Retortable packaging film with grease-resistance

Abstract

A retortable multilayer packaging film comprises a crosslinked heat seal layer and a crosslinked grease-resistant layer. The crosslinked heat seal layer is an outer film layer comprising a C 2-3 /C 3-20 alpha-olefin copolymer. The crosslinked grease-resistant layer comprising at least one member selected from the group consisting of (i) a crystalline anhydride-grafted C 2-3 /C 6-20 alpha-olefin copolymer having a density of from 0.93 g/cc to 0.97 g/cc, (ii) a crystalline C 2-3 /butene copolymer having a density of at least 0.92 g/cc, (iii) ionomer resin, and (iv) ethylene/unsaturated acid copolymer. The invention also pertains to packaging articles made from the film, packaged products utilizing the film in the package, and a packaging process utilizing the film

1 - 19 . (canceled) 
   
   
       20 . A process of preparing a retorted packaged product, comprising:
 (A) placing a product in a packaging article comprising a multilayer packaging film heat sealed to itself, the multilayer packaging film comprising:
 (i) a crosslinked heat seal layer comprising a C 2-3 /C 3-20  alpha-olefin copolymer, the heat seal layer being an outer layer; 
 (ii) a crosslinked grease-and-fat-resistant layer comprising at least one member selected from the group consisting of:
 (a) a crystalline anhydride-grafted C 2-3 /C 6-20  alpha-olefin copolymer having a density of from 0.93 g/cc to 0.97 g/cc, 
 (b) a crystalline C 2-3 /butene copolymer having a density of at least 0.92 g/cc, 
 (c) ionomer resin, and 
 (d) ethylene/unsaturated acid copolymer; and 
 
 (iii) an O 2 -barrier layer; and 
 wherein the grease-resistant layer is between the heat seal layer and the O 2 -barrier layer; and 
   (B) sealing the article closed so that the product is surrounded by the multilayer packaging film;   (C) retorting the packaged product by heating the packaged product to a temperature of from 212° F. to 300° F. for a period of from 10 minutes to 3 hours in the presence of pressurized steam.   
   
   
       21 . The process according to  claim 20 , wherein the product comprises at least one member selected from the group consisting of chili, rice, beans, olives, beef, pork, fish, poultry, corn, eggs, tomatoes, and nuts. 
   
   
       22 . The process according to  claim 20 , wherein the packaged product is heated to a temperature of at least 230° F. for a period of at least about 75 minutes. 
   
   
       23 . The process according to  claim 22 , wherein the packaged product is heated to a temperature of at least 240° F. for a period of at least about 90 minutes. 
   
   
       24 . The process according to  claim 20 , wherein the packaged product is heated to a temperature of at least 240° F. for a period of at least 2 hours. 
   
   
       25 . The process according to  claim 20 , wherein the packaged product is heated to a temperature of at least 250° F. for a period of at least 90 minutes. 
   
   
       26 . The process according to  claim 20 , wherein the retorting of the packaged product is carried out by placing the packaged product in an environment pressurized to from 20 to 100 psi in the presence of the pressurized steam. 
   
   
       27 . The process according to  claim 20 , wherein the retorting of the packaged product is carried out by placing the packaged product in an environment pressurized to from 30 to 40 psi in the presence of the pressurized steam. 
   
   
       28 . The process according to  claim 20 , wherein the film is produced as a fully coextruded film with all of the layers emerging from a single die at the same time. 
   
   
       29 . The process according to  claim 20 , wherein grease in the product is in direct contact with the inside heat seal layer of the package during retorting of the package. 
   
   
       30 . The process according to  claim 29 , wherein the product comprises at least one member selected from the group consisting of chili, soup, sauce, and taco meat. 
   
   
       31 . The process according to  claim 29 , wherein the retortable film does not substantially swell, substantially weaken, or substantially delaminate during retorting or thereafter during storage, shipping, and handling. 
   
   
       32 . The process according to  claim 20 , wherein the grease-resistant layer comprises crystalline anhydride-grafted C 2-3 /C 6-20  alpha-olefin copolymer having a crystallinity of from 5 to 75 percent, as measured by ASTM D3417. 
   
   
       33 . The process according to  claim 20 , wherein the grease-resistant layer comprises crystalline anhydride-grafted C 2-3 /C 6-20  alpha-olefin copolymer having a crystallinity of from 10 to 65 percent, as measured by ASTM D3417. 
   
   
       34 . The process according to  claim 20 , wherein the grease-resistant layer comprises crystalline anhydride-grafted C 2-3 /C 6-20  alpha-olefin copolymer having a crystallinity of from 20 to 60 percent, as measured by ASTM D3417. 
   
   
       35 . The process according to  claim 20 , wherein the grease-resistant layer also serves as a tie layer between the seal layer and the O 2 -barrier layer. 
   
   
       36 . The process according to  claim 20 , wherein the seal layer comprises a blend of isotactic polypropylene and homogeneous ethylene/butene copolymer. 
   
   
       37 . The process according to  claim 20 , wherein the multilayer packaging film further comprises a skin layer which is a second outer layer, and a tie layer between the O 2 -barrier layer and the skin layer. 
   
   
       38 . The process according to  claim 37 , wherein the skin layer comprises a blend of isotactic polypropylene and homogeneous ethylene/butene copolymer.