WO2016149297A1

WO2016149297A1 - Tabbed innerseals with enhanced tab strength

Info

Publication number: WO2016149297A1
Application number: PCT/US2016/022536
Authority: WO
Inventors: Robert William Thorstensen-Woll
Original assignee: Selig Sealing Products, Inc.
Priority date: 2015-03-16
Filing date: 2016-03-16
Publication date: 2016-09-22

Abstract

Tabbed sealing members providing a more robust top-mounted tabbed structure that, in many cases, can be used as intended even if over bonded to a container rim. In part, the tabbed sealing members herein provide robust tab strength due to a composite layer including an amorphous polymer positioned underneath the tab and a tab hinge joint. In some approaches, the tabbed sealing members may also provide tamper evidence at the same time in view of an optional internal fracture or rupture layer that fails internally by horizontally separating into two complete portions thereof.

Description

TABBED INNERSEALS WITH ENHANCED TAB STRENGTH CROSS REFERENCE TO RELATED APPLICATION [0001] This application claims benefit of the United States Provisional Application No. 62/133,743 filed March 16, 2015, which is hereby incorporated by reference in its entirety. FIELD [0002] The disclosure relates to tabbed seals for containers, and in particular, tabbed seals for containers having enhanced tab strength. BACKGROUND [0003] It is often desirable to seal the opening of a bottle, jar or other container using a sealing member or inner seal. Often a cap or closure is then screwed or placed on the neck or container opening. In use, a consumer typically removes the cap or closure to gain access to the seal and removes or otherwise peels the seal from the container in order to dispense or gain access to its contents. [0004] These container seals often include an induction- or conduction-type inner seal covering the container’s opening where the seal generally conforms to the shape of the opening such that a circular container opening is sealed with a round disk approximately the same size as the opening and its rim or upper surface. These prior seals commonly had a lower layer of heat activated sealing material to secure a periphery of the seal to the rim or upper surface surrounding the container’s opening. Upon exposing the seal to heat, the lower layer bonds to the container rim. In many cases, these seals included a foil layer to provide induction heat to activate the lower heat seal layer. These prior seals tended to provide good sealing, but can be difficult for a consumer to remove because there was nothing for the consumer to grab for removing 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. [0005] In some instances, the lower layer of heat activated sealing material is over sealed or over bonded to the container. Often, the container sealing operation is over bonded out of an abundance of caution to make sure that the seal adequately bonds to the container. This is often accomplished by the container sealing operation being run longer or hotter than recommended to achieve an adequate seal for the particular heat seal layer and container assembly. While this over bonding may greatly enhance the bond of the seal to the container rim, the increased bond strength of the seal to the container may result in an undesired situation in which the consumer has difficulty removing the seal from the container due to the strong bond. In some cases, the bond is so great that the consumer tears the seal when trying to remove it such that the seal is removed in multiple small pieces. [0006] Yet other types of sealing members have a tab defined on the top of the seal. These top-tabbed or top-mounted seals offer the advantage of a large tab, which provides more grasping area for the consumer to hold and peel off the seal. In this approach, the tab can be formed by a full layer of material extending across the entire surface of the sealing member, but the full layer is only bonded to a portion of the seal to form this top-mounted tab. In situations where the container sealing operation is over bonded as mentioned above, the bond to the container can sometimes be greater than the tear strength of the top-mounted tab. Thus, when a consumer attempts to remove the seal using the top mounted tab, the tab can tear (often at its hinge joint to the seal) before the over bonded seal separates from the container rim. This type of failure is undesired and can be frustrating to a consumer. BRIEF DESCRIPTION OF THE DRAWINGS [0007] FIG.1 is a perspective view of an exemplary tabbed sealing member configured to compensate for over bonded seals and, in some instances, to provide tamper evidence; [0008] FIGS.2a and 2b are perspective and cross-sectional views of a tabbed sealing member including an optional internal fracture or rupture layer and an amorphous polymer underneath the top-mounted tab; [0009] FIGS.3a and 3b are perspective and cross-sectional views of the tabbed sealing member during pulling of the tab showing the internal fracturing or rupturing of the optional internal fracture layer; [0010] FIGS.4a and 4b are perspective and cross-sectional views of the tabbed sealing member after separation of the tab portion, which leaves a membrane still adhered to the container with a portion of the optional internal fraction layer exposed on its top surface; [0011] FIG.5 is an image of an exemplary fracture joint showing fiber separation of an exemplary internal fracture layer; [0012] FIG.6 is a cross-sectional view of an alternative tabbed sealing member including a polymer insulation or heat redirection layer, an amorphous polymer, and an optional internal fracture layer underneath the top-mounted tab; and [0013] FIG.7 is a cross-sectional view of yet another alternative tabbed sealing member including polymer insulation or heat redirection layer and an amorphous polymer underneath the top-mounted tab. DETAILED DESCRIPTION [0014] The various tabbed sealing members or inner seals described herein provide a more robust top-mounted tabbed structure that, in many cases, can be used as intended even if over bonded to a container rim. In part, the tabbed sealing members herein provide robust tab strength due to an amorphous polymer positioned underneath the tab and the tab hinge joint. In some approaches, the tabbed sealing members may also provide tamper evidence at the same time in view of an optional internal fracture or rupture layer that fails internally by horizontally separating into two complete portions thereof. The sealing members preferably have top- mounted tabs that are defined wholly within a perimeter of the sealing member, which may be formed via a partial layer of adhesive and/or a release layer that prevents the tab from bonding to the layers below it. [0015] In one aspect or embodiment, the tabbed sealing member includes a unique co- extruded polymer layer (preferably, a co-extruded polyester layer) including amorphous polymer regions or layers and crystalline or semi-crystalline polymer regions or layers

