WO1997002997A1

WO1997002997A1 - Top-tabbed sealing member for a container and method of making same

Info

Publication number: WO1997002997A1
Application number: PCT/US1996/010659
Authority: WO
Inventors: Robert P. Arens; Hak-Rhim Han; Dee Lynn Johnson; Pierre H. Lepere
Original assignee: Minnesota Mining And Manufacturing Company
Priority date: 1995-07-12
Filing date: 1996-06-20
Publication date: 1997-01-30
Also published as: AU6337096A

Abstract

A sealing member (10) having a sealing membrane (20) and an improved grip tab arrangement (30) for use with containers (60) having an opening defined by a rim. The tab structure can be extrusion coated directly onto the sealing membrane eliminating the need for an adhesive layer between the membrane and the tab. In one embodiment, the sealing member (10) is non-metallic, polymeric laminate, and the sealing member includes a pressure activated adhesive (50) for bonding to the container (60) without the use of induction heating. Also disclosed are containers sealed with the inventive sealing members and methods of making such sealing members.

Description

TOP-TABBED SEALING MEMBER FOR A CONTAINER AND METHOD OF MAKING SAME

TECHNICAL FIELD

The present invention relates generally to sealing members for use with containers having an opening defined by a rim and more particularly to sealing members having an improved grip tab arrangement and non-metallic construction, and methods for making such sealing members.

BACKGROUND OF THE INVENTION

Many products are distributed in plastic or other containers having a screw-on or snap-on cap or the like which forms the primary closure ofthe container. It is often desirable to provide a secondary closure for the container Such secondary closures can take the form of a sealing member often referred to as an innerseal. Such sealing members can provide a more positive seal than the cap alone, such as by providing a membrane having desired oxygen and moisture barrier properties.

It is known to include various grip tabs on sealing members to provide a convenient means for a user to remove the sealing member from the container. One such tab. known as an ear tab, is an extension ofthe sealing member membrane itself which extends beyond the rim ofthe sealed container Such ear tabs suffer from the disadvantages that their size must be limited to avoid interfering with the threads on the container neck, and that the ear tab often bonds at its lower surface to the side of the container neck, making it less convenient for a user to grasp it.

An improvement over the ear tab exists, and is commonly referred to as a top tab. Such top tabs are disclosed, for instance, in the following U.S. Patents:

1. U.S. Patent No. 4,961,986, "Sealing Member for a Container," issued to

Galda et al., discloses a sealing member comprising a membrane and a first sheet. In one embodiment, the membrane comprises a foil layer to provide adequate sealing and to allow induction heating the sealing member to seal it to the container with a heat activated adhesive. The first sheet typically comprises polyester, and is bonded in part to the top surface ofthe foil membrane, leaving a free portion ofthe sheet to form a tab to be grasped by a user. In one disclosed embodiment, the sheet and sealing member are bonded together by an adhesive layer between the two.

2. U.S. Patent No. 5,004,1 11, "Internally Delaminating Tabbed Innerseal for a Container and Method of Applying," issued to McCarthy, discloses an innerseal which includes a body portion having an upper surface and a structure connected to the upper surface for grasping by a user. In one embodiment, the body portion comprises a membrane including a foil layer and an adhesive layer for bonding to a sealing layer. The sealing layer is a heat activated layer for sealing to the container, and the foil in the membrane enables induction heating ofthe sealing layer. The structure to be grasped by the user includes a tab portion and a force transmitting layer connected to the body portion by a second adhesive layer.

3. U.S. Patent No. 5,265,745, "Tamper Evident Top Tab Innerseal," issued to Pereyra et al.. discloses a multilayer innerseal having a grip tab extending across the innerseal. The innerseal includes a base layer, which in one embodiment is a metallic layer for allowing induction heating of a heat activated bonding layer to adhere the innerseal to a container. The tab includes a reinforcing layer which is bonded to the base layer by a bonding layer, typically comprising a heat activated adhesive. The base layer and the heat activated adhesive on the tab reinforcing layer each heated and then brought into contact under pressure to bond the tab to the base layer.

Another sealing member having a top tab is commercially sold as Safe-Gard™ Top-Tabbed Innerseal, available from Minnesota Mining and Manufacturing Company, St. Paul, Minnesota. The Safe-Gard innerseal comprises a facing for sealing to the container, the facing including in sequence, a heat sealable film layer adjacent the container, a polyester layer, and a foil layer. The foil layer allows induction heating to seal the facing to the container. The Safe-Gard innerseal also comprises a tabbing material which includes a heat sealable layer for bonding to the foil layer ofthe facing, and a polyester layer on top of that. The innerseal is constructed by heating the tabbing material and the facing, and contacting the two under pressure to thereby seal a portion ofthe tabbing material to the foil ofthe facing. A paper or polyester deadening member is bonded to a portion ofthe tabbing material heat seal layer adjacent to the foil layer ofthe facing. This keeps a portion ofthe tabbing material from bonding to the foil, thereby forming a free tab to be gripped by a user.

While the above top tabbed sealing members have their own utility, there is still a desire to provide a sealing member with an improved top tab which can be manufactured more easily, with less material, and at lower cost than the previously known innerseals. It is desirable to provide a sealing member in which the tab can be securely, yet conveniently, attached to the sealing membrane without the need for separate bonding and strengthening layers in the tab.

It is also desirable to provide a sealing member in which the metallic layer can be omitted from the sealing membrane. This can be done by including a pressure sensitive adhesive; a pressure, torque, or shear activated adhesive; or other cold sealing adhesive to seal the sealing member to the container. This provides the following advantages. By using such an adhesive, expensive induction heating equipment is not needed. By omitting induction heating, the energy costs of applying the sealing member can be reduced and the possibility of damaging the container rim with excessive heat is eliminated. Because metal caps tend to shield induction energy, metal caps are not desirable for use with a heat activated innerseal, but can be conveniently used with a pressure activated sealing member.

The high temperatures caused by induction heating can cause the tab structure of known sealing members to soften or melt to such a degree that it bonds to the inner surface ofthe cap ofthe container. Therefore, known heat activated top tab innerseals typically include a relatively heat resistant material such as a film of oriented polyester as the uppermost layer ofthe tab structure. However, polyester is not sufficiently tear resistant to serve alone as the grip tab for removing the sealing member. The problem of tear resistance is aggravated by the manufacturing process of extruded films used in known sealing members. Typically, the films comprising the facing and the tab are fed together under heat and pressure, with a deadening member between portions thereof, to attach the tab and facing. The resulting sealing member has a tab whose base is attached to the facing along a line parallel to the machine direction ofthe polyester tab film. The machine direction of an extruded film is typically the direction which is least resistant to tearing. This tends to make the polyester tab material more likely to tear in the machine direction, parallel to the base ofthe tab. It is therefore often necessary to form the top tab structure as a laminate to include a tear resistant material in combination with the heat resistant polyester layer. By eliminating induction heating, it is not necessary to include oriented polyester film as a temperature stable component ofthe pull tab, and it is therefore possible to use other, more tear resistant materials which do not require an additional tear resistant layer.

