Surface-treated multi-layered polymer film

Abstract

A sealable polymeric film structure comprising (a) a core layer including a thermoplastic polymer, the core layer having a machine side and a product side that is on a side of the film opposite from the machine side; and (b) a sealable skin layer positioned on the product side of the core layer, the sealable skin layer including a thermoplastic polymer, wherein an exterior surface of the sealable skin layer has a receding Cahn value of at least about 0.48; and wherein in some heat—sealable embodiments, the sealable skin layer sealed to itself has a MST of from about 175° F. to about 220° F., with a jaw pressure of 20 psi for 0.75 seconds and a minimum acceptable seal strength of 200 g/in at 175° F., on a Wrap-Ade™ Crimp Sealer Model J or K.

1 . A method of preparing a heat-sealable polymeric film structure including a product side and a machine side, the method comprising the steps of: 
 (a) coextruding: 
 i) a core layer including a thermoplastic polymer, the core layer having a machine side and a product side opposite from the machine side; and  
 ii) a heat-sealable skin layer positioned on the product side of the core layer, the heat-sealable skin layer including a thermoplastic polymer;  
 wherein the product side exterior surface of the coextruded film structure has a receding Cahn value of at least about 0.48;  
   wherein the sealable skin layer when sealed to itself has a MST of from about 175° F. to about 220° F., with a jaw pressure of 20 psi for 0.75 seconds and a minimum acceptable seal strength of 200 g/in at 175° F., on a Wrap-Ade™ Crimp Sealer Model J or K;    (b) orienting the coextruded film structure in at least one direction; and    (c) surface treating the product side exterior surface of the film with one of corona treatment, flame treatment, and plasma treatment.    
   
   
       2 . The method of preparing a heat-sealable film according to  claim 1 , wherein the product side exterior surface of the film has a Cahn value of from about 0.6 to about 0.87.  
   
   
       3 . The method of preparing a heat-sealable film according to  claim 1 , wherein the product side exterior surface of the film has a Cahn value of from about 0.65 to about 0.78.  
   
   
       4 . The method of preparing a heat-sealable film according to  claim 1 , further comprising the step of: 
 coextruding a second skin layer on the machine side of the core layer, the second skin layer comprising a thermoplastic polymer.    
   
   
       5 . The method of preparing a heat-sealable film according to  claim 1 , further comprising the step of: 
 coextruding a product side tie layer comprising a thermoplastic polymer, the product side tie layer positioned between the core layer and the sealable skin layer.    
   
   
       6 . The method of preparing a heat-sealable film according to  claim 1 , further comprising the step of: 
 coextruding a machine side tie layer comprising a thermoplastic polymer, the machine side tie layer positioned between the core layer and the second skin layer.    
   
   
       7 . The method of preparing a heat-sealable film according to  claim 1 , wherein the exterior surface of the polymeric film structure on the machine side of the film has a receding Cahn value of not greater than about 0.20.  
   
   
       8 . The method of preparing a heat-sealable film according to  claim 1 , wherein the exterior surface of the polymeric film structure on the machine side of the film comprises a receding Cahn value of not greater than about 0.17 dynes/cm.  
   
   
       9 . The method of preparing a heat-sealable film according to  claim 1 , wherein the core layer further comprises a cavitating agent.  
   
   
       10 . The method of preparing a heat-sealable film according to  claim 1 , wherein the thermoplastic polymer of the core layer comprises at least one of a polyolefin, polyester, and polylactic acid.  
   
   
       11 . The method of preparing a sealable film according to  claim 1 , wherein the thermoplastic polymer of the sealable layer further comprises a polymer selected from the group consisting of polyester, polylactic acid, polypropylene, polyethylene, polybutylene, copolymers or terpolymers of C 2 -C 40  olefins, copolymers or terpolymers of ethylene and C 3 -C 40  olefins, copolymers or terpolymers of propylene and C 2 -C 40  olefins, and copolymers or terpolymers of ethylene, propylene, and butene.  
   
   
       12 . The method of preparing a sealable film according to  claim 4 , wherein the thermoplastic polymer of the second skin layer comprises at least one of a polyolefin, polyester, and a polylactic acid.  
   
