AUSTRALIA Patents Act COMPLETE SPECIFICATION (ORIGINAL) Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: Selig Sealing Products, Inc. Actual Inventor(s): David John O'Brien, Victor Sachs, Joseph Smelko, Robert William Thorstensen-Woll Address for Service and Correspondence: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: CONTAINER CLOSURE Our Ref: 927585 POF Code: 791/489739 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): - 1- 1A CONTAINER CLOSURE The present application is a divisional application from Australian patent application number 2010235879 (which is a divisional of 2007249092), the entire 5 disclosures of which are incorporated herein by reference. When packaging a wide variety of materials ranging from pharmaceutical tablets to instant coffee in containers such as bottles and jars a closure can be provided in the form of a seal connected to the neck of the container and a screw cap covering and protecting the seal and providing a reclosable cap after the seal has 10 been removed to gain access to the contents of the container. A convenient way of providing such a closure is to provide the undersurface of the seal with a heat sensitive adhesive coating or a meltable plastics layer covered by a metal foil. The metal foil can provide the substrate of the seal or the seal may include a separate substrate made from paper or plastics material. Such a seal is then placed against the 15 top of the neck of a container and sandwiched against it by the applied screw cap, whilst the closure is subjected to an induction heating step which heats the metal foil and in turn activates the heat sensitive adhesive layer or melts the plastics layer so that, on cooling, the seal bonds to the top of the neck of the container. It is difficult for the eventual consumer to remove such seals and so attempts 20 have been made to provide a tab extending sideways from the neck of the container so that the consumer can grip this to facilitate the removal of the seal. One difficulty with this is that the eddy currents induced in the foil during inductance heating are induced mainly in the periphery of the seal. When the seal includes a tab they are therefore induced around the edge of the tab which is remote from the neck of the 25 container so that the seal is often not completely fixed to the top of the neck of the container adjacent the tab. One way of overcoming this, which is proving popular at present, is the so called "Top Tab" (Registered trademark) system, which is described fully in US-A 4961986. This system includes a multilayer substrate which is partly de-laminated to 30 provide a lifting tab lying wholly within the circumference of the container neck. Typically, the lifting tab occupies about 50% of the seal area for seals of a diameter up to 36 mm and then the tab remains this size for seals of larger diameter. In US-A 4961986 this is achieved by forming the substrate from multiple layers which are adhered together over only a part of their extent. US-A-5702015 also discloses such a C:poford\SPEC-927585.doc 2 seal but, in this case, the sealed substrate is formed by an extrusion process in which a first layer of plastics material is extruded, followed by extrusion lamination of a second layer of release material using a third layer of extrusion material which is of the same composition to that of the first layer which integrates with the first layer 5 where the second layer is not present. In this way the tab, which is formed by the third layer, is formed integrally with the first layer without the need for adhesive between the layers. As shown in US-A-4961986 the screw-cap may include some form of liner in addition to the seal material. At present, one of the difficulties of the "Top Tab" (RTM) 10 system is that it is, essentially, a two-component system with the seal material and the liner provided separately and having to be fitted inside a screw-cap in two separate operations. This naturally adds to the expense and difficulty of using the system. Accordingly, in commercial use, at present, the "Top Tab" (RTM) System is normally used without a separate liner. 15 The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed in Australia before the priority date of 20 each claim of this application. According to a first aspect of the present invention, there is provided a vessel closing assembly for adhesion into a screw cap, said assembly including a seal laminate having lower layers which form an induction heating sealable system for attaching the seal laminate to the neck of a container, and an attachment surface at a 25 top of said seal laminate, a layer of a rubbery pressure sensitive adhesive coated on said attachment surface of the seal laminate with a coating weight in the range 3 to 6 g/m2, a release layer and a stiff film layer, wherein the stiff film layer has a thickness in the range 8 to 40 pm and the release layer is adhered between an upper surface of the adhesive layer and a lower surface of the stiff film layer, and a foamed 30 thermoplastics liner with a thickness in the range 0.4 to 1.1 mm and a density in the range 250 to 500 g/I attached to an upper surface of the stiff film layer, wherein the peel strength of the lower surface of the stiff film layer at the release layer is in the range 20 to 90 g/25 mm. C ponwor"iPEC-927585.doc 3 According to a second aspect of the present invention, there is provided a method of manufacture of a vessel closing assembly, the method including the steps of providing a liner laminate and a seal laminate each having an attachment surface; depositing a release substance on a first one of the attachment surfaces; and bonding 5 the liner laminate and the seal laminate by an adhesive layer disposed between a second one of the attachment surfaces and the release substance; wherein a bonding force between the release substance and said first attachment surface is sufficiently weaker than that between the adhesive layer and release substance so that said release substance is transferable to the adhesive layer upon removal of the liner 10 laminate from the seal laminate; and said release substance is deposited on the first attachment surface in an amount sufficient to render the adhesive no longer tacky when surface in an amount sufficient to render the adhesive no longer tacky when said release substance is erred to said adhesive layer upon said removal of the liner laminate from the seal laminate. 