Method for production of paper

Abstract

The present invention relates to a method for the production of paper from a suspension containing cellulosic fibers comprising adding to the suspension and/or to a formed paper prepared from the cellulosic suspension i) a nitrogen-containing organic compound separately and/or in conjunction with, ii) an aqueous dispersion of an acid anhydride and iii) at least one shading dye, draining the suspension on a wire to form a paper.

1 . A method for production of paper from an aqueous suspension containing cellulosic fibers comprising adding to the suspension and/or to a paper web prepared from the suspension i) a nitrogen-containing organic compound, ii) an aqueous dispersion of an acid anhydride; and iii) at least one shading dye, draining the suspension on a wire to form a paper. 
     
     
         2 . The method according to  claim 1 , wherein the shading dye absorbs electromagnetic radiation in the visible spectrum without significantly emitting electromagnetic radiation or without emitting electromagnetic radiation. 
     
     
         3 . The method according to  claim 2 , wherein electromagnetic radiation is absorbed in the spectrum from about 380 nm up to about 750 nm. 
     
     
         4 . The method according to  claim 2  or  3 , wherein electromagnetic radiation is absorbed in the spectrum from about 380 nm up to about 495 nm and/or from about 590 nm up to about 750 nm. 
     
     
         5 . The method according to any of the preceding claims, wherein the dye is selected from the group consisting of dioxazines and organic compounds comprising at least a phthalocyanine moiety. 
     
     
         6 . The method according to any of the preceding claims, wherein the nitrogen-containing organic compound has a molar mass of up to about 500 g/mol. 
     
     
         7 . The method according to any of the preceding claims, wherein the nitrogen-containing organic compound is an amine or a quaternary ammonium compound thereof. 
     
     
         8 . The method according to any of the preceding claims, wherein the nitrogen-containing organic compound is an amine or quaternary ammonium compound thereof having a molar mass up to about 180 g/mol. 
     
     
         9 . The method according to any of the preceding claims, wherein the nitrogen-containing organic compound is comprised in the aqueous dispersion comprising an acid anhydride. 
     
     
         10 . The method according to  claim 9 , wherein the aqueous dispersion comprising an acid anhydride further comprises an anionic polyelectrolyte. 
     
     
         11 . The method according to  claim 10 , wherein the anionic polyelectrolyte comprises colloidal silica-based particles. 
     
     
         12 . The method according to  claim 11 , wherein the colloidal particles have a particle size from about 1 to about 100 nm. 
     
     
         13 . The method according to any of the preceding claims, wherein the cellulosic fibers have a kappa number of less than about 8. 
     
     
         14 . The method according to any of the preceding claims, wherein the cellulosic fibers have a brightness of more than about 83. 
     
     
         15 . The method according to any of the preceding claims, wherein the conductivity of the cellulosic suspension is at least about 2.0 mS/cm. 
     
     
         16 . The method according to any of the preceding claims, wherein the suspension further comprises at least one optical brightening agent. 
     
     
         17 . Paper obtainable according to the method as defined by any of the preceding claims. 
     
     
         18 . Paper comprising acid anhydride and/or derivatives thereof, a nitrogen-containing organic compound and at least one shading dye, wherein the paper has no visual agglomerations of pigments. 
     
     
         19 . The paper according to  claim 18 , wherein the pigments are bluish. 
     
     
         20 . Use of a nitrogen-containing organic compound being an amine or quaternary ammonium compound thereof having a molar mass less than about 180 g/mol in a method for producing paper from a suspension as an additive for improving the distribution of dyes in the paper, wherein the suspension comprises at least one shading dye. 
     
     
         21 . The use according to  claim 20 , wherein the nitrogen-containing organic compound is comprised in an aqueous dispersion comprising an acid anhydride.