Seal Stock Laminate

Abstract

A method for producing a primary laminate including a tabstock the steps of; feeding a seal laminate comprising bottom food contact layers including a foil layer and a top polyester layer to a laminating station wherein either the foil layer or the underside of the polyester layer has been printed; simultaneously feeding a tabstock, which is narrower than the seal laminate, to the laminating station such that the bottom of the tabstock and the top polyester layer of the seal laminate come into contact to form a primary substrate, the top face of which is partly comprised of the top face of the tabstock and partly comprised of the top polyester layer of the heat sealable laminate, prior to reaching the laminating station; simultaneously feeding a plastic film stock which has top and bottom surfaces to the laminating station; and continuously extruding a polymeric adhesive between the top face of the primary substrate and bottom surface of the plastic film stock such that the two are adhered together with a bond strength greater than 15 N/cm as measured when the tabstock is pulled at 90° to the machine direction and at 180° to the primary substrate to form a primary laminate including a tabstock. The primary laminate formed can then be laminated to a board or synthetic secondary liner.

1 . A method for producing a primary laminate including a tabstock the method comprising the steps of:
 a) feeding a seal laminate comprising bottom food contact layers including a foil layer and a top polyester layer to a laminating station;   b) simultaneously feeding a tabstock, which is narrower than the seal laminate, to the laminating station such that the bottom of the tabstock and the top polyester layer of the seal laminate come into contact to form a primary substrate, the top face of which is partly comprised of the top face of the tabstock and partly comprised of the top polyester layer of the seal prior to reaching the laminating station;   c) simultaneously feeding a plastic film stock which has top and bottom surfaces to the laminating station; and   d) continuously extruding a polymeric adhesive between the top face of the primary substrate and bottom surface of the plastic film stock such that the two are adhered together with a bond strength greater than 15 N/cm when the tabstock is pulled at 90° to the machine direction and at 180° to the primary substrate, to form a primary laminate including a tabstock.   
     
     
         2 . The method according to  claim 1 , wherein either the foil layer or the underside of the polyester layer which form part of the seal laminate have been printed. 
     
     
         3 . The method according to  claim 1 , wherein the plastic film stock is formed from a material selected from the group consisting of polyethylene terephthalate, polyamide, polyethylene or a composite of the aforementioned materials. 
     
     
         4 . The method according to  claim 3 , wherein the plastic film stock is polyethylene terephthalate. 
     
     
         5 . The method according to  claim 1 , wherein the top polyester layer of the seal laminate is polyethylene terephthalate. 
     
     
         6 . The method according to  claim 1 , wherein the polymeric adhesive has a melt flow index in the range from 5 to 25 dg/min. 
     
     
         7 . The method according to  claim 1 , wherein the tabstock is formed of polyethylene terephthalate. 
     
     
         8 . The method according to  claim 1 , wherein the tabstock includes a coloured or printed PET layer. 
     
     
         9 . The method according to  claim 1 , wherein in step (b), the tabstock comprises a plurality of narrow tabstocks arranged at regularly spaced intervals. 
     
     
         10 . The method according to  claim 1 , wherein the thickness of the top plastic film layer of the heat sealable laminate is in the range from 12 to 36 μm. 
     
     
         11 . The method according to  claim 1 , wherein the thickness of the plastic film stock is in the range from 12 to 36 μm. 
     
     
         12 . The method according to  claim 1 , wherein the thickness of the tabstock is in the range from 12 to 25 μm. 
     
     
         13 . The method according to  claim 1 , wherein the polymeric adhesive is ethylene methyl acrylate. 
     
     
         14 . A method of making a laminate according to  claim 1  comprising the further steps of:
 a) feeding the primary laminate including a tabstock to a first laminating station;   b) simultaneously feeding a secondary seal stock which has an overall stiffness in the range from 200-1200 gcm and has an upper face for contact with a container closure and a lower face for sealing against a container, to the laminating station;   c) extruding a second polymeric adhesive through a die head between the top plastic film face of the primary laminate including a tabstock and the lower face of the secondary seal stock to form a seal stock laminate.   
     