There are further reasons why it is desirable to provide a pressure activated sealing member which does not require a foil layer for induction heating. Without metal foil as a component ofthe sealing member, both the raw material costs of producing the sealing member and the cost of waste from handling foil as a manufacturing component can be reduced. And the presence of both metal and polymeric materials in a sealing member results in a mixed waste stream element which cannot be conveniently recycled by the end user after removal from the container

SUMMARY OF THE INVENTION One aspect ofthe invention presents a sealing member in which the tab sheet is extrusion coated to the membrane, thus eliminating the need for a separate adhesive between the tab sheet and the membrane. The sealing member is for use with a container having an opening defined by a rim, and comprises a membrane for sealing the opening ofthe container, the membrane including a first surface and a second surface, and a tab sheet including a bonding surface extrusion coated onto said membrane. The tab sheet is bonded at a portion ofthe bonding surface to the second surface ofthe membrane thereby forming a composite portion ofthe sealing member and leaving a free portion ofthe tab sheet unbonded thereby forming a separated portion ofthe sealing member. The free portion ofthe tab sheet forms a tab to be gripped by a user. The sealing member includes adhesive means on the first surface of the membrane for adhering the sealing member to the rim ofthe container.

The above sealing member preferably has a membrane which comprises a non- metallic film. This is advantageously accomplished by using an adhesive which does not require induction heating to bond the sealing member to the container. The adhesive preferably comprises a substantially tack-free pressure-activated adhesive, shear-activated adhesive, or torque-activated adhesive

In the above sealing member, the tab sheet comprises a first material at the bonding surface and the membrane comprises a second material at the second surface, and the first and said second materials are selected to allow said tab sheet to be extrusion coated onto said membrane. In one embodiment, the first and second materials are the same material.

Another aspect ofthe invention presents a sealing member for use with a container having an opening defined by a rim, the sealing member comprising a membrane for sealing the opening ofthe container, the membrane including a first surface and a second surface and a tab sheet including a bonding surface, an integral portion, a free portion, and a separating member, wherein the tab sheet is bonded at the bonding surface to the second surface of said membrane. The sealing member has a composite portion comprising a continuous laminate ofthe tab sheet and the membrane and a separated portion comprising upper and lower components separable from one another. The upper component comprises the free portion ofthe tab sheet. The separating member is disposed between the free portion ofthe tab sheet and the membrane and is adapted to allow the upper component to be separated from the lower component. The sealing member also includes adhesive means disposed on the first surface ofthe membrane for adhering the sealing member to the rim ofthe container.

In one embodiment ofthe above sealing member, the free portion, the separating member, and the integral portion are unitary with one another. The integral portion and the separating member can be bonded at the bonding surface to the second surface of said membrane, and the free portion extends from said integral portion and overlays the separating member. In such an arrangement, the free portion is separable from the separating member. In one preferred embodiment, the thickness ofthe integral portion measured peφendicular to the bonding surface is substantially the same as the combined thicknesses ofthe free portion and separating member.

In the above sealing member, there can be an adhesive layer between the bonding surface ofthe tab sheet and the second surface ofthe membrane to adhere the tab sheet to the membrane. Alternatively, the tab sheet can be extrusion coated onto the second surface ofthe membrane.

A further aspect ofthe invention presents a container sealed by any ofthe above sealing members. In one aspect, the tab sheet is bonded to the membrane with a first bond strength and the membrane is adhered to the container rim with a second bond strength less than said first bond strength This allows the sealing member to be removed as a unit from the container by pulling the tab The membrane preferably comprises a non-metallic membrane having oxygen and/or water barrier performance at least as good as the container.

Another aspect ofthe invention presents a sealing member comprising a non- metallic, polymeric membrane for sealing the opening ofthe container, the membrane including a first surface, a second surface, and a periphery; and a tab sheet including a bonding surface. The tab sheet is attached at a portion ofthe bonding surface to the second surface ofthe membrane thereby forming a composite portion ofthe sealing member and leaving a free portion ofthe tab sheet unbonded thereby forming a separated portion ofthe sealing member. The free portion ofthe tab sheet comprises a tab to be gripped by a user, and separated from the composite portion by a boundary having a first end and a second end. The first and second ends ofthe boundary extend to the periphery ofthe membrane, and the boundary is remote from the periphery in a direction peφendicular to the boundary. The sealing member also includes a substantially tack-free pressure-activated adhesive disposed on the first surface ofthe membrane for adhering the sealing member to the rim ofthe container.

In still another aspect ofthe invention, a method for forming a sealing member is presented. The method comprises the steps of: a) providing a membrane; b) extrusion coating a tab sheet onto the membrane to thereby bond the tab sheet to the membrane at a composite portion ofthe sealing member; and c) maintaining a free portion ofthe tab sheet out of contact with the membrane to prevent the free portion from bonding to the membrane.

In yet a further aspect ofthe invention. a method for forming sealing member stock for the production of a sealing member is presented. The method comprises the steps of: a) providing a membrane stock; b) extrusion coating a tab sheet stock onto the membrane stock tp thereby bond the tab sheet stock to the membrane at a composite portion ofthe sealing member stock; and c) maintaining a free portion of the tab sheet stock out of contact with the membrane to prevent the free portion from bonding to the membrane stock. In one embodiment ofthe method, step c) comprises inteφosing a deadening member stock between the free portion ofthe tab sheet stock and the membrane stock. Alternatively, step c) can comprise inteφosing a plurality of strips of deadening member stock at spaced locations between the tab sheet stock and the membrane stock to thereby create a plurality of composite portions and a plurality of free portions.

Another aspect ofthe invention presents a second method for forming a sealing member for use with a container. The method comprises the steps of: a) extruding a unitary tab sheet including a bonding surface, an integral portion, a separating member, and a free portion, wherein the integral portion and the separating member comprise the bonding surface, and wherein the free portion extends from the integral portion and is adapted to overlay the separating member; b) maintaining the free portion out of contact with the separating member to prevent the free portion from bonding to the separating member; c) bonding the bonding surface ofthe tab sheet to a major surface of a membrane; and d) providing adhesive means on the membrane opposite the tab sheet for adhering the sealing member to a container rim. Step c) can comprise extrusion coating the tab sheet onto the membrane or adhering the bonding surface of the tab sheet to the major surface ofthe membrane.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further explained with reference to the appended Figures, wherein like structure is referred to by like numerals throughout the several views, and wherein: Figure 1 is a cross sectional view of a first embodiment of a sealing member according to the present invention;

Figure 2 is a schematic view of an apparatus for providing a sealing member according to the present invention;

Figure 3 is a cross sectional view of a sealing member stock constructed by the apparatus of Figure 2, from which individual sealing members can be formed;

Figure 4 is an isometric view ofthe sealing member stock of Figure 3;

Figure 5 is a cross sectional view of a container sealed with a sealing member according to the present invention;

Figure 6 is a graphical representation depicting release pressure versus activation time for sealing members according to the present invention;

Figure 7 is a view ofthe container of Figure 5, with the cap removed and the sealing member partially removed;

Figure 8 is a cross sectional view of a second embodiment of a sealing member according to the present invention; Figure 9 is a partial isometric view of an extruder die for use in forming the sealing member of Figure 8; Figure 10 is a cross sectional view of a variation ofthe embodiment of Figure 8;

Figure 11 is an end view of a third embodiment of a sealing member constructed according to the present invention; and Figures 12A and 12B are isometric views of tools for use in fabricating the embodiment of Figure 11.

