Method of Producing a Fibrous Web

Abstract

A method of manufacturing a fibrous web comprising a filler. According to the method, the filler is fed into the fibre slush and a fibrous web is formed of the filler-bearing fibre slush, and this web is dried at the paper or cardboard machine. The filler used is a composite material which comprises cellulose or lignocellulose fibrils, onto which light-scattering material particles have been precipitated. According to the present invention, the filler is brought into contact with the dispersant before it is mixed into the fibre slush. With this solution it is possible to significantly improve the light-scattering properties of papers and cardboards, without decreasing the retention of the filler.

1 . A method of manufacturing a fibrous web comprising a filler, according to which method
 a filler is mixed into the fibre slush, and   a fibrous web is formed of the filler-bearing fibrous slush, and this web is dried at the paper or cardboard machine, whereby   a composite material, comprising cellulose or lignocellulose fibrils, onto which light-scattering material particles have been precipitated, is used as the filler,   characterized in that   to improve the light-scattering properties of the fibrous web, the filler is brought into contact with the dispersant before it is mixed into the fibre slush.   
   
   
       2 . The method according to  claim 1 , characterized in that the upper limit of the addition of the dispersant is that percentage of the dispersant which corresponds to the minimum viscosity of the water suspension formed of the dispersant and the mineral particles in the filler. 
   
   
       3 . The method according to  claim 1 , characterized in that the dispersant used is anionic polyacrylate or polyphosphate. 
   
   
       4 . The method according to  claim 3 , characterized in that the dispersant used is anionic polyacrylate which has a percentage of the dry matter of the fibrous web of approximately 0.05-0.3 weight %. 
   
   
       5 . A method according to  claim 1 , characterized in that a fibrous web is prepared, the filler percentage of which is at maximum approximately 15 weight % of the dry weight of the web. 
   
   
       6 . A method according to  claim 1 , characterized in that the filler comprises cellulose or lignocellulose fibrils, which are prepared from vegetable fibres by refining and screening, and the thickness of which is less than 5 μm. 
   
   
       7 . The method according to  claim 6 , characterized in that the light-scattering material particles have been precipitated onto such fibrils, the size of which corresponds to a fraction which penetrates a 50 mesh screen, and/or the average thickness of which is 0.1-10 μm and the average length 10-1500 μm. 
   
   
       8 . The method according to  claim 6 , characterized in that the light-scattering material particles are inorganic salts which can be generated from their initial materials by precipitation in an aqueous intermediate agent. 
   
   
       9 . The method according to  claim 8 , characterized in that the light-scattering material particles are calcium carbonate, calcium oxalate, calcium sulphate, barium sulphate or mixtures of them. 
   
   
       10 . A method according to  claim 8 , characterized in that the percentage of the inorganic salts of the filler weight is 75-85 weight %. 
   
   
       11 . A method according to  claim 1 , characterized in that a fibrous web is prepared, in which at least most of the dispersant is attached to the material particles of the filler. 
   
   
       12 . A method according to  claim 1 , characterized in that the filler, which is fed as a fresh feed into the slush, comprises essentially only fibril-based composite material. 
   
   
       13 . A method according to  claim 1 , characterized in that a fibrous web is prepared, which comprises not only composite material but a particle-like filler, too, which is brought by the circulating water. 
   
   
       14 . A method of improving the light-scattering property of a fibrous web, which comprises a filler, which in turn comprises cellulose or lignocellulose fibrils and light-scattering mineral particles which have been precipitated onto the fibrils, said method comprising attaching a dispersant to at least most of the mineral particles of the filler. 
   
   
       15 . The method according to  claim 14 , characterized in that the upper limit of the addition of the dispersant is the same as that percentage of dispersant that corresponds to the minimum viscosity of the water suspension formed by the dispersant and the mineral particles in the filler. 
   
   
       16 . The method according to  claim 14 , characterized in that anionic polyacrylate or polyphosphate is used as the dispersant. 
   
   
       17 . The method according to  claim 16 , characterized in that anionic polyacrylate, one which has a percentage of approximately 0.05-0.3 weight % of the dry matter of the fibrous web, is used as the dispersant. 
   
   
       18 . The method according to  claim 14 , characterized in that a fibrous web is prepared, the filler percentage of which is at maximum approximately 15 weight % of the dry weight of the web.