Low shrink force shrink film

Abstract

The multilayer shrink film of the present invention provides very low shrink tension approximating some PVC films, while providing relatively high free shrink characteristics and relatively low shrink temperatures. The preferred film has three layers including a relatively thick core layer comprising a polymeric material or blend of polymeric materials having a relatively low melting point, typically less than about 100° C., two outer layers comprising a polymeric material or blend of polymeric materials having a relatively high melting point, typically greater than about 100° C., the material of the outer layers having a melting point at least about 10° C. higher than the melting point of the material of the core layer.

1. A multilayer shrink film comprising:
 (a) a core layer comprising a polymeric material or blend of polymeric materials having an olefin component and a relatively low melting point; and    (b) two outer layers comprising a polymeric material or blend of polymeric materials comprising 
 (i) an olefin component or  
 (ii) a polyester, and  
 having a relatively high melting point;  
   wherein said film has a maximum average machine direction shrink tension of no more than about 300 pounds per square inch, and a maximum average transverse direction shrink tension of no more than about 300 pounds per square inch, said shrink tension values as measured by ASTM D 2838; and    wherein the material of the outer layer has a melting point at least about 10° C. higher than the melting point of the material of the core layer.    
     
     
       2. A multilayer shrink film according to  claim 1  wherein the two outer layers are each derived from a blend of two linear low density polyethylene resins. 
     
     
       3. A multilayer shrink film according to  claim 1  wherein the core layer comprising a polymeric material selected from the group consisting of:
 (a) ethylene vinyl acetate copolymer;    (b) very low density polyethylene;    (c) ethylene butyl acrylate copolymer;    (d) ethylene methyl acrylate copolymer; and    (e) blends of these materials.    
     
     
       4. A multilayer shrink film according to  claim 3  wherein the core layer comprises an ethylene vinyl acetate copolymer having between about 5% and about 20% by weight of vinyl acetate. 
     
     
       5. A multilayer shrink film according to  claim 3  wherein the core layer comprises a blend of ethylene vinyl acetate copolymer, ethylene butyl acrylate copolymer, and mineral oil. 
     
     
       6. A multilayer shrink film according to  claim 1  wherein the core layer comprises between about 40% and 95% of the total film structure. 
     
     
       7. A multilayer shrink film according to  claim 1  wherein the outer layers each comprise a polymeric material selected from the group consisting of:
 (a) polyester;    (b) linear low density polyethylene;    (c) low density polyethylene;    (d) high density polyethylene;    (e) polypropylene; and    (f) ethylene propylene copolymer.    
     
     
       8. A multilayer shrink film according to  claim 1  wherein the film layers are cross-linked. 
     
     
       9. A multilayer shrink film according to  claim 1  wherein the shrink tension of the film is substantially controlled by the core layer. 
     
     
       10. A multilayer shrink film comprising:
 (a) a core layer comprising a polymeric material or blend of polymeric materials having an olefin component and a relatively low melting point; and    (b) two outer layers comprising a polymeric material or blend of polymeric materials comprising 
 (i) an olefin component or  
 (ii) a polyester, and  
 having a relatively high melting point;  
   wherein said film has a maximum average machine direction free shrink at 205° F. of at least about 20% and an average transverse direction free shrink at 205° F. of at least about 20%, said free shrink values as measured by ASTM D 2732; and    wherein the material of the outer layer has a melting point at least about 10° C. higher than the melting point of the material of the core layer.    
     
     
       11. A multilayer shrink film according to  claim 10  wherein the two outer layers each comprise a blend of two linear low density polyethylene resins. 
     
     
       12. A multilayer shrink film according to  claim 10  wherein the core layer comprises a polymeric material selected from the group consist of:
 (a) ethylene vinyl acetate copolymer;    (b) very low density polyethylene;    (c) ethylene butyl acrylate copolymer; and    (d) ethylene methyl acrylate copolymer; and    (e) blends of these materials.    
     
     
       13. A multilayer shrink film according to  claim 12  wherein the core layer comprises an ethylene vinyl acetate copolymer having between about 5% and about 20% by weight of vinyl acetate. 
     
     
       14. A multilayer shrink film according to  claim 12  wherein the core layer comprises a blend of ethylene vinyl acetate copolymer, ethylene butyl acrylate copolymer, and mineral oil. 
     
     
       15. A multilayer shrink film according to  claim 12  wherein the core layer comprises between about 40% and 95% of the total film structure. 
     
     
       16. A multilayer shrink film according to  claim 12  wherein the outer layers each comprise a polymeric material selected from the group consisting of:
 (a) a polyester;    (b) linear low density polyethylene;    (c) low density polyethylene;    (d) high density polyethylene;    (e) polypropylene; and    (f) ethylene propylene copolymer.    
     
     
       17. A multilayer shrink film according to  claim 12  wherein the film layer are cross-linked. 
     
     
       18. A multilayer shrink film according to  claim 12  wherein the free shrink of the film is substantially controlled by the core layer. 
     
     
       19. A multilayer shrink film comprising:
 ( a )  a single core layer comprising a blend of about  50   %  by weight or more ethylene vinyl acetate copolymer, and up to about  50   %  by weight very low density polyethylene; and      ( b )  two outer layers comprising a polymeric material or blend of polymeric materials comprising  
 ( i )  an olefin component or    
 ( ii )  a polyester, and    
     having a relatively high melting point;        wherein said film has a maximum average machine direction shrink tension at  205 ° F. of no more than about  300  pounds per square inch, and a maximum average transverse direction shrink tension at  205 ° F. of no more than about  300  pounds per square inch, said shrink tension values as measured by ASTM D  2838 ; and        wherein the material of the outer layer has a melting point at least about  10 ° C. higher than the melting point of the material of the core layer.      
     
