Patent Application
20070110934
This invention is directed to container closures that provide a barrier to gases, particularly oxygen, carbon dioxide and nitrogen, that may transfer to or from the container sealed by the closure. The invention particularly pertains to a multiple layer closure liner with a nylon gas barrier, and at least one associated layer which provides the desired mechanical sealing with a container. Alternatively or additionally, a scavenging material may be incorporated into the nylon and/or non-nylon layers of the liner. Nanoparticles may be incorporated into the passive nylon barrier layer.
Closures for containers are effective barriers if the closures can both be adequately sealed onto a container after the container is filled, and can be subsequently opened easily by a consumer. To this end, so-called composite closure constructions, including an outer molded plastic shell, and an inner, disc-like sealing liner, have proven to be highly commercially successful, providing the desired sealing properties, while facilitating convenient consumer use. Closures of this type are illustrated in U.S. Pat. Nos. 4,497,765 and 4,938,370, both hereby incorporated by reference.
Container closures that are designed to prevent the transfer of gases to or from the container may include a liner that may be made of multiple layers. Ethylene vinyl acetate (“EVA”) is a common liner material and is known to provide a suitable seal of the closure to the container while also maintaining an opening torque in a range that is easily applied by the end user or consumer.
EVA closure liners are known to have a relatively high gas transmission rate, which presents a particular problem when the container to be sealed contains a carbonated beverage. In order to maintain the carbonated quality of the beverage, a particular carbon dioxide gas pressure must be maintained in the container. Carbonated beverages have a limited shelf life due, at least in part, to the gas transmission properties of the EVA liner.
Another problem with liners or closures that have a relatively high gas transmission rate is that oxygen may enter the container. Oxygen can degrade the taste of a carbonated beverage over time and may adversely effect other properties of the product in the container. This can be particularly problematic in the case of beer and other fermented beverages.
Reduction of gas transmission to or from containers has been improved by careful selection of container materials, however, a significant amount of gas transmission to or from the container still takes place through the closure. Some container formulations have included types of nylon. Closure liners that have been designed to reduce the amount of gas transmission through the closure have included polyvinylidene chloride (“PVDC”), polyethylene naphthalene (“PEN”), ethylene vinyl alcohol co-polymer (“EVOH”), and mixtures of these polymers. Because the EVA material does not provide a complete barrier to gas transfer this material has been layered with other compositions but, where EVA is tied to polyolefinic layers, the layers may delaminate in a relatively short period of time.
Metal or plastic closures for use with containers carrying beer, juice or soft drinks have included liners of a polymeric heterogeneous blend of unvulcanized and uncrosslinked butyl rubber and a thermoplastic polymer. Foamed polymer sealing layers have been used to retard, but not completely prevent, the migration of oxygen and carbon dioxide through container closures. However, the shelf life of products with these foamed liners may be only slightly improved with a retardation of oxygen migration, as there exists an obvious relationship between the rate of oxygen ingress to the container and the shelf life of the product.
Multiple layer closure liners have been used to inhibit gas transfer to and from containers. One example of a multiple layer closure liner has a gas barrier layer of ethylene vinyl alcohol copolymer (“EVOH”) sandwiched between layers of EVA. These liners are formed by coextrusion process to prevent the gas barrier layer from being exposed to moisture. The EVOH barrier liners typically were comprised of nine coextruded layers. The layers of such liners may be bonded via an adhesive, or tie, layer to polyolefinic layers. These liners also may delaminate in a short period of time. Also, the effectiveness of EVOH as a barrier is reduced in environments with greater than about 70-80% of relative humidity. In container headspace, such as that for soft drink bottles, relative humidity may reach levels of 95-100%. Liners of this type were generally expensive and did not perform well.
Accordingly, there exists a need for a closure liner that provides an improved barrier to gas transfer to and from the container. There is further a need for such liners to avoid degradation while maintaining or improving the ease of manufacture of the liners.
The invention provides such a liner and method for making the liner that results in a closure that is more impervious to gas transfer, resists degradation and delamination and is easily manufactured. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.
The multiple layer liners of the present invention are for container closures that inhibit ingress of oxygen and egress carbon dioxide or other transfer gases into and from the container. Closures with liners of the type described here are particularly useful for sealing and storing bottles of beverages that are subject to taste degradation or reductions in quality associated with a loss of carbonation or introduction of oxygen. Such beverages in particular include carbonated soft drinks and beer.