DETAILED DESCRIPTION OF THE INVENTION

Referring to Figure 1, there is seen a first embodiment of a sealing member 10 constructed in accordance with the present invention. Sealing member 10 generally comprises bottom surface 12 for sealing against the rim of a container opening, composite portion 14, separated portion 16, membrane 20, and tab sheet 30.

Membrane 20 includes first major surface 22 and second major surface 24. First surface 22 is to be adhered to the rim of a container by suitable adhesive means 50 as described in greater detail below. Second surface 24 has attached thereto a tab sheet 30 as described in greater detail below. The material for membrane 20 is selected to provide the desired sealing ofthe container opening. It should be suitably strong and tear resistant to retain the contents ofthe sealed container. It should also be selected to provide the desired barrier properties for preserving the contents ofthe container. For example, membrane 20 should be selected to provide adequate moisture barrier properties and oxygen barrier properties commensurate with the container itself. It should be kept in mind that typically it is not necessary for the membrane 20 to provide greater barrier properties than the container. The membrane 20 can comprise a single layer or multiple layer construction.

In a preferred embodiment, the membrane 20 does not include a metal foil layer, which has heretofore been used in many known sealing members for two main reasons. First, a metal foil layer has been previously employed to provide adequate barrier properties to the sealing member. Second, a metal foil layer has been previously employed to provide a means for induction heating the sealing member to adhere the sealing member to the container with a heat activated adhesive. With the pressure activated adhesives employed in the present invention, described in detail below, it is not necessary to provide the capability for induction heating.

In one preferred embodiment, membrane 20 comprises a laminate construction as follows. The laminate comprises sequential layers of polypropylene, ethylene vinyl alcohol copolymer (EVOH), and polypropylene. On both sides ofthe EVOH layer are suitable tie layers such as a polypropylene based adhesive resin. The tie layers serve to bond the EVOH layer to the polypropylene layers, and to prevent water from coming in direct contact with the EVOH layer. Such contact is not desirable because it degrades the barrier properties ofthe EVOH. One suitable adhesive for the tie layer is available commercially as Admer™ QF551 A from Mitsui Petrochemicals (America), LTD, New York. New York. One suitable commercial source of polypropylene is Fina 3576 polypropylene, available from Fina Oil & Chemical Company of Dallas, Texas. One suitable commercial source of EVOH is Eval F101 available from EVAL Company of America, of Lisle, Illinois. In one preferred construction, the polypropylene layers are each 0.038 mm (0 0015 in) thick, the tie layers are each 0 005 mm (0.0002 in) thick, and the EVOH layer is 0 01 mm ( 0004 in) thick. Alternatively, the membrane 20 can comprise any membrane providing sufficient strength, tear resistance, and barrier properties as is known in the an

Tab sheet 30 is disposed on second major surface 24 of membrane 20. In one preferred embodiment illustrated in Figure 1. tab sheet 30 includes bonding surface 32 for bonding the tab sheet to membrane 20, and second major surface 34 opposite the bonding surface 32. The tab sheet 30 includes a bonded portion 36 and free portion or tab 38. Boundary 37 extends between the bonded portion 36 and free portion 38. Free portion 38 includes free edge 39 opposite the boundary 37. The free portion 38 forms a tab suitable to be gripped by a user to remove the sealing member 10 from a sealed container. Bonding surface 32 is bonded at bonded portion 36 to the second major surface 24 ofthe membrane with a sufficiently strong bond that a user can pull the tab 38 to remove the sealing member 10 as an integral unit from a sealed container. As used and understood by the present applicants, the term "bond" is used by those skilled in the art, particularly as used in the Galda et al. and McCarthy references discussed above, to indicate that the tab sheet and membrane of a sealing member are joined by any suitable means providing a sufficiently strong attachment to allow a user to grasp and pull the tab to remove the sealing member as a unit from a sealed container. The term bond encompasses, but is not limited to, bonding means such as adhesives including pressure sensitive and heat activated adhesives, and fused bonds such as achieved by ultrasonic welding and melt-fusing In one particularly preferred embodiment ofthe present invention, the tab sheet 30 is extrusion coated directly onto the membrane 20 as described in greater detail below, thereby fusing the bonding surface 32 ofthe tab sheet 30 to the second surface 24 of the membrane

The material for tab sheet 30 should be chosen so as to provide an adequately strong bond to membrane 20 at the bonded portion 36 The thickness and material of the tab sheet 30 should also be chosen to provide an adequately strong tab sheet 30 to allow a user to grasp free portion 38 to pull sealing member 10 as a single unit from a sealed container As discussed above, it is not necessary to include in tab sheet 30 a particularly heat resistant material such as polyester, which must be reinforced with a tear resistant layer, because the sealing member 10 is not subject to induction heating This allows tab sheet 30 to comprise a single layer which can be chosen to provide adequate strength, tear resistance, and bond capabilities In one preferred embodiment, the thickness of tab sheet 30 is 0 13 mm (0 005 in), although thicker or thinner tab sheets may be employed Suitable materials for tab sheet 30 include polypropylene such as Fina 3576 polypropylene, polypropylene/ethylene vinyl acetate copolymer, such as Fina EOD 95-08, both available from Fina Oil & Chemical Company, copolymers of polypropylene and polyethylene, and polypropylene homopolymers such as Exxon 1024 available from Exxon Chemical Company of Houston, Texas. While the tab sheet 30 preferably comprises a single layer for ease of manufacturing, it is of course possible to employ a laminate as tab sheet 30. A deadening member 40 is included on the tab sheet bonding surface 32 at the free portion 38, to prevent the bonding surface 32 from being bonded to the membrane 20 in the area ofthe tab or free portion 38. Deadening member 40 has first major surface 42 facing the membrane 20, and second major surface 44 bonded to the underside ofthe free portion 38. Deadening member 40 can be any suitable material that can withstand being bonded to the free portion 38 as described below, and prevent bonding ofthe free portion to the membrane 20. Suitable materials for deadening member 40 include paper and treated polyethylene terephthalate (PET).

The above described construction provides a sealing member 10 having a composite portion 14 and a separated portion 16 divided by boundary 37. The sealing member 10 is a continuous laminate in the composite portion 14. That is, the various elements ofthe sealing member are not separable in the composite portion 14 of sealing member 10. In contrast, the sealing member 10 includes two separable components in the separated portion 16. The free portion 38 of tab sheet 30 is one component that is separable from another component, the membrane 20, in the separated portion 14 ofthe sealing member 10 The free portion 38 can pivot towards and away from membrane 20 about boundary 37 as indicated by arrow A in Figure 1.

