Method for treating ligno-cellulosic materials

Abstract

The present invention relates to a method for treating pectin-containing ligno-cellulosic raw materials in a high-yield pulping process utilizing one or more treatment stages at alkaline conditions. The invention provides a method for controlling the alkaline treatment step, wherein the alkali is applied at a low temperature treatment stage before one or more consecutive treatment stages at the same or higher temperature. The present invention also provides pulp, paper, board or tissue obtained with said method.

1 . A method for treating pectin-containing ligno-cellulosic raw materials in a high-yield pulping process utilizing one or more treatment stages at alkaline conditions, wherein the alkaline chemicals are applied at a low temperature treatment stage (T 1 ), meaning the point when alkali for the first time is in contact with the pectin-containing material, before one or more consecutive treatment stages at the same or higher temperature (T 2 ). 
     
     
         2 . The method of  claim 1 , wherein the reaction temperature in T 1  is 70° C. or below. 
     
     
         3 . The method of  claim 1 , wherein the alkaline treatment stage is performed before mechanical defibration or consecutive alkaline bleaching stage(s). 
     
     
         4 . The method of  claim 1 , wherein the pectins in the treated material are methyl-esterified. 
     
     
         5 . The method of  claim 4 , wherein the methyl-esterification degree is 20-100%, determined as the percentage of galacturonic units containing one methyl-ester group. 
     
     
         6 . The method of  claim 1 , wherein pectin-containing raw material is wood, chopped raw ligno-cellulosic material, or high-yield pulp. 
     
     
         7 . The method of  claim 1 , wherein the alkali source originates from hydroxides, carbonates, or sulfites. 
     
     
         8 . The method of  claim 1 , wherein stage T 1  comprises the application of other chemicals selected from the group consisting of chelating agents, stabilizing agents, bleaching agents, and combinations thereof. 
     
     
         9 . The method of  claim 1 , wherein the dosage of alkali is in the range of 0.1% to 10% (w/w) of the dry-based pectin-containing material. 
     
     
         10 . The method of  claim 1 , wherein the treatment time of T 1  is in the range of 1 second to 24 hours. 
     
     
         11 . The method of  claim 1 , wherein stage T 2  comprises the application of chemicals are selected from the group consisting of alkali, chelating agents, stabilizing agents, bleaching agents, and combinations thereof. 
     
     
         12 . The method of  claim 1 , wherein the temperature in the T 2  stage is in the range of 70-210° C. 
     
     
         13 . Pulp obtained by the method of  claim 1 . 
     
     
         14 . Paper, board or tissue obtained from the pulp of  claim 13 .