Multilayered fibrous product and process for the production thereof

Abstract

The multi-layer fibrous product and a process for producing it. According to the present invention the fibre product comprises at least two overlapping fibre layers, whereby the one that forms the top layer of the product contains filler and is lighter than the layer under it and is at least essentially opaque. According to the present invention the filler of the top layer consists at least partially of cellulose or lignocellulose fibrils, on which light scattering material particles have been precipitated. The present invention can be used, for example, to produce white surface liner with a lighter top layer without impairment of the strength of the surface. Thus, the grammage of the layer can be at least about 5% by weight less than a top layer, which has the corresponding opacity and formation, and which has been produced from the same fibre material and mineral pigments.

1 . A multi-layer fibrous product comprising of at least two overlapping fibre layers ( 1 ,  2 ;  3 - 6 ), of which the one ( 1 ;  3 ), which forms the top layer, contains filler and is lighter than the layer under it ( 2 ;  4 - 6 ) and it is at least essentially opaque, charactericed in that 
 the filler of the top layer ( 1 ;  3 ) consists at least partially of cellulose or lignocellulose fibrils, on which light scattering material particles have been precipitated.    
     
     
         2 . A fibrous product according to  claim 1 , charactericed in that the filler comprises cellulose or lignocellulose fibrils produced by refining and screening from plant fibres, the average thickness of which is less than 5 μm.  
     
     
         3 . A fibrous product according to  claim 2 , charactericed in that the light scattering material particles has been precipitated over fibrils corresponding to a fraction that passes 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 product according to any of  claims 1  to  3 , charactericed 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 product according to  claim 4 , charactericed in that the light scattering material particles are calcium carbonate, calcium oxalate, calcium sulphate, barium sulphate or mixtures thereof.  
     
     
         6 . A fibrous product according to any of the preceding claims, characterised in that it comprises white lined top liner or coated white lined liner.  
     
     
         7 . A fibrous product according to any of the preceding claims, characterised in that its grammage is preferably about 50 to 500 g/m 2 , typically about 80 to 350 g/m 2 , in which case the grammage of the top layer is about 20 to 125 g/m 2 , preferably about 50 to 70 g/m 2 .  
     
     
         8 . A fibrous product according to any of the preceding claims, characterised in that the distribution of the grammage between the top and back layers are between about 20/80 . . . 40/60.  
     
     
         9 . A fibrous product according to any of the preceding claims, characterised in that the top layer ( 1 ;  3 ) is produced from chemical cellulose pulp comprising hardwood pulp, softwood pulp or a mixture thereof.  
     
     
         10 . A fibrous product according to any of the preceding claims, characterised in that the back layer comprises 1 to 5 layers ( 2 ;  4 - 6 ) that have been produced from virgin fibre or recycled fibre.  
     
     
         11 . A fibrous product according to any of the preceding claims, characterised in that the grammage of the top layer is at least about 5% by weight, preferably at least 10% by weight, less than the top layer that has been produced from the same fibre material and mineral pigments and that has corresponding opacity and formation.  
     
     
         12 . A process for producing a multi-layer product, according to which process a filler-containing fibre layer, which forms the surface ( 1 ;  3 ) of the fibre product and covers the back layer, is fitted on top of a backing layer ( 2 ;  4 - 6 ) that consists of at least of one fibrous layer, characterised in that the top layer ( 1 ;  3 ) is formed from slush of fibre material, to which a product comprising cellulose or lignocellulose fibrils, on which light scattering material particles have been precipitated, is added as a filler.  
     
     
         13 . A process according to  claim 12 , characterised by using a filler that comprises cellulose or lignocellulose fibrils produced from plant fibres by refining and screening, having an average thickness of less than 5 μm.  
     
     
         14 . A process according to  claim 13 , characterised by using a filler, in which the light scattering material particles have been precipitated on fibrils corresponding to a fraction that passes through a 50 mesh screen and/or having an average thickness of 0.1 to 10 μm and an average length of 10 to 1500 μm.  
     
     
         15 . A process according to any of  claims 12  to  14 , characterised by using a filler in which at least 80% of the precipitated light scattering pigment particles are attached to the fibrils.  
     
     
         16 . A process according to any of the  claims 12  to  15 , characterised in that the top layer is coated in a paper machine with a pigment-containing coating mixture.  
     
     
         17 . A method according to any of  claims 12  to  16 , characterised in that the top layer ( 1 ;  3 ) and the back layer(s) ( 2 ;  4 - 6 ) are formed separately on the Fourdriner wire and couched when still wet.