Method for manufacturing mechanical pulp and use of the mechanical pulp

Abstract

A method for treating mechanical pulp. Resinous mechanical pulp is brought into process in a process water flow. The resinous pulp is ozonated at a temperature between 80 and 87° C. and at pH less than 4. The pH of the pulp is adjusted after the ozonation process to correspond to the pH required in bleaching. The pulp is bleached.

1 . A method for treating mechanical pulp, the method comprising:
 bringing resinous mechanical pulp into a process in a process water flow,   ozonating the resinous pulp at a temperature which is between 80 and 87° C., and at pH which is less than 4,   adjusting the pH of the pulp after the ozonation process to correspond to a pH required in bleaching, and   bleaching the pulp.   
     
     
         2 . The method according to  claim 1 , wherein the resinous pulp is ozonated in more than one step. 
     
     
         3 . The method according to  claim 1 , wherein an amount of ozone is at most 1 g/1 g pitch to be split calculated from a theoretical pitch content. 
     
     
         4 . The method according to  claim 2 , wherein the resinous pulp is ozonated before two successive mass pulp silos. 
     
     
         5 . The method according to  claim 1 , wherein a part of the process water flow is replaced by water which is cleaner than the process water flow after ozonating the pulp but before bleaching the pulp. 
     
     
         6 . The method according to  claim 5 , wherein the part of the process water flow is replaced by circulating water from a paper machine. 
     
     
         7 . The method according to  claim 1 , wherein the pulp is ozonated at a consistency which is between 0.5 and 4%. 
     
     
         8 . The method according to  claim 1 , wherein the pulp is bleached with dithionite or peroxide. 
     
     
         9 . The method according to  claim 1 , further comprising:
 utilizing the pulp in paper manufacture.   
     
     
         10 . The method according to  claim 8 , wherein the pulp is at least partially made of pine. 
     
     
         11 . The method according to  claim 8 , wherein the pulp consists of pine. 
     
     
         12 . The method according to  claim 1 , wherein the resinous pulp is ozonated at a temperature which is between 80 and 85° C. 
     
     
         13 . The method according to  claim 1 , wherein the resinous pulp is ozonated in two steps.