Dispensing – Collapsible wall-type container – Nonmetallic
Reexamination Certificate
2000-05-08
2003-08-05
Jackson, Monique R. (Department: 1773)
Dispensing
Collapsible wall-type container
Nonmetallic
C222S105000, C428S035200, C428S035400
Reexamination Certificate
active
06601732
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to novel uses of the oxygen scavenging compositions described in the co-pending Australian patent application No. 55537/94. In particular, the invention relates to novel uses of oxygen scavenging compositions in packaging materials comprising a gas and vapour barrier-forming layer or coating.
BACKGROUND OF THE INVENTION
A wide variety of foods and other materials are susceptible to loss in quality during storage under atmospheric levels of oxygen. The damage can arise from chemical oxidation of the product, from microbial growth, and from attack by vermin—much of which may be avoided by reducing the oxygen availability in the environment of the materials. In the field of packaging, relatively low-oxygen atmospheres have traditionally been generated by vacuum packing and inert gas flushing. Such methods are not, however, generally applicable for various reasons. For example:
soft porous foods such as cakes cannot be subjected to strong vacuum:
fast filling speeds generally preclude substantial evacuation of, or thorough inert gas flushing of, food packages:
filling some gas-flushed containers, such as beer bottles often results in occlusion of air:
evacuation or flushing offers no residual capacity for removal of oxygen, which may have desorbed from the food or entered the package by leakage or permeation.
As a consequence there has been much interest in chemical techniques for generating low-oxygen atmospheres and deoxygenating liquid or semi-liquid foods.
In the abovementioned Australian patent application No. 55537/94 (the entire disclosure of which is incorporated herein by reference), the present applicants describe novel oxygen scavenging compositions which may be readily activated or “triggered” (ie. brought to their oxygen scavenging form) as required by exposure to predetermined conditions, for example, light of a certain intensity or wavelength (eg. UV) or by application of heat, &ggr;-irradiation, corona discharge or an electron beam. These compositions (and packaging materials including the compositions) may therefore be stored under standard conditions, then triggered to the activated state just prior to use. The oxygen scavenging compositions, once activated, are capable of continuing to scavenge oxygen from an oxygenated atmosphere or liquid in substantial darkness for periods ranging from up to a few minutes or hours to over 100 days.
The novel oxygen scavenging compositions described in application No. 55537/94 are hereinafter referred to as “the oxygen scavenging compositions”. These compositions comprise at least one reducible organic compound which is reduced and/or subsequently oxidised independently of each of constant illumination with visible light and the presence of a transition metal catalyst. The most preferred reducible organic compounds are quinones such as benzoquinone, anthraquinone (eg. 9,10-anthraquinone) and napthoquinone (eg. 1,4-napthoquinone): photoreducible dyes (e.g. methylene blue, azo, thiazine, indigoid and triarylmethane compounds): and carbonyl compounds which have absorbance in the UV spectrum particularly, when provided in a in polymerized. copolymerised, or oligomerised form.
In addition, the oxygen scavenging compositions described in application No. 55537/94 may include a scavenging component reactive to activated oxygen species (e.g. peroxide) which may be generated during the scavenging of molecular oxygen. Preferred examples of the activated oxygen scavenging component include antioxidants, amines, organic phosphines (e.g. triphenylphosphine) and organic phosphites (e.g. triphenylphosphite) and sulfur compounds such as thiols, thioethers and thioesters. Alternatively, the activated oxygen scavenging component may be embodied within the reducible organic compound itself, for example a quinone having an amine group.
Further, the compositions may include a source of labile hydrogen or electrons which may be abstracted by the reducible organic compound as it is brought to its activated state. Such sources of labile hydrogen or electrons include compounds such as the salts of sulfonic or carboxylic acids.
As described in application No. 55537/94, the at least one reducible organic compound, the activated oxygen scavenging component and/or the source of labile hydrogen or electrons may be in the form of a polymer, copolymer or oligomer, thereby providing an advantage of permitting the use of the oxygen scavenging compositions in the form of films (monolayer and multilayer) for a wide variety of applications. In multilayer laminate films, the at least one reducible organic compound and activated oxygen scavenging component may be provided in the same layer or in distinct layers.
The copolymerised form of the reducible organic compound is a copolymer of a monomer containing the reducible organic compound bound with one or more monomers which might be used in packaging polymers.
It is evident from the descriptions of vises in application No. 55537/94, that the oxygen scavenging compositions can be utilised in a wide variety of packaging materials and package forms. However, the applicants have now recognised further novel uses and modes of use for the oxygen scavenging compositions.
DISCLOSURE OF THE INVENTION
Thus, in a first aspect, the present invention provides a flexible packaging material comprising a film, co-extrusion or laminate comprising one or more layers of an oxygen scavenging composition(s) in combination with at least one gas and vapour barrier-forming layer or coating, wherein said oxygen scavenging composition(s) comprises at least one reducible organic compound which is reduced when the composition(s) is subjected to predetermined conditions, the reduced form of the organic compound(s) being oxidisable by ground state molecular oxygen, and wherein the reduction and/or subsequent oxidation of the organic compound(s) occurs independently of each of constant illumination with visible light and the presence of a transition metal catalyst.
Preferably, the said barrier-forming layer or coating is an oxygen barrier-forming layer or coating such as a film layer of a high oxygen barrier polymer (e.g. polyvinyl alcohol, ethylene vinyl alcohol copolymer and polyethylene naphthalate) which may also be coated with a further barrier polymer such as polyvinylidene chloride or its copolymers, or a coating of a substance selected from the group consisting of carbon (particularly in the crystalline form of diamond), aluminium, aluminium oxide, and oxides and nitrides of metals, including silicon oxides.
The one or more layers of the oxygen scavenging composition may be laminated or extrusion-coated onto a barrier-forming layer. Barrier-forming coatings may be applied directly to the surface of a layer of the oxygen scavenging composition or, for example, to a laminated film. Barrier-forming coatings may be applied by vacuum techniques which are well known to persons skilled in the art.
The innermost layer(s) comprising the oxygen scavenging composition (“the scavenger layer(s)”) or another fusible layer or an adhesive layer, may be considered as forming “the sealant layer” of the packaging material. The flexible packaging material according to the first aspect may further comprise one or more layers of a solid packaging material such as aluminium foil or paper. Further, the oxygen scavenging composition may be blended or dispersed in one or more layers of the flexible packaging material. Where the oxygen scavenging composition includes an activated oxygen scavenging component, the at least one reducible organic compound and the activated oxygen scavenging component may be present in the same or distinct layers.
In use, the gas and vapour barrier-forming layer or coating will normally be present on the outside of the package relative to the scavenging layer facing the surrounding environment. The oxygen scavenging layer(s) are, therefore, normally adjacent to the package contents, although contact between the contents and the oxygen scavenging layer(s) may be avoided by providing a space
Horsham Mark Andrew
Rooney Michael Laurence
Commonwealth Scientific and Industrial Research Organisation
Jackson Monique R.
McDermott & Will & Emery
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