Heat-shrinkable, heat-sealable polyester film for packaging

Abstract

The invention provides a packaging film comprising a heat-shrinkable, heat-sealable polyester shrink film. The film comprises a homopolymer or copolymer of polyethylene terephthalate, preferably coated with a solvent-based, heat-seal coating, e.g., an amorphous copolyester. The film may be metallized and/or laminated to other films, e.g., ionomer films. The films and laminated are useful in various packaging applications including cook-in or non-cook bags for packaging meats, as well as lidding applications

What is claimed is:  
     
         1 . A heat shrink film for packaging comprising: 
 (a) a heat shrink film comprising a polymer having at least 80% by weight polyethylene terephthalate polymer, wherein said film is biaxially oriented in the range of about 5% to about 55%, said film having an outer surface and an inner surface; and    (b) a solvent-based, heat-seal coating on at least one of the outer surface and inner surface.    
     
     
         2 . The heat shrink film of  claim 1  wherein the solvent-based, heat-seal coating comprises an adhesive selected from the group consisting of ethylene vinyl acetate copolymers, polyethylene terephthalate copolymers, and combinations thereof.  
     
     
         3 . The heat shrink film of  claim 1  wherein the temperature at which shrinkage of the film is initiated is about 80 degrees C. or higher.  
     
     
         4 . The heat shrink film of  claim 1  wherein the heat shrink film additionally comprises a metallized layer below the solvent-based, heat-seal coating.  
     
     
         5 . The heat shrink film of  claim 1  wherein the film is laminated to one or more additional layers to form a laminated film.  
     
     
         6 . The heat shrink film of  claim 4  wherein the one or more additional layers are selected from the group consisting of: nylon, polypropylene, polyethylene, ionomer, ACR, ethylene vinyl acetate, polyethylene terephthalate, polystyrene, ethylene vinyl alcohol, polyvinylidene chloride, and combinations thereof.  
     
     
         7 . A bag formed from the heat shrink film of  claim 1 .  
     
     
         8 . A package formed from the heat shrink film of  claim 1 .  
     
     
         9 . The package of  claim 8  wherein the heat shrink film additionally comprises a metallized layer on the inner surface, and the solvent-based, heat-seal coating resides on the metallized layer, and wherein the package after shrinkage exhibits the property of pearlessence while the functional barrier to oxygen and moisture is retained.  
     
     
         10 . A ovenable, cook-in package for packaging food formed from the bag of  claim 7 .  
     
     
         11 . A method to package an article, comprising the steps of: 
 (a) wrapping the article in a shrink film comprising a polymer having at least 80% by weight polyethylene terephthalate polymer, wherein said film is biaxially oriented in the range of about 5% to about 55%, said film having an outer surface and an inner surface, said inner surface having coated thereon a solvent-based, heat-seal coating;    (b) heat-sealing the required sides to form a bag;    (c) sealing the bag with the article therein; and    (d) shrinking the bag by applying heat.    
     
     
         12 . A tamper-resistant packaging container capable of venting vapor comprising, in combination: 
 a) an open rigid or semi-rigid container having a floor portion and side walls upwardly extending therefrom, said side walls having an outside surface;    b) a heat-shrink film having an inner surface and a solvent-based heat seal coating applied on such inner surface, said inner surface of said film in intimate sealing contact with at least a portion of the outside surface of the side walls, and wherein the heat-shrink film comprises: 
 i) a polymer having at least 80% by weight polyethylene terephthalate polymer; and  
 ii) wherein said film is biaxially oriented in the range of about 5% to about 30%.  
   
     
     
         13 . The packaging container of  claim 8 , wherein the heat-shrink film is biaxially oriented in the range of 10% to about 20% and wherein the film has a thickness between 12 and 75 micrometers.  
     
     
         14 . The packaging container of  claim 8  wherein the heat-seal coating comprises an adhesive selected from the group consisting of ethylene vinyl acetate copolymers, polyethylene terephthalate copolymers, and combinations thereof.  
     
     
         15 . The packaging container of  claim 8  wherein the inner surface of the heat-shrink film additionally comprises a metallized layer between the inner surface and solvent-based heat-seal coating.  
     
     
         16 . A tamper-resistant heat-shrink lidding film, having an inner surface, for covering a rigid or semi-rigid container having an outside surface, said film comprising at least 80 percent by weight of a polyethylene terephthalate homopolymer or copolymer, having a plurality of sides and a thickness of 12-75 micrometers, and being biaxially oriented in the range of about 5%-30% shrink factor; and said inner surface comprising a solvent-based heat-seal coating thereon, wherein: 
 a) said film is intimate contact with at least a portion of the outside surface of said container;    b) when the sides of said film are heated, said film remains in tamper resistant engagement with said container, hermetically sealing said container, yet allowing air and moisture to move in and out of said lidding film upon heating.    
     
     
         17 . The tamper-resistant lidding film of  claim 12 , wherein said film is biaxially oriented in the range of about 7-20% shrink factor, and said film has a thickness between 25 and 60 micrometers.  
     
     
         18 . The tamper-resistant lidding film of  claim 12  wherein said film additionally has a metallized coating on the outside surface in between such surface and the solvent-based, heat-seal coating.  
     
     
         19 . The tamper-resistant lidding film of  claim 12 , wherein said lidding film is torn or ruptured, indicating package removal or tampering has occurred, when said container is no longer securely sealed and said film is removed from the sealing position.  
     
     
         20 . A heat-shrink film laminate for packaging comprising multiple film layers wherein: 
 (a) at least one film layer of the laminate comprises a film of a polymer having at least 80% by weight polyethylene terephthalate polymer, wherein said film is biaxially oriented in the range of about 5% to about 55%;    (b) a solvent-based laminating adhesive between film layers of the laminate; and,    (c) a second or additional film layers of the laminate comprises a polymer selected from the group consisting of: nylon, polypropylene, polyethylene, ionomer, ACR, ethylene vinyl acetate, polyethylene terephthalate, polystyrene, ethylene vinyl alcohol, polyvinylidene chloride, and combinations thereof.