(preferably, amorphous polyester regions and crystalline or semi-crystalline polyester regions) to provide enhanced composite strength to the tab, an unexpected strong bond to a polyolefin, and to support the interface or hinge joint of the tab relative to the lower seal structure. The co- extruded polymer layer (preferably, polyester) includes a thin upper amorphous polymer layer or region (preferably amorphous polyester) combined with a thicker, lower crystalline polymer layer or region (preferably crystalline polyester). This co-extruded amorphous and crystalline polymer composite (preferably polyester composite) strengthens the interface of the tab at its hinge joint due, at least in part, to the amorphous polymer being able to dissipate tensile stress from tab pulling and from an unexpectedly enhanced bond to polyolefin polymers in the upper laminate. As used herein, when a crystalline polymer is mentioned, it will refer to a crystalline or a semi-crystalline polymer. [0016] As mentioned, the tab may be formed by a partial bond or partial layer of adhesive between the upper and lower laminate portions of the sealing member. In many instances, the amorphous polyester may also provide an enhanced bond forming the tab. This was unexpected. Amorphous polyester, while understood to form good heat seal bonds to itself or other polyester materials, was not expected to form a strong bond to polyolefin polymers, polyethylene, or copolymers of polyethylene such as, for instance, ethylene vinyl acetate. Thus, it was discovered that the amorphous polyester in the context of the tabbed sealing members herein may compensate for the tendency of the container sealing operation to over bond the seals (as discussed above) because the amorphous polyester permits greater pulling forces on the tab via a strong bond to the upper laminate layers, stress dissipation and/or a strengthened partial bond forming the tab. [0017] In other aspects or embodiments, the tabbed sealing members herein may also include an optional internal fracture or internal rupture layer that is configured to internally rupture or internally fracture, preferably horizontally, into two complete separate portions. Upon rupture, a first or upper separated portion remains with the tab (and other layers associated with the tab) and is removed from the container completely, and the second or lower separated portion of the fractured layer (and other layers associated therewith) remains bonded to the container and continues to cover the container’s opening. A consumer then needs to puncture the second or lower portion of the internal fracture layer as well as any other remaining layers bonded thereto to gain access to the container’s contents. This internal fracture layer, when used, also compensates for over bonded seals because the failure point in the seal is the internal failure of this fracture layer and, thus, it purposely fails before the seal debonds from the container or before the tab or other layers tear. Accordingly, the functionality of the seal is not dependent on the bond strength to the container so long as the failure point of the internal fracture layer is less than the bond strength to the container and the tear strength of the tab to the seal. [0018] In another aspect or embodiment, a tabbed sealing member is provided with a foamed polymer layer, either with or without the optional internal fracture layer, combined with the above described coextruded polymer layer with amorphous and crystalline regions. When used with the foamed polymer layer and the top mounted tab, the co-extruded amorphous polymer also provides a strong interface along the tab hinge joint (and preferably above the foam). [0019] In general, the concepts herein describe a pull-tab sealing member (or laminate sheets having free portions thereof for forming such pull-tab sealing member when die cut from the sheet) for a container including an upper laminate partially bonded to a lower laminate forming a free portion that creates a pull-tab. The pull-tab sealing member has a lower layer that is capable of being heat sealed to a container’s mouth or opening. In one aspect, the sealing members herein include the pull or grip tab defined in the upper laminate portion wholly within a perimeter of the sealing member due to the upper laminate being partially bonded to the lower laminate. The various sealing members and laminates herein include improved structures to form a more robust and stronger tab as set forth above and, in some approaches, provide tamper evidence. [0020] With sealing members including a top-mounted tab (often defined wholly within a perimeter of the sealing member), upon pulling of the tab, there is a stress focal point right