Patent Application
20180208357
The disclosure relates to a pull-tab sealing member for closing the mouth of a container, and more particularly, to a pull-tab sealing member having a tab formed with a sub tab layer underneath to provide concentric stability between peripheral portions of the sealing member and central portions of the sealing member during heat sealing to a container rim.
It is often desirable to seal the opening of a container using a removable or peelable seal, sealing member, or inner seal. Often a cap or other closure is then screwed or placed over the container opening capturing the sealing member therein. In use, a consumer typically removes the cap or other closure to gain access to the sealing member and then removes or otherwise peels the seal from the container in order to dispense or gain access to its contents.
Initial attempts at sealing a container opening utilized an induction- or conduction-type inner seal covering the container's opening where the seal generally conformed to the shape of the opening such that a circular container opening was sealed with a round disk approximately the same size as the opening. These prior seals commonly had a lower heat activated sealing layer to secure a periphery of the seal to a rim or other upper surface surrounding the container's opening. Upon exposing the seal to heat, the lower layer bonded to the container's rim. In many cases, these seals included a foil layer capable of forming induction heat to activate the lower heat seal layer. These prior seals tended to provide good sealing, but were often difficult for a consumer to remove because there was nothing for the consumer to grab onto in order to remove the seal. Often, the consumer needed to pick at the seal's edge with a fingernail because there was little or no seal material to grasp.
Other types of seals for containers include a side tab or other flange that extended outwardly from a peripheral edge of the seal. These side tabs are generally not secured to the container rim and provide a grasping surface for a consumer to hold and peel off the seal. These side tabs, however, extend over the side of the container rim and often protrude into a threaded portion of the closure. If the side tab is too large, this configuration may negatively affect the ability of the seal to form a good heat seal. The side tabs (and often the seal itself) can be deformed or wrinkled when the closure or other cap is placed on the container due to contact between the closure (and threads thereof) and tabbed part of the seal. To minimize these concerns, the side tabs are often very small; thus, providing little surface area or material for a consumer to grasp in order to remove the seal.
Yet other types of seals include a sealing member having a tab defined on the top of the seal. One approach of these prior seals includes a partial layer of coated pressure sensitive adhesive to secure the tab to a layer of metal foil. The tab was formed by a full layer extending across the entire surface of the sealing member, but the full layer was only bonded to half of the seal to form the tab. This type of top-tabbed seal offered the advantage of a larger tab, which provided more grasping area for the consumer to hold and peel off the seal, but required a full additional layer of material in order to form the tab. In other approaches, the seal may include a tab formed from the additional full layer of film combined with an additional full layer of adhesive utilizing a part paper or part polymer layer, called a tab stock, to form the tab. This part layer is inserted between the additional full layer of adhesive and lower seal portions to prevent the tab from sticking to the layers below, which formed the tab. In all the prior types of top-tabbed-like seals, the gripping tab was formed by a full layer of material (or a full layer of material and a full layer of adhesive) that extended across the entire surface of the seal.
As mentioned above, a cap or other closure is typically screwed or otherwise secured to a finish or neck of a container. This captures the sealing member between the top of the cap and container rim. In many instances, the cap has an annular bead or downwardly protruding ring (sometimes called a bead line) on the underside of its top inner surface. This annular bead is sized and positioned to generally correspond with an upper land area of the container rim when the cap is secured to the container. This annular bead helps provide pressure to secure the sealing member to the rim land area. However, many of the prior sealing members included a foam layer to provide insulation from heat generated during the heat sealing process. In some cases, there can be problems with the foam layer interacting with the cap annular bead during the cap sealing process. Heat from the cap sealing process combined with the focused downward pressure from the annular bead on the foam layer in the sealing member can damage or result in deterioration of the foam layer in the areas above the container rim. In extreme cases, the foam may melt or air cells in the foam may collapse. This shortcoming is more prevalent when the cap sealing process is over sealed (that it, when too much heat is applied or heat is applied for too long during the cap sealing process).
This melting and/or cell collapse may result in exposure of the metal foil or other polymer layers below the foam at the peripheral areas of the sealing member. In some cases, when the consumer lifts up the tab to remove the sealing member, the consumer is presented with an unsightly seal having an uneven foam layer under the tab with intact center portions of foam and melted or damaged edge portions of the foam. In extreme cases, the outer peripheral portions of the foam may melt completely, which exposes the metal foil or other layers under the tab.
When confronted with a heat management problem during a cap sealing process, such as the one set forth in the background, the conventional approach would be to add more insulation. In the case of tabbed sealing members with a foam layer, additional insulation may be obtained by adding further foamed polymers or by increasing the thickness of any existing foamed polymer layers. It is well understood that foaming of a polymer layer decreases its thermal conductivity and, thus, increases the ability of the foamed polymer to provide insulation and hinder the transfer of heat. Thicker foams would also logically compensate for the added pressure due to the cap's annular bead. Thus, the logical approach to solve the deteriorating foam issues of prior sealing members would have been to include a thicker foam layer or include additional foam layers to provide more insulation to hinder the flow of heat and/or to better absorb the downward pressure from the cap's annular bead.
