Coated fibrous web and process for the production thereof

Abstract

The present invention relates to a coated fibrous web and a method for producing it. According to the present invention, a coated fibrous web comprises a filler-containing base web that has a pigment-containing coating layer on at least one surface. The filler of the base web consists at least partially of cellulose or lignocellulose fibrils, on the surface of which light scattering material particles have been deposited. The filler comprises cellulose or lignocellulose fibrils having an average thickness less than 5 μm produced from plant fibres by refining and screening. Considerable advantages are achieved with the present invention. With the help of the composite filler, the formation of the fibrous web can be improved significantly without impairing the retention, which makes is possible to achieve an extremely smooth substrate for the coating. The smoothness of the surface can also be improved. Furthermore, the fines-based carrier fraction of the filler compresses the surface of the base paper so that the coating does not penetrate too much into the fibre network. Due to these reasons even a small amount of coating produces good coverage and quality improving cost-efficiency.

1 . A coated fibrous web comprising 
 a filler-containing base web, which has a pigment-containing coating layer at least on one of the surfaces,    characterised in that    the filler of the base web consists at least partially of cellulose or lignocellulose fibrils, on which light scattering material particles have been precipitated.    
     
     
         2 . A fibrous web according to  claim 1 , characterised in that the filler comprises cellulose or lignocellulose fibrils that have an average thickness of less than 5 μm, produced by refining and screening of plant fibres.  
     
     
         3 . A fibrous web according to  claim 2 , characterised in that the light scattering material particles are precipitated on fibrils, which correspond to a fraction passing through a 50-mesh screen and/or having an average thickness of 0.01 to 5 μm and an average length of 10 to 1500 μm.  
     
     
         4 . A fibrous web according to any of  claims 1  to  3 , characterised in that the light scattering material particles are inorganic salts that can be formed from their source materials by precipitating in an aqueous medium.  
     
     
         5 . A fibrous web according to  claim 4 , characterised in that the light scattering material particles are calcium carbonate, calcium oxalate, calcium sulphate, barium sulphate or mixtures thereof.  
     
     
         6 . A fibrous web according to any of  claims 1  to  5 , characterised in that the material particles are precipitated on the fibrils.  
     
     
         7 . A fibrous web according to  claim 6 , characterised in that the amount of the light scattering material particle in proportion to the amount of fibrils is 0.0001 to 95% by weight, preferably about 0.1 to 90% by weight, most suitably about 60 to 80% by weight, based on the amount of filler, and about 0.1 to 60% by weight, preferably 0.5 to 50% by weight of paper.  
     
     
         8 . A fibrous web according to any of the preceding claims, characterised in that it is coated with calcium carbonate, gypsum, aluminium silicate, kaolin, aluminium hydroxide, magnesium silicate, talc, titanium oxide, barium sulphate, zinc oxide, synthetic pigment or mixtures thereof.  
     
     
         9 . A fibrous web according to any of the preceding claims, characterised in that the filler, which comprises cellulose or lignocellulose fibrils, over which the light scattering material particles have been precipitated, forms from 10 to 100% by weight of the filler of the base web.  
     
     
         10 . A fibrous web according to any of the preceding claims, characterised in that the filler, which comprises cellulose or lignocellulose fibrils, on which the light scattering material particles have been precipitated, forms from 10 to 100% by weight of the fibre material of the base web.  
     
     
         11 . A fibrous web according to any of the preceding claims, characterised in that it comprises coated, wood-containing or wood-free paper.  
     
     
         12 . A method of producing a fibrous web, according to which method a pigment-containing coating layer is applied at least on one surface of a base web containing fibre material, characterised by forming the base web from a slush of the fibre material, to which a product comprising cellulose or lignocellulose fibrils, on which light scattering material particles have been deposited, is added as a filler.  
     
     
         13 . A method according to  claim 12 , characterised by using a filler that comprises cellulose or lignocellulose fibrils having an average thickness of less than 5 μm produced by refining and screening plant fibres.  
     
     
         14 . A method according to  claim 12 , characterised by using a filler, the light scattering material particles of which have been deposited on fibrils, which correspond to a fraction, which passes through a 50-mesh screen and/or have an average thickness of 0.1 to 10 μm and an average length of 10 to 1500 μm.  
     
     
         15 . A method according to any of  claims 12  to  14 , characterised by using a filler in which at least 80% of the light scattering pigment particles are attached to the fibrils.  
     
     
         16 . A method according to  claim 12 , characterised by coating the base web in a paper machine with a pigment containing coating mixture.