at the juncture or hinge joint where the tab pivots upwardly. Generally, the tensile 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 and/or tearing of the tab at this hinge joint. This failure tends to occur more often in prior tabbed sealing member designs when the layer immediately below the tab is a foamed polymer but may also occur in other types of layers depending on the thickness, compositions, and/or density of such layers under the tab. In the present approaches, various structural support layers forming the tab and/or below the tab provide a more robust tabbed seal. For one, the structures herein may provide a more rigid, non-foam layer at or below the tab pivot or hinge joint and also a more rigid, non-foam layer underneath the focal point of the tab pulling stress or right at the tab hinge or pivot point to provide a more robust laminate structure upon tab pulling. [0021] In the present approaches, the pulling stresses are dissipated throughout an amorphous polymer layer or region, such as amorphous polyester, and throughout a denser, more rigid layer providing a more robust tab capable of withstanding even stronger heat seal bonds to containers. It was not expected that an amorphous polymer layer, such as an amorphous polyester layer would have resulted in an improved tabbed seal in the context of the tabbed sealing members herein. For one, the amorphous polyester was not commonly appreciated to form bonds with polyolefin polymers, rather it was expected to form heat seal bond to itself or other polyester. Amorphous polyester (aPET) is widely reported as not forming strong bonds to polyolefin polymers. Thus, it was unexpected that use of a co- extruded polyester composite with an amorphous layer or region would have formed a strong bond to polyolefin polymers, such as polyethylene, or copolymers of polyethylene such as ethylene vinyl acetate (EVA). [0022] Turning to more of the details and as generally shown in Figures herein, tabbed sealing members are shown exhibiting enhanced tab strength. In FIG.1, a generic tabbed sealing member 10 is provided as a laminate 12 formed from flexible sheet materials or extruded film materials with a lower laminate portion 14 for bonding to a container’s rim 16 and an upper laminate portion 18 forming a free portion and a gripping tab 20 that is defined wholly within a perimeter 22 of the tabbed sealing member 10. The tab 20 is formed due to the upper laminate 18 being partially bonded to the lower laminate 14 and forming a free portion that can be pivoted upwardly. In use, by pulling on or grasping the tab 20, a user can pivot the tab upwardly about a hinge joint 21 as shown in FIG.1 and use the tab 20 to remove the sealing member 10 from a container rim or other container portion 16 or to separate the tab and one portion of the internal fracture layer from another portion of the internal fracture layer as discussed more below. [0023] FIGS.2a and 2b show a tabbed sealing member 100 including a laminate of multiple layers, sheets, polymer coatings, or extruded materials that also includes a tab 120 defined wholly within a perimeter of the seal. The sealing member 100 includes an optional fracture layer 102 in a lower laminate 113, which is configured to internally rupture or fracture within a pre-defined layer of the laminate. The internal failure is a cohesive-like failure where the optional internal fracture layer 102 internally fails along a generally horizontal failure junction to form two separate portions after failure. The sealing member 100 may also include a lower heat seal layer 104, an induction heating layer 106 (such as foil), a polymer support layer or composite 108 that includes a co-extruded amorphous polymer top surface, portion or region 112 (preferably amorphous polyester) and a crystalline or semi-crystalline polymer bottom surface, portion, or region 110 (preferably crystalline or semi-crystalline polyester). These combined layers form the lower laminate 113. It will be appreciated that adhesive tie layers may be included between any of the layers shown in FIG.2b. For example, there may be an adhesive tie layer between the heat seal layer 104 and the foil layer 106 and/or an adhesive tie layer between the layer 108 and the layer 102. [0024] The tabbed sealing member 100 may also include an upper laminate 115 that is partially bonded to the lower laminate 113 to form a free portion or the gripping tab 120. This may be formed by a partial layer of adhesive, or as shown, a so-called release layer or tab stock 116 that is bonded to the layers in the upper laminate 115 but not bonded to the layers in the lower laminate 113. The upper laminate may also include a bonding layer 114 that, in some approaches