Multilayer heat shrinkable film comprising styrene polymer or a blend of styrene polymers

Abstract

The present invention provides a multilayer heat shrinkable film incorporating an oxygen barrier material and layer comprising a styrene polymer or blend of styrene polymers, where the shrinkage of the film in at least one of MD, TD is at least 30% at 90° C. The invention is further directed to a method of manufacturing a bag from said multilayer heat shrinkable film.

1 . A five-layer heat shrinkable oxygen barrier film comprising:
 a) an outer layer consisting essentially of a styrene amorphous copolymer;   b) a first bonding layer adjacent to the outer layer, the first bonding layer consisting essentially of a blend of ethylene methyl acrylate copolymer, ethylene vinyl acetate copolymer, and metallocene-catalyzed linear low density polyethylene;   c) a barrier core layer adjacent to the first bonding layer, the barrier core layer consisting essentially of an oxygen barrier polymer;   d) a second bonding layer adjacent to the barrier core layer, the second bonding layer consisting essentially of a blend of ethylene methyl acrylate copolymer, ethylene vinyl acetate copolymer, and metallocene-catalyzed linear low density polyethylene; and   e) an inner sealing layer adjacent to the second bonding layer, the inner sealing selected from the group consisting of an ethylene vinyl acetate copolymer, a very low density polyethylene, a plastomer, and blends thereof,   
       wherein the heat shrinkable, oxygen barrier film has a shrinkage in at least one direction of at least 30% at a temperature of 90° C., and an oxygen transmission rate less than about 20 cc/liter-m2/24 hrs/atm, measured at 23° C. and 75% relative humidity. 
     
     
         2 . The film as recited in  claim 1 , wherein the styrene amorphous copolymer has a styrene content exceeding 50% by weight of the copolymer. 
     
     
         3 . The film as recited in  claim 1 , wherein the styrene amorphous copolymer comprises styrene and butadiene. 
     
     
         4 . The film as recited in  claim 1 , wherein the styrene amorphous copolymer comprises styrene and isoprene. 
     
     
         5 . The film as recited in  claim 1 , wherein the styrene amorphous copolymer comprises styrene and ethylene. 
     
     
         6 . The film as recited in  claim 1 , wherein the oxygen barrier polymer comprises a vinylidene chloride copolymer. 
     
     
         7 . The film as recited in  claim 6 , wherein the vinylidene chloride copolymer comprises vinylidene chloride and vinyl chloride. 
     
     
         8 . The film as recited in  claim 6 , wherein the vinylidene chloride copolymer comprises vinylidene chloride and methyl acrylate. 
     
     
         9 . The film as recited in  claim 1 , wherein the oxygen barrier polymer comprises a polyamide. 
     
     
         10 . The film as recited in  claim 1 , wherein the oxygen barrier polymer comprises ethylene vinyl alcohol. 
     
     
         11 . The film as recited in  claim 1 , wherein the inner sealing layer comprises a plastomer having a density less than about 0.905 grams/cm3. 
     
     
         12 . The film as recited in  claim 11 , wherein the plastomer is metallocene-catalyzed. 
     
     
         13 . The film as recited in  claim 11 , wherein the inner sealing layer further comprises an ethylene vinyl acetate copolymer. 
     
     
         14 . The film as recited in  claim 11 , wherein the inner sealing layer further comprises very low density polyethylene. 
     
     
         15 . The film as recited in  claim 1 , wherein the film is formed as a tubular article. 
     
     
         16 . The film as recited in  claim 1 , wherein the film is formed as a flat sheet. 
     
     
         17 . The film as recited in  claim 1 , wherein the film is formed as a bag. 
     
     
         18 . The film as recited in  claim 1 , wherein the film is irradiated. 
     
     
         19 . The film as recited in  claim 1 , wherein the barrier core layer has a thickness between about 0.1 mils and about 0.5 mils. 
     
     
         20 . The film as recited in  claim 1 , wherein the inner sealing layer has a thickness between about 0.4 mils and about 2.0 mils. 
     
     
         21 . The film as recited in  claim 1 , having a shrinkage of at least 30% in at least two directions at a temperature of 90° C. 
     
     
         22 . A multi-layer film comprising:
 an abuse layer comprising styrene-butadiene block copolymer;   a first tie layer adjacent the abuse layer comprising ethylene vinyl acetate;   a gas barrier layer adjacent the first tie layer comprising polyvinylidene chloride;   a second tie layer adjacent the gas barrier layer comprising ethylene vinyl acetate; and   a sealant layer adjacent the second tie layer comprising a metallocene-catalyzed polymer,   
       wherein the metallocene-catalyzed polymer is at least one of selected from linear low density polyethylene and or ultra low density polyethylene, and 
       wherein the film is heat shrinkable and shrinks at temperatures between about 75° C. and about 90° C. 
     
     
         23 . The film as recited in  claim 22 , wherein the thickness of the abuse layer comprises about 11% to about 12% of total film thickness. 
     
     
         24 . The film as recited in  claim 23 , wherein the thickness of the first tie layer comprises about 5% to about 15%, the thickness of the gas barrier layer comprises about 5% to about 15%, the thickness of the second tie layer comprises about 35% to about 55%, and the thickness of the sealant layer comprises about 5% to about 15%, each based on the total film thickness. 
     
     
         25 . The film as recited in  claim 24 , wherein the abuse layer is about 12%, the first tie layer is about 14%, the gas barrier layer is about 9%, the second tie layer is about 54%, and the sealant layer is about 11%, based on total film thickness. 
     
     
         26 . The film as recited in  claim 22 , wherein the film has a total thickness of about 1.5 mils to about 2.5 mils. 
     
     
         27 . The film as recited in  claim 22 , wherein the styrene-butadiene block copolymer comprises about 75 wt % polystyrene based on the total weight of the polystyrene and butadiene. 
     
     
         28 . The film as recited in  claim 22 , wherein the first tie layer and the second tie layer, independently, have a density of between about 0.92 g/cm 3  and about 0.98 g/cm 3 . 
     
     
         29 . The film as recited in  claim 28 , wherein the density of each tie layer is about 0.942 g/cm 3 . 
     
     
         30 . The film as recited in  claim 22 , wherein the metallocene-catalyzed sealant comprises metallocene-catalyzed linear low density polyethylene.