The tabbed sealing members of the present application, however, take the unconventional approach of including one or more non-foamed, polymer layers between a tab and a foamed polymer layer in a seal laminate to provide a more robust tabbed sealing member. The sealing members of the present application are unexpectedly better able to withstand additional or excessive heating during the cap sealing process when combined with a cap or closure including the annular bead on its inner surface. The approach of the present application is unconventional because the non-foamed, polymer layer(s) have a higher thermal conductivity and are more rigid (as compared to foam) and would be expected to conduct more heat and not absorb the downward pressure of the cap as well as foam during the cap sealing process.
It was unexpectedly discovered that including one or more of these non-foamed, polymer layers between the tab and the foam actually helped reduce foam damage due to melting and cell collapse at the outer peripheral edge when the tabbed sealing members are exposed to excessive heating and the cap's annular bead during a cap sealing process. In some approaches, the non-foam, polymer layer(s) are positioned in the laminate between the tab and foam layers to be at least co-extensive with a peripheral edge of the tab and to extend inwardly along with the tab only part way across the seal. In other approaches, the non-foam, polymer layers(s) may also extend over the entire seal structure. In this manner, the non-foam, polymer layer(s) provides improved concentric stability to the sealing member and to the foamed polymer layer under the tab during cap sealing process. Concentric stability is the ability of the tabbed sealing member to generally maintain the integrity and cell structure of the foamed polymer layer at its peripheral edge above the container rim land area generally consistent with the integrity and cell structure of the foam layer at radially inner portions away from the edge. This concentric stability is achieved via the unconventional approach of using a thermally conductive and more rigid non-foam polymer rather than the conventional approach of using additional or thicker foamed insulation layers to address issues with the flow of heat and added pressure of the cap's annular bead during cap sealing.
In a first aspect, this disclosure provides a concentrically stable tabbed sealing member with a foam layer therein for sealing to a rim surrounding a container opening. The concentrically stable tabbed sealing member includes a multi-layer laminate with an upper laminate portion partially bonded to a lower laminate portion forming a gripping tab defined wholly within a perimeter of the sealing member. The gripping tab is arranged and configured for removing the sealing member from a container opening. The lower laminate portion below the gripping tab (such as when viewed through a cross-section extending through the tab) includes at least a seal layer for bonding to the container rim, a metal layer for heating the seal layer, and a polymer foam layer above the metal layer. Other layers may be included as needed.
To provide concentric structural support, the tabbed sealing members, in one approach (when viewed, for instance, through a cross-section extending through the tab), include one or more non-foam, polymer sub-tab layers between the polymer foam layer and the gripping tab. The non-foam, polymer sub-tab layer may be bonded to the upper surface of the lower laminate which may be a foam layer. In some approaches, the one or more non-foam, polymer sub-tab layers may be coextensive with at least the gripping tab at a periphery thereof. For instance, the one or more non-foam, polymer sub-tab layers may be partial layers coextensive with the tab or, as discussed more below, coextensive with a so-called tab stock layer. In other approaches, the one or more non-foam, polymer sub-tab layers may also extend over the entire sealing member between the upper laminate portion and polymer foam layer of the lower laminate portion. Even though the sub-tab layer is a non-foam polymer and tends to conduct more heat than a foamed polymer, it provides concentric structural support to the polymer foam layer at its periphery thereof relative to portions of the polymer foam layer radially inward from the periphery when exposed to heating and the cap's annular bead during a cap sealing process.
In another approach, this disclose also includes a container and cap assembly that includes the concentrically stable tabbed sealing member with foam mentioned above. The container includes a rim surrounding an opening thereof, and the cap closes the opening of the container. The cap includes a downwardly extending annular bead on a top inner surface thereof. The annular bead is arranged and configured to generally align with a land area of the container rim when the cap is received on a neck or other finish of the container.
In yet another approach, a pull-tab sealing member for a container is described herein containing an upper laminate forming a pull-tab bonded to a lower laminate capable of being heat sealed to a container's mouth or opening. The upper laminate defines a pull tab wholly within a perimeter or circumference of the seal. The sealing member includes a sub tab polymer layer underneath the tab and bonded to the lower laminate, but not bonded to the tab itself. This sub tab layer adds structural support to stabilize the sealing member and tab to aid in minimizing folding, wrinkles, creases, and the like. The sub tab polymer layer can be coextensive with the tab, extend slightly beyond the tab, but not extend the full width of the sealing member, or the sub-tab polymer layer may extend the full surface area of the sealing member. For instance, the sub tab polymer layer may be coextensive with a tab stock, be coextensive with the full upper laminate, or may be other sizes as needed for a particular application. This sub tab polymer layer can, in some approaches, be particularly advantageous in seals with relatively thin lower laminates (such as about 3 mils or less), but can be used in a wide variety of seals needing structural support with a tab. The sub tab layer may aid in providing concentric stability of the sealing member.