when combined with the release layer 116, forms the partial bond 117 with the lower laminate 113. Above the bonding layer 114, there may be a polymer support layer 118, such a polyester layer. FIGS.2a and 2b illustrate the seal 100 prior to tab pulling. [0025] FIGS.3a and 3b illustrate the tabbed sealing member 100 in exemplary approaches of being removed from a container via tab pulling (either perpendicular to the hinge joint or parallel to the hinge joint) with the optional internal fracture layer 102 starting to fail or rupture horizontally along an internal failure junction 103. As shown, the layer 102 fractures into two portions: a top separated portion 102a and a bottom separated portion 102b. This failure tends to be a cohesive-like internal failure because the laminate structure does not separate along any interface between laminate layers, but the layer 102 fractures, ruptures, or fails internally thereof and not along either of the interfaces of the top or bottom surfaces of layer 102 with the layers adjacent to it. By one approach, layer 102 may be a paper, cellulose, glassine, woven synthetic fiber, polymer layer, or polymer fiber layer where the failure may be internal separation of fibers and/or breakage of paper fibers, cellulose fibers, glass fibers, or polymer synthetic fibers. The failure mode is generally horizontally and internally to the layer 102 and may include fibers separating from other fibers within the layer such as that shown in the exemplary image of FIG.5 or, in other approaches, the failure mode may be individual fibers breaking or shearing apart as the layer fails along the failure junction 103. If a polymer film layer is used for layer 102, the separation may be an internal cohesive failure of the polymer material. [0026] In FIGS.4a and 4b, the tabbed sealing member 100 is illustrated after tab pulling and separation of the optional internal fracture layer 102 into two separate portions 102a and 102b. As layer 102 tears or ruptures, the exposed surfaces of layers 102a and 102b may have a rougher surface texture Shown in FIGS.4a and 4b is a top seal portion 130 (including the tab 120) that is removed and separated from a lower seal portion 140. [0027] The layers in the top seal portion 130 remain bonded together and includes the tab 120, top support layer 118, bonding layer 114, release layer 116 (if used), the amorphous and crystalline polymer (preferably polyester) layer 108, and the top portion 102a of the (now ruptured or fractured) internal fracture layer 102. These layers remain bonded together in one piece. [0028] The layers of the bottom seal potion 140 also remained bonded together and sealed to the container rim 16. This portion includes the lower heat seal layer 104, the induction heating layer or foil 106, and the bottom portion 102b of the (now ruptured or fractured) internal fracture layer 102. To gain access to the container contents, a user now simply needs to puncture the bottom seal portion 140. To this end, the lower seal portion, in some approaches, may not include any polymer layers that provide resistance to puncturing, such as polyester or other polymer layers with a density of 1 g/ml or more. In some approaches, the bottom seal portion 140 may also be free of foamed layers with densities less than 0.6 g/ml, which also tend to provide resistance to puncturing due to the thickness of such layers often used in the laminates. [0029] Optionally, the tabbed sealing member 100 may further include a polymer foamed layer 107 such as illustrated in the alternative tabbed sealing member 100 of FIG.6. In this approach, the polymer foamed layer 107 may be above the optional internal fracture layer 102 and below the amorphous and crystalline layer 108 (optional adhesive tie layers may be used as needed). This layer provides heat insulation to the layers above the foil. In yet other approaches, layer 107 may be a non-foamed heat-distribution polyolefin layer having the specific material characteristics as described in more details below. [0030] FIG.7 illustrates yet another approach of a tabbed sealing member 1000 to provide enhanced tab strength and to compensate for over bonded seals. In this approach, the seal includes a upper laminate 1115 at least partially bonded to a lower laminate 1113 to form a gripping tab 1120 defined wholly within a perimeter of the sealing member. [0031] The lower laminate 1113 includes a lower heat seal layer 1004, an induction heatable layer 1006 such as foil, an optional polymer insulation layer 1007 (such as a polymer foam layer or a non-foam polyolefin heat redistribution layer), and a co-extruded amorphous and crystalline polymer support layer 1008 providing a top surface of the lower laminate.

