Method of producing paper and cardboard

Abstract

A method of producing paper or cardboard using a bleached cellulosic pulp, which contains hemicelluloses. According to invention a significant portion, at least 5 wt-%, preferably about 8 to 30 wt-%, of the hemicelluloses are removed from the pulp. The hemicelluloses taken from one bleached pulp can then be transferred to another resulting in two pulps with varying properties, one pulp with properties related to low hemicelluloses content in the fiber wall and the other with properties related to high hemicelluloses content on the fiber surface.

1 - 30 . (canceled) 
     
     
         31 . A method of producing paper or cardboard using a bleached cellulosic pulp, which contains hemicelluloses, comprising:
 a. removing from 5 wt % to 20 wt % of the hemicelluloses from the pulp before using the pulp for making paper or cardboard, and either   b1. contacting the hemicelluloses removed from the pulp with chemical, chemimechanical or mechanical pulps used for production of paper and paper board products under conditions conducive to adsorption of the hemicelluloses onto the cellulosic or lignocellulosic fibers of the chemical, chemimechanical or mechanical pulps, or   b2. using the hemicelluloses removed from the pulp as a raw material for the manufacture of chemicals,   and wherein the total yield of the bleached cellulosic pulp is lowered by about 1 to 8 wt %, by the removal of the hemicelluloses.   
     
     
         32 . (canceled) 
     
     
         33 . The method according to  claim 31 , wherein the bleached cellulosic pulp comprises a pulp prepared by alkaline pulping of a raw material predominantly composed of deciduous tree. 
     
     
         34 . The method according to  claim 31 , wherein the bleached cellulosic pulp comprises a pulp prepared by kraft pulping of wood of the  Betula  species. 
     
     
         35 . The method according to  claim 31 , wherein the hemicelluloses are removed by extraction using an aqueous solution or dispersion of an alkaline substance or an enzyme or a mixture thereof. 
     
     
         36 . The method according to  claim 35 , wherein the extraction is carried out at a consistency of about 0.1 to 25%. 
     
     
         37 . The method according to  claim 35 , comprising using an aqueous solution containing an alkaline substance selected from the group of alkali metal and earth alkaline metal hydroxides and carbonates or mixtures thereof. 
     
     
         38 . The method according to  claim 35 , wherein the aqueous solution of an alkaline substance comprises white liquor or green liquor. 
     
     
         39 . The method according to  claim 35 , wherein the aqueous solution contains 0.01 to 5 M of the alkaline substance. 
     
     
         40 . The method according to  claim 35 , wherein the extraction with an aqueous solution or dispersion of an alkaline substance or a mixture of alkaline substances is carried out at ambient temperature and pressure for 1 min to 24 hours. 
     
     
         41 . The method according to  claim 35 , wherein the extraction with an aqueous solution or dispersion of an alkaline substance or a mixture of alkaline substances is carried out at an elevated temperature of 20-150° C. for 1 min to 24 hours. 
     
     
         42 . The method according to  claim 35 , wherein the aqueous solution contains at least one hydrolytic enzyme selected from the group of hemicellulases and pectinases. 
     
     
         43 . The method according to  claim 42 , wherein the hydrolytic enzyme comprises a xylanase. 
     
     
         44 . The method according to  claim 31 , wherein the hemicelluloses are selectively removed from the pulp essentially without degrading them. 
     
     
         45 . The method according to  claim 31 , wherein the hemicelloses are recovered in the form of an aqueous dispersion or solution. 
     
     
         46 . The method according to  claim 31 , wherein the hemicelluloses are recovered in the form of an aqueous dispersion which is fed to the headbox of a paper or cardboard machine where they are contacted with the fibres in the furnish. 
     
     
         47 . The method according to  claim 31 , wherein the hemicelluloses are adsorbed onto the fibers at a consistency of about 0.05 to 20%. 
     
     
         48 . The method according to  claim 47 , wherein the adsorption of the hemicelluloses onto the fibers is carried out at alkaline conditions. 
     
     
         49 . The method according to  claim 31 , wherein the concentration of hemicelluloses in the aqueous dispersion or solution used for adsorption of hemicelluloses onto the fibers is about 0.1 to 50 g/l. 
     
     
         50 . The method according to  claim 31 , wherein the recovered hemicelluloses comprise mainly xylan. 
     
     
         51 . The method according to  claim 31 , wherein the hemicelluloses are adsorbed onto cellulosic or lignocellulosic fibers used for paper or cardboard in order to improve mechanical strength properties, including tensile strength, bonding and elasticity. 
     
     
         52 . The method according to  claim 51 , wherein the hemicelluloses taken from one bleached pulp are transferred to another similar or identical pulp resulting in two pulps with varying properties, one pulp with properties related to low hemicelluloses content in the fiber wall and the other with properties related to high hemicelluloses content on the fiber surface. 
     
     
         53 . (canceled) 
     
     
         54 . The method according to  claim 31 , further comprising using the bleached pulp, subsequent the hemicellulose removal step, as a raw material for the production of various paper and cardboard products. 
     
     
         55 . The method according to  claim 54 , comprising using the bleached pulp is used for producing a paper or cardboard product exhibiting one or several improved properties from the group of brightness, resistance against yellowing, drainability and water retention. 
     
     
         56 . The method according to  claim 54 , comprising using the bleached pulp for producing fine papers. 
     
     
         57 . The method according to  claim 31 , wherein the bleached cellulosic pulp comprises bleached birch pulp, the hemicelluloses comprise xylan, and step b2 comprises using xylan removed from the bleached birch pulp as a raw material for producing xylitol or furfural.