Thermoformable packaging film

Abstract

This invention is directed to a thermoformable film comprising a composite structure of at least three layers firmly adhered to one another, a top and bottom layer and an inner layer; wherein the top and bottom layer of the composite structure comprise a film layer of an ethylene vinyl acetate copolymer comprising 1 to 25% by weight, based on the weight of the copolymer, of a polymerized vinyl acetate and 75 to 99% by weight, based on the weight of the copolymer, of polymerized ethylene and the inner layer of the composite structure comprises a film of a polymer blend of the following: (a) 40 to 95% by weight, based on the weight of the polymer blend, of an ethylene based copolymer comprises repeating polymerized units of (1) at least 50% by weight, based on the weight of the copolymer, of ethylene, (2) 1 to 30% by weight, based on the weight of the copolymer, of acrylic acid or methacrylic acid; and (3) up to 40% by weight, based on the weight of the copolymer, of an alkyl acrylate or an alkyl methacrylate,  wherein the copolymer has 5 to 100% of the acid groups neutralized with metal ion selected from the following group: zinc, magnesium, sodium and lithium; and (b) 5 to 60% by weight, based on the weight of the polymer blend, of a metallocene catalyzed polyethylene; other thermoformable film constructions, such as, a 2 layer construction and constructions greater than 3 layers, such as 5 layers, and a mono layer of the film of a blend of the ethylene based copolymer and the metallocene catalyzed polyethylene also are part of this invention.

1 . A thermoformable film comprising a composite structure comprising at least three layers firmly adhered to one another, a top and bottom layer and an inner layer; 
 wherein the top and bottom layer of the composite structure comprise a film layer of ethylene-vinyl acetate copolymer consisting essentially of 1 to 25% by weight, based on the weight of the copolymer, of a polymerized vinyl acetate and 75 to 99% by weight, based on the weight of the copolymer, of polymerized ethylene and the inner layer of the composite structure comprises a film of a polymer blend consisting essentially of    (a) 40 to 95% by weight, based on the weight of the polymer blend, of an ethylene based copolymer consisting essentially of repeating polymerized units of 
 (1) at least 50% by weight, based on the weight of the copolymer, of ethylene,  
 (2) 1 to 30% by weight, based on the weight of the copolymer, of acrylic acid or methacrylic acid; and  
 (3)up to 40% by weight, based on the weight of the copolymer, of an alkyl acrylate or an alkyl methacrylate,  
    wherein the copolymer has 5 to 100% of the acid groups neutralized with metal ion selected from the group consisting of zinc, magnesium, sodium and lithium; and    (b) 5 to 60% by weight, based on the weight of the polymer blend, of a metallocene catalyzed linear polyethylene.    
   
   
       2 . The thermoformable film of  claim 1  having a total thickness of 25-500 microns and wherein the top layer comprises 10-40% of the total thickness, the inner layer comprises 20-80% of the total thickness and the bottom layer comprises 10-40% of the total thickness.  
   
   
       3 . The thermoformable film of  claim 2  wherein ethylene-vinyl acetate copolymer of the top and bottom layer consists essentially of 2 to 15% by weight of polymerized vinyl acetate and 85 to 98% by weight of polymerized ethylene and has a melt index of 0.1 to 50 g/10 minutes determined according to ASTM D 1238 Condition E.  
   
   
       4 . The thermoformable film of  claim 1  wherein the inner layer consists essentially of a polymer blend of 65-85% by weight, based on the weight of the polymer blend of an ethylene based copolymer and 15-35% by weight, based on the weight of the polymer blend, of a metallocene catalyzed polyethylene.  
   
   
       5 . The thermoformable film of  claim 4  in which the metallocene catalyzed polyethylene is selected from the group consisting of linear high density polyethylene, linear medium density polyethylene, linear low density polyethylene and linear ultra low density polyethylene.  
   
