Packaging laminate, method of producing a packaging container and the packaging container

Abstract

Packaging laminate ( 10 ) for a packaging container, which packaging laminate comprises a structural base layer ( 4 ), and an inside layer ( 6 ). According to the invention, said inside layer ( 6 ) comprises a sealing ply ( 2 ) of a heat sealable thermoplastic material, which sealing ply is arranged to be the outermost layer on one side of the laminate ( 10 ), intended to be arranged on the inside of said container, said heat sealable thermoplastic material exhibiting a melt enthalply lower than 115 J/g. The invention also relates to a method of producing packaging containers from the packaging laminate, and to a packaging container produced from the packaging laminate.

1 . Packaging laminate ( 10 ) for a packaging container, which packaging laminate comprises a structural base layer ( 4 ), and an inside layer ( 6 ), 
 characterised in that said inside layer ( 6 ) comprises a sealing ply ( 2 ) of a heat sealable thermoplastic material, hereinafter denoted the second thermoplastic material, which sealing ply ( 2 ) is arranged to be the outermost layer on one side of the laminate ( 10 ), intended to be arranged on the inside of said container, said second thermoplastic material exhibiting a melt enthalpy lower than 115 J/g.    
     
     
         2 . Packaging laminate according to  claim 1 , characterised in that said sealing ply ( 2 ) exhibits a grammage of 2-10 g/m 2 , preferably 3-8 g/m 2  and even more preferred at least 3 g/m 2  but less than 5 g/m 2 .  
     
     
         3 . Packaging laminate according to  claim 1  or  2 , characterised in that a first ply ( 1 ) of the inside layer ( 6 ) consists of a first thermoplastic material which is different from said second thermoplastic material.  
     
     
         4 . Packaging laminate according to  claim 3 , characterised in that said first ply ( 1 ) is a polyethylene (PE) ply, preferably a low density polyethylene (LDPE) ply, even more preferred a linear low density polyethylene (LLDPE) and most preferred a C6 or C8 linear low density ply, in that said first ply ( 1 ) exhibits a grammage of 3-30 g/m 2 , preferably 4-10 g/m 2  and even more preferred 5-8 g/m 2 , and in that said first ply ( 1 ) is arranged in direct contact with said sealing ply ( 2 ).  
     
     
         5 . Packaging laminate according to any one of the preceding claims, characterised in that said inside layer ( 6 ) comprises a third ply ( 3 ) of a thermoplastic material, which third ply is a polyethylene (PE) ply, preferably a low density polyethylene (LDPE) ply, which third ply ( 3 ) exhibits a grammage of 10-30 g/m 2 , preferably 15-25 g/m 2 , and is arranged in direct contact with said structural base layer ( 4 ) in the packaging laminate ( 10 ).  
     
     
         6 . Packaging laminate according to any one of the preceding claims, characterised in that said inside layer ( 6 ) comprises a fourth ply ( 7 ) of a thermoplastic material, which fourth ply preferably is a low density polyethylene (LDPE) ply, which fourth ply ( 7 ) per se consists of 1-5 sub-plies and which fourth ply ( 7 ) exhibits a grammage of 5-30 g/m 2 , preferably 8-20 g/m 2  and even more preferred 10-15 g/m 2 .  
     
     
         7 . Packaging laminate according to any one of the preceding claims, characterised in that said structural base layer ( 4 ) is a paper or paperboard layer or a layer of mineral-filled polyolefin which preferably exhibits a thickness which is at least 6 times, preferably at least 8 times and even more preferred at least 10 times as thick as said inside layer ( 6 ).  
     
     
         8 . Packaging laminate according to  claim 3 , characterised in that the melt enthalpy of said second thermoplastic material is lower than a melt enthalpy of said first thermoplastic material, and preferably lower than the melt enthalpy of any thermoplastic material in any ply in the inside layer ( 6 ).  
     
     
         9 . Packaging laminate according to any one of the preceding claims, characterised in that said second thermoplastic material exhibits a melt enthalpy lower than 105 J/g, preferably lower than 95 μg, but at least 40 J/g, preferably at least 50 J/g.  
     
     
         10 . Packaging laminate according to any one of the preceding claims, characterised in that said second thermoplastic material is a metallocene polyethylene material, preferably a metallocene low density polyethylene material, even more preferred a metallocene linear low density polyethylene material.  
     
     
         11 . Method in connection with the production of a packaging container, characterised in the steps of 
 a) choosing or manufacturing a web shaped packaging laminate ( 10 ) according to any one of claims  1 - 10 ,    b) converting said packaging laminate to a continuous tube ( 23 ) by overlapping two longitudinal edges of the web shaped packaging laminate ( 10 ) and heat sealing the overlapped edges to provide a longitudinal seal ( 31 ),    c) filling the tube ( 23 ) with contents,    d) intermittently performing transversal seals ( 32 ) by mechanically pressing together two transversal anvil jaws while the filled tube ( 23 ) is arranged them between,    e) while at the same time providing energy to the packaging laminate ( 10 ) at an area of said transversal seal ( 32 ).    
     
     
         12 . Method according to  claim 11 , characterised in that said energy is provided as ultrasonic energy.  
     
     
         13 . Method according to  claim 11  or  12 , characterised in that said mechanical pressing and said providing of energy is performed during a time interval of 100-250 milliseconds, preferably 140-220 milliseconds.  
     
     
         14 . Method according to any one of claims  11 - 13 , characterised in that said mechanical pressing is performed at 1-10 MPa.  
     
     
         15 . Method according to any one of claims  11 - 14 , characterised in that a continuous sealing strip ( 34 ) is provided to cover an inside seam of the longitudinal seal ( 31 ), which sealing strip preferably is constituted by a polypropylene strip.  
     
     
         16 . Packaging container which is manufactured from a packaging laminate according to any of claims  1 - 10 .  
     
     
         17 . Packaging container according to  claim 16 , characterised in that it comprises a longitudinal seal ( 31 ) and two transversal seals ( 32 ) which each of them overlaps the longitudinal seal ( 31 ), thus defining a room for the contents of the container, said transversal seals being strong and liquid-tight also at overlaps between the transversal seals and the longitudinal seal in the packaging container.  
     
     
         18 . Packaging container according to  claim 17 , characterised in that said transversal seals ( 32 ) have been performed by transversally, mechanically pressing together the packaging laminate so that the outermost heat sealable ply ( 2 ) is pressed together with itself, while providing energy, preferably ultrasonic energy, to the packaging laminate ( 10 ) at an area of said transversal seals ( 32 ).