In other aspects of this disclosure, the upper laminate of the seal does not extend the full width of the sealing member in order to define the gripping tab. To this end, the pull-tab sealing members herein may also combine the advantages of a tabbed sealing member with a large gripping tab defined completely within the perimeter of the seal, but achieve such functionality with less material (in view of the part layers of the upper laminate) and permit such a tab structure to be formed on many different types of pre-formed lower laminates. This partial upper laminate can be combined with the sub tab layer described above and/or additional upper layers (such as a full paper layer) as needed for particular applications. The partial upper laminate structure is advantageous, in some approaches, for use with a seal configured for large or wide mouth containers, such as containers with an opening from about 30 to about 100 mm (in other approaches, about 60 to about 100 mm). These seals may also be used with 38 mm or 83 mm container openings, or can be used with any sized container.
In yet another aspect of this disclosure, the tab may be formed by a full layer or partial layer of material combined with a partial width composite adhesive structure that includes a polyester core with upper and lower adhesives on opposite sides thereof. This partial composite adhesive structure bonds the upper laminate to the lower laminate to form the gripping tab. The partial composite adhesive structure may also be combined with the above mentioned sub tab layers. In this approach, the sub tab is adhered to the lower laminate and not adhered to the upper laminate to enhance structural support.
In further aspects of this disclosure, the sealing members herein may include a pull or grip tab defined in the upper laminate portion wholly within a perimeter or circumference of the sealing member wherein an upper surface of the sealing member is partially defined by the upper laminate portion and partially defined by the lower laminate portion. In one approach of this aspect, the top surface of the sealing member is provided by a minor portion of the upper laminate and a major portion of the lower laminate. In other approaches of this aspect, the lower laminate is partially exposed at a top surface of the seal with about 50 percent to about 75 percent (or more) of the lower laminate exposed at the top surface of the entire seal. The seals of this aspect allow consumers to remove the sealing member using the tab (as in a conventional pull-tab seal) and/or puncture the sealing member by piercing the exposed lower laminate portion to provide push/pull functionality depending on the preference of the consumer. Prior tabbed seals having a top-defined gripping tab via a full width film layer generally did not allow the functionality of easy piercing because the additional full layers used to form the tab rendered the seal too difficult to pierce.
In such aspects, the seals of the present disclosure defining a tab wholly within a perimeter or circumference of the seal (but formed by a partial layer) also provide an improved ability for the tabbed sealing member to function in a two-piece seal and liner combination. In a two-piece seal and liner combination, the tabbed sealing member is temporarily adhered across its top surface to a liner. After container opening and removal of a cap or closure, the sealing member stays adhered to the container mouth and the liner separates and remains in the container's cap.
In some prior versions of two-piece seal and linear assemblies, the bottom layer of the sealing member is a heat seal layer that is activated by heating, such as by induction or conduction heating, in order to adhere or bond an outer periphery of the sealing member to a rim surrounding the mouth of a container. In the two-piece seal and liner combination, an upper surface of the sealing member is temporarily adhered to a lower surface of the liner by a release layer, which is often a heat-activated release layer, such as an intervening wax layer. During heating to bond the sealing member to the container, heat not only activates the lower heat seal layer, but also travels upwardly through the seal to melt the intervening wax across the entire surface of the sealing member to separate the liner from the sealing member. Often, the melted wax is absorbed by the liner in order to permit easy liner separation from the sealing member. As can be appreciated, for this sealing member and liner combination to function properly, the intervening wax layer needs to be melted across the entire surface of the sealing member. If the wax is not melted evenly all the way across the sealing member upper surface, the liner may not properly separate from the lower seal portion.
As the prior tabbed seals required additional full layers of material (film and adhesive) to form the tab, these additional layers would tend to negatively affect heat transfer upwardly through the seal. This shortcoming of less upward heat transfer limits the ability of top-tabbed-type seals to be used in the two-component liner and seal assembly because the required additional full layers of material (film and adhesive) to form the tab often led to issues with the proper melting the wax for liner separation.
These shortcomings of prior tabbed seals in the context of a two-piece liner and seal combinations tended to be even more pronounced in view of further shortcomings of some induction heating equipment. In an induction seal, a metal foil is often included in the seal to generate heat for activation of the heat seal. This heat is generated due to the induction apparatus forming eddy currents in the foil layer. The induction heat from the foil melts the lower heat seal layer for bonding to the container rim. In a common two-piece assembly, the induction heating generated by the foil layer is also used to melt the intervening wax layer (as mentioned above); however, the induction heating generated by the foil layer at the center of the seal is often lower than the induction heating generated by the foil at the periphery of the seal laminate. The center of the laminate is farthest away from the induction coil in the induction heating apparatus and the eddy currents in the foil are weakest at the center of the disk, which can form a cold spot in the center of the seal. This shortcoming tends to be further exaggerated in wide seals (such as those about 60 mm in diameter or larger or seals about 60 to about 100 mm across) because the center is much farther from the induction coil. Normally, such variation in induction heating between the edges of the seal laminate and the center is generally not an issue because heat is needed most at the seal's periphery for bonding to the container rim at the periphery of the seal laminates. In prior two-piece seals without top-oriented tabs, there was less material to hinder the upwardly directed flow of heat. However, when attempting to use the top-type-tabbed seals in a two-piece liner and seal combination, the extra full layers forming the tab often created problems when attempting to use induction heat to melt the intervening wax layer, especially in the center of the seal where the induction heating was the lowest.
