Thermoformable barrier films

Abstract

The invention relates to a thermoformable multilayer foil encompassing at least one polyolefin layer based on a thermoplastic polyolefin, olefin copolymer, or mixture of these, and at least one gas-barrier layer, where the oxygen transmission of the multilayer foil is at most 0.5 cm 3 m −2 d −1 bar −1 .

1 . A thermoformable multilayer foil encompassing at least one polyolefin layer based on a thermoplastic polyolefin, olefin copolymer, or mixture of these, and at least one gas-barrier layer, where the oxygen transmission of the multilayer foil is at most 0.5 cm 3  m −2  d −1  bar −1 .  
     
     
         2 . The multilayer foil as claimed in  claim 1 , which encompasses 
 n gas-barrier layers B i , where i=from 1 to n; and    n+1 polyolefin layers P i , where i=from 1 to n+1,    where    n=1, 2, 3, 4, or 5;    the polyolefin layers, respectively identical or different, are based on a thermoplastic polyolefin, olefin copolymer, or mixture of these; and    for a given i, the gas-barrier layer B i  has been arranged between the polyolefin layers P i  and P i+1 .    
     
     
         3 . The multilayer foil as claimed in  claim 1  or  2 , wherein the gas-barrier layer or gas-barrier layers, respectively identical or different, are based on ethylene-vinyl alcohol copolymer.  
     
     
         4 . The multilayer foil as claimed in  claim 2  or  3 , wherein n>1,  
       where 
 the total of the layer thicknesses of the gas-barrier layers is at least 20 μm; and/or  
 for a given i, the layer thickness of the gas-barrier layer B i  deviates by at most 5 μm from the layer thickness of the gas-barrier layer B i+1 .  
 
     
     
         5 . The multilayer foil as claimed in any of  claims 2  to  4 , which has a protective layer S which forms at least one of the two surface layers of the multilayer foil, where the protective layer S 
 is based on a thermoplastic polyolefin, olefin copolymer, or mixture of these; and/or    has a layer thickness of at least 100 μm; and/or    comprises a filler.    
     
     
         6 . The multilayer foil as claimed in any of  claims 2  to  5 , wherein the polyolefin layer P 1  or the polyolefin layer P n+1  forms a surface layer of the multilayer foil and, if appropriate, is heat-sealable.  
     
     
         7 . The multilayer foil as claimed in any of  claims 2  to  6 , which encompasses n intermediate layers Z i , where i=from 1 to n, and n intermediate layers Z i ′, where i=from 1 to n, where, for a given i, the gas-barrier layer B i , on its side facing toward the polyolefin layer P i , directly adjoins the intermediate layer Z i , and on its side facing the polyolefin layer P i+1  directly adjoins the intermediate layer Z i ′.  
     
     
         8 . The multilayer foil as claimed in  claim 7 , wherein the intermediate layers, respectively identical or different, are based on a polyamide, copolyamide, or mixture of these.  
     
     
         9 . The multilayer foil as claimed in  claim 7  or  8 , wherein, for a given i, the ratio of the layer thickness of the intermediate layer Z i  and/or of the intermediate layer Z i ′ to the layer thickness of the gas-barrier layer B i  is respectively in the range from 3:1 to 1:7.  
     
     
         10 . The multilayer foil as claimed in any of  claims 7  to  9 , which encompasses n adhesion-promoter layers H i , where i=from 1 to n, and n adhesion-promoter layers H i ′, where i=from 1 to n, where, for a given i, the adhesion-promoter layer H i  has been arranged between the polyolefin layer P i  and the intermediate layer Z i  and the adhesion-promoter layer H i ′ has been arranged between the intermediate layer Z i ′ and the polyolefin layer P i+1 .  
     
     
         11 . The multilayer foil as claimed in any of the preceding claims, wherein, after deep-draw thermoforming with a deep-draw thermoforming ratio of 1:3, any amount by which the oxygen transmission in the region subjected to deep-draw thermoforming is smaller than that in the regions not subjected to deep-draw thermoforming is at most 25%.  
     
     
         12 . The multilayer foil as claimed in any of the preceding claims, whose total layer thickness is at least 150 μm.  
     
     
         13 . A packaging tray encompassing a thermoformed multilayer foil as claimed in any of  claims 1  to  12 .  
     
     
         14 . The packaging tray as claimed in  claim 13 , which has an oxygen transmission of at most 0.5 cm 3  m −2  d −1  bar −1  not only in the thermoformed regions but also in the non-thermoformed regions.  
     
     
         15 . A packaging encompassing a packaging tray as claimed in  claim 13  or  14 .  
     
     
         16 . The packaging as claimed in  claim 15 , wherein the packaging tray has been sealed by a lid foil, and the interior space formed by packaging tray and lid foil in the packaging is at subatmospheric pressure.  
     
     
         17 . The packaging as claimed in  claim 16 , wherein the lid foil has been metallized.  
     
     
         18 . The packaging as claimed in  claim 16  or  17 , wherein the lid foil encompasses a plurality of layers of which at least one is based on a polyester, copolyester, or mixture of these.  
     
     
         19 . A transport container encompassing a packaging as claimed in any of  claims 15  to  18 .