     
       20. The multilayer shrink film of  claim 19  wherein the core layer comprises about  80 %  by weight ethylene vinyl acetate copolymer and about  20   %  by weight very low density polyethylene.    
     
     
       21. The multilayer shrink film of  claim 19  wherein at least one of the outer layers comprises linear low density polyethylene.  
     
     
       22. The multilayer shrink film of  claim 19  wherein both outer layers comprise linear low density polyethylene.  
     
     
       23. A multilayer shrink film comprising:
 ( a )  a single core layer comprising greater than  75   % , by weight of the core layer, of an ethylene vinyl acetate copolymer; and      ( b )  two outer layers comprising a polymeric material or blend of polymeric materials comprising  
 ( i )  an olefin component or    
 ( ii )  a polyester, and    
     having a relatively high melting point;        wherein said film has a maximum average machine direction free shrink at  205 ° F. of at least about  20   %  and an average transverse direction free shrink at  205 ° F. of at least about  20   % , said free shrink values as measured by ASTM D  2732 ;        wherein the material of the outer layer ha a melting point at least about  10 ° C. higher than the melting point of the material of the core layer.      
     
     
       24. A multilayer shrink film according to  claim 23  wherein the two outer layers are each derived from a blend of two linear low density polyethylene resins.  
     
     
       25. A multilayer shrink film according to  claim 23  wherein the core layer further comprises a polymeric material selected from the group consisting of:
 ( a )  very low density polyethylene;      ( b )  ethylene butyl acrylate copolymer;      ( c )  ethylene methyl acrylate copolymer; and      ( d )  blends of these materials.      
     
     
       26. A multilayer shrink film according to  claim 23  wherein the core layer comprises an ethylene vinyl acetate copolymer having between about  5 %  and about  20   %  by weight of vinyl acetate.    
     
     
       27. A multilayer shrink film according to  claim 23  wherein the core layer comprises a blend of ethylene vinyl acetate copolymer, ethylene butyl acrylate copolymer, and mineral oil.  
     
     
       28. A multilayer shrink film according to  claim 23  wherein the outer layers each comprise a polymeric material selected from the group consisting of:
 ( a )  polyester;      ( b )  linear low density polyethylene;      ( c )  low density polyethylene;      ( d )  high density polyethylene;      ( e )  polypropylene; and      ( f )  ethylene propylene copolymer.      
     
     
       29. A multilayer shrink film according to  claim 23  wherein the film layers are cross- linked.    
     
     
       30. A multilayer shrink film comprising:
 ( a )  a single core layer comprising a blend of about  75   %  by weight ethylene vinyl acetate copolymer, and about  25   %  by weight ethylene butyl acrylate copolymer; and      ( b )  two outer layers comprising a polymeric material or blend of polymeric materials comprising  
 ( i )  an olefin component or    
 ( ii )  a polyester, and    
     having a relatively high melting point;        wherein said film has a maximum average machine direction shrink tension at  205 ° F. of no more than about  300  pounds per square inch, and a maximum average transverse direction shrink tension at  205 ° F. of no more than about  300  pounds per square inch, said shrink tension values as measured by ASTM D  2838 ; and        wherein the material of the outer layer has a melting point at least about  10 ° C. higher than the melting point of the material of the core layer.      
     
     
       31. A multilayer shrink film comprising:
 ( a )  a single core layer comprising a blend of about  75   % , by weight of the core layer, of an ethylene vinyl acetate copolymer; and      ( b )  two outer layers comprising a polymeric material or blend of polymeric materials comprising  
 ( i )  an olefin component or    
 ( ii )  a polyester, and    
     having a relatively high melting point;        wherein said film has a maximum average machine direction shrink tension at  205 ° F. of no more than about  300  pounds per square inch, and a maximum average transverse direction shrink tension at  205 ° F. of no more than about  300  pounds per square inch, said shrink tension values as measured by ASTM D  2838 ;        wherein the material of the outer layer has a melting point at least about  10 ° C. higher than the melting point of the material of the core layer.      
     
     
       32. A multilayer shrink film according to  claim 31  wherein the two outer layers are each derived from a blend of two linear low density polyethylene resins.  
     
     
       33. A multilayer shrink film according to  claim 31  wherein the core layer further comprises a polymeric material selected from the group consisting of:
 ( a )  very low density polyethylene;      ( b )  ethylene butyl acrylate copolymer;      ( c )  ethylene methyl acrylate copolymer; and      ( d )  blends of these materials.      
     
     
       34. A multilayer shrink film according to  claim 31  wherein the core layer comprises an ethylene vinyl acetate copolymer having between about  5 %  and about  20   %  by weight of vinyl acetate.    
     
     
       35. A multilayer shrink film according to  claim 31  wherein the core layer comprises a blend of ethylene vinyl acetate copolymer, ethylene butyl acrylate copolymer, and mineral oil.  
     
     
       36. A multilayer shrink film according to  claim 31  wherein the outer layers each comprise a polymeric material selected from the group consisting of:
 ( a )  polyester;      ( b )  linear low density polyethylene;      ( c )  low density polyethylene;      ( d )  high density polyethylene;      ( e )  polypropylene; and      ( f )  ethylene propylene copolymer.      
     
     
       37. A multilayer shrink film according to  claim 31  wherein the film layers are cross- linked.