Production of paper board and cardboard

Abstract

Paper, board and cardboard are produced by draining a paper stock in the presence of at least one cationic polymer on a wire by a process in which a mixture of at least one substantially linear, cationic polyelectrolyte and an optical brightener is added to the paper stock before sheet formation, said mixture containing at least two parts by weight of the polyelectrolyte per part by weight of the optical brightener.

1 . A process for the production of paper and cardboard comprising draining a paper stock in the presence of at least one cationic polymer on a wire, and wherein a mixture comprising at least one substantially linear, cationic polyelectrolyte selected from polymers containing vinylamine units, copolymers of acrylamide and cationic monomers or polymers of diallyldimethylammonium chloride, one or more optical brighteners, one or more solvents, and optionally, a retention and drainage aid, is added to the paper stock before sheet formation, and wherein at least two parts by weight of the polyelectrolyte is used per part by weight of the optical brightener.  
     
     
         2 . The process as claimed in  claim 1 , wherein the at least one cationic polyelectrolyte is a hydrolyzed homopolymer of N-vinylformamide having a degree of hydrolysis from 1 to 99 mol %.  
     
     
         3 . The process as claimed in  claim 1 , wherein the at least one cationic polyelectrolyte is selected from copolymers of acrylamide and cationic monomers, and wherein the cationic monomers are monomers containing an amino group or an ammonium group.  
     
     
         4 . The process as claimed in  claim 1 , wherein at least 5 parts by weight of at least one cationic polymer is used per part by weight of optical brighteners.  
     
     
         5 . The process as claimed in  claim 1 , wherein the mixture comprises: 
 (i) from 0.05 to 5% by weight of the one or more optical brighteners,    (ii) from 1 to 30% by weight of the at least one substantially cationic polymer,    (iii) from 98.95 to 65% by weight of the one or more solvents and optionally the retention and drainage aid.    
     
     
         6 . A process for producing paper, board or cardboard, each having high degree of whiteness, comprising adding to paper stock a mixture comprising: 
 (i) from 0.05 to 5% by weight of at least one optical brightener,    (ii) from 1 to 30% by weight of at least one substantially cationic polymer selected from polymers containing vinylamine units, copolymers of acrylamide and cationic monomers or polymers of diallyldimethylammonium chloride, and    (iii) from 98.95 to 65% by weight of at least one solvent and optionally a retention and drainage aid.    
     
     
         7 . A paper, board or cardboard obtained by a process as claimed in  claim 1 .  
     
     
         8 . The process as claimed in  claim 2 , wherein at least 5 parts by weight of at least one cationic polymer is used per part by weight of optical brighteners.  
     
     
         9 . The process as claimed in  claim 3 , wherein at least 5 parts by weight of at least one cationic polymer is used per part by weight of optical brighteners.  
     
     
         10 . The process as claimed in  claim 2 , wherein the mixture comprises: 
 (i) from 0.05 to 5% by weight of the one or more optical brighteners,    (ii) from 1 to 30% by weight of the at least one substantially cationic polymer,    (iii) from 98.95 to 65% by weight of the one or more solvents and optionally the retention and drainage aid.    
     
     
         11 . The process as claimed in  claim 3 , wherein the mixture comprises: 
 (i) from 0.05 to 5% by weight of the one or more optical brighteners,    (ii) from 1 to 30% by weight of the at least one substantially cationic polymer,    (iii) from 98.95 to 65% by weight of the one or more solvents and optionally the retention and drainage aid.    
     
     
         12 . The process as claimed in  claim 4 , wherein the mixture comprises: 
 (i) from 0.05 to 5% by weight of the one or more optical brighteners,    (ii) from 1 to 30% by weight of the at least one substantially cationic polymer,    (iii) from 98.95 to 65% by weight of the one or more solvents and optionally the retention and drainage aid.    
     
     
         13 . A paper, board or cardboard obtained by a process as claimed in  claim 2 .  
     
     
         14 . A paper, board or cardboard obtained by a process as claimed in  claim 3 .  
     
     
         15 . A paper, board or cardboard obtained by a process as claimed in  claim 4 .  
     
     
         16 . A paper, board or cardboard obtained by a process as claimed in  claim 5 .  
     
     
         17 . A composition comprising: 
 (i) from 0.05 to 5% by weight of at least one optical brightener,    (ii) from 1 to 30% by weight of at least one substantially cationic polymer selected from polymers containing vinylamine units, copolymers of acrylamide and cationic monomers or polymers of diallyldimethylammonium chloride, and    (iii) from 98.95 to 65% by weight of at least one solvent and optionally a retention and drainage aid.