In further approaches of this disclosure, the tab is formed wholly within a perimeter of the sealing member, but the upper laminate and layers forming that tab are spaced from central portions and regions of the sealing member. In some approaches, the layers defining the tab in the upper laminate are provided by a circular segment that is less than a semicircle within the sealing member's upper surface. As discussed more below, in some approaches, the upper laminate circular segment forming the tab is defined by a chord (that does not extend through the center of the sealing member) and the perimeter of the sealing member along its circumference between opposing endpoints of the chord. In this manner, the lower laminate is exposed at the center and center portions of the seal so that the center portions are free of the layers forming the tab (and upper laminate). This is advantageous in a two-piece assembly because it permits greater upwardly directed heat flow in the center portions of the seal to melt the intervening wax layer more easily than the prior tabbed seals.
Turning to more of the specifics,
For simplicity, this disclosure generally may refer to a container or bottle, but the sealing members herein may be applied to any type of container, bottle, package or other apparatus having a rim or mouth surrounding an access opening to an internal cavity. In this disclosure, reference to upper and lower surfaces and layers of the components of the sealing member refers to an orientation of the components as generally depicted in figures and when the sealing member is in use with a container in an upright position and having an opening at the top of the container. Different approaches to the sealing member will first be generally described, and then more specifics of the various constructions and materials will be explained thereafter. It will be appreciated that the sealing members described herein, in some cases, function in both a one-piece or two-piece sealing member configuration. A one-piece sealing member generally includes just the sealing member bonded to a container rim. A cap or closure may be also used therewith. A two-piece sealing member includes the sealing member temporarily bonded to a liner. In this construction, the sealing member is bonded to a container's rim, and the liner is configured to separate from the sealing member during heating to be retained in a cap or other closure used on the container. In a two-piece construction, a wax layer, for example, may be used to temporarily bond the sealing member to a liner. Other types of releasable layers may also be used to provide a temporary bond between the seal and liner, but the releasable layers are generally heat activated.
In this first approach, the circular segment forming the upper laminate 12 includes the tab portion 16, which is free to pivot upwardly at a pivot line 34 because the tab 16 is not adhered to the lower laminate 14. The circular segment forming the upper laminate 12 also includes an adhered portion 30 that is directly bonded to the lower laminate 14 or any intervening layers between the upper and lower laminates. The adhered portion 30 extends between the pivot line 34 and segment chord 20. In some approaches (turning to
The lower laminate 14 is not particularly limited and can be any single or multiple layer film structure, sheet, or laminate as needed for a particular application. For instance, lower laminate 14 may be from about 1 mil to about 20 mils thick, and in some approaches, about 7 to about 10 mils thick and include a lower heat seal layer for bonding to a container rim, a metal layer for heating the heat seal layer, and a polymer foam layer above the metal layer. In some approaches, however, particular laminate structures of the lower laminate 14 are more advantageous for certain applications.
In
The lower sealant or heat seal layer 100 may be composed of any material suitable for bonding to the rim of a container, such as but not limited to induction, conduction, or direct bonding methods. Suitable adhesives, hot melt adhesives, or sealants for the heat sealable layer 100 include, but are not limited to, polyesters, polyolefins, ethylene vinyl acetate, ethylene-acrylic acid copolymers, surlyn, and other suitable materials. By one approach, the heat sealable layer may be a single layer or a multi-layer structure of such materials about 0.2 to about 3 mils thick. By some approaches, the heat seal layer is selected to have a composition similar to and/or include the same polymer type as the composition of the container. For instance, if the container includes polyethylene, then the heat seal layer would also contain polyethylene. If the container includes polypropylene, then the heat seal layer would also contain polypropylene. Other similar materials combinations are also possible.
Support layer 102 may be optional in the laminate 114. If included, it may be polyethylene terephthalate (PET), nylon, or other structural polymer layer and may be, in some approaches, about 0.5 to about 1 mil thick.
Next, the membrane layer 104 may be one or more layers configured to provide induction heating and/or barrier characteristics to the seal 10. A layer configured to provide induction heating is any layer capable of generating heat upon being exposed to an induction current where eddy currents in the layer generate heat. By one approach, the membrane layer may be a metal layer, such as, aluminum foil, tin, and the like. In other approaches, the membrane layer may be a polymer layer in combination with an induction heating layer. The membrane layer may also be or include an atmospheric barrier layer capable of retarding the migration of gases and moisture at least from outside to inside a sealed container and, in some cases, also provide induction heating at the same time. Thus, the membrane layer may be one or more layers configured to provide such functionalities. By one approach, the membrane layer is about 0.3 to about 2 mils of a metal foil, such as aluminum foil, which is capable of providing induction heating and to function as an atmospheric barrier.
Layer 106 may be an insulation layer or a heat-redistribution layer. In one form, layer 106 may be a foamed polymer layer. Suitable foamed polymers include foamed polyolefin, foamed polypropylene, foamed polyethylene, and polyester foams. In some forms, these foams generally have an internal rupture strength of about 2000 to about 3500 g/in. In some approaches, the foamed polymer layer 106 may also have a density less than 0.6 g/cc and, in some cases, about 0.4 to less than about 0.6 g/cc. In other approaches, the density may be from about 0.4 g/cc to about 0.9 g/cc. The foamed polymer layer may be about 1 to about 5 mils thick.