   
       6 . (canceled)  
   
   
       7 . (canceled)  
   
   
       8 . A thermoformable film comprising a composite structure comprising two layers firmly adhered to one another, a top and bottom layer; 
 wherein the top layer of the composite structure comprise a film layer of ethylene-vinyl acetate copolymer consisting essentially of 1 to 25% by weight, based on the weight of the copolymer, of a polymerized vinyl acetate and 75 to 99% by weight, based on the weight of the copolymer, of polymerized ethylene and the bottom layer of the composite structure comprises a film of a polymer blend consisting essentially of    (a) 40 to 95% by weight, based on the weight of the polymer blend, of an ethylene based copolymer consisting essentially of repeating polymerized units of 
 (1) at least 50% by weight, based on the weight of the copolymer, of ethylene,  
 (2) 1 to 30% by weight, based on the weight of the copolymer, of acrylic acid or methacrylic acid; and  
 (3) up to 40% by weight, based on the weight of the copolymer, of an alkyl acrylate or an alkyl methacrylate,  
    wherein the copolymer has 5 to 100% of the acid groups neutralized with metal ion selected from the group consisting of zinc, magnesium, sodium and lithium; and    (b) 5 to 60% by weight, based on the weight of the polymer blend, of a metallocene catalyzed linear polyethylene.    
   
   
       9 . A thermoformable film comprising a polymer blend consisting essentially of 
 (a) 40 to 95% by weight, based on the weight of the polymer blend, of an ethylene based copolymer consisting essentially of repeating polymerized units of 
 (1)at least 50% by weight, based on the weight of the copolymer, of ethylene,  
 (2) 1 to 30% by weight, based on the weight of the copolymer, of acrylic acid or methacrylic acid; and  
 (3)up to 40% by weight, based on the weight of the copolymer, of an alkyl acrylate or an alkyl methacrylate,  
    wherein the copolymer has 5 to 100% of the acid groups neutralized with metal ion selected from the group consisting of zinc, magnesium, sodium and lithium; and    (b) 5 to 60% by weight, based on the weight of the polymer blend, of a metallocene catalyzed linear polyethylene.    
   
   
       10 . The thermoformable film of  claim 9  containing 2-15% by weight, based on the weight of the polymer blend, of ethylene-vinyl acetate copolymer.  
   
   
       11 . A thermoformed package comprising the film of  claim 1  thermoformed into a shape structure for holding an object and having a cover positioned on the thermoformed shaped structure and firmly adhered to the film.  
   
   
       12 . The thermoformed package of  claim 11  in which the cover is a non-woven polyolefin web.  
   
   
       13 . The thermoformable film of  claim 1  in which the metallocene catalyzed linear polyethylene is selected from the group consisting of linear high density polyethylene, linear medium density polyethylene, linear low density polyethylene and linear ultra low density polyethylene.  
   
   
       14 . A thermoformable film comprising a composite structure comprising at least three layers firmly adhered to one another, a top and bottom layer and an inner layer; wherein the top and bottom layer of the composite structure comprise a film layer of ethylene-vinyl acetate copolymer consisting essentially of 1 to 25% by weight, based on the weight of the copolymer, of a polymerized vinyl acetate and 75 to 99% by weight, based on the weight of the copolymer, of polymerized ethylene and the inner layer of the composite structure comprises a film of a polymer blend consisting essentially of 
 (a) 40 to 95% by weight, based on the weight of the polymer blend, of an ethylene based copolymer consisting essentially of repeating polymerized units of 
 (1) at least 50% by weight, based on the weight of the copolymer, of ethylene; and  
 (2) 1 to 30% by weight, based on the weight of the copolymer, of acrylic acid or methacrylic acid,  
    wherein 5 to 100% of the acid groups of the acrylic acid and/or methacrylic acid are neutralized with metal ion selected from the group consisting of zinc, magnesium, sodium and lithium; and    (b) 5 to 60% by weight, based on the weight of the polymer blend, of a metallocene catalyzed linear polyethylene.    
   
   
       15 . The thermoformable film of  claim 14 , wherein the inner layer consists essentially of a polymer blend of 65 to 95% by weight of the ethylene based copolymer and 5 to 35% by weight of the metallocene catalyzed linear polyethylene, based on the weight of the polymer blend.  
   
