High strength dimensionally stable core

Abstract

A paperboard having improved strength and water resistance comprises a standard paperboard furnish modified by adding 5-60 lbs/ton alum, 3-40 lbs/ton of liquid size, and 16-50 lbs/ton modified cationic starch. A more preferred formulation has a paperboard furnish, 4-40 lbs of alum per ton of furnish, 3-12 lbs of liquid size per ton of furnish, and 30-40 lbs of cationic starch per ton of furnish Other additives such as a dry strength agent and microparticle silica may be added. Paperboard cores spirally wound from the paperboard of the invention exhibit shorter cure time, higher strength, improved dimensional stability, and reduced moisture migration.

1 . Paperboard having improved resistance to moisture migration, comprises a paperboard furnish, 5-60 lbs of alum per ton of furnish, 3-40 lbs of size per ton of furnish, and 16-50 lbs of cationic starch per ton of furnish.  
   
   
       2 . Paperboard as in  claim 1 , wherein said furnish comprises 25-70 percent doubleliner Kraft, 25-70% recycled paperboard containers, and 30-50% core waste.  
   
   
       3 . Paperboard as in  claim 2 , having a freeness of 150-270 csf.  
   
   
       4 . Paperboard as in  claim 1  further comprising 2-8 lbs of dry strength agent per ton of furnish.  
   
   
       5 . Paperboard as in  claim 1 , further comprising 0.2-1. lb of microparticle silica per ton of furnish.  
   
   
       6 . Paperboard having improved strength and resistance to moisture migration, comprises a paperboard furnish, 4-40 lbs of alum per ton of furnish, 3-12 lbs of size per ton of furnish, and 30-40 lbs of cationic starch per ton of furnish.  
   
   
       7 . Paperboard as in  claim 6 , wherein said furnish comprises 25-70 percent doubleliner Kraft, 25-70% recycled paperboard containers, and 30-50% core waste.  
   
   
       8 . Paperboard as in  claim 6 , the paperboard having a water absorption of less than 400 cgs.  
   
   
       9 . Paperboard as in  claim 6  further comprising 2-8 lbs of dry strength agent per ton of furnish.  
   
   
       10 . Paperboard as in  claim 6 , further comprising 0.2-1. lb of microparticle silica per ton of furnish.  
   
   
       11 . Paperboard as in  claim 9 , wherein said alum is about 4-12 lbs per ton of furnish.  
   
   
       12 . A high strength, dimensional stable paperboard core, comprising a plurality of spirally wound paperboard plies, said paperboard comprising a paperboard furnish, 5-60 lbs of alum per ton of furnish, 3-40 lbs of size per ton of furnish, and 16-50 lbs of cationic starch per ton of furnish.  
   
   
       13 . A core as in  claim 12 , wherein said paperboard further comprises 2-8 lbs of dry strength agent per ton of furnish.  
   
   
       14 . A core as in  claim 12  wherein said paperboard further comprises 0.2-1. lb of microparticle silica per ton of furnish.  
   
   
       15 . A high strength, dimensional stable paperboard core, comprising a plurality of spirally wound paperboard plies, said paperboard comprising a paperboard furnish comprised of 25-70 percent doubleliner Kraft, 25-70% recycled paperboard containers and 30-50% core waste; 5-60 lbs of alum per ton of furnish; 3-40 lbs of size per ton of furnish; and 16-50 lbs of cationic starch per ton of furnish; said paperboard having a water absorption of less than 400 cgs.