In other approaches, the layer 106 may be a non-foam heat distributing or heat re-distributing layer. In such approach, the non-foam heat distributing film layer is a blend of polyolefin materials, such as a blend of one or more high density polyolefin components combined with one or more lower density polyolefin components. Suitable polymers include but are not limited to, polyethylene, polypropylene, ethylene-propylene copolymers, blends thereof as well as copolymers or blends with higher alpha-olefins. By one approach, the non-foam heat distributing polyolefin film layer is a blend of about 50 to about 70 percent of one or more high density polyolefin materials with the remainder being one or more lower density polyolefin materials. The blend is selected to achieve effective densities to provide both heat sealing to the container as well as separation of the liner from the seal in one piece.
When used in the seal 10, effective densities of the non-foam heat distributing polyolefin layer 106 may be between about 0.96 g/cc to about 0.99 g/cc. Above or below this density range, unacceptable results are obtained with non-foam layers because the layer provides too much insulation or does not effectively distribute heat. By another approach, the non-foam heat distributing layer is a blend of about 50 to about 70 percent high density polyethylene combined with low to medium density polyethylene effective to achieve the density ranges described above.
In addition, effective thicknesses of the non-foam heat distributing layer are selected to achieve such performance in combination with the density. One approach of an effective thickness may be about 2 to about 10 mils. In other approaches, layer 106 may be about 2 to about 5 mils thick, in other approaches, about 2 to about 4 mils thick, and in yet other approaches, about 2 to about 3 mils thick. Thicknesses outside this range tend to be unacceptable for heat redistribution because the layer does not provide enough insulation or does not effectively distribute heat as needed to achieve the dual performance characteristics of liner separation and seal member bonding.
On top of the lower laminate 14 is an optional, outer polymer support layer 108, which may be a non-foam PET, nylon, or other structural-type polymer layer(s) such as polyolefin or copolymers thereof. In one approach, outer layer 108 may be the one or more non-foam, polymer film or layers (or the non-foam, polymer sub tab layers discussed herein) mentioned above to provide concentric stability to the sealing member and polymer foam layer underneath it. In one form, layer 108 may be an asymmetrical polyester film having an upper layer of an amorphous polyester and a lower layer of a crystalized polyester layer. The amorphous polyester layer may have a lower melting point than the crystalized polyester and may aid in achieving a good bond with the upper laminate 12 and improve processing over hot rollers and other equipment during seal manufacture. In one approach, the layer 108 is a co-extruded layer with the crystalized layer being thicker than the amorphous layer. In the seal, the amorphous layer may form the bond with the upper laminate 12 and form the upper surface 32 of the lower laminate 14. The upper laminate 14 may also include other layers as needed for a particular application, which may be layers in between the various layers discussed herein as appropriate for a particular application. In other approaches, layer 108 may be one or more layers of a polyolefin. In some approaches, to provide concentric stability, layer 108 may be about 1 to about 5 mils thick and have a density of about 0.9 to about 1.5 g/ml (in some cases about 0.9 to about 1.2, and in other cases, about 0.9 to about 1.0 g/ml, and in yet other cases about 0.9 to about 0.96 g/ml).
Turning to
As explained previously, the layers forming the upper laminate may extend only partially across the sealing members 10 as generally shown in
Turning back to
In the approach of
When using the tab stock 124, the tab 16 is defined or formed via the tab stock 124 that extends only part way across the upper laminate 12. More specifically, the tab stock 124 forms the tab 16 because it bonds to the heat-activated bonding layer 120 and generally prevents layer 122 (and any layers above) from adhering to the upper surface 32 of the lower seal laminate 14 (or sub-tab polymer layer) across at least a portion thereof as generally shown in
The heat-activated bonding layer 120 may include any polymer materials that are heat activated or heated to achieve its bonding characteristics or application to the seal. By one approach, the heat-activated bonding layer may have a density of about 0.9 to about 1.0 g/cc and a peak melting point of about 145° F. to about 155° F. A melt index of the bonding layer 120 may be about 20 to about 30 g/10 min (ASTM D1238). Suitable examples include ethylene vinyl acetate (EVA), polyolefin, 2-component polyurethane, ethylene acrylic acid copolymers, curable two-part urethane adhesives, epoxy adhesives, ethylene methacrylate copolymers and the like bonding materials. As shown, the heat activated bonding layer 120 extends the full width of the laminate segment 12 (but not the full width or length of the entire seal 10 or the entire lower laminate 14). In other approaches, the laminate 12 may only include a partial layer of adhesive and, thus, not use the tab stock layer 124 discussed above. In other approaches, the bonding layer 120 extends the full width of the seal and is partially bonded to the lower laminate portion and partially bonded to the tab stock 124. In yet other approaches, the bonding layer 120 is partially bonded to the polymer support layer 108.