Preferably, layer 1008 is a co-extruded amorphous and crystalline polyester layer and is consistent to layer 108 described previously. [0032] The upper laminate 1115 includes a top polymer support layer 1118 (such as PET, PEN, nylon and the like), a bonding layer 1114 that provides a partial bond 1117 to the top surface of the lower laminate, and an optional partial release layer 1116 that is bonded to the layers above it but not bonded to the layers below it (that is, the top surface of the lower laminate). [0033] As shown in FIG.7, the laminate may also include optional adhesive tie layers 1150 as needed to bond the various layers together, such as between layers 1008 (co-extruded polyester layer) and the optional foam layer 1007, between the optional foam layer 1007 and the foil layer 1006, and, in some instances, between the foil layer 1006 and the sealant layer 1004. These optional adhesive tie layers are described more below. [0034] The tabbed laminate structures described in this disclosure exhibits an enhanced tab bond strength of up to about 5000 g/in of pulling force and, in other approaches, up to about 4800 g/in of pulling forces due, at least, in part to the included composite layer 108 or 1008. In some approaches, tab bond strength is greater than about 3800 g/in and up to about 5000 g/in. This increased level of tab strength is approximately a 25 percent increase of prior tabbed seals that do not have the amorphous and crystalline layer under a tab. The increased tab strength may be due to the amorphous polymer layer (such as amorphous polyester) supporting the tab, tab hinge joint, and forming the at least partial bond to the upper laminate. [0035] 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 members discussed herein 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 an upper surface of the sealing member to the liner. During induction heating, the wax layer melts and is typically absorbed into the liner. Thus, the liner separates from the sealing member. The liner then generally stays in the cap, and the sealing member generally stays adhered to the container rim. Other types of releasable layers (other than wax) may also be used to provide a temporary bond between the seal and liner. Any of the exemplary tabbed sealing members herein may also be combined with a liner that is wax bonded to the top surface of the tabbed sealing member. In some cases there may be a paper layer as the top layer in the lower laminate, and it absorbs the wax, and the liner is a foam (typically not wax absorbing) [0036] Turning to more details, the various layers set forth in the embodiments and approaches above will be described in more detail below. It will be appreciated that any of the above desdribed approaches or embodiments can includes any of the materials, [0037] If included, any of the mentioned structural polymer layers (such as layer 118 or layer 1118) may be polyethylene terephthalate (PET), nylon, polyethylene naphthalate (PEN), or other structural polymer layer and may be, in some approaches, about 0.5 to about 3 mil thick. The PET may be a conventional semi-crystalline sheet or film of material. The polymer support layers (118 or 1118) can also be selected from a variety of suitable non-foamed polymer materials that are capable of providing structural support at a relatively thin thickness. For example, the polymer materials may be uni-axially oriented polymers or bi-axially oriented polymers, such as uni-axially oriented polypropylene and bi-axially oriented polypropylene. The support layers may also be copolymers and/or blown film layers. By one approach, the support layer may be oriented in a cross-web direction only. In some approaches, these axially oriented polymers may have a modulus of elasticity in a longitudinal direction of greater than about 2,000 N/mm². In other cases, the film may have a modulus of elasticity in a cross- direction of about 4,000 N/mm² or greater. Some films may be bi-axially oriented and have both the longitudinal and cross-web modulus of elasticity mentioned above. In other approaches, the various polymer support or structural layers may be about 2 to about 5 mils thick. [0038] Any of the laminates herein may also include a polymer foam layer (such as layer 107 or 1007). For example, the polymer foam may be a polyethylene foam layer. Other suitable polymer foams include polypropylene or propylene-ethylene copolymers. Polyethylene foam is preferred because of desired bonding behavior and bond strength to the foil layer. The thickness of foam layer may be at least about 0.003 inches, more preferably at least about 0.005 inches and, in some approaches, about 0.003 to about 0.010 inches. If the thickness is too thin the heat from the induction sealing process can melt the foam. Also, the desired bond strength might not be achieved. Furthermore, if the foam is too thin, it will provide less compression and the bond achieved via induction heating can become less reliable. When the foam is thicker than about 0.010 or even 0.008 inches, the benefits begin to stop and material's cost and bulkiness can present problems in the context of an induction bonding process. In some forms, the polymer foam layer may have an internal rupture strength of about 2000 to about 3500 g/in. In some approaches, the foamed polymer layer 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. [0039] The amorphous and crystalline co-extruded polymer layer or composite (such as layer 108 or 1008) may preferably be a co-extruded asymmetrical polymer with two different structural forms of polymer within a single composite polymer layer. For example, there may be a thin amorphous polymer region, surface, or layer on one surface (in some approaches, about 1 mil or less in amorphous thickness) and a thicker, crystalline or semi-crystalline polymer region, surface, or layer on the other surface. Preferably, the polymer layer or composite 108 or 1008 is polyester, such as polyethylene terephthalate (PET) and includes an amorphous polyester layer, region, or surface and a crystalline or semi-crystalline region, surface or layer on the opposite surface thereof. By one approach, the co-extruded polymer layer or composite is about 0.5 mil to about 1.5 mil thick with the amorphous region, surface or layer being about 25% or less of the total thickness of this layer. [0040] The amorphous polymer layer, region, or surface (preferably the amorphous polyester layer, region, or surface) forms a strong bond to the bondable layers 114 or 1114 and, in particular, EVA. As previously described, however, this strong bond was unexpected due to