15 Since the seal includes a free tab, its uppermost layer or layers are not completely attached to the remainder of the seal. It was expected that this partly de laminated structure would lead to considerable difficulties when attempts were made to form a one-component wadding and seal system. However, we have discovered that this is not the case and, by incorporating a release layer in the attachment 20 between the seal and the wadding the initial unscrewing of the screw-cap by the eventual consumer allows the two halves of the single component system to separate at the release layer without, in any way, damaging the liftable tab or seal. Preferably the attachment means is formed by a layer of polyethylene terephthalate which forms the uppermost layer of the seal substrate, and which is 25 coated with a release layer formed by nitrocellulose or a silicone compound, and a layer of low density polyethylene to act as an adhesive between the release layer and the undersurface of the liner. The nitrocellulose or silicone compound coated onto the polyethylene terephthalate bonds tightly onto this layer. The layer of low density polyethylene bonds tightly onto the wadding but frangibly onto the nitrocellulose or 30 silicone layer. When subject to a parting force in a direction generally perpendicular to the seal and liner, the bond strength between the nitrocelluclose or silicon compound and the polyethylene can be easily exceeded so that the seal and liner components separate from one another. C:Vofvord\SPEC-927585.doc 4 The liner may be formed by a layer of food grade cardboard or a layer of foamed plastic material such as foamed polyethylene. In this case a layer of polypropylene may be included between the foamed layer and the layer of low density polyethylene of the attachment means. 5 Alternatively, the attachment means can be formed from an upper layer of polyethylene terephthalate which forms the uppermost layer of the seal substrate which is coated with an adhesive layer. The bottom layer of the liner system can be a layer of PET which is coated with a release layer, for example cellulose acetate propionate (CAP) which is subsequently adhered to the adhesive layer of the 10 attachment means. When subject to a parting force in a direction generally perpendicular to the seal and liner, the binding strength between the adhesive and coated PET is easily exceeded so the seal and liner components separate from one another with separation point being between the release layer and the upper PET layer. 15 The seal preferably includes an induction heating sealable system comprising a layer of aluminium foil coated on its lowermost face with a hot melt adhesive. A layer of polyethylene teraphthaiate may be interposed between the hot melt adhesive and the aluminium foil layer to isolate the foil from the contents of the container and so prevent corrosion of the foil layer. The seal also includes a substrate which may 20 include a paper laminate as described in US-A-4961986 but preferably includes a layer of foamed polymer such as a foamed polyolefin, for example, polyethylene, bonded to the foil layer and a layer of polyethylene teraphthalate bonded to the foamed layer. A further layer of polyethylene teraphthalate, nylon or polypropylene may be interposed between the layer of polyethylene teraphthalate and the foam in 25 the region where they are not bonded together. The seal substrate may include an upper layer of foamed plastics such as ethylvinyl acetate foam interposed between the layer of polyethylene foam and the layer of polyethylene teraphthalate. In this way the liftable tab then also includes a foam layer. The screw-cap is generally conventional and may include a multi-turn screw 30 thread or a multi-start part turn screw thread. Preferably it includes a circumferentially extending rib or series of fingers which hold the combined one-component liner and seal in place during initial application of the cap to the container and continue to hold the liner portion in place during subsequent opening and closing of the cap. Preferably the cap is arranged so that there is sufficient clearance between the top of C.%pofwordSPEC-927585.doc 5 the cap and the rib or fingers that the entire one-component liner and seal can rotate with respect to the cap, This allows the liner to be separated from the seal under a peel force perpendicular to the liner and seal. The container may be made of glass or plastics material such as polyethylene, polyester, polyvinyl chloride, polypropylene, 5 polystyrene or acrylonitrile butadiene styrene. Two embodiments of a one component liner and seal system in accordance with this invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a cross-section through a first example with a vertical dimension 10 greatly exaggerated; Figure 2 is a cross-section through a second embodiment, again with a vertical dimension greatly exaggerated; Figure 3 is a cross-section through a screw cap showing the liner and seal in place; and, 15 Figure 4 is a perspective view showing the seal in place on the neck of a container. The one-component liner