   
       13 . The method of preparing a heat-sealable film according to  claim 1 , wherein an exterior surface on the machine side of the film has a Cahn value of not greater than about 0.20.  
   
   
       14 . The method of preparing a heat-sealable film according to  claim 1 , wherein the exterior surface on the machine side of the film has a Cahn value not greater than about 0. 17.  
   
   
       15 . A method of packaging a product within a heat-sealable polymeric film, the method comprising the steps of: 
 (a) drawing a heat-sealable polymeric film structure through a packaging machine from an inlet side of the packaging machine to an outlet side of the packaging machine, the heat-sealable polymeric film structure including a product side and a machine side, the multilayer film comprising (i) a core layer comprising a thermoplastic polymer, the core layer having a machine side and a product side, and (ii) a heat-sealable skin layer comprising a thermoplastic polymer, wherein an exterior surface of the heat-sealable skin layer has a receding Cahn value of at least about 0.48, and wherein the sealable skin layer when sealed to itself has a MST of from about 175° F. to about 220° F., with a jaw pressure of 20 psi for 0.75 seconds and a minimum acceptable seal strength of 200 g/in at 175° F., on a Wrap-Ade™ Crimp Sealer Model J or K, wherein the product side exterior surface of the film is surface treated with one of corona treatment, flame treatment, and plasma treatment; and    (b) positioning a product on the product side of the heat-sealable multilayer film;    (c) engaging a first exterior portion of the product surface of the heat-sealable skin layer with one of (i) a second exterior portion of the product surface and (ii) the machine side exterior surface of the film, to form a seal area over the engaged portions of the heat-sealable skin layer and create a product space with the film; and    (d) applying heat to at least a portion of the seal area to bond the heat-sealable skin layer to the engaged exterior portion machine side to encase at least a portion of the product within the product space.    
   
   
       16 . The method of preparing a heat-sealable film according to  claim 15 , further comprising the step of: 
 surface treating the exterior surface of the polymeric film structure on the machine side of the film with one of flame treatment, corona treatment, and plasma treatment; and    applying one of a printing ink and a coating composition on at least about 10% of the area of the exterior surface on the machine side of the film.    
   
   
       17 . The method according to  claim 15 , wherein the exterior surface of the heat-sealable skin layer has a Cahn value of from at least about 0.60 to about 0.87.  
   
   
       18 . The method according to  claim 15 , wherein the exterior surface of the heat-sealable skin layer has a Cahn value of from about 0.65 to about 0.78.  
   
   
       19 . The method according to  claim 15 , wherein the core layer further comprises a cavitating agent.  
   
   
       20 . The method of  claim 15 , wherein the product comprises one of water, an aqueous-based product, or dairy-based product.  
   
   
       21 . The method of  claim 15 , wherein the water, aqueous-based, or dairy-based product is substantially frozen.  
   
   
       22 . The method of  claim 21 , wherein the aqueous-based or dairy-based product comprises at least one of an ice cream treat, a sugar-based treat, a sugar-free treat, and a yogurt treat.  
   
   
       23 . A packaged product encased in a heat-sealable film structure, comprising: 
 a product; and    a packaging film at least partially encasing the product, the packaging film comprising a product side and a machine side;    (a) a core layer including a thermoplastic polymer, the core layer having a machine side and a product side; and    (b) a heat-sealable skin layer positioned on the product side of the film, the heat-sealable skin layer including a thermoplastic polymer, wherein an exterior surface of the sealable skin layer has a receding Cahn value of at least about 0.6 to about 0.85, and wherein the heat-sealable skin layer sealed to itself has a MST of from about 175° F. to about 220° F., with a jaw pressure of 20 psi for 0.75 seconds and a minimum acceptable seal strength of 200 g/in at 175° F., on a Wrap-Ade™ Crimp Sealer Model J or K.    
   
   
       24 . The packaged product of  claim 23 , wherein the product comprises one of a water based product and a dairy based product.  
   
   
       25 . The packaged product of  claim 23 , wherein the product is substantially frozen.  
   
   
       26 . The packaged product of  claim 23 , wherein the product comprises one of an ice cream treat, a sugar-based treat, a sugar-free treat, and a yogurt-based treat.