer A comprises medium density polyethylene.  
     
     
         16 . The film of  claim 1  further comprising a coating applied to layer A.  
     
     
         17 . The film of  claim 16  wherein the coating applied to layer A is an acrylic coating.  
     
     
         18 . A thermoplastic multi-layer film for forming hermetic seals on packages comprising: 
 (a) layer A comprising polyethylene having a first side and a second side;    (b) layer B comprising polypropylene having a first side and a second side, wherein the first side of layer B is adjacent to the second side of layer A;    (c) layer C comprising a copolymer having a first side and a second side, wherein the first side of layer C is adjacent to the second side of layer B; and    (d) an adhesion promoting coating applied to the second side of layer C.    
     
     
         19 . A method of producing a thermoplastic multi-layer film comprising the steps of: 
 (a) coextruding a first layer comprising polyethylene; a second layer comprising polypropylene; and a third layer comprising a copolymer;    (b) coating said third layer wherein said coating comprises an adhesion promoting coating.    
     
     
         20 . The method of  claim 19  further comprising the step of orienting said film in the machine direction at an elevated temperature;  
     
     
         21 . The method of  claim 20  further comprising the step of orienting said film in the transverse direction at an elevated temperature.  
     
     
         22 . The method of  claim 19  further comprising the step of coating said first layer wherein said coating comprises an acrylic coating.  
     
     
         23 . The method of  claim 19  further comprising the step of corona treating said third layer.  
     
     
         24 . The method of  claim 19  further comprising the step of flame treating said third layer.  
     
     
         25 . The method of  claim 19  further comprising the step of plasma treating said third layer.  
     
     
         26 . The method of  claim 19  wherein the coating step is a reverse direct gravure coating process.  
     
     
         27 . The method of  claim 19  wherein the film produced has a MST below 170 degrees fahrenheit.  
     
     
         28 . The film of  claim 1  wherein the film has a MST below 170 degrees fahrenheit.