Coated cardboard and a method of producing the same

Abstract

A coated food cardboard that is comprised of a cardboard layer and a coating layer at least on one side of it, and a method of producing it. Between the coating layer and the cardboard surface is formed by dispersion coating a barrier layer that is comprised of binder and slate-like pigments. The layer is formed of a dispersion that is prepared by dispersing slate-like pigment in water and mixing this with a non-hydrophobic binder. The cardboard has excellent barrier properties and it can be used, for example, in such a pigment coated cardboard, in particular fresh fibre cardboard that has good properties of mineral oil migration and fat penetration prevention.

1 . Coated food cardboard which comprises a cardboard layer and a coating layer on at least one side of it, further comprising a barrier layer between the coating layer and the cardboard containing binder and slate-like mineral pigment. 
     
     
         2 . The cardboard according to  claim 1 , wherein the barrier layer is formed by dispersion coating. 
     
     
         3 . The cardboard according to  claim 1 , wherein the barrier layer comprises non-hydrophobic binder. 
     
     
         4 . The cardboard according  claim 1 , wherein the pigment and the binder together form a network structure, which is capable of slowing down the penetration of unwanted substance molecules through the barrier layer. 
     
     
         5 . The cardboard according  claim 1 , wherein the barrier layer comprises of its dry matter 5-70% mineral pigment and 95-30% binder, in particular it comprises of its dry matter approximately 15-60% mineral pigment and 85-40% binder, possibly together with the additives of the dispersion. 
     
     
         6 . The cardboard according to  claim 1 , wherein the binder of the barrier layer is starch, such as cooked or cold soluble surface sizing starch slurry, polyvinyl alcohol, ethylene vinyl alcohol or a mixture thereof. 
     
     
         7 . The cardboard according to  claim 1 , wherein the slate-like mineral pigment of the barrier layer is kaolin, talc or a mixture thereof. 
     
     
         8 . The cardboard according to  claim 1 , wherein the weight of the barrier layer is approximately 1-50 g/m 2 , in particular approximately 5-40 g/m 2 , most suitably approximately 10-30 g/m 2 , per cardboard side. 
     
     
         9 . The cardboard according to  claim 1 , wherein the coating layer comprises binder and light-refracting pigment or mixture of pigments. 
     
     
         10 . The cardboard according to  claim 1 , wherein the coating layer comprises pigment, which refracts light better than the slate-like mineral pigment of the barrier layer, in particular the pigment of the coating layer is calcium carbonate, titanium dioxide, calcium sulphate, aluminium silicate, aluminium hydroxide, magnesium silicate or barium sulphate or a mixture thereof. 
     
     
         11 . The cardboard according to  claim 1 , wherein on both sides of the cardboard layer there are coating layers and preferably, barrier layers that comprise binder and slate-like mineral pigment are arranged between both coating layers and the corresponding cardboard surfaces. 
     
     
         12 . The cardboard according  claim 1 , wherein there is a surface sizing agent layer between the cardboard surface and the barrier layer. 
     
     
         13 . A method of producing coated cardboard, according to which method onto the cardboard is applied a coating mixture that comprises light-refracting pigment, in order to form a coating layer, wherein between the coating layer and the cardboard surface is formed, by dispersion coating, a barrier layer that is comprised of binder and slate-like pigments. 
     
     
         14 . The method according to  claim 13 , wherein the barrier layer is formed of a dispersion that is prepared by dispersing slate-like pigment in water and mixing this into a non-hydrophobic binder. 
     
     
         15 . The method according to  claim 13 , wherein the barrier layer is formed of a dispersion that is prepared by dispersing slate-like pigment in water, particularly in order to generate a pigment dispersion that has a solids content of over 50%, and this dispersion is combined with a binder by mixing, in which case the pigment share of the dry matter of the dispersion that is used to form the barrier layer, is approximately 5-70%, in particular approximately 15-60%. 
     
     
         16 . The method according to  claim 13 , wherein the dispersion is applied at the cardboard machine, after any surface sizing and before any pigment coating, preferably the dispersion is applied directly at the cardboard machine after surface sizing and before pigment coating. 
     
     
         17 . The method according to  claim 13 , wherein the dispersion is applied as at least two different layers. 
     
     
         18 . The method according to  claim 17 , wherein the first dispersion layer is applied with a film size press, such that a barrier layer is achieved that follows the surface shapes and the roughness of the cardboard web. 
     
     
         19 . The method according to  claim 17 , wherein the second dispersion layer is applied with a blade coating unit or a bar coating unit. 
     
     
         20 . the method according to  claim 17 , wherein after the application of the second dispersion layer, the barrier layers are left unformulated or formulated by using a rotating or static, smooth or grooved bar, an air knife, or a metallic or ceramic blade. 
     
     
         21 . The method according to  claim 13 , wherein the dispersion layer is applied from the pigment slurry, the dry matter content of which is 10-40% calculated by weight of the slurry. 
     
     
         22 . The method according to  claim 13 , wherein a barrier layer is formed, the grammage of which is approximately 1-50 g/m 2 , in particular approximately 5-40 g/m 2 , most suitably approximately 10-30 g/m 2 , per cardboard side. 
     
     
         23 . The method according to  claim 13 , wherein a non-hydrophobic binder, polyvinyl alcohol, ethylene vinyl alcohol or a mixture thereof, is used to form the dispersion. 
     
     
         24 . The method according to  claim 13 , wherein the cardboard is surface sized before it is dispersion coated with a dispersion that forms the barrier layer. 
     
     
         25 . The method according to  claim 13 , wherein the cardboard is coated, possibly after surface sizing, before it is dispersion coated with a dispersion that forms the barrier layer. 
     
     
         26 . The method according to  claim 13 , wherein a coating layer is formed that comprises pigment that refracts light better than the late-like mineral pigment in the barrier layer, in particular the coating layer pigment is calcium carbonate, precipitated calcium carbonate, titanium dioxide, calcium sulphate, aluminium silicate, aluminium hydroxide, magnesium silicate or a mixture thereof. 
     
     
         27 . The method according to  claim 13 , wherein on both sides of the cardboard layer, are brought coating layers that comprise slate-like mineral pigment, are arranged between both coating layers and the corresponding cardboard surfaces. 
     
     
         28 . (canceled) 
     
     
         29 . (canceled)