the amorphous nature of the polymer or polyester and that amorphous polyesters were not expected or even recommended to form strong bonds with polyolefin polymers. By one approach when the bondable layers are EVA (and not wishing to be limited by theory), the random nature of the polymer or polyester chains in the amorphous polymer may promote strong bonds with the acetate branches in the EVA layer through, in some instances, physical or mechanical interlocking of the acetate branching (along with chemical or adhesive bonding) into an interface formed with or between the amorphous polyester chains. To this end, it may be preferable for the EVA to includes at least about 20 percent vinyl acetate branching and, in other approaches about 20 to about 40 percent vinyl acetate, and in yet other approaches, about 20 to about 30 percent vinyl acetate. Below 20 percent vinyl acetate in the bonding layer may be insufficient to form the bonds needed with the amorphous polymer layer, region, or surface. [0041] Co-extruded polymer layer 108 or 1008 (a composite of the amorphous region or layer and crystalline or semi-crystalline region or layer) may have a combined density greater than about 1 g/ml and, in some approaches, about 1 to about 1.5 g/ml to provide a strong layer underneath the tab. In some approaches, the amorphous portions or regions may have a density lower than the crystalline portions or regions of the coextruded polymer. In some approaches, the amorphous layer or portions may exhibit a heat seal temperature between about 200 and about 400°F. In other approaches, the crystalline layer or portions may exhibit a melt temperature of about 255°F to about 260°F. [0042] While not wishing to be limited by theory, the amorphous polymer, such as the amorphous polyester, may not only form an unexpected strong bond with the bonding polymer layer 114 or 1114, such as EVA, it may also readily scatter or dissipate tab pulling tensile stresses at the tab hinge joint 21 downwardly into the amorphous polymer region. While not wishing to be limited by theory, the amorphous structure of the polymer molecules may aid in absorbing or dissipating the pulling tensile stresses imparted on the laminate via the tab because the amorphous nature of the polymer may allow the material to flow, blend, or stretch more easily than the crystalline material as the stresses are imparted to the tab by pulling. The crystalline or semi-crystalline portion provides strength and structure to the layer. This amorphous and crystalline co-extruded polymer layer or region (again, preferably polyester) may be about 10 to about 30 microns thick and, in some approaches, about 10 to about 20 microns thick and the crystalline portions may be about 75 percent or more of the total thickness of the coextruded polymer layer. [0043] There may also be various adhesive or adhesive tie layers (not shown in some of the figures but may be added between any layers as needed) that directly bond or secure various layers together. In some approaches, the tie layer is layer 1150. For instance, thin adhesive layers may be used to secure layers together as needed for a particular application, and may be, for example, about 0.2 to about a 0.5 mil (or less) adhesive, such as a coated ethylene vinyl acetate (EVA), polyolefins, 2-component polyurethane, ethylene acrylic acid copolymers, curable two part urethane adhesives, epoxy adhesives, ethylene methacrylate copolymers and the like bonding materials. [0044] The optional internal fracture layer 102 ruptures or cleaves internally all the way across the layer substantially horizontally and generally does not tear vertically. As mentioned above, layer 102 may be a paper, glassine, cellulose, polymer film, polymer fiber, fiber mat or sheet (woven or non-woven). The paper layer may be cellulose fibers. In some approaches, layer 102 may be about 2 to about 8 thousands of an inch thick and may have an internal failure or bust strength of no more than about 20 psi and, in some approaches, about 10 to about 20 psi, and in other approaches, about 10 to about 16 psi. To function in this failure mode, the failure junction burst strength is less than the bond strengths (of the heat seal layer to the container and the other layers to each other) and tear strengths of the other layers within the laminate. In addition, the bond of the heat seal layer to the container also is stronger than the failure junction or burst strength. As can be appreciated, tabbed laminate 100 including optional layer 102 is configured to function no matter how much over bonding the lower sealant is sealed to the container rim and, the stronger the bond to the container, the easier it may be for a consumer to rupture layer 102 upon tab pulling. In some approaches, layer 102 may be about 0.5 to about 3 mils thick. [0045] As mentioned, the tabbed sealing member may include optional non-foamed heat distribution layers. If used, the non-foam heat distributing layer may be a non-foam heat distributing polyolefin film layer. By one approach, the non-foam heat distributing polyolefin 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. [0046] By one approach, effective densities of the non-foam heat distributing polyolefin layer may be between about 0.96 g/cc to about 0.99 g/cc. Above or below this density range, unacceptable results are obtained 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. [0047] 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, such layer 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 were unacceptable 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. [0048] Suitable adhesives, hot melt adhesives, or sealants for the lowermost heat sealable layer (such as layers 104 or 1004) may include, but are not limited to, polyesters, polyolefins, ethylene vinyl acetate, ethylene-acrylic acid copolymers, surlyn, and other suitable materials. By one approach, the lowermost 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 contains polyethylene, then the heat seal layer would also container polyethylene. If the container contains polypropylene, then the heat seal layer would container polypropylene. Other similar materials combinations are also possible. [0049] By one approach, any membrane or foil layer (such as layer 106 or 1006) may be one or more layers configured to provide induction heating and barrier characteristics to the seal. 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. [0050] The bonding layer or heat-activated bonding layers (e.g., 114 or 1114) may include any polymer materials that are heat activated or heat applied to achieve its bonding

