Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2001-03-14
2003-08-19
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S144000
Reexamination Certificate
active
06608116
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to closures of the type used to close off and seal containers, particularly containers having a relatively narrow opening such as liquid containers.
The closures of the present invention may be classified as internal closures or as external closures—internal closures are those which have at least a part thereof configured for engagement with an internal portion of a container, and external closures are those which make no contact with the interior of a container.
The present invention relates most particularly to non-threaded, internal closures for use with liquid containers having relatively narrow necks and thus relatively narrow openings. Such container may be wine bottles, champagne bottles, liqueur or spirit bottles, or other similar containers for beverages, and such internal closures are commonly referred to as stoppers.
However, it must be appreciated that the closures of the present invention are to be in no way limited to only these types of closures for only this type of container.
BACKGROUND OF THE INVENTION
By far the most commonly used material for such container closures is natural cork. However, natural cork closures have inherent performance problems that sometimes result in spoilage of the container's contents, be it loss of flavor, oxidation, tainting or leakage.
The wine closure industry in general has observed a phenomenon known as cork taint over many years. Industry estimates of the incidence of cork taint can range from a 1% to a 10% spoilage of bottled wines. The most common chemical associated with cork taint is 2, 4, 6 Trichloroanisole (TCA) which can affect wines at exceptionally low levels when they come into contact with infected cork.
Leakage of wine past the cork is another commonly observed problem and this can manifest itself in two ways. Firstly, the wine may travel through the main body of the cork due to imperfections and defects, particularly in the case of poor quality cork. Secondly, wine travel between the cork and the neck of the bottle can occur due to a lack of seal between the two surfaces. Such leakage may ultimately lead to oxidation of the contents of the bottle.
Natural cork performance is also related to the humidity or moisture content of the closure and the cork can loose its elastic properties if it dries out. Such a situation can lead to breakage and crumbling on extraction, resulting in particles of cork entering the contents of the container. Similarly, dust and small particles can also enter the wine after compression during the corking process due to cracks and imperfections in the cork.
In the past, problems such as these have generally been accepted as a necessary evil in the use of natural cork as the material of choice. However, in more recent times, different types of synthetic substitutes to natural cork have been developed. Thus, there have been attempts at developing closures made of synthetic materials, and many such developments have aimed at producing closures which do not exhibit the same performance problems which are known to be inherent in natural cork closures.
It is an aim of the present invention to produce a closure which would be an acceptable substitute for natural cork closures, whilst reducing or removing the properties that tend to induce spoilage.
SUMMARY OF THE INVENTION
In the past, manufactures of synthetic closures have often failed to understand the precise nature of the problems that exist in developing an acceptable substitute for natural cork closures. However, the present invention has arisen as a result of the identification and understanding of these problems by the present inventors.
Indeed, the inventors have identified that the development of an acceptable substitute for natural cork is reliant on an understanding that the problem lies with the resistance to movement and frictional force created between the closure and the container wall, not with the permeability or chemical reactivity of the closure composition.
In this respect, most past attempts at developing suitable synthetic closures have centered on the use of materials which are chemically inert and/or which do not allow gas permeation into or out of the container. However, these properties are obvious matters of material selection that do not greatly effect the ultimate performance of the closure. In particular, it is relatively simple exercise for a skilled person to select a suitable plastic material that is chemically inert, and virtually every such suitable plastic material will be virtually gas impermeable due to the closure thickness which are used.
However, the present invention has identified that the crucial aspect of such closures performing successfully is their ability to rapidly seal with the wall of a container, and permanently maintain their position in the neck of the container until removal.
Accordingly, the present invention provides a foamed closure for a container, wherein the closure consists essentially of:
a blend of one or more copolymers of ethylene and one or more metallocene catalyzed polyolefins, there being a major proportion of the ethylene copolymers and a minor proportion of the metallocene catalyzed polyolefins.
The copolymers of ethylene may include ethylene polymerized with comonomers such as vinyl acetate, methyl acrylate and the like, where the comonomer imparts flexibility or softness to the polyethyle, and will preferably be ethylene vinyl acetate (EVA). In this respect, a combination of any one or more of these materials may be used.
The metallocene catalyzed polyolefins may be any such polyolefin which provides the closure with an ability to deform elastically. For example, in the application of an internal closure to a wine bottle or the like, elastic deformation allows for pressure to be exerted and maintained on the internal surface of the neck of the bottle for long periods. This pressure needs to be maintained for the expected shelf life of the contained liquid. The resilience of the closure also serves to minimize the effect of variations in the surface and dimensions of the neck on the sealing of the closure with the wall of the bottle. However, many materials used in the past have not had the required resilience, and thus may have provided an initial seal but have not provided an acceptable seal over time. Such materials have been materials that have deformed plastically, thereby relaxing the pressure exerted.
The metallocene catalyzed polyolefin is preferably a metallocene catalyzed polyethylene (such as Dow-“AFFINITY”, Exxon-“EXACT”, DuPont-“ENGAGE” or Mitsui-“INVOLVE”, which is formed by polymerization of comonomers using a metallocene catalyst. The metallocene catalyst may alternatively be referred to in the art as a constrained geometry catalyst or a single site catalyst. Such metallocene catalyzed poly ethylene materials also have the advantage of being chemically inert.
In the broadest form of the invention, it will be appreciated that the percentage amounts of the components will vary according to the size of the closure and the grade selection of the component being used. However, reference to a “major proportion” in the preferred form of the invention is to be understood to mean that the one or more copolymers of ethylene are provided in an amount from about 60% to about 90% (by weight), preferably from about 65% to 80% (by weight) and more preferably from about 70% to 75% (by weight). In determining the percentage amount of the copolymers in any given composition, reference should be made to all materials present which are copolymers of ethylene.
Furthermore, in relation to the metallocene catalyzed polyolefins of the disclosure of the present invention, reference to a “minor proportion” in the preferred form is to be understood to mean that the polyolefins are provided in an mount from about 10% to about 40% (by weight). In determining the percentage amount of the minor component in any given composition, reference should be made to all materials present that are metallocene catalyzed polyolefins that al
McMahon William James
Symons John Martin
Anthony Smith Australia Pty Ltd
Foelak Morton
Schwegman Lundberg Woessner & Kluth P.A.
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