and seal 1 comprises a wadding portion 2 and a seal portion 3 attached together. The one-component wadding and seal 1 is formed by a laminate of a number of layers which, starting from the. bottom comprise a coating of 20 hot melt adhesive 4 deposited typically at a rate of in the range 25 to 38 g/m 2 and may include polyester coatings, ethylene vinyl acetate, polypropylene, ethylene acrylic acid -co--polymers, or Surlyn (rtm); a layer of aluminium foil 5 for instance 20 or 25 microns thick; a layer of polymeric adhesive 6 applied, for instance at a rate in the range of 3 g/m 2 to 20; a layer of polyethylene foam 7 125-250 microns thick; a 25 layer of polyethylene terephthalate 8 extending only part way across the layer of foam 7 and not adhered to the layer of foam 7; a layer of polymeric adhesive 9 applied, for instance at a rate of 50 g/m; a layer of polyethylene terephthalate layer 10 23 microns thick which is adhered both to the foam 7 and the polyethylene terephthalate layer 8; a layer 11 of nitrocellulose applied at a rate of 1 - 2 g/m 2 , which acts as a release 30 layer; a layer 12 of low density polyethylene deposited at a rate of 20 g/m 2 and, a layer 13 of food grade cardboard typically 700 to 900 microns thick. The adhesive layers 6 and 9 are typically ethylene vinyl acetate copolymer, polyethylene or polyurethane. The layer of low density polyethylene 12 is typically CApofward\SPEC-927585 doc 6 applied in a molten state and, on cooling, bonds tightly to the cardboard 13 and adequately to the nitrocellulose layer 11. As a result of the presence of the polyethylene teraphthalate layer 10, the nitrocellulose layer 11 and the low density polyethylene layer 12 a bond is formed 5 between the seal portion 3 and the liner portion 2. However, this attachment includes a weakened zone formed by the weak bond formed between the release layer 11 and the low density polyethylene layer 12. This bond is adequate to hold the two portions 2 and 3 together during subsequent processing and handling but weak enough so that when subjected to an appropriate parting force in the upright direction as shown 10 in the Figures, the liner portion 2 separates from the seal portion 3. The presence of the polyethylene terephthalate partial layer 8 and the fact that it is not bonded to the foam layer 7 provides a separate tab portion formed by the layer 8 and 10 which is not adhered to the layer 7 and so forms a liftable tab 50 (shown in Figure 4) which will be described subsequently. 15 The second embodiment which is shown in Figure 2 is identical to the first from the layer 4 to the layer 12 but, in this example the layer 12 is attached to a layer 14 of polypropylene film 20 microns thick. A layer of polypropylene polyethylene polymeric. adhesive 15 applied at a rate of 20 g/m 2 adheres the polypropylene layer 14 to a layer of expanded polyethylene foam 16 of typical thickness 1.0 or 1.6 mm. A layer of 20 polypropylene polyethylene polymeric adhesive 17 applied at a rate of 20 g/m 2 adheres the expanded polyethylene foam 16 to a layer 18 of polypropylene film of 20 microns thick. In this second embodiment the liner portion 2 is essentially formed by an expanded polyethylene foam 16 covered by polypropylene layers 14 and 28 which replaces the food grade cardboard used in the first example. 25 After formation of the laminate it is die cut to form individual discs of one component liner and seal 1. The one-component liner 1 is press-fitted inside the top of a screw cap 20 and held in place by a circumferential rib 21. The one-component liner and seal 1 is sized so as to be able to rotate freely in the top of the cap 20 whilst, at the same time, being held securely in place by the rib 21. In use, a screw cap 30 equipped with a one-component liner and seal 1 in accordance with the present invention is screwed onto the open neck of a bottle 30 so sandwiching the one component liner and seal 1 between the open neck of the bottle 30 and the top of the cap 20 . The cap 20 and bottle 30 are then subjected to an induction heating step in which the aluminium foil 5 is heated around its periphery by the generation of eddy C:pofWor\SPEC-9275S5.doc 7 currents within it which, in turn, melts the coating 4 of hot melt adhesive to bond the seal portion 3 onto the open neck of the bottle 30. The sealed container is then distributed. When the screw cap 20 is removed from the bottle 30 by the eventual user the 5 seal portion 3 remains adhered to the open neck of the bottle 30 whilst the liner portion 1 is retained by the rib 21 in the top of the cap 20. The seal portion 3 and liner portion 2 part at the nitrocellulose release layer 11 during this initial removal of the cap 20 from the neck of the bottle 30. The eventual consumer can then easily remove the seal portion 3 from the neck of the bottle 30 merely by gripping the tab portion 50 10 formed by the layers 8 and 10 with the manual force applied to the tab 50 overcoming the adhesion provided between the hot melt coating 4 and the neck of the bottle 30 to enable the entire seal portion 3 to be removed to allow the eventual user to gain access to the contents of the bottle 30. The liner portion 2 remains adhered within the cap to form a secondary seal when reclosed. 15 Throughout the description and claims of this specification the word "comprise" and variations of that word, such as "comprises" and "comprising", are not intended to exclude other additives or components or integers. The invention described herein is susceptible to variations, modifications and/or additions other than those specifically described and it is to be understood that 20 the invention includes all such variations, modifications and/or additions which fall within scope of the following claims. C:Vx OrdSPEC-927585.oc