Disintegratable brown sack paper

Abstract

The present invention includes a method of manufacturing a sack paper having a Gurley porosity (ISO 5636-5) of less than 25 s, comprising the steps of: a) mixing an unbleached pulp with a bleached pulp to obtain a pulp mixture in such proportions that the dry weight ratio of unbleached pulp to bleached pulp in the pulp mixture is between 7:1 and 1:1; and b) forming the sack paper from said pulp mixture, wherein starch is added in an amount of 1-7 kg/ton paper.

1 - 15 . (canceled) 
     
     
         16 . A method of manufacturing a sack paper having a Gurley porosity (ISO 5636-5) of less than 25 s, comprising the steps of:
 a) providing a pulp having a Kappa number (SCAN-C 1:00) of 15-40;   b) subjecting the pulp to high consistency (HC) refining and optionally low consistency (LC) refining to obtain refined pulp, wherein the energy supply of the LC refining is less than 120 kWh/ton paper; and   c) forming the sack paper from said pulp mixture,   
       wherein the amount of starch added in the method is 1-7 kg/ton paper and the amount of hydrophobic size added in the method is less than 2 kg/ton. 
     
     
         17 . The method of  claim 16 , wherein the Gurley porosity (ISO 5636-5) of the sack paper is less than 20 s. 
     
     
         18 . The method of  claim 16 , wherein the Kappa number (SCAN-C 1:00) of the pulp provided in step a) is 20-35. 
     
     
         19 . The method of  claim 16 , wherein the geometric tensile energy absorption index (ISO 1924-3) of the sack paper is at least 2 J/g. 
     
     
         20 . The method of  claim 16 , wherein the grammage (ISO 536) of the sack paper is 50-140 g/m 2 , such as 60-120 g/m 2 . 
     
     
         21 . The method of  claim 16 , wherein the pulp provided in step a) is a chemical pulp. 
     
     
         22 . The method of  claim 16 , wherein at least 50% of the dry weight of the pulp provided in step a) is softwood pulp. 
     
     
         23 . The method of  claim 16 , wherein step c) comprises creping. 
     
     
         24 . The method of  claim 16 , wherein the amount of hydrophobic size is less than 1.5 kg/ton paper. 
     
     
         25 . The method of  claim 16 , wherein the amount of starch is 1-5 kg/ton paper. 
     
     
         26 . The method of  claim 16 , wherein step a) comprises conversion of wood into a pulp having a Kappa number (SCAN-C 1:00) of 25-40 using Kraft pulping. 
     
     
         27 . The method of  claim 16 , wherein the energy supply of the LC refining is less than 110 kWh/ton paper. 
     
     
         28 . The method of  claim 17 , wherein the Gurley porosity (ISO 5636-5) of the sack paper is less than 15 s. 
     
     
         29 . The method of  claim 17 , wherein the Gurley porosity (ISO 5636-5) of the sack paper is less than 10 s. 
     
     
         30 . The method of  claim 19 , wherein the geometric tensile energy absorption index (ISO 1924-3) of the sack paper is at least 2.8 J/g. 
     
     
         31 . The method of  claim 20 , wherein the grammage (ISO 536) of the sack paper is 60-120 g/m 2 . 
     
     
         32 . The method of  claim 20 , wherein the grammage (ISO 536) of the sack paper is 70-110 g/m 2 . 
     
     
         33 . The method of  claim 21 , wherein the chemical pulp is Kraft pulp. 
     
     
         34 . The method of  claim 22 , wherein at least 90% of the dry weight of the pulp provided in step a) is softwood pulp. 
     
     
         35 . The method of  claim 24 , wherein the amount of hydrophobic size is less than 1.0 kg/ton paper. 
     
     
         36 . The method of  claim 24 , wherein the amount of hydrophobic size is less than 0.5 kg/ton paper. 
     
     
         37 . The method of  claim 24 , wherein the amount of hydrophobic size is less than 0.3 kg/ton paper. 
     
     
         38 . The method of  claim 24 , wherein the amount of hydrophobic size is 0 kg/ton paper. 
     
     
         39 . The method of  claim 25 , wherein the amount of starch is 1-5 kg/ton paper. 
     
     
         40 . The method of  claim 25 , wherein the amount of starch is 2-5 kg/ton paper. 
     
     
         41 . The method of  claim 27 , wherein the energy supply of the LC refining is less than 100 kWh/ton paper.