Method in the manufacture of a packaging laminate, a plant in the manufacture of the packaging laminate, and the thus manufactured packaging laminate

Abstract

A method in the manufacture of a web-shaped packaging laminate ( 22 ) comprising a core layer ( 24 ) of paper or paperboard, the method including the steps of coating ( 38 ) a first side of a material web ( 40 ) of paper or paperboard with an outer layer ( 26 ) of thermoplastic material, an thereafter forming, with the aid of laser burning ( 46, 48 ) on the thus thermo-plastic coated first side of the packaging laminate ( 22 ), a perforation line ( 32 ) through said thermoplastic layer ( 26 ) and said core layer ( 24 ). After said coating ( 38 ) with the thermoplastic material but before the formation of the perforation line, the packaging laminate ( 22 ) is compressed ( 44, 10 ) on said first side for the formation of a compression line ( 30 ) in which said core layer ( 24 ) is compressed, whereafter said perforation line ( 32 ) is formed in said compression line ( 30 ). The present invention also relates to a plant in the manufacture of the packaging laminate, as well as the thus produced packaging laminate ( 22 ).

1 . In the manufacture of a web-shaped packaging laminate, comprising a core layer of paper or paperboard, a method comprising the steps of coating a first side of a material web of paper or paperboard with an outer layer of thermoplastic material, and thereafter, with the aid of laser burning forming, on the thus thermoplastic coated first side of the packaging laminate, a perforation line through said thermoplastic layer and said core layer, comprising the step, after said coating with the thermoplastic material, but before the formation of the perforation, of compressing the packaging laminate on said first side, for the formation of a compression line in which said core layer is compressed, whereafter said perforation line is formed in said compression line.  
     
     
         2 . The method as claimed in  claim 1 , wherein the compression line and the perforation line are formed in relation to one another such that a build-up of thermoplastic residual material around the perforation line, after the laser burning, will substantially be located entirely below the level of the surrounding surface of the packaging laminate, the core layer preferably being compressed by at most 70%, preferably at most 60% but at least 20%, preferably at least 30% of its original thickness in said compression line.  
     
     
         3 . The method as claimed in  claim 1 , wherein the compression is considerably wider than the perforation line, preferably at least 1.5 times, as wide, and even more preferably at least twice as wide, but at most ten times as wide, preferably at most five times as wide.  
     
     
         4 . The method as claimed in  claim 1 , wherein said web-shaped packaging laminate is further processed after the forming of the perforation line, on rollers and/or by rolling up on a reel.  
     
     
         5 . A plant in the manufacture of a web-shaped packaging laminate comprising a core layer of paper or paperboard, the plant comprising a coating station for forming a coating layer of a thermoplastic material on a first side of said core layer, followed by a perforation station including a laser burner, the perforation station being disposed to form a laser-burned perforation line on the first side of the packaging laminate through said thermoplastic layer and said core layer, characterised by comprising a compression station between said coating station and said perforation station, including a compression tool disposed to form a compression line on said first side of the packaging laminate, and that said perforation station is disposed to form said perforation line in said compression line.  
     
     
         6 . The plant as claimed in  claim 5  wherein said compression tool includes a roller which displays a projecting compression portion around its circumference, said projecting compression portion being preferably 1-3 mm and even more preferably 1.5-2.5 mm wide and preferably 0.2-2 mm and even more preferably 0.2-1 mm high above the surrounding surface of the roller, as well as a counter roller which preferably displays a smooth circumferential surface, a gap between said roller and said counter roller being adjustable.  
     
     
         7 . The plant as claimed in  claim 5  wherein it includes additional, subsequent stations for further processing or handling of the packaging laminate, including rollers and/or stations for rolling up the packaging laminate on a reel.  
     
     
         8 . A packaging laminate comprising a core layer of paper or paperboard as well as a thermoplastic coating layer on a first side thereof, displaying a laser-burned perforation line through the core layer and the thermoplastic layer, wherein said perforation line is disposed in a compression line on the first side of the packaging laminate, in which compression line said core layer is compressed.  
     
     
         9 . The packaging laminate as claimed in  claim 8 , wherein the compression line and the perforation line are formed in relation to one another so that a build-up of thermoplastic residual material around the perforation line is substantially located entirely below the level of the surrounding surface of the packaging laminate, the core layer preferably being compressed in said compression line by at most 70%, preferably at most 60% but at least 20%, preferably at least 30% in relation to its thickness surrounding the compression line.  
     
     
         10 . The packaging laminate as claimed in  claim 8  wherein the compression line is considerably wider than the perforation line, preferably at least 1.5 times as wide, and even more preferably at least twice as wide, but at most ten times as wide, preferably at most five times as wide.  
     
     
         11 . The packaging laminate as claimed in  claim 8 , wherein said thermoplastic coating layer displays a surface weight or grammage of 20-50 g/m 2 , preferably 20-40 g/m 2 , and that it preferably includes a thermoplastic material selected from the group essentially comprising polyethylene and polypropylene.