Paper or paperboard product and a process for production of a paper or paperboard product

Abstract

The present invention relates to a paper or paperboard product comprising a furnish wherein said furnish comprises a cationic polymer in an amount of above 1.5% by weight, an anionic polymer and microfibrillated cellulose. The invention further relates to a process for the production of said product.

1 . A paper or paperboard product comprising a furnish which comprises a cationic polymer and an anionic polymer wherein the furnish further comprises microfibrillated cellulose, and that the amount of cationic polymer is above 1.5% by total weight percent of the furnish. 
     
     
         2 . The paper or paperboard product according to  claim 1  wherein the furnish comprises cellulosic fibers. 
     
     
         3 . The paper or paperboard product according to  claim 1  wherein the furnish comprises 1-30% by weight of rnicrofibrillated cellulose. 
     
     
         4 . The paper or paperboard product according to  claim 1  wherein the cationic polymer is cationic starch or amphoteric starch. 
     
     
         5 . The paper or paperboard product according to  claim 1  wherein the anionic polymer is carboxymethyl cellulose (CMC). 
     
     
         6 . The paper or paperboard product according to  claim 1  wherein the product is a multiply product comprising at least two paper or paperboard plies. 
     
     
         7 . The paper or paperboard according to  claim 6  wherein the product comprises at least three plies and that the ply located in the middle of the product comprises furnish comprising cationic polymer, anionic polymer and microfibrillated cellulose. 
     
     
         8 . The paper or paperboard according to  claim 1  wherein the product is a multiply board wherein the furnish comprising cationic polymer, anionic polymer and MFC forms at least one ply of the product, wherein the board has a z-strength of 250-400 kPa and a density of the formed ply of between 300-550 kg/m3. 
     
     
         9 . A process for producing a paper or paperboard product which process comprises the steps of:
 providing a furnish comprising fibers,   adding more than 1.5% by weight of cationic polymer to the furnish,   adding microfibrillated cellulose to the furnish,   adding anionic polymer to the furnish and   conducting the furnish to a wire in order to form a web.   
     
     
         10 . The process according to  claim 9  characterized in that 1-30% by weight of microfibrillated cellulose is added to the furnish. 
     
     
         11 . The process according to  claim 9  wherein cationic polymer, the anionic polymer and MFC are added separately to the furnish. 
     
     
         12 . The process according to  claim 9  wherein cationic polymer first is added to the furnish in a first step, which first step is followed by addition of MFC in a second step, which second step is followed by addition of anionic polymer in a third step. 
     
     
         13 . The process according to  claim 9  wherein the cationic polymer is added in a single addition point. 
     
     
         14 . The process according to  claim 9  wherein cationic polymer and microfibrillated cellulose is mixed and thereafter added to the furnish followed by addition of anionic polymer to the furnish.