Fixation of optical brightening agents onto papermaking fiber

Abstract

The present invention relates to a method of increasing the brightness of pulp, pulp made from such methods and methods of using such pulp.

1 . A method of making pulp and/or a paper substrate, comprising contacting a plurality of fibers in solution with at least one optical brightener after the last bleaching/extraction stage  
   
   
       2 . The method according to  claim 1 , wherein the contacting is performed at a point in the pulp making or papermaking process prior to a Blend Chest/Machine Chest Stages.  
   
   
       3 . The method according to  claim 1 , wherein the fibers in solution are at a consistency of greater than about 4%.  
   
   
       4 . The method according to  claim 1 , wherein the fibers in solution are a consistency of from 7 to 15%.  
   
   
       5 . The method according to  claim 1 , wherein from 1 to 15 lbs/ton of OBA is contacted with the fibers.  
   
   
       6 . The method according to  claim 1 , wherein the pH of the solution during the contacting of the OBA with fibers is from 3.5 to 5.5.  
   
   
       7 . The method according to  claim 1 , wherein the temperature when the OBA is contacted with the fibers is from 60 to 80° C.  
   
   
       8 . The method according to  claim 1 , wherein the OBA is contacted with the fibers for a duration of time of from 0.5 to 6 hours.  
   
   
       9 . The method according to  claim 1 , wherein the contacting is performed at a point in the pulp making or papermaking process prior to a refining stage.  
   
   
       10 . The method according to  claim 1 , comprising contacting a plurality of fibers in solution with at least one optical brightener after the last bleaching/extraction stage in the absence of a retention aid.  
   
   
       11 . The method according to  claim 1 , further comprising refining the fibers and OBA wherein the refining is selected from at least one member selected from the group consisting of chemical refining, mechanical refining, thermochemical refining, thermomechanical refining, and chemithermomechanical refining.  
   
   
       12 . The pulp made by the method according to  claim 1 .  
   
   
       13 . The pulp made by the method according to  claim 1 , wherein the pulp is bleached chemithermomechanical pulp.  
   
   
       14 . The pulp made by the method according to  claim 1 , wherein the pulp is fluff pulp.  
   
   
       15 . The pulp made by the method according to  claim 1 , wherein the pulp is papermaking pulp.  
   
   
       16 . The pulp or paper substrate made by the method according to  claim 1 , wherein the pulp or paper substrate has an ISO brightness that is not less than 90.  
   
   
       17 . The pulp or paper substrate made by the method according to  claim 1 , wherein the pulp or paper substrate has a CIE whiteness that is not less than 130.  
   
   
       18 . The pulp or paper substrate made by the method according to  claim 1 , wherein the pulp or paper substrate has a CIE whiteness that is not less than 130 and an ISO brightness that is not less than 90.  
   
   
       19 . The method according to  claim 1 , further comprising contacting additional OBA with the fibers at a coater.  
   
   
       20 . The method according to  claim 1 , further comprising contacting additional OBA with the fibers at a size press.