Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1997-07-10
2001-02-27
Anthony, Joseph D. (Department: 1714)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S036600, C428S036910, C428S066400, C428S322700, C215S348000, C252S188280
Reexamination Certificate
active
06194042
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a closure liner and more specifically to a multi-layer closure liner which features gas barrier improved sealing characteristics and which includes an oxygen scavenging capacity.
2. Brief Description of the Related Art
Typically closures used in conjunction with plastic bottles are produced from commodity grade thermoplastic resins—polypropylene being presently the most popular resin due to a proper combination of physical properties and a low cost. However, such materials exhibit a relatively low resistance to permeation by gases such as air. Thus, the contents of the bottles made of this material will, irrespective of measures such as hot filling, inert gas flushing or vacuum degassing, tend to be, upon standing, exposed to atmospheric oxygen and thus subject to the possibilities of detrimental oxidation.
More specifically, oxygen which is a strong oxidizer, will chemically react with the content of the package/container and eventually will tend to make the product unusable due to chemical changes which will take place. Products which are subject to a chemical oxidation include, way of example only, foods and beverages, dyes, cosmetic products, photo chemicals and adhesives. Vitamin C is particularly susceptible to the effects of oxygen and products containing such material are prone to degradation and are apt to undergo changes in flavor, color or odor.
To overcome this drawback it has been proposed to make the bottle of a material which is less gas permeable. However, even under these circumstances, the closure member or cap can become a problem in that it is formed of a material which exhibits a lower resistance to gas permeation than the remainder of the bottle. That is to say, if a bottle or container is produced from a plastic which exhibits good gas barrier characteristics, such as PET—Polyethylene terephthalate, for example, or is made using a sophisticated multilayer material with relatively high gas barrier per unit area, then the surface area of the closure in an overall amount of the gas transmission is apt to become significant and must be given consideration.
However, due to the complexity of the process currently employed in the manufacture of plastic closures, which are mostly produced by injection molding using thermoplastic resins in multi-cavity molds, there are great technical and economical difficulties in designing a process which will allow the production of closures with suitably high gas barrier properties. Therefore, in order to reduce gas transmission rate through the closure area of the container, high-barrier liners are being used to provide a necessary seal as well as gas barrier characteristics.
Some presently used high-barrier liners are produced by the lamination of the coextruded Skin/Foam/Skin products with so-called barrier films or aluminum foil. However, this type of “passive” measure of preventing the invasion of oxygen into the interior of a container has met with only limited success and it has been accordingly proposed to actively scavenge oxygen in the head space which remains in a filled container in an effort to protect the contents of the container from the detrimental oxidizing effects of oxygen.
For example, U.S. Pat. No. 4,756,436 to Morita et al. discloses the use of a specially configured cap in which two compartments are separated from each other by a gas permeable liquid proof sheet. The lower of the two compartments contains an amount of oxygen scavenger, while the upper compartment is communicated with the head space above the liquid which is filled into the bottle, by small diameter passages. However, this arrangement while possibly being effective, is expensive to make and assemble and is not particularly suited for application with screw threads of the nature used in common plastic containers.
U.S. Pat. No. 4,287,995 to Moriya discloses a closure arrangement wherein an oxygen absorbent is disposed in a compartment which is defined below or in a layer of elastic packing material, and separated from the contents of the container by a gas permeable film. While this arrangement may be less complex and therefore less expensive to manufacture that than discussed above, it does not exact any measures which totally prevent the invasion of gas from outside of the container and therefore has not been totally successful in protecting the contents of the container from exposure to oxygen over prolonged periods of storage.
U.S. Pat. No. 4,279,350 to King teaches an oxygen scavenging system wherein a catalyst is used to convert oxygen, which has passed through a gas permeable water proof layer, into water, which is then trapped by the water proof layer. This arrangement is also devoid of measures to prevent the invasion of oxygen from outside of the vessel or container, and thus has tended to be less efficient than desired over prolonged periods of time.
U.S. Pat. No. 4,840,280 to Schvester discloses the provision of a layer of material containing an oxygen absorber and the provision of a film of polydialkyl siloxane to prevent the oxygen absorbing layers from direct contact with liquid stored in the vessel. Again there is no effort to prevent the invasion of external oxygen and only the oxygen which remains in the head space immediately after filling is considered.
Accordingly, there has not been any successful proposal of a commercially feasible low cost easy to produce liner which can be readily used in place of existing liners and which will a) prevent the ingress of oxygen containing air, and b) scavenge undesirable oxygen in the head space above the product filled into a vessel or container.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a high barrier closure liner having a multilayer polymer structure which can be obtained using simultaneous extrusion of individual polymers and their admixtures through common co-extrusion hardware.
It is a further object of the present invention to provide a high barrier multilayer closure liner which can be produced by either laminating or more preferably simultaneously extruding a plurality of different polymers in a manner wherein the layers include a gas barrier layer and preferably an oxygen absorbing agent containing layer.
It is yet another object of the invention to provide a multilayer closure liner wherein a foamed or cellular layer which is used to endow resiliency on the liner, is, in the preferred embodiments, also used to house the oxygen absorbing agent and thus improve the manner in which oxygen can be removed from the interior of the container.
In order to accomplish the above and other objects and to provide a liner which can be used in place of existing conventional liners used in a closure for a container, a multiple layer liner sheet is coextruded in a manner wherein the outer layers are skin layers formed of a gas permeable material. These layers enclose a gas barrier layer and one or more foamed layer which isolate the gas barrier layer which prevents the invasion of oxygen from the ambient atmosphere. An oxygen scavenging agent is preferably incorporated into a foam layer to remove oxygen from the head space to safeguard the contents of the container. The foamed layer(s) provides the liner with the required resiliency, the volume for the inclusion of an adequate amount of oxygen absorbing material, and also provides a cellular structure which allows the gas molecules the freedom to move about and quickly come into contact with the oxygen scavenging material. In a preferred embodiment, as the gas barrier layer is formed of a resin which is not melt-compatible with the materials which the foam layer and skin layers are formed of, tie layers of adhesive are extruded on either side of the gas barrier layer to ensure integrity when the coextruded sheet is formed into individual liners.
More specifically, a first aspect of the invention resides in a multi-layer liner for a container closure comprising: a first skin layer formed of a first material which exh
Burns Bruce
Finkelstein Harvey
Flores Victor
McKenna Richard
Verdel Anatoly
Anthony Joseph D.
Stroock & Stroock & Lavan LLP
Tri-Seal Holdings, Inc.
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