By one approach, the heat-activated bonding layer 120 is EVA with a vinyl acetate content of about 20 to about 28 percent with the remaining monomer being ethylene in order to achieve the bond strengths to securely hold the upper laminate to the lower laminate. In some cases, a vinyl acetate content lower than 20 percent is insufficient to form the robust structures described herein. By one approach, bonding layer 120 may be about 0.5 to about 3.5 mil of EVA, in other approaches about 0.5 to about 2.5 mils of EVA, in other approaches, about 0.5 to about 1.5 mils of EVA and, in yet other approaches, about 0.5 to about 1.0 mils of EVA; however, the thickness can vary as needed for a particular application to achieve the desired bonds and internal strength.
With sealing members including a tab defined wholly within a perimeter of the sealing member, upon pulling of the tab, there is a generally stress focal point right at the juncture or hinge joint 34 where the tab pivots upwardly. Generally, the stress upon tab pulling radiates downwardly and away from this hinge joint into the layers below the tab and, in some cases, results in a tearing of the layer immediately below the tab. This failure tends to occur more often in prior tabbed sealing members when the layer immediately below the tab is a foamed polymer. In the present approaches, the structural support layer 108 is also advantageous because it provides a more rigid, non-foam layer underneath the focal point of the tab pulling stress to provide a more robust laminate structure upon tab pulling. In the present approaches, the pulling stresses are dissipated throughout a denser, more rigid layer providing a more robust tab capable of withstanding even stronger heat seal bonds to containers. The density of the non-foam polymer layer under the tab, in some approaches, may be about 0.9 to about 1.2 g/cc. The sub-tab layer may also be about 1 to about 5 mils thick.
The approach of
As can be appreciated, for this separation to occur cleanly and properly, the wax needs to melt across the entire surface area of the seal 101. With prior seals having a full layer of film and in some cases a full layer of adhesive, there was additional material at the center portion of the seal that the upwardly directed heat needed to transfer through. As the center portions of the seal are farthest from the induction coils and, thus, generating the lowest levels of induction heat, the center of the seal was previously prone to not generating sufficient heating in a two-component assembly when an upper laminate included full layers forming the tab. This poor central upwards heat transfer was often made worse if the seal had an insulation layer that further limited upward heat transfer, or if the seal was large (such as about 60 mm or greater).
The seal of
In some approaches, the liner 302 can be formed of one or more layers of cardboard, pulp board, or a synthetic compressing agent (such as a synthetic foam or synthetic fibers) that is effective for absorbing the release layer 304, such as wax, upon being activated by heating. In one approach, the liner 302 may include a layer of foamed plastic material to which a paper layer (not shown) has been adhered to a bottom surface thereof. In this approach, the paper layer is the layer in contact with the release layer 304 for absorbing the molten wax or other activated components thereof. By another approach, the liner 302 may have a thickness in the range from about 400 to about 1800 microns. Synthetic foam or fibers may also be useful as materials or the liner if they are formed into a layer with a suitable compression factor comparable to pulp board of the type traditionally used in induction seals. For example, low density polyethylene (LDPE), coextruded LDPE, polypropylene (PP), and polystyrene (PS) foam or fibers may also be used as the liner. The synthetic material selected should have a sufficient absorbency, suitable pore volume, and structure to absorb substantially all of the wax used in the seal. The dimensions of the compressing agent absorbing material will vary according to the application and the size of the opening of the container and size and construction of the closure being used.
By one approach, the release layer 304 may be a wax layer. The wax may include any suitable wax material which will melt within the temperature range to which the sealing member is to be subjected by an energy source during the induction sealing process. For example, the wax layer may include paraffin, microcrystalline waxes, and blends thereof. By one approach, the wax layer may comprise a blend of paraffin wax and microcrystalline wax wherein the proportion of microcrystalline wax used in the wax layer is adjusted to provide the wax layer being formulated to enhance the ability of the wax to be absorbed by the liner. Alternatively, the wax layer may include microcrystalline wax modified with other polymeric additives to enhance its initial bonding properties. For instance, the wax layer may comprise microcrystalline wax modified with at least one of ethylene vinyl acetate and polyisobutylene.
In general, the application of induction energy to the sealing member heats the membrane layer 104 to a temperature, in some approaches, from about 300 to about 450° F. The volume or thickness of the wax layer, therefore, should be selected such that substantially all of the wax will melt during the manufacturing process and be absorbed by the compressing agent.
The tab 16 of the upper laminate circular segment may also define a second circular segment and may be defined by a second angle α2 between radius lines extending outwardly from the center C to secondary chord endpoints 300 and 302 on opposite sides of a chord defining the pivot line 34 of about 90 to about 120°, in other approaches, about 100 to about 115°, and in yet other approaches, about 105 to about 112°. In this manner, the seals define a tab 16 that wholly defined within a perimeter of the seal in a ratio of tab surface area to the surface area of the bond area 30 of about 1:1 to about 3:1 and in some approaches, about 1:1 to about 2:1. These ratios are achieved even when the upper laminate portion 12 is less than about 50 percent of the seal, in some approaches, less than about 40 percent of the seal, and in yet other approaches, less than about 35 percent of the seal's upper surface area.
