Container closure

Abstract

Method of manufacture of a vessel closing assembly for adhesion into a screw cap in which a liner laminate comprising a substrate layer and a layer of stiff film on at least one side of the substrate layer, having an attachment surface for attachment to the seal laminate, is attached to a seal laminate comprising induction heat sealable layers for sealing at one side to a container and comprises at least one stiff film layer and an attachment surface at the other side whereby the attachment surface of the seal laminate faces the side of the liner laminate formed by the stiff film, the joining involving the steps of: providing a release surface on one of the attachment surfaces; applying a pressure sensitive adhesive composition, from a liquid composition to one of the attachment surfaces and drying the composition to leave an adhesive coating; and contacting the attachment surfaces to adhere the liner laminate to the seal laminate.

1 . Method of manufacture of a vessel closing assembly for adhesion into a screw cap in which a liner laminate comprising a substrate layer and a layer of stiff film on at least one side of the substrate layer, having an attachment surface for attachment to the seal laminate, is attached to a seal laminate comprising induction heat sealable layers for sealing at one side to a container and comprises at least one stiff film layer and an attachment surface at the other side whereby the attachment surface of the seal laminate faces the side of the liner laminate formed by the stiff film, the joining involving the steps of: 
 providing a release surface on one of the attachment surfaces;    applying a pressure sensitive adhesive composition, from a liquid composition to one of the attachment surfaces and drying the composition to leave an adhesive coating; and    contacting the attachment surfaces to adhere the liner laminate to the seal laminate.    
     
     
         2 . A method according to  claim 1  wherein the vessel closing assemblies are cut from the pair of adhered laminates and adhered into screw cap in a procedure separate to the laminate adhesion procedure.  
     
     
         3 . The method according to  claim 2  in which the assemblies are adhered into the caps by a hot melt adhesive.  
     
     
         4 . The method according to  claim 1  in which the release surface is provided by coating the relatively stiff film with release material.  
     
     
         5 . The method according to  claim 3  in which the release layer is a cellulose acetate proprionate coating.  
     
     
         6 . The method according to  claim 5  in which the coating weight of the CAP layer is in the range I to 3 g 1 m.  
     
     
         7 . The method according to claim I in which the release layer is a silicone coating.  
     
     
         8 . The method according to claim I in which the liner is formed from foamed thermoplastics material.  
     
     
         9 . The method according to  claim 8  in which the foamed thermoplastics material is polypropylene faced polyethylene foam.  
     
     
         10 . The method according to  claim 8  in which the thickness of the foamed thermoplastics material is in the range 0.4 to 1.1 mm.  
     
     
         11 . The method according to  claim 8  in which the density of the foamed thermoplastics material is in the range 250 to 500 gll.  
     
     
         12 . The method according to claim I in which the stiff layer is formed from a polyester or polypropylene.  
     
     
         13 . The method according to  claim 12  in which the stiff layer is polyethylene terephthalate.  
     
     
         14 . The method according to  claim 1  in which the thickness of the stiff film is in the range 8.0 to 4 Opm.  
     
     
         15 . The method according to claim I in which the stiff layer is white polyethylene terephthalate.  
     
     
         16 . The method according to claim I in which the pressure sensitive adhesive composition is formulated with a natural or synthetic latex with high elongation properties.  
     
     
         17 . The method according to  claim 1  in which the release surface is on the stiff film layer and the pressure sensitive adhesive composition is applied to the surface of the release layer.  
     
     
         18 . The method according to  claim 1  in which the release surface is on the stiff film surface and the pressure sensitive adhesive composition is applied to the top surface of the seal laminate.  
     
     
         19 . The method according to  claim 1  in which the peel strength of the attachment surface at the release layer is in the range 20 to 90 g/25 mm.  
     
     
         20 . The method according to claim I in which the peel strength of the attachment surface at the release surface is in the range 30 to 60 g/25 mm.  
     
     
         21 . The method according to claim I in which the pressure sensitive adhesive composition is a cohesive adhesive.  
     
     
         22 . The method according to  claim 1 , wherein prior to applying the pressure sensitive adhesive composition, the attachment surface of the seal laminate is corona treated.  
     
