Method for manufacturing heat-sealable packaging material having barrier layer containing cycloolefin copolymer

Abstract

Method of manufacturing polymer-coated heat-sealable packaging material and sealed packages (e.g., carton, box, or bag packages for dry and liquid foods). The material includes a fiber base of packaging paper or packaging board, an outer polymeric heat sealing layer such as LDPE, and an inner polymeric water vapor barrier layer which is partly or totally formed of an amorphous cycloolefin copolymer. In the method, the cycloolefin copolymer water vapor barrier and the heat sealing layers are brought onto the fiber base by an extrusion step, and in accordance with the manufacturing method, they can be placed on one side of the fiber base or on both sides of the fiber base for achieving a moisture barrier on both sides of the package. Also, polymeric oxygen barrier layers, such as EVOH or polyamide layers, can be incorporated into the packaging material. By using the cycloolefin copolymer as an extruded water vapor barrier layer, curling of the packaging material is prevented.

1 . A method for manufacturing a heat-sealable packaging material, in which superimposed polymeric coating layers are extruded onto a fibre base, said layers comprising in the following order: 
 an outermost polymeric heat sealing layer;    a polymeric water vapor barrier layer, the water vapor penetration of which is lower than that of the heat sealing layer, the water vapor barrier layer incorporating cycloolefin copolymer (COC);    a tie layer; and    an innermost polymeric oxygen barrier layer,    wherein the layers are brought onto the fiber base in a single step by coextrusion,    wherein the layers are adhered directly to each other without additional layers between them, and    wherein the water vapor barrier layer as produced by extrusion are amorphous without post-crystallisation occurring in the polymer.    
   
   
       2 . The method according to  claim 1 , wherein only one side of the fibre base is coated with polymer.  
   
   
       3 . The method according to  claim 1 , wherein on both sides of the fibre base there is an outermost heat sealing layer and an inner water vapor barrier layer containing COC.  
   
   
       4 . The method according to  claim 1 , wherein the water vapor barrier layer is formed in its entirety of COC.  
   
   
       5 . The method according to  claim 1 , wherein the water vapor barrier layer is formed of a mixture of COC and low-density polyethylene (LDPE).  
   
   
       6 . The method according to  claim 1 , wherein the weight of the water vapor barrier layer containing COC is 5-50 g/m 2 .  
   
   
       7 . The method according to  claim 6 , wherein the weight of the water vapor barrier layer containing COC is 7-30 g/m 2 .  
   
   
       8 . The method according to  claim 7 , wherein the weight of the water vapor barrier layer containing COC is 10-20 g/m 2 .  
   
   
       9 . The method according to  claim 1 , wherein the material of the heat sealing layer is low-density polyethylene (LDPE).  
   
   
       10 . The method according to  claim 9 , wherein the weight of the LDPE heat sealing layer is 5-50 g/m 2 .  
   
   
       11 . The method according to  claim 10 , wherein the weight of the LDPE heat sealing layer is 5-30 g/m 2 .  
   
   
       12 . The method according to  claim 11 , wherein the weight of the LDPE heat sealing layer is 7-20 g/m 2 .  
   
   
       13 . The method according to  claim 1 , wherein the oxygen barrier layer is formed of ethyl vinyl alcohol copolymer (EVOH), polyamide (PA), or a mixture of these.  
   
   
       14 . The method according to  claim 13 , wherein the weight of the oxygen barrier layer is 3-15 g/m 2 .  
   
   
       15 . The method according to  claim 14 , wherein the weight of the oxygen barrier layer is 5-10 g/m 2 .  
   
   
       16 . The method according to  claim 1 , wherein a packaging board is manufactured, the weight of the fibre base of which is 130-500 g/m 2 .  
   
   
       17 . The method according to  claim 16 , wherein a packaging board is manufactured, the weight of the fibre base of which is 170-300 g/m 2 .  
   
   
       18 . The method according to  claim 1 , wherein a packaging paper is manufactured, the weight of the fibre base of which is 20-120 g/m 2 .  
   
   
       19 . The method according to  claim 18 , wherein a packaging paper is manufactured, the weight of the fibre base of which is 40-100 g/m 2 .  
   
   
       20 . A polymer-coated heat sealable packaging material, comprising a fibre base and a combination of coextruded superimposed polymeric coating layers, the combination comprising an innermost polymeric oxygen barrier layer, a tie layer, a polymeric water vapor barrier layer incorporating cycloolefin copolymer (COC), and an outermost polymeric heat sealing layer in that order, the water vapor barrier layer as produced by extrusion being amorphous without post-crystallisation occurring in the polymer.  
   
   
       21 . The packaging material according to  claim 20 , wherein the layers in said combination are adhered directly to each other without a binding agent between them.  
   
   
       22 . A sealed package, formed by folding and heat sealing of a packaging material comprising a fibre base and, inside the fibre base, a combination of coating layers consisting of a polymeric oxygen barrier layer, a tie layer, a polymeric water vapor barrier layer incorporating cycloolefin copolymer (COC), and a polymeric heat sealing layer in that order, the heat sealing layer forming the interior surface of the package, and the water vapor barrier layer as produced by extrusion being amorphous without post-crystallisation occurring in the polymer.  
   
   
       23 . The sealed package according to  claim 22 , wherein the layers in said combination are adhered directly to each other without a binding agent between them.  
   
   
       24 . The sealed package according to  claim 22 , wherein both the exterior and the interior surfaces of the package are provided with a water vapor barrier layer containing COC and a heat sealing layer.  
   
   
       25 . The sealed package according to  claim 22 , which a box package for dry food formed of polymer-coated board.  
   
   
       26 . The sealed package according to  claim 22 , which is a carton package for liquid food formed of polymer-coated board.  
   
   
       27 . The sealed package according to  claim 22 , which is a bag package formed of polymer-coated paper.