The sealing member 10 can be constructed by the apparatus 100 as illustrated schematically in Figure 2. Membrane stock 120 is unwound from unwind roll 100 and is fed between nip roll 102 and chill roll 103. Simultaneously, deadening member stock 140 is unwound from unwind roll 101 and is fed between nip roll 102 and chill roll 103 such that first surface 142 ofthe deadening member stock is adjacent second major surface 124 ofthe membrane stock. As seen more clearly in Figure 3, deadening member stock 140 is narrower than membrane stock 120. If desired, several spaced strips of deadening member stock 140 can be fed onto membrane stock 120 to form a plurality of composite portions 114 and separated portion 1 16. As illustrated in Figure 3, two such strips of deadening member stock 140 are provided. Returning to Figure 2, extruder 106 extrudes the material which will form the tab sheet stock 130. The tab sheet stock 130 is extrusion coated onto the membrane stock and deadening members. Bonding surface 132 thus overlays second surface 124 ofthe membrane stock, with the strips of deadening member stock between the membrane stock 120 and tab sheet stock 130. The laminate of membrane stock 120, deadening member stock 140, and tab sheet stock 130 then passes between nip roll 102 and chill roll 103, with chill roll 5 103 adjacent tab sheet stock 130. Chill roll 103 quickly quenches the extruded tab sheet stock 130 and thereby maximizes its amoφhous properties to provide toughness and tear resistance. The laminate then passes through idler rolls 104 and past adhesive coater 107. Adhesive coater 107 applies adhesive 150 to the first surface 122 of the membrane stock 120 to allow the sealing members to be bonded to the rim of a 0 container. The completed sealing member stock 1 10 is then wound onto wind up roll 105. Depending on the type of adhesive used, it may be desirable to place a release liner on the exposed surface of adhesive 150 before winding the sealing member stock 1 10 onto windup roll 105.

5 The tab sheet 30 ofthe present invention preferably has a sufficiently high tear resistance to allow the sealing member 10 to be removed as a single unit from a sealed container without tearing the tab 38. It has been found that tab sheets having a tear resistance of at least 100 grams as measured on an Elmendorf tear test apparatus are suitable for use with the present invention, although the present invention is not () thereby limited. Quenching the tab stock extrudate 130 provides amorphous properties to the tab sheet material to help increase the tear resistance as illustrated by the following examples.

Examples 1-4 5 Films of various thickness were extruded onto a casting roll maintained at various quenching temperatures. The material ofthe films was polypropylene available commercially from Exxon as 1024 polypropylene. These films were not extrusion coated onto a membrane to form a sealing member, but provide a useful indication of the effect of quenching on the tab sheet. The films were subjected to tear testing on an 0 Elmendorf tear test apparatus. As seen by the data presented in Table 1, reducing the quenching temperature of the extruded film increases the tear resistance. Table 1

Example Film Thickness Casting Roll Temperature Tear Resistance (mils) (Deg. F) (grams)

1 4.0 150 33

2 4.0 90 65

3 4.5 150 39

4 4.5 55 150

Figure 3 illustrates a cross section of sealing member stock 1 10 manufactured by the method and apparatus of Figure 2. Because tab sheet stock 130 is in a softened state when it exits the extruder 106 and is extrusion coated onto the second surface 124 of membrane stock 120, the bonding surface 132 ofthe tab sheet stock 130 fuses to the membrane in the area ofthe composite portions 1 14 between strips of deadening member stock 140. The fusion is substrate to substrate, which obviates the need for a separate adhesive or bonding layer between the membrane and the tab sheet. This also eliminates the need for a subsequent manufacturing step in which a previously formed tab sheet must be bonded to the membrane, as is the case with previously known sealing members. Accordingly, the material of the tab sheet stock 130 should be chosen to be capable of being extrusion coated to the membrane 120 to form a sufficiently strong bond between the two. This can be accomplished by selecting the same material for the tab sheet and the membrane, or by selecting compatible materials which can be melt fused to one another by extrusion coating When either or both of the membrane stock 120 and tab sheet stock 130 comprise a laminate, the material ai second surface 124 of membrane 120 and the material at the bonding surface 132 of the tab sheet stock 130 should be selected to be compatible with one another. The bonding surface 132 ofthe tab sheet stock 130 also bonds to the second surface 144 of the strips of deadening member stock 140 in the area ofthe free portion 138 ofthe tab sheet stock. The first surface 142 ofthe deadening member stock 140 does not bond to the second surface 124 ofthe membrane 120, thereby allowing the free portion 134 ofthe tab sheet stock to remain free to form a tab (as illustrated in Figure 1). Individual sealing members 10 are then cut by die cutting, or any other suitable method, from the sealing member stock 110 along cut lines 160 as illustrated in Figures 3 and 4. The cut lines are positioned such that the free edge 39 of tab 38 is within the width ofthe strips of deadening member stock 140. In one preferred embodiment, the boundary 137 is approximately in the middle of sealing member 10 so that bonded portion 36 and free portion 38 ofthe tab sheet 30 are approximately the same area. This provides a sufficiently large bonded portion 36 for secure attachment ofthe tab sheet 30 to the membrane 20, while also ensuring a sufficiently large free portion 38 to be conveniently gripped by a user. However, the relative size ofthe bonded and free portions can be varied as desired. Sealing member 10 is illustrated herein as being circular. However, sealing member 10 may be made in any desired shape compatible with the shape ofthe container rim on which the sealing member is to be used.

For ease of manufacturing, the periphery ofthe tab sheet 30 is preferably coextensive with the periphery ofthe membrane 20 This allows all components ofthe assembled sealing member 10 to be conveniently cut along line 160 from the sealing member stock 1 10 in a single step. However, it is not necessary that the periphery of the tab sheet 30 be the same as that ofthe membrane 20 The periphery ofthe tab sheet 30 can be varied, for example, by extruding strips of tab sheet stock 130 which are not coextensive with the membrane stock 120, or by cutting the periphery 39 of free portion 38 to be different from the periphery ofthe membrane 20 underneath it

Other means than deadening member strip 140 may be employed to maintain free portion 138 unbonded to membrane 120. For instance, a suitable coating may be applied to second surface 124 of membrane 120. The coating can be applied in a pattern corresponding to the arrangement ofthe deadening member stock 140 as illustrated in Figures 3 and 4. Suitable coatings include silicon, microcrystalline wax, UV coated inks, and fluorocarbons. Alternatively, a suitable deadening member stock 140 may be applied in strips so as to bond to the second surface 122 ofthe membrane 120 to prevent the tab sheet stock 130 from bonding to the membrane. The sealing member 10 includes adhesive 50 on second surface 12 ofthe sealing member. Adhesive 50 can be any known type of adhesive suitable for use with a sealing member. In a preferred embodiment, the adhesive 50 is not a heat activated adhesive. This allows the sealing member to be fabricated without a metal foil layer as would be necessary to enable induction heating of sealing members which include a heat activated adhesive. Accordingly, the adhesive 50 preferably comprises a water based (gummed) adhesive, pressure sensitive adhesive, or more preferably, a pressure, shear, or torque activated adhesive, or other cold seal adhesive. Preferably, the adhesive is initially tack-free, or substantially tack free for ease of handling. This eliminates the need for a release liner over adhesive 50 which might otherwise be necessary with pressure sensitive adhesives and other adhesives having a substantial initial tack.

