Papermaking Method

Abstract

There is provided a method of producing a paper on a paper machine, comprising the steps of: a) providing a pulp, such as a mixture of hardwood pulp and softwood pulp; b) adding cationic glyoxylated polyacrylamide (G-PAM) to the pulp; c) forming a web from the pulp in a forming section comprising a head box; d) pressing the web in a press section; e) drying the web in a drying section; and f) optionally calendering the web in a calender.

1 . A method of producing a paper on a paper machine, comprising the steps of:
 a) providing a pulp, such as a mixture of hardwood pulp and softwood pulp;   b) adding cationic glyoxylated polyacrylamide (G-PAM) to the pulp;   c) forming a web from the pulp in a forming section comprising a head box;   d) pressing the web in a press section;   e) drying the web in a drying section; and   f) optionally calendering the web in a calender.   
     
     
         2 . The method of  claim 1 , wherein the pulp is refined. 
     
     
         3 . The method of  claim 1 , wherein the pH of the pulp is in the range of 4.8-5.5 when the cationic G-PAM is added. 
     
     
         4 . The method of  claim 1 , wherein the consistency of the pulp is in the range of 1.5-3.0% when the cationic G-PAM is added. 
     
     
         5 . The method of  claim 1 , wherein cationic G-PAM is added in a total amount of 1.5-3.0 kg/tonne dry fiber. 
     
     
         6 . The method of  claim 1 , wherein the pulp is not subjected to refining after the cationic G-PAM addition. 
     
     
         7 . The method of  claim 1 , further comprising adding an anionic polymer to the pulp before the cationic G-PAM is added. 
     
     
         8 . The method of  claim 7 , wherein the pH of the pulp is in the range of 6.5-8.0 when the anionic polymer is added. 
     
     
         9 . The method of  claim 1 , further comprising adding at least one hydrophobic size to the pulp. 
     
     
         10 . The method of  claim 9 , wherein the pH of the pulp is in the range of 4.8-5.5 and the consistency of the pulp is in the range of 1.5-3.0% when the at least one hydrophobic size is added. 
     
     
         11 . The method of  claim 1 , further comprising adding clay to the pulp in such an amount that the ash content of the paper is in the range of 2.0-5.5%. 
     
     
         12 . The method of  claim 1 , wherein consistency of the pulp in the head box is 0.20-0.60%. 
     
     
         13 . The method of  claim 1 , wherein the calender is a soft nip calender operated at a line load of 60-170 kN/m, and/or a temperature of 100-200° C. 
     
     
         14 . The method of  claim 1 , wherein the grammage measured according to ISO 536:2019 of the paper is at least 100 g/m 2 and/or the density measured according to ISO 534:2011 of the paper is at least 600 kg/m 3 . 
     
     
         15 . The method of  claim 1 , wherein the specific formation number measured according to SCAN-P 92:09 of the paper is below 1.00 √g/m. 
     
     
         16 . The method of  claim 2 , wherein the pulp is refined such that the Schopper-Riegler number measured according to ISO 5267-1:1999 of the pulp in the head box is 20-30. 
     
     
         17 . The method of  claim 7 , wherein the anionic polymer is polyacrylamide (A-PAM). 
     
     
         18 . The method of  claim 9 , wherein the at least one hydrophobic size is a rosin size and/or AKD.