   
       16 . A thermoformable film comprising a composite structure comprising two layers firmly adhered to one another, a top and bottom layer; 
 wherein the top layer of the composite structure comprise a film layer of ethylene-vinyl acetate copolymer consisting essentially of 1 to 25% by weight, based on the weight of the copolymer, of a polymerized vinyl acetate and 75 to 99% by weight, based on the weight of the copolymer, of polymerized ethylene and the bottom layer of the composite structure comprises a film of a polymer blend consisting essentially of    (a) 40 to 95% by weight, based on the weight of the polymer blend, of an ethylene based copolymer consisting essentially of repeating polymerized units of 
 (1) at least 50% by weight, based on the weight of the copolymer, of ethylene; and  
 (2) 1 to 30% by weight, based on the weight of the copolymer, of acrylic acid or methacrylic acid,  
    wherein 5 to 100% of the acid groups of the acrylic acid and/or methacrylic acid are neutralized with metal ion selected from the group consisting of zinc, magnesium, sodium and lithium; and    (b) 5 to 60% by weight, based on the weight of the polymer blend, of a metallocene catalyzed linear polyethylene.    
   
   
       17 . The thermoformable film of  claim 16 , wherein the bottom layer consists essentially of a polymer blend of 65 to 95% by weight of the ethylene based copolymer and 5 to 35% by weight of the metallocene catalyzed linear polyethylene, based on the weight of the polymer blend.  
   
   
       18 . A thermoformable film comprising a polymer blend consisting essentially of 
 (a) 40 to 95% by weight, based on the weight of the polymer blend, of an ethylene based copolymer consisting essentially of repeating polymerized units of 
 (1) at least 50% by weight, based on the weight of the copolymer, of ethylene; and  
 (2) 1 to 30% by weight, based on the weight of the copolymer, of acrylic acid or methacrylic acid,  
    wherein 5 to 100% of the acid groups of the acrylic acid and/or methacrylic acid are neutralized with metal ion selected from the group consisting of zinc, magnesium, sodium and lithium; and    (c) 5 to 60% by weight, based on the weight of the polymer blend, of a metallocene catalyzed linear polyethylene.    
   
   
       19 . The thermoformable film of  claim 18 , wherein the polymer blend consists essentially of 65 to 95% by weight of the ethylene based copolymer and 5 to 35% by weight of the metallocene catalyzed linear polyethylene, based on the weight of the polymer blend.  
   
   
       20 . A thermoformable film comprising a composite structure comprising at least five layers firmly adhered to one another; 
 wherein the first, third, and fifth layers of the composite structure comprise a film of ethylene-vinyl acetate copolymer consisting essentially of 1 to 25% by weight, based on the weight of the copolymer, of a polymerized vinyl acetate and 75 to 99% by weight, based on the weight of the copolymer, of polymerized ethylene; and wherein the second and fourth layers of the composite structure comprise a film of a polymer blend consisting essentially of 
 (a) 40 to 95% by weight, based on the weight of the polymer blend, of an ethylene based copolymer consisting essentially of repeating polymerized units of  
 (1) at least 50% by weight, based on the weight of the copolymer, of ethylene,  
 (2) 1 to 30% by weight, based on the weight of the copolymer, of acrylic acid or methacrylic acid; and  
 (3) 0 to 40% by weight, based on the weight of the copolymer, of an alkyl acrylate or an alkyl methacrylate,  
   wherein the copolymer has 5 to 100% of the acid groups neutralized with metal ion selected from the group consisting of zinc, magnesium, sodium and lithium; and 
 (b) 5 to 60% by weight, based on the weight of the polymer blend, of a metallocene catalyzed linear polyethylene.  
   
   
   
       21 . The thermoformable film of  claim 20 , wherein the second and fourth layers consist essentially of a polymer blend of 65 to 95% by weight of the ethylene based copolymer and 5 to 35% by weight of the metallocene catalyzed linear polyethylene, based on the weight of the polymer blend.