Suitable pressure activated adhesives include butadiene-nitrile random copolymers such as those disclosed in U.S. Patent No. 4,935,273, "Pressure-Activated Innerseals and Containers Using Same" (Ou-Yang); and U.S. Patent No. 4,977,003, "Nontacky Acrylonitrile/Butadiene Adhesive Tape" (Brown et al ). Ou-Yang discloses a butadiene-nitrile copolymer substantially free of cross-links having a nitrile content of up to 31%) (preferably about 18 to 30%>) by weight. Brown discloses an uncrosslinked copolymer of about 10 to 50% (preferably about 20 to 40%) by weight of acrylonitrile and about 50 to 90% by weight of at least one of butadiene and isoprene.

Suitable torque or shear activated adhesives include those disclosed in U.S. Patent No. 4,327, 147, "Shear- Activated Innerseal" (Ou-Yang). The '147 patent teaches an adhesive utilizing about 1 to 15 parts by weight (preferably about 3 to 15) of a block copolymer having the general formula A-B-A, about 1 to 25 parts by weight (preferably about 5 to 25) of an organic tackifier for the block copolymer, and about 60 to 100 parts by weight (preferably about 70 to 90) of a hydrocarbon material. The elastomeric B component ofthe block copolymer is a conjugated diene prepared from a material such as isoprene, butadiene, copolymers of ethylene or styrene and butadiene as well as their homologues such as polymers of ethylene and butylene, and the like. Preferably, the elastomeric blocks comprise at least about 70% by weight of the block copolymer. The resinous A blocks ofthe copolymer are preferably prepared from monovinyl aromatic hydrocarbons, particularly those ofthe benzene series such as styrene. The A blocks preferably comprise at most 30% by weight ofthe block copolymer. The tackifier is compatible with the elastomeric block and is also preferably compatible with the resinous block ofthe copolymer. The tackifier may be present in amounts of from 1 to 25 parts by weight, preferably in the weight ratio of tackifier to block copolymer of about 1.7: 1. Useful tackifiers include aliphatic and aromatic hydrocarbon resins, hydrocarbon monomers, rosins, and modified resins Useful hydrocarbons include microcrystalline wax and amoφhous polypropylene

Still further suitable cold seal adhesives are disclosed in U.S Patent No 4,930,646, "Capliner Innerseal Composite Utilizing Cold Seal Adhesive" (Emslander)

One particularly preferred non-tacky, pressure activated adhesive is available commercially as a heat activated adhesive as EA-876S Hot Melt Adhesive, from Eastman Chemical Company of Kingsport, Tennessee, presently believed to comprise a low molecular weight polypropylene adhesive comprising at least 90% hydrocarbon polymer and no more than 10% modifiers and additives The present inventors have surprisingly discovered the unexpected result that this adhesive, intended to be a heat activated adhesive, also functions as a pressure activated adhesive when employed with the present invention under the correct conditions This adhesive is particularly well suited for use with sealing members 10 to be sealed to polypropylene containers This adhesive can preferably be applied to sealing member 10 in a layer approximately 0 025 to 0.10 mm (0.001 to 0.004 in) thick, and more preferably approximately 0 064 mm (0.0025 in) thick, although more or less may be used as desired

Another commercially available hot melt adhesive which the present inventors have surprisingly discovered acts as a pressure activated adhesive is Zeon Nipol DN- 3335M hot melt adhesive, available from Zeon Chemicals, Inc., of Louisville, Kentucky. This elastomer comprises a copolymer of acrylonitrile/butadiene. This adhesive is particularly well suited for use with sealing members 10 to be sealed to polyethylene, polyester, and polyvinyl chloride containers.

The adhesive 150 can be applied to the first surface 122 ofthe membrane stock

120 by any conventional technique. For non-tacky, pressure activated adhesives, preferable coating techniques include known hot-melt techniques. For solution- prepared adhesives, suitable techniques include roll coating, bar coating, or rotogravure coating.

A sealed container according to the present invention is illustrated in Figure 5. Container 60 includes opening 62 bounded by rim 64. and threaded neck 66 for engagement with a threaded cap 70. The container can comprise any suitable material that is known in the art, such as polyethylene, polypropylene, polyester, and poly vinyl chloride. Cap 70 includes top wall 72 having inner surface 74, and side wall 76 including threads 78 for engagement with the threaded neck ofthe container. The cap can comprise any suitable material as is known in the art such as polypropylene, high density polyethylene, and polystyrene.

To seal the container, sealing member 10 is initially placed inside the cap 70 adjacent inner surface 74, with bottom surface 12 of the sealing member facing away from the top 72 ofthe cap. The cap 70 is then applied to the container 60 and adequate torque is applied to create sufficient pressure between the sealing member 10 and the container rim 64 to activate the pressure activated adhesive. After a suitable amount of time, a secure bond is formed between the sealing member 10 and the container rim 64. Even when a pressure, shear, or torque activated adhesive is used, it may be possible to heat the sealing member to increase the bond ofthe sealing member 10 to the container, or to reduce the amount of activation time necessary to achieve a desired bond. The sealing member 10 should have a sufficiently large diameter so as to at least partially overlap the surface of rim 64. Preferably, the diameter ofthe sealing member 10 is slightly larger than the diameter ofthe outermost periphery ofthe rim 64. The innerseal 10 ofthe present invention is particularly well suited for use with containers employing threaded caps. However, the present invention is not so limited, and the innerseal may be used with containers having a snap fit cap arranged to maintain sufficient pressure to seal the sealing member 10 to the container rim. Alternatively, external means may be provided to maintain an initial pressure for enough time to seal the sealing member to the container Such an arrangement can be used with or without a cap being ultimately placed over the sealing member 10

When a pressure, shear, or torque activated adhesive is used, the cap torque and sealing time are chosen so as to provide an adequately secure bond between the innerseal 10 and container rim 64 For example, when adhesive 50 comprises a 0 064 mm (0 0025 in) thick layer of Eastabond EA876 Hot Melt Adhesive described above, and the innerseal is used to seal a polypropylene container having a 38 mm diameter cap, it has been found that a torque of 20 inch-pounds maintained for 24 hours provides a sufficient seal The effect of sealing time for a given torque is demonstrated by the following examples

Examples 5-19

Sealing members 10 were constructed generally according to the embodiment described above with respect to Figures 1 -4 by extrusion coating a 0 13 mm (0 005 in) thick tab sheet stock 130 onto a membrane 120 comprising a 0 064 mm (0 0025 in) thick film of Exxon 1024 polypropylene Adhesive layer 150 comprising a 0 064 mm (0 0025 in) thick layer of Eastabond EA876 Hot Melt Adhesive was hot-melt coated onto surface 122 ofthe sealing member stock Individual sealing members 10 were then cut from the resulting sheet member stock The sealing members 10 were placed in 38 mm diameter caps which were then screwed onto 100 cc polypropylene containers The caps were applied with 20 inch-pounds of torque, and were allowed to sit at room temperature for varying adhesive activation times before testing the bond strength between the sealing member and container As employed here, the adhesive was a pressure activated adhesive After the desired activation time, the cap was unscrewed from the container, and the container was then subjected to internal pressure by injecting air from a 40 psi source at a rate of 30 cc/min. The pressure at which the container leaked, indicating a release in the bond between the sealing member 10 and the container rim, is tabulated below in Table 2 as release pressure, and presented graphically in Figure 6. It is seen that the innerseals constructed according to Examples 5-19 achieved a maximum bond at approximately 2 hours.