Turning to
Turning to
The sub tab 202 may be a paper layer adhered to the lower laminate via a hot melt adhesive or a film layer (polyolefin, polyester, nylon, etc.) heat bonded or adhered to the lower laminate via a thin coating of adhesive. In some approaches, the sub tab 202 may be about 1 to about 5 mils thick and, in other approaches, about 1 to about 2 mils thick. The sub tab layer may be coextensive with the tab stock 124, which may also be a paper layer so that this approach presents a paper to paper interface between the tab 16 of the upper laminate 12 and the lower laminate 214. While the sub tab is shown in the figures to be a partial layer, the sub tab layer may also extend the entire width and surface area of the seal (not shown) as needed for a particular application as discussed previously and as discussed more below. The sub tab layer 202 provides structural support and aids in minimizing the formation of folds, creases, wrinkles and other deformities when the tab layer is applied to the lower laminate. The sub tab layer 202 may be particularly advantageous in providing structural support for lower laminates that are 3 mils or less as these are the most prone to such structural defects during handling and cap sealing and, in some cases, when combined with a gripping tab. For example, the sub tab layer 202 may aid in providing the concentric structural stability discussed previously during a cap heat scaling process.
In
In this approach, a tab 215 is formed from a polymer layer 350, which may be a structural polymer layer such as polyester (PET), PEN, nylon, or the like. Above the layer 350 may be an additional support layer, such as backing layer 222 (which may be bonded to layer 350 via adhesive layer 224, which is not shown in
The heat bondable materials 356 and 358 may include any polymer materials that are heat activated or heat applied to achieve its bonding characteristics. By one approach, the heat-bondable layer may have a density of about 0.9 to about 1.0 g/cc and a peak melting point of about 145° F. to about 155° F. A melt index of the heat bondable material may be about 20 to about 30 g/10 min (ASTM D1238). Suitable examples include ethylene vinyl acetate (EVA), polyolefin, 2-component polyurethane, ethylene acrylic acid copolymers, curable two-part urethane adhesives, epoxy adhesives, ethylene methacrylate copolymers and the like bonding materials.
By another approach, the heat bondable material is EVA with a vinyl acetate content of about 20 to about 28 percent with the remaining monomer being ethylene in order to achieve the bond strengths in order to securely hold the upper laminate to the lower laminate. A vinyl acetate content lower than 20 percent is insufficient to form the robust structures described herein. By one approach, layer 352 may include upper and lower layer 356 and 358 about 0.5 to about 1.5 mil of EVA and, in other approaches, about 0.5 to about 1.0 mils of EVA; however, the thickness can vary as needed for a particular application to achieve the desired bonds and internal strength.
Sealing member 300 may also include the sub tab layer 202 discussed above to provide structural support to the layers above and below the tab. The sub tab layer 202, in this approach, may have similar characteristics as the sub tab layer discussed above. The layer 202 is bonded to the upper surface of the lower laminate and not bonded to the layer(s) 350 forming the tab 215.
In alternative approaches, the sub tab layer 202 may, instead of being coextensive with the primary tab 16 or any tab stock 124 thereof, may extend laterally beyond the boundaries of the tab 16 or tab stock 124. In some approaches, the sub tab layer could be coextensive with the upper laminate or extend over half of the sealing member. In this approach, the sub tab layer could help improve adhesion of the upper laminate to the lower laminate. For instance, if a foam layer is used for the sub tab 202, then the sub tab could extend beyond the tab and tab stock further towards the center of the seal C to engage the bonding area 128, for example, to improve the bond therewith. In this approach, a strong bond would be needed between the extended sub tab layer 202 and the upper surface of the lower laminate (such as the foil layer.)
In another approach, if the sub tab layer 202 was a paper or other absorbent material, then temporarily bonding-type materials or adhesives could be applied to the upper surface of the sub tab to temporarily bond the upper surface of the sub tab to the tab 16 or the tab stock 124 in the upper laminate. In this manner, the temporary bond between the sub tab layer 202 and layers above it in the upper laminate would temporarily bond and/or hold the tab to the lower laminate in order to secure the upper tab substrate for maintaining concentric and/or lateral stability of the entire liner layers, including the tab interface to the lower layer, prior to heat activation and during normal handling and cap assembly.
By one approach, the temporary bond between the sub tab and upper laminate tab or tab stock could be by a wax layer, such as the previously described waxes. In this manner, upon heating to secure the sealing member to the container rim, the heat generated would melt the wax, which would release the tab or tab stock from the sub tab layer and free the tab for normal use. The wax could then be absorbed into the paper or other absorbent material of the sub tab layer similar to how wax is melted and absorbed by a liner in the two-piece assembly constructions described above. The wax could be applied or coated to the top surface of the sub tab layer prior to construction of the sealing member or applied in-line to this component during seal assembly. Alternatively, the temporary bond between the sub tab layer and the upper layers above it could employ alternative release mechanisms, such as dissimilar polymers (such as for example, different polymers on the sub tab and adjacent layers), slip additive loadings to the sub tab or other adjacent layers, cold seal release technology that may provide a temporary bond but would be easily peelable for a consumer to pivot the tab upwardly. In addition, the sub tab layer may further be formed of synthetic short non-woven fibers that are intertwined to form an absorbent sheet, similar to that described in U.S. Pat. No. 7,850,033, which is incorporated herein by reference in its entirety. When forming a temporary bond with the sub tab layer 202, and in some approaches due to the location in the laminate structure, any wax that may be used to form the temporary bond may be a wax with a higher melt point than the waxes discussed above with the two-piece seal and liner constructions. This higher melt point wax can be used in this location without impeding any functionality of the seal and release of the sub tab layer from the other layers during heat sealing. This is because the sub tab layer is positioned closer to the induction heating layer in some approaches.