characteristics. 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 144, 244, and 344 may be about 20 to about 30 g/10 min (ASTM D1238). Suitable examples include ethylene vinyl acetate (EVA), polyolefins, 2-component polyurethane, ethylene acrylic acid copolymers, curable two-part urethane adhesives, epoxy adhesives, ethylene methacrylate copolymers and the like bonding materials. [0051] By one approach, the heat-activated bonding layer is EVA. In general, EVA is effective for the heat-activated bonding layer because of its thermal bonding characteristics, such that it readily bonds to layers and forms a bond thereto greater than the internal rupture strength mentioned above. By one approach, the heat-activated bonding layer, as mentioned above, may have a vinyl acetate content of about 20 to about 40 percent (in other approaches, about 20 to about 30 percent) with the remaining monomer being ethylene in order to achieve the bond strengths and, in some cases, the internal rupture strengths to provide the improved seals herein. A vinyl acetate content lower than 20 percent is generally insufficient to form the robust structures described herein. As described above, the heat-activated bonding layer may have a selected thickness relative to the total thickness of the upper laminate to help achieve functionality of the seal. If the heat-activated bonding layer is too thick when the foamed polymer layer is positioned above it, it becomes difficult to achieve satisfactory bonds and there is too much volume or mass of the heat-activated bonding layer that tends to ooze out from the seal upon later induction or conduction heating. If the heat-activated bonding layer is too thin, the bond strengths to the lower laminate can be inadequate resulting in the tab peeling away from the lower laminate upon seal removal. If the bonding layer is too thin, then the tab also does not have the sufficient internal strength to prevent tearing. By one approach, bonding layer may be about 0.5 to about 1.5 mil of EVA (or any other polymer mentioned above) and, in other approaches, about 0.5 to about 1.0 mils of EVA (or any other polymer mentioned above); however, the thickness can vary as needed for a particular application to achieve the desired bonds and internal strength. [0052] The various layers of the sealing member are preferably assembled via a heat or thermal lamination process forming a sheet of the described layers. Adhesive coating and/or extrusion lamination may also be used to assemble the various layers. During thermal lamination, heating is applied to the web in order to activate the various heat-activated layers in the laminate structure in order to form the sealing member. The resulting laminate sheet of the sealing members can be cut into appropriate sized disks or other shapes as needed to form a vessel closing assembly or tabbed sealing member. The die cut generally cuts through the various release layers 116 or 1116 so that the free portion associated with the release layer forms the gripping tab. The cut sealing member is inserted into a cap or other closure which, in turn, is applied to the neck of a container to be sealed. The screw cap can be screwed onto the open neck of the container, thus sandwiching the sealing member between the open neck of the container and the top of the cap. Heat or induction current or other sealing is then applied to seal the bottom subassembly of layers forming the seal portion to the neck of the container. [0053] It will be understood that various changes in the details, materials, and