Table 2

To open the container, a user first unscrews cap 70 to expose the sealing member 10. The user then grasps and lifts the free portion 38 ofthe tab sheet 30 as illustrated in Figure 7 and pulls in a direction colinear to the tab 38 with sufficient force to release the bond between the sealing member 10 and the container rim 64 so that the sealing member preferably comes off as a single unit. The adhesive is preferably selected and activated so as to provide an adequately strong bond between the sealing member 10 and the container 60, while allowing the sealing member 10 to be removed as a single unit from the container. Because ofthe arrangement ofthe tab ofthe present invention, the sealing member initially lifts off the container rim 64 in the area ofthe base line 37 ofthe free portion or tab 38. This lifting is generally peφendicular to the container rim. Upon continued pulling ofthe tab 38 by the user, the composite portion ofthe 14 ofthe sealing member then separates from the container rim. Lastly, the separated portion 16 ofthe sealing member peels off of the container rim as the user pulls the tab 38 generally parallel to the plane ofthe container rim 64. This removal mechanism is the result ofthe tab arrangement, in which the tab 38 is attached to the sealing member along line 37 at the base ofthe tab 38, with line 37 extending substantially across the width ofthe sealing member and being remote from the edge of the sealing member and container in the direction perpendicular to the base line 37 In this regard, the pressure, torque, and shear activated adhesives ofthe present invention can be advantageously employed with any sealing member having a tab arrangement which provides a similar removal sequence to that just described Such tab arrangements are taught, for example, in U S Patent No 4,934,544, "Z-Tab Innerseal for a Container and Method of Application" (Han et al ), U S Patent No 4,961,986, "Sealing Member for a Container" (Galda et al ), and U S Patent No 5,004, 1 1 1, "Internally Delaminating Tabbed Innerseal for a Container and Method of Applying," (McCarthy)

An alternate embodiment of the sealing member 210 is illustrated in Figure 8 In this embodiment, the tab sheet 230 is formed to have a free portion 238 and separating member 235 opposite one another, and configured to have the free portion 238 separable from the separating member 235 The free portion 238 and separating member 235 are each unitary parts along with the integral portion 236 ofthe tab sheet 230 That is, the integral portion 236, separating member 235. and free portion 238 are all formed from as a single, integral member In this embodiment, the composite portion 214 ofthe sealing member 210 comprises a continuous, unseparated laminate ofthe membrane 220 and tab sheet 230, joined to one another at the bonding surface 232 ofthe tab sheet and the second surface 224 ofthe membrane The separated portion 216 ofthe sealing member comprises two components separable from one another. The free portion 238 of the tab sheet forms the first component The membrane 220 and the separating member 235 ofthe tab sheet together comprise the second component ofthe separated portion 216 ofthe sealing member. Free portion 238 can bend towards and away from the separable portion 224 in direction A along the boundary or living hinge 237 between the integral portion 236 and the free portion 239. In a manner similar to the above described embodiments, there is adhesive 250 disposed on the first major surface 222 of membrane 220 for sealing the sealing member 210 to rim of a container.

The sealing member 210 can be constructed with the extruder die 206 illustrated in Figure 9. Extruder die 206 includes orifice 280 configured to extrude the tab sheet 230 as a single, unitary element. Orifice 280 includes portion 282 for forming the integral portion 236 ofthe tab sheet, portion 284 for forming the free portion 238 ofthe tab sheet, and portion 286 for forming separating member 235 of the tab sheet Preferably, the extruder orifice 280 is configured to extrude a tab sheet 230 in which the thickness ofthe integral portion 236 is substantially equal to the combined thicknesses ofthe free portion 238 and separating member 235. Suitable means should be provided to maintain the free portion 238 out of contact with the separating member 235 until the tab sheet has sufficiently cooled to prevent these two elements form bonding together. Suitable means include providing a relatively cool air jet or a mechanical arm to maintain the free portion 238 out of contact with separating member 235.

Extruder 206 can be used to extrusion coat the tab sheet 230 directly onto the membrane 220 as was described with respect to the manufacturing process illustrated in Figure 2. Alternatively, the tab sheet 230 can be extruded and handled as a separate element ofthe sealing member 210 to be subsequently bonded to the membrane 220 In such an embodiment, the prefabricated tab sheet 230 can be bonded to the membrane 220 by any suitable means, including adhesives, heat bonding, sonic welding, and the like.

One advantage ofthe embodiment of Figure 8 is the absence of a deadening member on the lower surface ofthe free portion 238. This can reduce the amount of materials used in the sealing member and provide a reduction in manufacturing cost. Absence of a deadening member also allows the tab portion to be conveniently formed such that the thickness ofthe integral portion 236, measured peφendicular to bonding surface 232, is approximately equal to the combined thickness ofthe free portion 238 and separating member 235. This provides for a sealing member of substantially constant thickness when the free portion 238 rests against the separating member 235. This constant thickness allows the cap to impart a substantially uniform pressure to the sealing member around the circumference ofthe container rim, thus providing a more uniform seal between the sealing member and the container.

An alternative to the embodiment of Figure 8 is illustrated in Figure 10 In this embodiment, the tab sheet 220a is extruded such that the periphery 239a of free portion 238a is not coextensive with the periphery ofthe tab sheet 220a or membrane 230 (not illustrated) The living hinge 237a extends along its length across the width ofthe sealing member Similarly, periphery 239a extends as a straight line across the width ofthe sealing member, preferable parallel to the living hinge line 237a As in the embodiment of Figure 8, the free portion 238a, separating member 235a, and integral portion 236a, are a unitary construction, extruded unitary with one another As with the embodiment of Figure 8, the tab sheet 220a of Figure 10 can be extruded by an extruder having an orifice corresponding to the cross section ofthe tab sheet

Another alternate embodiment ofthe sealing member 310 is illustrated in Figure 1 1 In this embodiment, a single layer tab sheet 330 is provided, having sufficient thickness to allow a suitable cutting means to cut or skive the free portion as follows A vertical cut 342 is made from the top surface 318 ofthe tab sheet part way into the thickness ofthe tab sheet A horizontal cut 344 is made at the bottom ofthe vertical cut 342 Sealing members 310 then can be cut from the sheet stock along cut lines 360 Cuts 342 and 344 are preferably made in a single cutting step by moving sheet 330 relative to a suitable cutting tool 370. As illustrated in Figure 12 A, cutting tool 370 includes vertical portion 372 and horizontal portions 374, each with a sharp leading edge 376 for cutting lines 342 and 344 Optionally, cutting tool 370a can have swept back leading edges 376a on horizontal portions 374a, as illustrated in Figure 12B. Optionally, the cutting tool may be vibrated to enhance cutting performance. Individual sealing members are then cut along lines 360 as described previously.

