US2006213630A1PendingUtilityA1

Method for making a low density multi-ply paperboard with high internal bond strength

51
Individually held — no corporate assignee on recordPriority: Mar 22, 2005Filed: Mar 17, 2006Published: Sep 28, 2006
Est. expiryMar 22, 2025(expired)· nominal 20-yr term from priority
Inventors:Daniel Bunker
D21H 17/29D21H 17/28D21H 21/18D21H 23/10D21H 27/30
51
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Claims

Abstract

Methods for improving the internal bond strength of paperboard with greater than 25 percent crosslinked fiber in at least one ply are described. In the methods, additives are added to the slurry in various combinations and order while maintaining the ionic demand of the slurry at less than zero. Paperboard with high ZDT, Scott Bond and Taber Stiffness is obtained.

Claims

exact text as granted — not AI-modified
1 . A method for forming a paperboard comprising the steps of: 
 forming a slurry of cellulose fibers comprising crosslinked fibers;    adding a cationic fixative and mixing with said slurry;    adding an anionic starch subsequent to adding said cationic fixative;    adding a cationic starch subsequent to adding said anionic starch;    wherein, after each addition step, the slurry ionic demand is less than zero;    forming a fibrous web layer by withdrawing liquid from said slurry;    drying said web to form a paperboard.    
   
   
       2 . The method of  claim 1  wherein said crosslinked fibers are present at a level from 25 to 80 percent of the total fiber weight in at least one ply of the paperboard.  
   
   
       3 . The method of  claim 2  wherein the crosslinked fibers are present at a level from 40 to 75 percent of the total dry weight of the fiber weight in at least one ply of the paperboard.  
   
   
       4 . The method of  claim 1  wherein the total starch level is 50 to 120 lb/t.  
   
   
       5 . The method of  claim 1  wherein the total starch level is 60 to 100 lb/t.  
   
   
       6 . The method of  claim 1  wherein the total starch level is 80 to 90 lb/t.  
   
   
       7 . The method of  claim 1  wherein the cationic starch is added to the furnish before the anionic starch and the cationic fixative is added after the anionic starch.  
   
   
       8 . A method for forming a paperboard comprising the steps of: 
 forming a slurry of cellulose fibers comprising crosslinked fibers;    adding a cationic fixative and mixing with said slurry;    adding an anionic starch subsequent to adding said cationic fixative;    wherein, after each addition step, the slurry ionic demand is less than zero;    forming a fibrous web layer by withdrawing liquid from said slurry;    drying said web to form a paperboard.    
   
   
       9 . The method of  claim 8  wherein the anionic starch is added to the slurry before the cationic fixative.  
   
   
       10 . The method of  claim 8  wherein said crosslinked fibers are present at a level from 25 to 80 percent of the total fiber weight in at least one ply of the paperboard.  
   
   
       11 . The method of  claim 8  wherein the crosslinked fibers are present at a level from 40 to 60 percent of the total dry weight of the fiber weight in at least one ply of the paperboard.  
   
   
       12 . The method of  claim 8  wherein the total starch level is 50 to 120 lb/t.  
   
   
       13 . The method of  claim 8  wherein the total starch level is 60 to 100 lb/t.  
   
   
       14 . The method of  claim 8  wherein the total starch level is 80 to 90 lb/t.  
   
   
       15 . A method for forming a paperboard comprising the steps of: 
 forming a slurry of cellulose fibers comprising crosslinked fibers;    adding a cationic starch and mixing with said slurry;    adding an anionic starch subsequent to adding said cationic fixative;    wherein, after each addition step the slurry ionic demand is less than zero;    forming a fibrous web layer by withdrawing liquid from said slurry;    drying said web to form a paperboard.    
   
   
       16 . The method of  claim 15  wherein the anionic starch is added to the slurry before the cationic fixative.  
   
   
       17 . The method of  claim 15  wherein said crosslinked fibers are present at a level from 25 to 80 percent of the total fiber weight in at least one ply of the paperboard.  
   
   
       18 . The method of  claim 15  wherein the crosslinked fibers are present at a level from 40 to 60 percent of the total dry weight of the fiber weight in at least one ply of the paperboard.  
   
   
       19 . The method of  claim 15  wherein the total starch level is 50 to 120 lb/t.  
   
   
       20 . The method of  claim 15  wherein the total starch level is 60 to 100 lb/t.  
   
   
       21 . The method of  claim 15  wherein the total starch level is 80 to 90 lb/t.

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