arrangements of the process, laminates, laminate/substrate assemblies, 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 products and methods as expressed in the appended claims. For example, the laminates and assemblies 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.

Claims

CLAIMS What is claimed is: 1. A tabbed sealing member with increased tab strength, the sealing member comprising:

a multi-layer laminate including 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 for removing the sealing member from a container opening;

the lower laminate portion below the gripping tab including at least a heat seal layer for bonding to the container rim and a metal layer for heating the heat seal layer; and

a co-extruded polymer layer positioned at a top surface of the lower laminate portion and below the gripping tab, the co-extruded polymer layer having an amorphous top surface and a crystalline or semi-crystalline bottom surface.

2. The tabbed sealing member of claim 1, further comprising an internal fracture layer within the lower laminate portion, the internal fracture layer splitting internally upon tab pulling to separate into two portions where one separated portion remains bonded to the upper laminate and the other separated portion remains bonded to the lower laminate portion.

3. The tabbed sealing member of claim 1 or 2, further comprising a polymer insulation layer positioned below the co-extruded polymer layer.

4. The tabbed sealing member of claim 3, wherein the polymer insulation layer is one of a polymer foam layer or a non-foam polyolefin heat redistribution layer.

5. The tabbed sealing member of any preceding claim, wherein the co-extruded polymer layer is a co-extruded polyester including an amorphous polyester top surface and a crystalline or semi-crystalline polyester bottom surface.

6. The tabbed sealing member of claim 5, wherein the polyester is polyethylene terephthalate.

7. The tabbed sealing member of any preceding claim, wherein the amorphous top surface is about 25 percent or less of the total thickness of the coextruded polymer layer.

8. The tabbed sealing member of any preceding claim, wherein the co-extruded polymer layer is about 0.5 to about 1.5 mils thick.

9. The tabbed sealing member of any preceding claim, further including a partial release layer forming the gripping tab, the partial release layer bonded to one of the layers in upper laminate portion and not bonded to the lower laminate portion.

10. The tabbed sealing member of any preceding claim, wherein the upper laminate portion includes a heat bondable layer forming the partial bond to the lower laminate portion, the heat bondable layer directly bonding to the amorphous top surface of the co-extruded polymer layer.

11. A sheet for forming a tabbed sealing member with increased strength, the sheet comprising:

a multi-layer laminate including an upper laminate portion partially bonded to a lower laminate portion for forming a free portion that is not bonded to the lower laminate portion and formable into a gripping tab defined wholly within a perimeter of a formed tabbed sealing member, the gripping tab for removing a formed tabbed sealing member from a container opening during use;

the lower laminate portion below the free portion including at least a heat seal layer and a metal layer for heating the heat seal layer; and

a co-extruded polymer layer positioned at a top surface of the lower laminate portion and below the free portion, the co-extruded polymer layer having an amorphous top surface and a crystalline or semi-crystalline bottom surface.

12. The sheet of claim 11, further comprising an internal fracture layer within the lower laminate portion, the internal fracture layer splitting internally upon tab pulling of a formed tabbed sealing member during use to separate into two portions where one separated portion remains bonded to the upper laminate and the other separated portion remains bonded to the lower laminate.

13. The sheet of claim 11 or 12, further comprising a polymer insulation layer positioned below the co-extruded polymer layer.

14. The sheet of claim 13, wherein the polymer insulation layer is one of a polymer foam layer or a non-foam polyolefin heat redistribution layer.

15. The sheet of claims 11-14, wherein the co-extruded polymer layer is polyester including an amorphous polyester top surface and a crystalline or semi-crystalline polyester bottom surface.

16. The sheet of claim 15, wherein the polyester is polyethylene terephthalate.

17. The sheet of claims 11-16, wherein the amorphous top surface is about 25 percent or less of the total thickness of the co-extruded polymer layer.

18. The sheet of claims 11-17, wherein the co-extruded polymer layer is about 0.5 to about 1.5 mils thick.

19. The sheet of claims 11-18, further including a partial release layer for forming the free portion, the partial release layer bonded to one of the layers in upper laminate portion and not bonded to the lower laminate portion.

20. The sheet of claims 11-19, wherein the upper laminate portion includes a heat bondable layer forming the partial bond to the lower laminate portion, the heat bondable layer directly bonding to the amorphous top surface of the co-extruded polymer layer.