     
         23 . A vessel closing assembly for adhesion into a screw cap including a seal laminate having lower layers which form an induction heating sealable system for attaching the seal to the neck of a container to be sealed and a top layer of polyester which has been corona treated; a liner laminate comprising a substrate layer and a bottom layer of stiff polyester film which has a bottom surface with release properties; and a non-continuous layer of cold seal adhesive bonded between the top polyester layer of the seal laminate and the bottom surface of the stiff polyester film layer of the liner laminate; wherein 
 the bonding force between the adhesive and the top polyester layer of the seal laminate is sufficiently strong that the adhesive remains bonded to the top polyester layer upon removal of the liner laminate from the seal laminate by a shear force and the bonding force between the adhesive and the bottom surface of the stiff polyester film layer of the liner laminate is sufficiently upon removal of the liner laminate from the seal laminate.    
     
     
         24 . The vessel closing assembly according to  claim 23 , wherein the top polyester layer of the seal laminate is polyethylene terephthalate.  
     
     
         25 . The vessel closing assembly according to  claim 23 , wherein the bottom polyester layer of the liner is polyethylene terephthalate.  
     
     
         26 . The vessel closing assembly of  claim 25 , wherein the polyethylene terephthalate is Melinex 891.  
     
     
         27 . The vessel closing assembly of  claim 23 , wherein the adhesive is selected from the group consisting of latex containing synthetic cold seal adhesives.  
     
     
         28 . The vessel closing assembly of  claim 23 , wherein the adhesive is H B Fuller NP-4134M.  
     
     
         29 . The vessel closing assembly of  claim 23 , wherein the non-continuous adhesive layer is a pattern of regularly spaced dots of adhesive.  
     
     
         30 . The vessel closing assembly of  claim 23 , wherein the shear strength at the interface between the top polyester layer of the seal and the adhesive layer is in the range from 100 to 300 gcm  
     
     
         31 . The vessel closing assembly of  claim 23 , wherein the seat laminate includes an upper layer and a lower layer which are adhered in a first region but not in a second region and an intermediate layer interposed between the upper and lower layers and adhered to the upper layer but not the lower layer, so as to form a tab lying wholly within the circumference of the seal.  
     
     
         32 . The vessel closing assembly of  claim 31 , wherein the upper layer is ethylene vinyl acetate (EVA).  
     
     
         33 . The vessel closing assembly of  claim 31 , wherein the lower layer is a polymeric foam.  
     
     
         34 . The vessel closing assembly of  claim 33 , wherein the polymeric foam is high density polyethylene foam.  
     
     
         35 . The vessel closing assembly of  claim 31 , wherein the intermediate layer is polyethylene terephthalate.  
     
     
         36 . The vessel closing assembly of  claim 31 , wherein the liner laminate includes a top layer of polyethylene foam.  
     
     
         37 . The vessel closing assembly of  claim 23  which is cut and shaped so as to fit inside a screw cap.  
     
     
         38 . A screw cap which has adhered within it the vessel closing assembly according to  claim 31 .  
     
     
         39 . A container which is fitted with the screw cap according to  claim 38 .  
     
     
         40 . A method of forming a vessel closing assembly comprising the steps of: 
 providing a seal laminate comprising lower layers which form an induction heat sealable system and a top polyester layer;    corona treating the top polyester layer of the seal;    applying a cold seal adhesive onto the top polyester layer of the seal which has been corona treated, such that the resulting adhesive layer is not continuous and covers only a portion of the surface area of the top polyester layer;    providing a liner which has a bottom stiff polyester film layer which has a bottom surface with release properties; and    adhering the bottom stiff polyester film layer of the liner to the adhesive layer to form a laminate.    
     
     
         41 . The method of  claim 40 , wherein the laminate is cut to form a shaped vessel closing assembly.  
     
     
         42 . The method of  claim 40 , wherein the seal substrate includes an upper layer and a lower layer which are adhered in a first region but not in a second region and an intermediate layer interposed between the upper and lower layers and adhered to the upper layer but not the Lower layer so as to form a tab lying wholly within the circumference of the seal.