The invention provides a container closure with an outer shell having a top wall portion and a cylindrical side wall portion depending from the top wall portion. The closure includes a multiple layer liner positioned adjacent to an inside surface of the outer shell. The liner includes at least one nylon barrier layer, at least one non-nylon layer, and an adhesive layer bonding the nylon barrier layer to non-nylon layer.
In one form, the non-nylon material is an ethylene vinyl acetate-based material. In another form, the non-nylon layer is a combination of ethylene vinyl acetate and a polyolefinic material.
In anther form of the invention, the closure further comprises an active scavenging material within the layer of ethylene vinyl acetate-based material. In a further form, the active scavenging material is selected specifically to react with a chemical selected from the group consisting of oxygen, carbon dioxide and nitrogen.
In one form, the passive nylon barrier incorporates inorganic nanoparticles, such as mineral clay material, as a passive barrier to gas transmission. The incorporation of the nanoparticles is accomplished by an in situ polymerization method. Alternatively or additionally, a reactive scavenging material may be incorporated into the nylon and/or non-nylon layers of the liner.
In a preferred embodiment, the passive nylon barrier layer, EVA layer, and the adhesive layer originate from materials having processing parameters in overlapping and/or adjacent ranges. The resulting multiple-layer liners have an adhesive strength of at least 8.5 pounds per inch.
In one form the invention is a process for manufacturing a container closure liner, the process includes the steps of selecting a nylon barrier material having a range of processing parameters, selecting a material based on ethylene vinyl acetate having processing parameters in a range overlapping, or adjacent to, the nylon barrier materials processing parameters, selecting a tie material having processing parameters in a range overlapping the processing parameters of the nylon barrier material and the material based on ethylene vinyl acetate, and co-extruding the nylon barrier material, the tie material and the material based on ethylene vinyl acetate.
In yet another form, the invention is the container liner produced by the co-extrusion process described herein.
In yet another form, the invention is a multilayer liner for use in sealing a container, the liner comprising a co-extrusion of a passive barrier of nylon, a tie layer of adhesive material on the passive barrier of nylon, and two outer layers of non-nylon material.
Other features and advantages of the present invention will become readily apparent from the following detailed description, the accompanying drawings and the appended claims.
a is a view of section 3a-3a of
While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment of the invention, with the understanding that the present disclosure is to be considered as an exemplification of the invention and is not intended to limit the invention to the specific embodiment illustrated.
Referring to
The multiple layer liner 20, as depicted in
Materials based on EVA in combination with another polyolefinic material have not before been used in multilayer structures. The EVA-layers 22 described here are each of a thickness in the range of about 10 mils to about 12 mils. The tie layers 24 are about 0.3 to 0.8 mils thick, and preferably between about 0.3 and about 0.5 mils. The nylon layer 26 is about 1.0 mil to about 1.5 mils thick.
Additional reduction of gas transfer to and from the container may be achieved by the substitution of nylon with a nylon nanocomposite material. The nanoparticles within the nanocomposite material may be, for example, clay particles and may account for about 2% to about 5% by weight of the nylon layer 26. Preferably, the clay particles are mineral clay particles. An example of a suitable inorganic nanoparticle is montmorillonite.
The nylon layer 26 of the multiple layer liner 20 acts as a good barrier and significantly inhibits gas transmission to and from the container. Additional active inhibition of gas transmission to and from the container may be achieved by the incorporation of active scavengers to react with oxygen, carbon dioxide, or other transfer gases. Examples of active scavengers are polyamides, sulfite oxygen scavengers and ascorbate in combination with a sulfite. An example of an EVA2 where the layer contains a scavenger, is DF-6601, described earlier. It is important to have adequate water vapor transmission rate (“WVTR”) through layers of the liner that contain a scavenger in order to provide adequate moisture to the scavenger because moisture is a trigger to begin scavenger activity. In addition to inhibiting oxygen permeability, the EVA-based materials of the present invention also provide WVTR to provide adequate scavenger activity. Another suitable example of EVA2 is DF-30375, also from W.R. Grace, Epernon, France. Examples of suitable EVA1 materials (having no oxygen scavenger) include DF-6442, described earlier, and DF-30376, both also available from W.R. Grace, Epernon, France. Active scavengers have a capacity and once the capacity has been utilized, the passive nylon barrier, that may contain nanoparticles, and multiple layers of the liner are still in place. The capacity of the scavenger may be increased within the closure liner by incorporating the scavenger into more than one layer of EVA when multiple layers of EVA are used in the liner. Preferably, the scavenger is included in the EVA layer that is closest to the contents, i.e., facing the headspace 31, of the container to be sealed by the closure 10.