In one preferred embodiment, the tab sheet 330 is also the top layer of membrane laminate 320 as described above with reference to the embodiment of Figure 1. In a preferred construction, the laminate comprises bottom layer 322 of polypropylene, tie layer 324, EVOH layer 326, tie layer 328, and top layer of polypropylene 330 which also serves as the tab sheet. In one preferred construction, the bottom polypropylene layer 322 is 0.038 mm (0.0015 in) thick, the tie layers are each 0.005 mm (0.0002 in) thick, the EVOH layer is 0.01 mm (.0004 in) thick, and the top polypropylene layer is 0.165 mm (0.0065 in) thick. The sealing member 310 of this embodiment has composite portion 314 which is a continuous laminate of all ofthe layers ofthe sealing member. The sealing member also has separated portion 316 which has two separable components. Tab portion 338 is one separable component, separated by horizontal cut 344 from the separable member 335 ofthe tab sheet and the remaining layers ofthe membrane 320.

The present invention has now been described with reference to several embodiments thereof. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. It will be apparent to those skilled in the art that many changes can be made in the embodiments described without departing from the scope ofthe invention. Thus, the scope ofthe present invention should not be limited to the exact details and structures described herein, but rather by the structures described by the language ofthe claims, and the equivalents of those structures.

Claims

CLAIMS:

1. A sealing member for use with a container having an opening defined by a rim, the sealing member comprising: a) a membrane for sealing the opening ofthe container, said membrane including a first surface and a second surface; b) a tab sheet including a bonding surface extrusion coated onto said membrane, wherein said tab sheet is bonded at a portion of said bonding surface to said second surface of said membrane thereby forming a composite portion of said sealing member and leaving a free portion of said tab sheet unbonded thereby forming a separated portion of said sealing member, said free portion of said tab sheet comprising a tab to be gripped by a user; and c) adhesive means disposed on said first surface of said membrane for adhering said sealing member to the rim of the container

2. The sealing member of claim 1 , wherein said membrane comprises a non-metallic film.

3 The sealing member of claim 2, wherein said adhesive means comprises a substantially tack-free pressure-activated adhesive

4. The sealing member of claim 2, wherein said adhesive means comprises a substantially tack-free shear-activated adhesive.

5. The sealing member of claim 2, wherein said adhesive means comprises a substantially tack-free torque-activated adhesive.

6. The sealing member of claim 3, wherein said adhesive comprises a low molecular weight polypropylene-based pressure activated adhesive.

7. The sealing member of claim 3, wherein said adhesive comprises a copolymer of acrylonitrile and butadiene.

8. The sealing member of claim 1, further comprising a deadening member disposed on said bonding surface of said tab sheet at said free portion to prevent said free portion from bonding to said second surface of said membrane.

9. The sealing member of claim 1, wherein said tab sheet comprises a first material at least at said bonding surface and said membrane comprises a second material at least at said second surface, and wherein said first material and said second material are selected to allow said tab sheet to be extrusion coated onto said membrane.

10. The sealing member of claim 9, wherein said first and second materials are the same material.

1 1. The sealing member of claim 10, wherein said first and second materials comprise polypropylene.

12. The sealing member of claim 9. wherein said first and second materials are each selected from the group consisting essentially of: polypropylene/polyethylene copolymer and polypropylene homopolymer.

13. The sealing member of claim 2, wherein said membrane comprises a polymeric material.

14. The sealing member of claim 13, wherein said membrane comprises a laminate.

15. The sealing member of claim 14, wherein said laminate comprises sequential layers of polypropylene, a first tie layer, ethylene vinyl alcohol copolymer, a second tie layer, and polypropylene.

16. A sealed container comprising: a) a container comprising an opening defined by a rim; and b) a sealing member comprising: i) a membrane for sealing the opening of said container, said membrane including a first surface and a second surface; ii) a tab sheet including a bonding surface extrusion coated onto said membrane, wherein said tab sheet is bonded at a portion of said bonding surface to said second surface of said membrane thereby forming a composite portion of said sealing member and leaving a free portion of said tab sheet unbonded thereby forming a separated portion of said sealing member, said free portion of said tab sheet comprising a tab to be gripped by a user; and iii) adhesive means disposed on said first surface of said membrane for adhering said sealing member to said rim ofthe container; c) wherein said adhesive means is adhered to said rim to thereby seal said container opening with said sealing member.

17. The sealed container of claim 16, wherein said tab sheet is bonded to said membrane with a first bond strength and said membrane is adhered to said container rim with a second bond strength less than said first bond strength.

18. The sealed container of claim 16, wherein said membrane comprises a non-metallic membrane having oxygen barrier performance at least as good as said container.

19. The sealed container of claim 16, wherein said membrane comprises a non-metallic membrane having water barrier performance at least as good as said container.

20. A sealing member for use with a container having an opening defined by a rim, the sealing member comprising: a) a membrane for sealing the opening ofthe container, said membrane including a first surface and a second surface; b) a tab sheet including a bonding suiface, an integral portion, a free portion, and a separating member, wherein said tab sheet is bonded at said bonding surface to said second surface of said membrane; c) a composite portion of said sealing member comprising a continuous laminate of said tab sheet and said membrane; and d) a separated portion of said sealing member comprising upper and lower components separable from one another, wherein said upper component comprises said free portion of said tab sheet; e) said separating member being disposed between said free portion of said tab sheet and said membrane and adapted to allow said upper component to be separated from said lower component; and f) adhesive means disposed on said first surface of said membrane for adhering said sealing member to the rim ofthe container

21. The sealing member of claim 20, wherein said free portion, said separating member, and said integral portion are unitary with one another.

22. The sealing member of claim 21, wherein said integral portion and said separating member are bonded at said bonding surface to said second surface of said membrane, and wherein said free portion extends from said integral portion and overlays said separating member, and wherein said free portion is separable from said separating member.

23. The sealing member of claim 22, wherein the thickness of said integral portion measured perpendicular to said bonding surface is substantially the same as the combined thicknesses of said free portion and said separating member.

24. The sealing member of claim 22, wherein said sealing member further comprises an adhesive layer between said bonding surface of said tab sheet and said second surface of said membrane to adhere said tab sheet to said membrane

25 The sealing member of claim 22, wherein said tab sheet is extrusion coated onto said second surface of said membrane

26 The sealing member of claim 25, wherein said tab sheet comprises a first material at least at said bonding surface and said membrane comprises a second material at least at said second surface, and wherein said first material and said second material are selected to allow said tab sheet to be extrusion coated to said membrane

27 The sealing member of claim 26, wherein said first and second materials are the same material

28 The sealing member of claim 27, wherein said first and second materials comprise polypropylene

29 The sealing member of claim 20, wherein said membrane comprises a non-metallic film

30 The sealing member of claim 29, wherein said adhesive means comprises a substantially tack-free pressure-activated adhesive

3 1 The sealing member of claim 29, wherein said membrane comprises a polymeric material

32 The sealing member of claim 31 , wherein said membrane comprises a laminate

33. The sealing member of claim 32, wherein said laminate comprises sequential layers of polypropylene, a first tie layer, ethylene vinyl alcohol copolymer, a second tie layer, and polypropylene.

