Process for Producing a Paper or Board and a Paper or Board Produced According to the Process

Abstract

The present invention concerns a process for producing a paper or board product, which process comprises providing a furnish comprising fibers; subjecting a first portion ( 1 ) of the furnish to polymer treatment, in which polymers are added to the furnish in at least two steps; blending said polymer treated first portion with an untreated second portion ( 2 ) of the furnish; and dewatering the furnish on a wire to form a fiber web. By treating only a portion of the furnish, the strength of the resulting paper or board product is significantly improved whereas the bulk remains substantially unaffected. The invention also concerns a paper or board product produced according to the process.

1 . A process for producing a paper or board product, which process comprises: 
 providing a furnish comprising fibers;    subjecting a first portion ( 1 ) of the furnish to polymer treatment, in which polymers are added to the furnish in at least two steps blending said polymer treated first portion with an untreated second portion ( 2 ) of the furnish;    dewatering the furnish on a wire to form a fiber web.    
   
   
       2 . The process as claimed in  claim 1 , wherein said first furnish portion comprises 20-80% by weight of the total furnish weight.  
   
   
       3 . The process as claimed in claims  1  or  2 , wherein said first furnish portion comprises the longest fibers present in the furnish.  
   
   
       4 . The process as claimed in any of the preceding claims, wherein said first furnish portion comprises sulphate or sulfite pulp of soft wood fibers.  
   
   
       5 . The process as claimed in any of the preceding claims, wherein the furnish comprises fillers and optionally other paper making additives, which fillers and additives are added subsequent to the polymer treatment of said first furnish portion.  
   
   
       6 . The process as claimed in any of claims  1 - 4 , wherein the furnish comprises fillers and optionally other paper making additives, which fillers and additives are added prior to the polymer treatment of said first furnish portion.  
   
   
       7 . The process as claimed in any of the preceding claims, wherein the polymer used in each of the consecutive polymer treatment steps is interacting with the polymer used in the subsequent step.  
   
   
       8 . The process as claimed in any of the preceding claims, wherein at least one of the polymer treatment steps includes the addition of an anionic polymer, and at least one of the polymer treatment steps includes the addition of a cationic polymer.  
   
   
       9 . The process as claimed in  claim 8 , wherein the anionic polymer is CMC.  
   
   
       10 . The process as claimed in  claim 8 , wherein the cationic polymer is cationic starch.  
   
   
       11 . The process as claimed in any of the preceding claims, wherein the polymer treatment comprises two to seven steps.  
   
   
       12 . The process as claimed in  claim 10 , wherein the polymer treatment comprises three to seven steps.  
   
   
       13 . A board product produced according to the process of  claim 1 .  
   
   
       14 . A paper produced according to the process of  claim 1.