Fibrous web and process for the preparation thereof

Abstract

The invention relates to a fiber web and a method for preparing it. The fiber web comprises a filler-containing base web, which is possibly coated with a pigment-containing coating layer. According to the invention, 5-100% of the filler in the base web is made up of cellulose fibrils or lignocellulose fibrils with light-scattering material particles deposited thereon. These coated cellulose fibrils or lignocellulose fibrils constitute at maximum approx. 70% of the weight of the base web. The base web according to the invention contains more than 20% less retention agents than does a web which has the same formation but in which more than 95% of the filler is made up of filler particles known per se.

1 . A fiber web comprising
 a filler-containing base web optionally coated with a pigment-containing coating layer,   
     characterized in that
 5-100% of the filler in the base web is made up of cellulose fibrils or lignocellulose fibrils with light-scattering material particles deposited thereon, and 
 the coated cellulose fibrils or lignocellulose fibrils constitute at maximum approx. 70% of the weight of the base web, 
 
     wherein the base web contains 0 to 0.40% by weight of the mass of the fiber of a conventional retention agent selected from cationic starch and silica at a beta-formation of 10. 
   
   
       2 . The fiber web according to  claim 1 , characterized in that the filler comprises cellulose fibrils or lignocellulose fibrils prepared from vegetable fibers by beating and screening and having an average thickness smaller than 10 μm. 
   
   
       3 . The fiber web according to  claim 2 , characterized in that the light-scattering material particles are deposited on fibrils which correspond to a fraction passing a 50 mesh screen and/or the average thickness of which is 0.01-5 μm and average length 10-1500 μm. 
   
   
       4 . The fiber web according to  claim 1 , characterized in that the light-scattering material particles are inorganic or organic salts which can be formed from their source materials by precipitation in an aqueous medium. 
   
   
       5 . The fiber web according to  claim 4 , characterized in that the light-scattering material particles are calcium carbonate, calcium oxalate, calcium sulfate, barium sulfate or a mixture thereof. 
   
   
       6 . The fiber web according to  claim 1 , characterized in that the material particles are deposited on fibrils in order to produce a string-of-pearls-like filler. 
   
   
       7 . The fiber web according to  claim 6 , characterized in that the material particles are a calcium compound selected from the group consisting of calcium carbonate, calcium oxalate, and calcium sulfate and the amount of the calcium compound in proportion to the fiber amount is 0.0001-90% by weight. 
   
   
       8 . The fiber web according to  claim 1 , characterized in that it is coated with calcium carbonate, gypsum, aluminum silicate, kaolin, aluminum hydroxide, magnesium silicate, talc, titanium dioxide, barium sulfate, zinc oxide, synthetic pigment, or a mixture thereof. 
   
   
       9 . The fiber web according to  claim 1 , characterized in that the filler comprising cellulose fibrils or lignocellulose fibrils with light-scattering material particles deposited thereon constitutes 10-100% by weight of the filler in the base web. 
   
   
       10 . The fiber web according to  claim 1 , characterized in that the filler comprising cellulose fibrils or lignocellulose fibrils with light-scattering material particles deposited thereon constitutes 10-50% by weight of the fiber material in the base web. 
   
   
       11 . The fiber web according to  claim 1 , characterized in that the light-scattering material particles in the filler of the web are present in a substantially unflocculated form in the fiber web. 
   
   
       12 . The fiber web according to  claim 1 , characterized in that it is substantially free of ionic retention agents. 
   
   
       13 . The fiber web according to  claim 1 , characterized in that it comprises coated fine paper or printing or writing paper. 
   
   
       14 . The fiber web according to  claim 1 , characterized in that 5-90% of the filler in the base web is made up of cellulose fibrils or lignocellulose fibrils with light-scattering material particles deposited thereon. 
   
   
       15 . The fiber web according to  claim 14 , characterized in that the balance of the filler is made up of conventional pulverous fillers. 
   
   
       16 . A method for preparing a fiber web, according to which method there is prepared from a fiber material a slush from which a fiber web is formed in a paper or board machine, characterized in that
 to the slush of fiber material there is added as a filler a product comprising cellulose fibrils or lignocellulose fibrils with light-scattering material particles deposited thereon, this product constituting 5-100% of the filler and its amount being at maximum 70% of the mass of the fiber material, and   retention agents selected from cationic starch and silica are dosed into the slush in an amount of 0-0.40% by weight of the mass of the fiber material.   
   
   
       17 . The method according to  claim 16 , characterized in that a filler is used which comprises cellulose fibrils or lignocellulose fibrils prepared from vegetable fibers by beating and screening and having an average thickness smaller than 10 μm. 
   
   
       18 . The method according to  claim 17 , characterized in that a filler is used wherein the light-scattering material particles are deposited on fibrils which correspond to a fraction passing a 50 mesh screen and/or the average thickness of which is 0.1-5 μm and average length 10-1500 μm. 
   
   
       19 . The method according to  claim 16 , characterized in that a filler is used wherein at minimum 90% of the precipitated light-scattering pigment particles are attached to fibrils. 
   
   
       20 . The method according to  claim 16 , characterized in that the base web is coated in the paper machine with a pigment-containing coating mix. 
   
   
       21 . The fiber web according to  claim 2 , characterized in that the filler comprises cellulose fibrils or lignocellulose fibrils prepared from vegetable fibers by beating and screening and having a maximum average thickness of 5 μm. 
   
   
       22 . The method according to  claim 16 , characterized in that a filler is used which comprises cellulose fibrils or lignocellulose fibrils prepared from vegetable fibers by beating and screening and having a maximum average thickness of 5 μm. 
   
   
       23 . The method according to  claim 16 , characterized in that no ionic retention agents are dosed into the slush. 
   
   
       24 . The fiber web according to  claim 16 , characterized in that the conventional pulverous fillers are selected from natural or precipitated calcium carbonate, kaolin, talc, hydrogenated aluminum oxides, calcium sulfate, barium sulfate, calcium oxalate or titanium dioxide