34. A sealed container comprising: a) a container comprising an opening defined by a rim; and b) a sealing member comprising: i) a membrane for sealing the opening ofthe container, said membrane including a first surface and a second surface; ii) a tab sheet including a bonding surface, an integral portion, a free portion, and a separating member, wherein said tab sheet is bonded at said bonding surface to said second surface of said membrane; iii) a composite portion of said sealing member comprising a continuous laminate of said tab sheet and said membrane; and iv) a separated portion of said sealing member comprising upper and lower components separable from one another, wherein said upper component comprises said free portion of said tab sheet; v) said separating member being disposed between said free portion of said tab sheet and said membrane and adapted to allow said upper component to be separated from said lower component; and vi) adhesive means disposed on said first surface of said membrane for adhering said sealing member to the rim ofthe container; c) wherein said adhesive means is adhered to said rim to thereby seal said container opening with said sealing member.

35. The sealed container of claim 34, wherein said tab sheet is bonded to said membrane with a first bond strength and said membrane is adhered to said container rim with a second bond strength less than said first bond strength.

36. The sealed container of claim 34, wherein said membrane comprises a non-metallic membrane having oxygen barrier performance at least as good as said container.

37. The sealed container of claim 34, wherein said membrane comprises a non-metallic membrane having water barrier performance at least as good as said container

38 A method for forming a sealing member for use with a container having an opening defined by a rim, comprising the steps of a) providing a membrane, b) extrusion coating a tab sheet onto the membrane to thereby bond the tab sheet to the membrane at a composite portion ofthe sealing member, and c) maintaining a free portion ofthe tab sheet out of contact with the membrane to prevent the free portion from bonding to the membrane

39 The method of claim 38, wherein step c) comprises inteφosing a deadening member between the free portion ofthe tab sheet and the membrane

40 The method of claim 38, further comprising d) depositing an adhesive on the membrane opposite the tab sheet

41 A method for forming sealing member stock for the production of a sealing member for use with a container having an opening defined by a rim, comprising the steps of a) providing a membrane stock; b) extrusion coating a tab sheet stock onto the membrane stock to thereby bond the tab sheet stock to the membrane at a composite portion ofthe sealing member stock; and c) maintaining a free portion ofthe tab sheet stock out of contact with the membrane to prevent the free portion from bonding to the membrane stock

42. The method of claim 41, wherein step c) comprises inteφosing a deadening member stock between the free portion ofthe tab sheet stock and the membrane stock.

43. The method of claim 41, wherein step c) comprises inteφosing a plurality of strips of deadening member stock at spaced locations between the tab sheet stock and the membrane stock to thereby create a plurality of composite portions and a plurality of free portions.

44. The method of claim 41 , further comprising: d) depositing an adhesive on the membrane stock opposite the tab sheet stock.

45. The method of claim 41, further comprising the step of forming sealing members from the sealing member stock.

46. A method for forming a sealing member for use with a container having an opening defined by a rim. comprising the steps of a) extruding a unitary tab sheet including a bonding surface, an integral portion, a separating member, and a free portion, wherein the integral portion and the separating member comprise the bonding surface, and wherein the free portion extends from the integral portion and is adapted to overlay the separating member; b) maintaining the free portion out of contact with the separating member to prevent the free portion from bonding to the separating member; c) bonding the bonding surface ofthe tab sheet to a major surface of a membrane; and d) providing adhesive means on the membrane opposite the tab sheet for adhering the sealing member to a container rim.

47. The method of claim 46, wherein step c) comprises extrusion coating the tab sheet onto the membrane to thereby bond the bonding surface to the major surface ofthe membrane.

48. The method of claim 46, wherein step c) comprises adhering the bonding surface ofthe tab sheet to the major surface ofthe membrane.

49. A sealing member for use with a container having an opening defined by a rim, the sealing member comprising: a) a non-metallic, polymeric membrane for sealing the opening ofthe container, said membrane including a first surface and a second surface, b) a tab sheet including a bonding surface extrusion coated onto said membrane, wherein said tab sheet is bonded at a portion of said bonding surface to said second surface of said membrane thereby forming a composite portion of said sealing member and leaving a free portion of said tab sheet unbonded thereby forming a separated portion of said sealing member, said free portion of said tab sheet comprising a tab to be gripped by a user; and c) a substantially tack-free pressure-activated adhesive disposed on said first surface of said membrane for adhering said sealing member to the rim ofthe container

50. A sealing member for use with a container having an opening defined by a rim, the sealing member comprising: a) a non-metallic, polymeric membrane for sealing the opening ofthe container, said membrane including a first surface and a second surface; b) a tab sheet including a bonding surface extrusion coated onto said membrane, wherein said tab sheet is bonded at a portion of said bonding surface to said second surface of said membrane thereby forming a composite portion of said sealing member and leaving a free portion of said tab sheet bonded thereby forming a separated portion of said sealing member, said free portion of said tab sheet comprising a tab to be gripped by a user; c) a deadening member disposed on said bonding surface of said tab sheet at said free portion to prevent said free portion from bonding to said second surface of said membrane; and d) a substantially tack-free pressure-activated adhesive disposed on said first surface of said membrane for adhering said sealing member to the rim ofthe container.

51. A sealing member for use with a container having an opening defined by a rim, the sealing member comprising: a) a non-metallic, polymeric membrane for sealing the opening ofthe container, said membrane comprising a laminate including a first surface and a second surface, said laminate comprising a polypropylene layer at said second surface; b) a polypropylene tab sheet including a bonding surface extrusion coated onto said membrane, wherein said tab sheet is bonded at a portion of said bonding surface to said second suiface of said membrane thereby forming a composite portion of said sealing member and leaving a free portion of said tab sheet unbonded thereby forming a separated portion of said sealing member, said free portion of said tab sheet comprising a tab to be gripped by a user; and c) a substantially tack-free pressure-activated adhesive disposed on said first surface of said membrane for adhering said sealing member to the rim ofthe container

52. A sealing member for use with a container having an opening defined by a rim, the sealing member comprising: a) a non-metallic, polymeric membrane for sealing the opening ofthe container, said membrane including a first surface, a second surface, and a periphery; b) a tab sheet including a bonding surface, wherein said tab sheet is attached at a portion of said bonding surface to said second surface of said membrane thereby forming a composite portion of said sealing member and leaving a free portion of said tab sheet unbonded thereby forming a separated portion of said sealing member, said free portion of said tab sheet comprising a tab to be gripped by a user and separated from said composite portion by a boundary having a first end and a second end, said first and second ends extending to said periphery of said membrane, said boundary being remote from said periphery in a direction peφendicular to said boundary; and c) a substantially tack-free pressure-activated adhesive disposed on said first surface of said membrane for adhering said sealing member to the rim ofthe container.