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 multilayer heat shrinkable film comprising at least 
 a) a layer comprising an oxygen barrier material, and    b) a layer comprising a styrene polymer or a blend of styrene polymers,    where the film has a machine direction and a transverse direction and the shrinkage of the film in at least one of the machine direction or the transverse direction is at least 30% at 90° C.    
     
     
         2 . The multilayer heat shrinkable film of  claim 1 , wherein a layer of the multilaver film is an outer layer and the layer comprising the styrene polymer or the blend of styrene polymers is the outer layer of the film.  
     
     
         3 . The multilayer heat shrinkable film of  claim 1 , wherein between the layer comprising the styrene polymer or blend of styrene polymers and the barrier layer a bonding layer exists.  
     
     
         4 . The multilayer heat shrinkable film of  claim 3 , wherein the bonding layer contains ethylene ester copolymers or ethylene alpha olefin copolymers.  
     
     
         5 . The multilayer heat shrinkable film of  claim 1 , wherein the styrene polymer or the blend of styrene polymers is chosen from one or more of a styrene homopolymer or copolymer or terpolymer.  
     
     
         6 . The multilayer heat shrinkable film of  claim 1 , wherein at least one layer comprises a cycloolefin copolymer or a blend of cycloolefin copolymer and alpha olefin copolymer.  
     
     
         7 . The multilayer heat shrinkable film of  claim 1 , wherein the film additionally contains a heat sealable inner layer.  
     
     
         8 . The multilayer heat shrinkable film of  claim 7 , wherein the heat sealable inner layer comprises a heat sealable thermoplastic polymer or polymer blend.  
     
     
         9 . The multilayer heat shrinkable film of  claim 8 , wherein the heat sealable inner layer comprises alpha olefins.  
     
     
         10 . The multilayer heat shrinkable film of  claim 8 , wherein the heat sealable inner layer comprises a styrene copolymer or polypropylene, ethylene-propylene copolymer or an ionomer.  
     
     
         11 . The multilayer heat shrinkable film of  claim 2 , wherein the outer layer comprises a styrene copolymer in a blend with a slip agent.  
     
     
         12 . The multilayer heat shrinkable film of  claim 1 , wherein the styrene copolymer is one or more of SBC (styrene butadiene copolymers), SBS copolymers, SIS copolymers, SEBS copolymers, Ethylene Styrene interpolymers.  
     
     
         13 . The multilayer heat shrinkable film of  claim 1 , wherein the styrene content in one or more of the styrene polymer, copolymer or terpolymer is more than 50% by weight.  
     
     
         14 . The multilayer heat shrinkable film of  claim 1 , wherein the oxygen transmission rate through the entire multilayer film is below about 20 cc/l m 2 /24 hrs/atm.  
     
     
         15 . The multilayer heat shrinkable film of  claim 1 , wherein the oxygen barrier layer comprises polyamides (Nylon), hydrolyzed ethylene vinyl acetate copolymer (EVOH) or a vinylidene copolymer.  
     
     
         16 . The multilayer heat shrinkable film of  claim 7 , wherein the thickness of the heat sealable inner layer is between about 0.4 mils and about 2.0 mils.  
     
     
         17 . The multilayer heat shrinkable film of  claim 1 , wherein the barrier layer thickness is between about 0.1 mils to about 0.5 mils.  
     
     
         18 . The multilayer heat shrinkable film of  claim 1 , wherein one or more of the layers of the film additionally contain one or more film additives.  
     
     
         19 . The multilayer heat shrinkable film of  claim 1 , wherein the heat shrinkable multilayer film is in the form of a tubular article, flat sheets or bag.  
     
     
         20 . The multilayer heat shrinkable film of  claim 1 , wherein the multilayer heat shrinkable film is irradiated.  
     
     
         21 . The multilayer heat shrinkable film of  claim 1 , which comprises the following components: 
 a) an outer layer of a styrene amorphous copolymer;    b) an adjacent layer of a blend of EMA copolymer, EVA copolymer and metallocene LLDPE;    c) a barrier core layer comprising PVDC copolymer;    d) an adjacent layer of EVA copolymer or EMA copolymer, EVA copolymer and metallocene LLDPE; and    e) an inner sealing layer comprising EVA, VLDPE, or a plastomer or a blend thereof.    
     
     
         22 . The multilayer heat shrinkable film of  claim 9 , wherein the alpha olefin is a member of the polyethylene family.  
     
     
         23 . The multilayer heat shrinkable film of  claim 9 , wherein the alpha olefin is selected from the group consisting of linear low-density polyethylene (LLDPE), very low and ultra low density polyethylene (VLDPE and ULDPE respectively), plastomers and blends and copolymers thereof.  
     
     
         24 . The multilayer heat shrinkable film of  claim 8  wherein the heat sealable inner layer comprises a cycloolefin copolymer or a blend of a cycloolefin copolymer and alpha olefin copolymer, or ethylene vinyl acetate, plastomers, copolymers or blends thereof.  
     
     
         25 . A method for manufacturing a bag from a multilayer shrinkable film of  claim 1 , comprising the steps of: 
 a) forming a bag, in which the inner layer of the film forms the inside portion of the bag while the outer layer of the film forms the outside portion of the bag, wherein said film is the multilayer heat shrinkable film of  claim 1;     b) inserting a good to be packaged into the bag; and    c) sealing the bag by hot bar or impulse sealing.    
     
     
         26 . The multilayer heat shrinkable film of  claim 5 , wherein the styrene content in one or more of the styrene polymer, copolymer or terpolymer is more than 50% by weight.  
     
     
         27 . The multilayer heat shrinkable film of  claim 15 , wherein the vinylidene copolymer comprises one or more of vinylidene chloride-vinyl chloride (PVDC) or vinylidene chloride-methyl acrylate copolymer (MA-VDC).  
     
     
         28 . The multilayer heat shrinkable film of  claim 18 , wherein the one or more film additives comprise one or more of slip agents, antiblocking agents, colorants, odor inhibitors or oxygen inhibitors.