Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
1999-07-09
2001-07-03
Wood, Elizabeth D. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C526S308000, C526S348000, C252S188280, C252S397000, C428S035700, C428S035800, C428S035900, C428S349000, C428S516000, C428S035200, C428S035300
Reexamination Certificate
active
06255248
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a composition useful in scavenging oxygen from environments containing oxygen-sensitive products, particularly food and beverage products. More specifically, the oxygen scavenging composition includes a polymer having mer units derived from a strained, cyclic alkylene compound, a transition metal compound and, optionally, a photoinitiator.
BACKGROUND OF THE INVENTION
Limiting the exposure of oxygen-sensitive products to oxygen maintains and enhances the quality and shelf life of many products. For instance, by limiting the oxygen exposure of oxygen-sensitive food products in a packaging system, the quality of the food product can be maintained and spoilage retarded. In addition, such packaging also keeps the product in inventory longer, thereby reducing costs incurred from waste and having to restock.
In the food packaging industry, several techniques for limiting oxygen exposure have been developed. Common techniques include those where oxygen is consumed within the packaging environment by some means other than the packaged article or the packaging material (e.g., through the use of oxygen scavenging sachets), those where reduced oxygen environments are created in the package (e.g., modified atmosphere packaging (MAP) and vacuum packaging), and those where oxygen is prevented from entering the packaging environment (e.g., barrier films).
Sachets containing oxygen scavenging compositions can contain ferrous compositions, which oxidize to their ferric state, unsaturated fatty acid salts on an absorbent, and/or a metal-polyamide complex. The disadvantages of sachets include the need for additional packaging steps (to add the sachet to the package), the potential for contamination of the packaged article should the sachet break, and the danger of ingestion by a consumer.
Oxygen scavenging materials also have been incorporated directly into the packaging structure. This technique (hereinafter referred to as “active oxygen barrier”) can provide a uniform scavenging effect throughout the package and can provide a means of intercepting and scavenging oxygen as it passes through the walls of a package, thereby maintaining the lowest possible oxygen level throughout the package. Active oxygen barriers have been formed by incorporating inorganic powders and/or salts as part of the package. However, incorporation of such powders and/or salts can degrade the transparency and mechanical properties (e.g., tear strength) of the packaging material and can complicate processing, especially where thin films are desired. Also, these compounds as well as their oxidation products can be absorbed by food in the container, which can result in the food product failing to meet governmental standards for human consumption.
Oxygen scavenging compositions that include transition metal catalysts and ethylenically unsaturated hydrocarbon polymers which have an ethylenic double bond content of from 0.01 to 10 equivalents per 100 grams of polymer are known. However, because these polymers are amorphous, they can be difficult to blend and process with film-forming semicrystalline polymers conventionally used to make flexible packaging materials.
The use of a transition metal and a photoinitiator to facilitate initiation of effective scavenging activity of ethylenically unsaturated compounds is known. Because of the limited compatibility of the scavenger polymer with the film forming polymer, the amount of scavenger polymer in the blend must be limited and the resultant composition is difficult to process.
The use of a transition metal catalyst and a copolymer of ethylene and at least one vinyl unsaturated alicyclic monomer, preferably vinylcyclohexene, is known to provide excellent oxygen scavenging properties. However, prior to polymerization the vinylcyclohexene monomer is difficult to handle and has a strongly disagreeable odor.
Ideally, a polymeric material for use in an oxygen scavenging composition should exhibit good processing characteristics, be able to be formed directly into useful packaging materials or have high compatibility with those polymers commonly used to make packaging materials, and not produce byproducts which detract from the color, taste, or odor of the packaged product. Optimally, a packaging material formed from such a composition can retain its physical properties after significant oxygen scavenging.
SUMMARY OF THE INVENTION
Briefly, the present invention is directed to oxygen scavenger compositions comprising (i) a copolymer of, at least, ethylene and a strained, cyclic alkylene, preferably cyclopentene; (ii) a transition metal catalyst; (iii) optionally, a photoinitiator; and (iv) optionally, a polymeric diluent. This composition has been found to exhibit a high degree of processability, to be highly compatible with conventional polymers used in forming packaging materials, to exhibit significant ability to scavenge oxygen while part of a film or article used to package an oxygen sensitive product, and to produce insignificant amounts of organoleptic byproducts which can detract from the packaged product's odor, color, and/or taste.
In other aspects, the present invention provides an article which include at least one layer formed from a blend that includes the foregoing composition as well as a method of scavenging oxygen in which a packaging article, at least one layer of which is formed from a blend that includes the foregoing composition, is exposed to actinic or e-beam radiation so as to activate the composition.
The following definitions apply herein throughout unless a contrary intention is expressly indicated:
“polymer” means the polymerization product of one or more monomers and includes homopolymers, as well as copolymers;
“copolymer” means the polymerization product of two or more kinds of monomers;
“(meth)acrylate” means acrylate or methacrylate;
“photoinitiator” means a substance which, when activated by actinic radiation, enhances and/or facilitates the onset or initiation of one or more properties (e.g., oxygen scavenging) in another compound, thus resulting in a shorter induction period and/or an increase in the rate of oxygen uptake of the overall system;
“induction period” means the length of time beginning with the exposure to an actinic radiation and ending with the onset of one or more useful properties (e.g., oxygen scavenging); and
“antioxidant” means a material which can inhibit oxidative degradation and/or crosslinking of a polymer so as to, for example, prolong the useful lifetime of the polymer; to stabilize a polymer-containing composition during processing (e.g., extrusion, coating, lamination, etc.); and/or to prolong the shelf-life of the composition (prior to exposure thereof to actinic or electron beam radiation).
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The oxygen scavenging composition of the present invention includes one or more polymers that include mer units derived from a strained, cyclic alkylene, preferable cyclopentene. This polymer possesses sufficient crystallinity such that it is highly compatible with polymers conventionally used in the manufacture of packaging films and laminated structures (e.g., polyolefins and the like) and provides a composition which has good processing characteristics.
As is discussed above, most prior oxygen scavenging compounds have relied upon reaction of oxygen with a carbon-carbon double bond in an ethylenically unsaturated hydrocarbon of some type. The present invention differs from the prior art in that the mer units derived from a strained, cyclic alkylene do not present such a double bond. Instead, it is the strained configuration of the mer unit which allows for reaction with atmospheric oxygen. Ethylene/cyclopentene copolymers have been found to provide excellent oxygen scavenging properties without producing organoleptically significant by-products. Ethylene/cyclobutene copolymers are also within the scope of the present invention. Mer units derived from cyclohexene are not sufficiently strained to provide the desired reactivity during
Bansleben Donald A.
Opuszko Slawomir
Speer Drew V.
Cryovac Inc.
Quatt Mark B.
Wood Elizabeth D.
LandOfFree
Oxygen scavenging composition with improved properties and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Oxygen scavenging composition with improved properties and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Oxygen scavenging composition with improved properties and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2519311