In summary, the disclosure herein provide for, among other features, a tabbed sealing member for sealing to a rim of a container where the tabbed sealing member includes an overlapping upper laminate that may include a lower seal portion having a top surface with a total surface area and including a heat sealable layer configured for heat sealing to a container rim, an upper laminate at least partially bonded to the top surface of the lower seal portion to form a gripping tab defined wholly within a perimeter of the lower seal portion. In some approaches, the upper laminate has a top surface with a surface area less than the total surface area of the lower seal portion top surface and forming a circular segment defined by an edge forming a chord extending across the lower seal portion and spaced from a center of the tabbed sealing member. In some approaches, the sealing member further includes a sub tab layer coextensive with at least the gripping tab or extending the full extent of the seal. The sub tab layer is bonded to the top surface of the lower seal portion and not bonded to the gripping tab. The sub tab layer may be paper, polymers, polyester, and the like materials. In some approaches, a full backing layer is adhered to both the top surface of the upper laminate and the top surface of the lower seal portion. In some approaches, the backing layer is paper about 5 to about 10 mils thick.
In optional approaches, the tabbed sealing member may also include wherein an upper laminate with a heat activated bonding layer forming the at least partial bond to the top surface of the lower seal portion or a tab stock bonded to the heat activated bonding layer but not bonded to the top surface of the lower seal portion to form the gripping tab. In other approaches, an upper surface of the tabbed sealing member may be partially defined by a minor portion of the top surface of the upper laminate and a major portion of the top surface of the lower seal portion. The upper surface of the tabbed sealing member may also be temporarily bonded to a liner with portions of the liner are temporarily bonded to the top surface of the upper laminate and other portions of the liner are temporarily bonded to the top surface of the lower seal portion.
In some approaches, the lower seal portion may have a thickness and composition configured to be pierced through portions of the tabbed sealing member not covered by the upper laminate.
In some approaches, the circular segment forming the upper laminate may be defined by a sweep angle of the formula 2arccos (H1/radius). In some approaches, this angle may be about 125 to about 150°. In other approaches, the tab of the upper laminate is a circular segment being less than a semicircle and defined by a second sweep angle of the formula 2arccos (H2/radius). In some approaches, this angle may be about 90 to about 120°.
The circular segment of the upper laminate, in some forms, may cover about 10 to about 40 percent of the upper surface of the tabbed sealing member with the remainder of the upper surface being the top surface of the lower seal portion.
The lower seal portion, in some alternative approaches, may include a variety of different materials and layers. For instance, the lower seal portion may include a metal foil, and the top surface of the lower seal portion may be the metal foil. The lower seal portion may also include a foamed polymer, or the top surface of the lower seal portion may be a polymer film selected from polyolefin materials and polyester materials.
In other approaches, a tabbed sealing member for sealing to a rim of a container is described that includes a lower seal portion having a top surface with a total surface area and including a heat sealable layer configured for heat sealing to a container rim. The seal further includes an upper laminate at least partially bonded to the top surface of the lower seal portion to form a gripping tab defined wholly within a perimeter of the lower seal portion. The partial bond is formed by a composite layer of a polyester sandwiched between heat bondable materials on opposite sides of the polyester. The seal also includes a sub tab layer coextensive with the gripping tab. The sub tab layer is bonded to the top surface of the lower seal portion, but not bonded to the gripping tab. In some alternative approaches, the tabbed sealing the upper laminate includes a layer of polyester and a paper backing layer.
In optional approaches, the tabbed sealing members herein may include multi-component segmentation with a separate layer segmented from and adjacent to the upper laminate forming the tab. That is, the upper laminate may be adjacent to and separate from another segmented layer also bonded to the lower seal portion but distinct from the upper laminates discussed above. The segmented layer may be a single or multi-layer laminate that is the same thickness as the upper laminate forming the tab in the various approaches above. The segmented layer may be a paper layer.
It will be understood that various changes in the details, materials, and arrangements of the process, liner, seal, and combinations thereof, which have been herein described and illustrated in order to explain the nature of the products and methods may be made by those skilled in the art within the principle and scope of the embodied product as expressed in the appended claims. For example, the seals may include other layers within the laminate and between the various layers shown and described as needed for a particular application. Adhesive layers not shown in the Figures may also be used, if needed, to secure various layers together. Unless otherwise stated herein, all parts and percentages are by weight.
This application claims benefit of U.S. Provisional Application No. 61/791,788, filed Mar. 15, 2013, which is hereby incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61791788 | Mar 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15598780 | May 2017 | US |
| Child | 15926122 | US | |
| Parent | 14208122 | Mar 2014 | US |
| Child | 15598780 | US |