     
         15 . The method according to  claim 14 , wherein the second polymeric adhesive has a melt flow index in the range from 5 to 25 dg/min. 
     
     
         16 . The method according to  claim 14 , wherein the second polymeric adhesive is polyethylene. 
     
     
         17 . The method according to  claim 14 , wherein in step c) the second polymeric adhesive comprises two polymeric adhesives which are coextruded. 
     
     
         18 . The method according to  claim 17 , wherein the two polymeric adhesives are polyethylene and polypropylene. 
     
     
         19 . The method according to  claim 1 , wherein the length of the die head is in the range from 500 to 2000 mm. 
     
     
         20 . The method according to  claim 19 , wherein the gap of the die head is in the range from 500 to 700 μm. 
     
     
         21 . The method according to  claim 14 , wherein the secondary seal stock is pulpboard or kraftboard. 
     
     
         22 . The method according to  claim 21 , wherein the thickness of the pulpboard or kraftboard is in the range from 500 to 1000 μm. 
     
     
         23 . The method according to  claim 14 , wherein the secondary seal stock is a synthetic laminate. 
     
     
         24 . The method according to  claim 23 , wherein the synthetic laminate comprises a foam with a facing layer on each face thereof. 
     
     
         25 . The method according to  claim 24 , wherein the foam is polyethylene or polypropylene foam. 
     
     
         26 . The method according to  claim 24 , wherein the foam layer has a thickness in the range from 0.85 to 1.65 mm. 
     
     
         27 . The method according to either  claim 24 , wherein the facing layers have a thickness in the range from 20 to 70 μm. 
     
     
         28 . The method according to  claim 17 , wherein the facing layer comprises a homopolymer centre with a copolymer on each face thereof. 
     
     
         29 . The method according to  claim 28 , wherein the homopolymer is polypropylene and the copolymer is a polypropylene/polyethylene copolymer. 
     
     
         30 . The method according to  claim 28 , wherein the second polymeric adhesive comprises coextruded polypropylene and polyethylene such that the polypropylene is in contact with the lower face of the secondary seal stock and the polyethylene is in contact with the top polyester face of the primary laminate. 
     
     
         31 . The method according to  claim 1 , wherein the metal foil has a thickness in the range from 12 to 30 μm. 
     
     
         32 . The method according to  claim 31  wherein the metal foil is aluminum. 
     
     
         33 . The method according to  claim 1 , wherein the bottom layers of the seal laminate are induction heat sealable layers. 
     
     
         34 . The method according to  claim 1 , wherein bottom layer of the seal laminate is formed from glassine and layer is an adhesive layer. 
     
     
         35 . The method according to  claim 34 , wherein the adhesive layer consists of a water based adhesive or a polyethylene-based adhesive. 
     
     
         36 . The method according to  claim 1  wherein the bottom layers of the seal laminate are conduction heat sealable layers. 
     
     
         37 . A primary laminate comprising:
 a seal laminate comprising bottom food contact layers including a foil layer and a top polyethylene terephthalate layer;   a tabstock which has a top and bottom face wherein the bottom face is in contact with the top polyethylene terepthalate layer; and   a layer of plastic film adhered to the top face of the tabstock by an extruded polymeric adhesives.   
     
     
         38 . A laminate comprising:
 the primary laminate according to  claim 37  adhered to a secondary seal stock which has an overall stiffness in the range from 200-1200 gcm wherein the top plastic film layer of the primary laminate is adhered to the secondary seal stock by an extruded polymeric adhesive.   
     
     
         39 . A method which comprises taking the primary laminate of  claim 37  and cutting it into strips. 
     
     
         40 . The method according to  claim 39 , wherein the strips are then shaped to form vessel closing assembly. 
     
     
         41 . A screw cap which has retained within it the shaped vessel closing assembly according to  claim 40 . 
     
     
         42 . A container which is fitted with a cap according to  claim 41  wherein the seal laminate is sealed to the mouth of the container to enclose a liquid or solid substance.