Packages and methods for differential oxygen scavenging

Abstract

Packages and methods for protecting oxygen-sensitive products from damage or degradation due to oxygen contamination are provided. The packages contain at least two oxygen scavenging materials having different oxygen scavenging properties, arranged so that oxygen contamination from different sources is effectively eliminated. Preferred packages contain at least one oxygen scavenging material to effectively absorb head space oxygen, and at least one oxygen scavenging material to effectively absorb ingress oxygen.

I claim:  
     
         1 . A package for packaging an oxygen-sensitive product having an interior and an exterior, in which the product is sealed within the package interior and forms a space between the product and a portion of the package defining a head space wherein head space oxygen is contained, and in which ingress oxygen permeates the package to gain ingress to the package interior from the package exterior, wherein: 
 (1) the portion of the package defining a head space comprises a first material having an oxygen consumption rate and an oxygen capacity for scavenging the head space oxygen; and    (2) the remainder of the package comprises a second material having an oxygen consumption rate and an oxygen capacity for scavenging the ingress oxygen, and wherein at least one of the oxygen consumption rate or oxygen capacity of the first and second materials is different.    
     
     
         2 . The package of  claim 1 , wherein the oxygen-sensitive product has an oxygen consumption rate, and the package has an ingress oxygen permeation rate and an expected shelf-life, and wherein 
 a) the first material for scavenging head space oxygen has an oxygen consumption rate greater than about 0.5× the oxygen consumption rate of the packaged oxygen-sensitive product, and an oxygen capacity capable of absorbing at least about 90% of the head space oxygen; and    b) the second material for scavenging ingress oxygen has an oxygen consumption rate at least equal to the rate of ingress oxygen permeation of the package, and an oxygen capacity approximately equal to a value determined by multiplying the rate of ingress oxygen permeation of the package, the total area of the package, and the expected shelf life of the package.    
     
     
         3 . The package of  claim 1 , wherein the oxygen scavenging materials are compositions comprising one or more radiation activatable, oxidizable organic polymers and a transition metal catalyst.  
     
     
         4 . The package of  claim 3 , wherein the one or more oxidizable organic polymers are selected from the group consisting of ethylenically unsaturated hydrocarbons, polyvinylidene chloride, and polyethylenic compounds with pendant 3-cyclohexenyl moieties.  
     
     
         5 . The package of  claim 4 , wherein the polyethylenic compounds with pendant 3-cyclohexenyl moieties comprise ethylene-cyclohexenylmethyl acrylate copolymer (ECHA) or ethylene-methylacrylate-cyclohexeneylmethyl acrylate terpolymer (EMCM).  
     
     
         6 . The package of  claim 3 , wherein the transition metal catalyst is selected from the group consisting of iron, nickel copper, manganese and cobalt.  
     
     
         7 . The package of  claim 6 , wherein the transition metal catalyst is a transition metal salt.  
     
     
         8 . The package of  claim 7 , wherein the transition metal salt is cobalt (II) 2-ethylhexanoate or cobalt (II) neodecanoate.  
     
     
         9 . The package of  claim 3 , wherein said compositions comprise a polyvinylidene chloride-coated polyester film and a cobalt metal salt catalyst.  
     
     
         10 . The package of  claim 3 , wherein the compositions further comprise a photoinitiator.  
     
     
         11 . The package of  claim 10  wherein the photoinitiator is a low-migratory photoinitiator.  
     
     
         12 . The package of  claim 11  wherein the low-migratory photoinitiator is tribenzoyl triphenylbenzene (BBP 3 ).  
     
     
         13 . The package of  claim 1 , wherein the oxygen-sensitive product has an oxygen consumption rate, and the package has an oxygen permeation rate and an expected shelf-life, and wherein 
 a) the first material for scavenging head space oxygen has an oxygen consumption rate that reduces head space oxygen level at least about 90% over a period of one week, and an oxygen capacity capable of absorbing at least about 90% of the oxygen in the head space; and    b) the second material for scavenging ingress oxygen has an oxygen consumption rate at least equal to the rate of oxygen permeation of the package, and an oxygen capacity approximately equal to a value determined by multiplying the rate of oxygen permeation of the package, the total area of the package, and the expected shelf life of the package.    
     
     
         14 . A package for packaging oxygen-sensitive food comprising a top portion and a bottom portion, wherein the top portion comprises a first material having an oxygen consumption rate and an oxygen capacity for scavenging head space oxygen, and the bottom portion comprises a second material having an oxygen consumption rate and an oxygen capacity for scavenging ingress oxygen, wherein at least one of the oxygen consumption rate or oxygen capacity of the first and second materials is different.  
     
     
         15 . The package of  claim 14 , wherein the top portion of the package comprises the top ¼ to ⅓ of the package.