Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2000-09-18
2001-11-06
Anthony, Joseph D. (Department: 1714)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S036500, C428S036910, C428S322700, C215S347000, C215S348000, C215S228000
Reexamination Certificate
active
06312776
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved closure liner and, more specifically, to a multi-layer closure liner having an improved gas barrier characteristic and particularly suited for use with container closures for carbonated beverages or the like.
2. Brief description of the Related Art
Plastic containers have become widely used and commercially successful for holding and storing a wide variety of products. For example, plastic containers are now widely used to contain carbonated beverages. In fact, most bottles containing carbonated beverages are produced from polyethylene terephthalate (PET) or a similar material, which provides a low cost, light weight and durable container. Such containers are typically provided with a polyolefinic resin cap or closure and an ethylene vinyl acetate (EVA) liner.
One problem with the use of such containers for carbonated beverages is that this type of closure and liner have a relatively high gas transmission rate. Carbonated beverages rely on the maintenance of a certain amount of carbon dioxide gas pressure in the container to maintain the carbonated quality of the beverage. The problem, however, is that this type of container for carbonated beverages has a limited shelf life due to the gas transmission rate of the PET bottle, the polyolefinic closure and the EVA liner. In other words, such containers, closures and liners permit loss of carbonation because the resins used provide only a limited barrier to escaping carbon dioxide gas. Another and somewhat lesser problem, is that the container, closure and liner allow oxygen to enter the container which can degrade the taste of carbonated beverages over time and/or adversely affect other characteristics of a product contained therein.
The prior art has attempted to reduce the gas transmission rate of the container itself by providing a layer of resin therein having little or no permeability to gases, as evidenced, by U.S. Pat. Nos. 5,472,573; 4,391,863, 5,238,718; 4,980,211; 4,564,541; 4,451,512 and 4,528,219. While these prior art techniques have been helpful in reducing gas loss though the container itself, a significant amount of gas is still lost through the closure, including the closure liner.
Thus, a need exists for an improved closure liner having suitable compressibility and other physico-mechanical properties of existing EVA liners, but which prevents or significantly reduces gas transmission through the closure of the container, thereby extending the shelf life of carbonated beverages and the like.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide a multi-layer closure liner particularly suited for use in connection with container closures for carbonated beverages.
A further object of the present invention is to provide a multi-layer closure liner having a relatively low gas transmission rate as compared to prior art closure liners.
A more particular object of the present invention is to provide a multi-layer closure liner which reduces loss of carbonation and increases shelf-life for carbonated beverages and the like.
Another object of the present invention is to provide a closure liner which is inexpensive to manufacture and reliable in operation.
Still another object of the instant invention is to provide a closure liner which can easily be adapted for use with a variety of different closures for carbonated beverages containers and the like.
A further object of the present invention is to provide a closure liner which can be manufactured using existing manufacturing hardware.
Yet another object of the present invention is to provide a high barrier closure liner having a multi-layer polymer structure which can be manufactured using simultaneous extrusion of polymers through common co-extrusion hardware.
These and other objects are achieved by the instant invention, which provides a multi-layer closure liner including a gas barrier layer, a first tie layer on an upper surface of the gas barrier layer, a second tie layer on a lower surface of the gas barrier layer, a first polyolefinic resin layer on an upper surface of the first tie layer, and a second polyolefinic resin layer on a lower surface of the second tie layer.
In accordance with a more particular aspect of the instant invention, the polyolefinic resin layers may be made from recycled or low grade material to reduce the cost of the liner, and the liner further includes higher quality outer skin layers on the first and second polyolefinic layers. The low grade material may, for example, be material which is not FDA approved for food-contact applications. Such non-food contact grades of polyolefinic resins are typically more economical.
In accordance with a preferred embodiment of the invention, the gas barrier layer is ethylene vinyl alcohol copolymer (EVOH), the first and second tie layers are a functionalized polyolefin available, for example, from Millennium Petrochemicals and sold under the trade name Plexar, and the first and second polyolefinic resin layers are ethylene vinyl acetate (EVA).
In accordance with yet another aspect of the invention, the individual layers defining the closure liner are simultaneously formed using a co-extrusion process, so that the gas barrier layer is not exposed to moisture.
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Burns Bruce
Finkelstein Harvey
Flores Victor
McKenna Richard
Verdel Anatoly
Anthony Joseph D.
Hoffmann & Baron , LLP
Tri-Seal Holdings, Inc.
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