Stock material or miscellaneous articles – Hollow or container type article – Nonself-supporting tubular film or bag
Reexamination Certificate
1999-03-05
2001-09-11
Anthony, Joseph D. (Department: 1714)
Stock material or miscellaneous articles
Hollow or container type article
Nonself-supporting tubular film or bag
C428S036700, C428S036600, C428S518000, C426S398000, C252S188280
Reexamination Certificate
active
06287653
ABSTRACT:
FIELD OF THE INVENTION
The invention generally relates to compositions, articles and methods for scavenging oxygen in environments containing oxygen-sensitive products, particularly food and beverage products. As will be evident from the disclosure below, the term “oxygen scavenger” refers to compositions, articles or the like which consume, deplete or reduce the amount of oxygen from a given environment. By-product absorbing layers made from polymeric bases can be incorporated into multilayer packaging films to reduce the migration of the by-products of oxygen absorption, and thereby improve the quality of the product.
BACKGROUND OF THE INVENTION
It is well known that regulating the exposure of oxygen-sensitive products to oxygen maintains and enhances the quality and “shelf-life” of the product. For instance, by limiting the oxygen exposure of oxygen sensitive food products in a packaging system, the quality of the food product is maintained, and food spoilage is avoided. In addition such packaging also keeps the product in inventory longer, thereby reducing costs incurred from waste and having to restock inventory. In the food packaging industry, one means for regulating oxygen exposure that has been developed uses polymeric films made from the oxygen scavengers disclosed in U.S. Pat. No. 5,346,644 issued to Speer et al Sept. 13, 1994, and in copending U.S. Ser. No. 276,125 filed Jul. 15, 1994 for “Compositions, Articles and Methods for Scavenging Oxygen”. A method of initiating oxygen scavenging generally is disclosed in U.S. Pat. No. 5,211,875 issued to Speer et al. May 18, 1993, and in U.S. Ser. No. 263,596 filed Jun. 22, 1994. The references are incorporated herein by reference as if set forth in full. These oxygen scavengers have a demonstrable effect on the quality of certain food products. Further, these materials can be used as a lidstock or incorporated in multilayer packaging materials to produce thin, flexible, transparent films that are high oxygen barriers, or are capable of scavenging oxygen from the headspace of a package. These films are an effective substitute for a 15-40 micrometer layer of aluminum foil in some applications.
It has been found that the oxygen scavenging process may produce by-products such as organic acids or aldehydes that can result in off-odors and flavors. Migration of these by-products is not necessarily prevented by the presence of layers which are fairly effective barriers to other materials such as gaseous oxygen or carbon dioxide. However, if a layer containing an additive that reacts readily with oxidation by-products is employed in a multilayer package, the occurrence of off-odors or flavors that result from the oxygen scavenging process can be either reduced or prevented.
Various means of regulating off-odors and flavors in polymeric materials are known. For example, U.S. Pat. No. 5,340,884, issued to Mills et al. Aug. 23, 1994, relates to the use of polyester blended with low molecular weight polyamides instead of pure polyester to produce a high barrier resin with a reduced amount of residual acetaldehyde.
U.S. Pat. No. 4,908,151, issued to Inoue Mar. 13, 1990, teaches that an oxygen absorbent sachet can be made using a liquid unsaturated fatty acid, a transition metal, preferably iron, and a base. The base is disclosed to solidify the liquid unsaturated fatty acid and reduce odors caused by the reaction of the fatty acid with oxygen. The disclosure is directed to maximizing the available surface area of the acid, thereby enhancing its reactivity (Col. 8, lines 43-49). There is no indication that a useful oxygen absorbent can be formed into films and need not be separately packaged in a sachet.
Aldehyde-absorbing layers made of polyalkylene imines are known for incorporation into polyethylene and polypropylene films as a method of reducing the build-up of oil degradation by-products from snack foods, see U.S. Pat. No. 5,284,892 issued to Brodie et al., Feb. 8, 1994, for “Aldehyde Scavenging Compositions and Methods Relating Thereto” and in protective clothing as a barrier layer, see U.S. Pat. No. 5,391,426 issued to Wu Feb. 21, 1995. However, there has been no indication that incorporation of these materials in a multi-layer packaging film will be effective to reduce migration of the by-products of oxygen absorption that takes place within an ethylenically unsaturated film layer.
European Patent Publication 504 276 A1 discloses that cyclic urea derivatives can be incorporated in a sachet with an oxygen absorbent and an ethanol source. The cyclic urea derivative absorbs acetaldehyde produced by the oxidation of ethanol. The oxygen absorber is preferably iron filings or a zeolite powder. Neither polymeric oxygen scavengers nor the making of films is disclosed or discussed.
Japanese Kokai Patent No. HEI 5-247276 published Sep. 24, 1993 by Toppan Printing Co. discloses odor suppression in an oxygen barrier film by blending a variety of adsorbents into a monolayer film made of an oxygen scavenging resin. The reference discloses a wide variety of resins. All the experiments are directed to the combination of “natural zeolite” with polyethylenes and polypropylenes, which are different from the preferred oxygen scavengers used in the present invention, and which are acknowledged to degrade upon oxidation (page 6, lines 7-12).
SUMMARY OF THE INVENTION
It is an object of the invention to obtain a multilayer structure which is effective as an oxygen scavenger, absorbs the by-products of the oxygen scavenging reaction, enhances product quality, and is suitable for incorporating into an article containing an oxygen-sensitive product.
It is a further object of the invention to provide a novel multilayer structure suitable for use in packaging of food and beverage products.
The above-mentioned objects are obtained from a novel multilayer structure comprising:
(a) an oxygen barrier layer or layers;
(b) an oxygen scavenging layer or layers, and
(c) a by-product absorbing layer or layers.
The articles of this invention limit the oxygen exposure by acting as an active oxygen barrier or acting as means for scavenging oxygen from within the article. The addition of the by-product absorbing layer improves the effectiveness of the articles by reducing migration of the by-products of the oxygen scavenging and thereby enhances the product quality.
Such articles include flexible, transparent packaging films which are capable of high oxygen barrier or headspace oxygen scavenging and also have a reduced occurrence of off-odors and flavors.
It is a further object of this invention to provide a packaging film which maintains its oxygen barrier characteristics after exposure to elevated humidity and/or elevated temperature.
It is yet another object of this invention to provide such a film which can enhance the quality of an oxygen-sensitive product which is also sensitive to the presence of organic by-products such as aldehydes or carboxylic acids.
Further objects and advantages of the present invention will be apparent from the description that follows.
DESCRIPTION OF THE INVENTION
The invention can be used in packaging articles having several forms. Suitable articles include, but are not limited to, rigid containers, flexible bags, or combinations of both. Typical rigid or semi-rigid articles include plastic, paper, glass, cardboard or foil laminate cartons or bottles and metal or composite cans such as juice containers, soft drink containers, and thermoformed trays or cups which have wall thicknesses in the range of 100 to 2000 micrometers. Typical flexible bags include those used to package many food items, and will likely have thicknesses of 5 to 400 micrometers. In addition the walls of such articles often comprise multiple layers of material. Though it may be preferable from the standpoint of packaging convenience or scavenging effectiveness to employ the invention as an integral part of the package wall, the invention can also be used as a non-integral packaging component such as full or partial coatings, bottle or jar cap liners, adhesive or non-
Blinka Thomas Andrew
Cotterman Ronald Lee
Morgan Charles Robert
Speer Drew Ve
Anthony Joseph D.
Cryovac Inc.
Quatt Mark B.
LandOfFree
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