The multiple layer liner 20 is co-extruded, suitably cut and fitted into the container closure 10. The co-extrusion process is simplified by the selection of material layers that have overlapping process parameters, or process parameters that are in a range near to the process parameters of the materials of the adjacent layers. The preferred nylon is XA-2908 This nylon contains nanoparticles that provide an additional passive barrier to gas transfer.
The range of processing temperatures determined by this invention to be useful for co-extruding the materials of the liner are listed in
Aside from their barrier properties, nylons, such as Nylon 6, are also useful for barrier closures due to their properties of puncture, tear and abrasion resistance, and for their thermo-formability. To obtain the narrowest range of temperatures required for manufacture of the structure of the closures disclosed herein, the nylon 6 preferably has a low melting temperature.
The adhesive load of liners manufactured by this method was analyzed. Samples of the co-extruded multi-layer material were tested as they came off-line and then again after 48 hours or more. The adhesive load was measured using the method prescribed by American Society for Testing and Materials (“ASTM”) D1876-2001. Results from the adhesive test are summarized in Table 1 and depicted in bar graph form in
For the following example Structures, T-peel testing was used to determine adhesive load as an indication of adhesive strength. These example structures, of course, should not be construed as in any way limiting the scope of the invention.
This example is the co-extrusion with a core material of the nylon copolymer Grivory HB EF 4581, tie material of PX on both sides of nylon copolymer in the co-extrusion and the EVA1 known as DF-6442 on both outer surfaces of the laminate. This Structure may be summarized as EVA1/PX/Grivory HB EF 4581/PX/EVA1.
This example is the co-extrusion with a core material of the nylon XA-2908, tie material of PX on both sides of XA-2908 in the co-extrusion and the EVA1 (DF-6442) on both outer surfaces of the co-extrusion. This Structure may be summarized as EVA1/PX/XA-2908/PX/EVA1.
This example is the co-extrusion with a core material of the nylon XA-2908, tie material of PX on both sides of the XA-2908 in the co-extrusion and EVA1 (DF-6442) on one outer surface of the co-extrusion and the EVA2 known as DF-6601 on the opposite outer surface of the co-extrusion. This Structure may be summarized as EVA1/PX/XA-2908/PX/EVA2.
This example is the co-extrusion with a core material of the nylon copolymer HB EF 4581, tie material of PX on both sides of nylon copolymer in the co-extrusion and the EVA1 DF-6442 on one outer surface of the co-extrusion and the EVA2 DF-6601 on the opposite outer surface of the co-extrusion. This Structure may be summarized as EVA1/PX/Grivory HB EF 4581/PX/EVA2.
This example is the co-extrusion with a core material of XA-2908, tie material of PX on both sides of the XA-2908 the co-extrusion and the EVA2 DF-6601 on both opposite, outer surfaces of the co-extrusion. This Structure may be summarized as EVA2/PX/XA-2908/PX/EVA2.
Removal torque was tested across a range of time and conditions. Containers with closures applied were cycled through several conditions and tested at various stages for removal torque. Bottles sealed with the closures having the multi-layer co-extruded liners described herein where moved from one controlled temperature area to another as described. Containers sealed with the standard multi-layer EVA (“Tri-Shield”) liner material included an EVOH barrier layer. The standard EVA liner is a nine-layer liner with EVOH as a barrier layer. Closures with liners were sealed onto containers and conditioned at a temperature of 95° F. for two days and then stored at ambient temperature (roughly 70° F.) for 24 hours. Removal torque was then measured. Then containers were conditioned at 40° F. for 10 days and transferred to ambient temperature for 24 hours prior to having removal torque tested. Then the closed containers were conditioned at 95° F. for two days and then returned to ambient temperature for 24 hours prior testing removal torque. Then the closed containers were conditioned again at 40° F. for 10 days, returned to ambient temperatures for 24 hours and tested for removal torque.
Closures containing the multiple layer liner with a nylon core were similarly sealed onto containers, conditioned and stored.
Closures 10 having only a passive nylon barrier 26 and a tie layer 28 bonding a layer of EVA1 or EVA2 material 30 to the passive nylon barrier also serve as good barriers against ingress and egress of gases such as oxygen, carbon dioxide and nitrogen. The EVA1 or EVA2 layer 28 will face the headspace 31 and form a seal with the container.
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Of course, variations of those preferred embodiments will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10282583 | Oct 2002 | US |
| Child | 11653678 | Jan 2007 | US |
