A method and a system for manufacturing a paperboard

Abstract

The present disclosure relates a cost-effective manufacturing method of barrier-based paperboard and paper webs which are recyclable and repulpable and which embody heat-sealing properties and blocking resistance. To incorporate said properties of the paperboard, the method involves several steps like, paper substrate preparation, pre-treatment of the same followed by coating a base barrier coating, a barrier coating, a heat-sealing coating, and a shield coating, and finally culminating in post-treatment of the paperboard and ending up by winding the board in rolls for marketability.

1 . A method of manufacturing paperboard comprising:
 a coating step; and   a post-treatment step;   wherein,   said coating step includes coating a paper substrate with multiple layers of coating, the multiple layers including:   a base barrier coating (A);   a barrier coating (B);   an optional heat-sealing coating (C); and   a shield coating (D),   wherein,   the coating step includes:   applying a base barrier coating (A) on the paper;   reducing the moisture content of the paper substrate by drying the base barrier coating (A) by means of a drying unit;   compressing and smoothening of the paper substrate;   applying a barrier coating layer (B);   compressing and smoothening of the paper substrate;   optionally applying a heat-sealing coating (C);   applying a shield coating (D);   moisturizing the resulting paper substrate after coating the paper substrate with multiple layers; and   wherein,   the post-treatment step includes   compressing and smoothening the paper substrate being the result of the coating step; and   drying the resulting paper substrate.   
     
     
         2 . The method of  claim 1 , further comprising a web-forming step and a pre-treatment step before the coating step,
 wherein the web forming step includes forming a web-shaped paper substrate of paper fibres; and   wherein the pre-treatment step includes:   drying and reducing the moisture content of paper pulp forming the paper substrate;   cooling the resulting paper substrate;   compressing and smoothening of the paper substrate; and   sealing surface fibres by means of surface sizer.   
     
     
         3 . The method of  claim 2 , wherein the web forming step includes adding an internally sizing agent. 
     
     
         4 . The method of  claim 2 , wherein the surface sizer is any one of film size press, a spray sizer, pond size press and a nip sizer, with one or more curtain applicators and/or one or more foam applicators. 
     
     
         5 . The method of  claim 1 , wherein the weight of the base barrier coating ranges between 1-17 g/m2, more preferably between 3-11 g/m2, and most preferably between 3-8 g/m2. 
     
     
         6 . The method of  claim 1 , wherein the weight of the barrier coating ranges between 1-14 g/m2, more preferably between 2-8 g/m2, and most preferably between 2-4 g/m2. 
     
     
         7 . The method of  claim 1 , wherein the weight of the heat sealing coating, if present, ranges between 1-11 g/m2, more preferably between 2-11 g/m2, yet more preferably between 2-5 g/m2, and most preferably between 2-4 g/m2. 
     
     
         8 . The method of  claim 1 , wherein the weight of the shield coating layer ranges between 1-10 g/m2, more preferably between 2-8 g/m2, yet more preferably between 2-6 g/m2, and most preferably between 2-4 g/m2. 
     
     
         9 . The method of  claim 1 , wherein the method further comprises applying a heat sealing coating (C), wherein preferably a composition of the heat sealing coating (C) is selected from copolymers of ethylene and methacrylic acid or acrylic acid. 
     
     
         10 . The method of  claim 1 , wherein the action of moisturizing the resulting paper substrate after coating the multiple layers in the coating step is performed by means of a spraying unit spraying a moistening agent onto the paper substrate. 
     
     
         11 . The method of  claim 10 , wherein the moistening agent is, mostly, preferably at least 99% by weight, and most preferably only, water. 
     
     
         12 . The method of  claim 10 , wherein the spraying unit sprays the moistening agent from nozzles with a spraying pressure between 1-100 MPa, preferably between 1-17 MPa, more preferably between 1-12 MPa, as measured at the nozzles. 
     
     
         13 . The method of  claim 1 , wherein the web-shaped paper substrate is moved at a web speed below 500 m/min while the action of moisturizing the resulting paper substrate after coating the multiple layers in the coating step is performed. 
     
     
         14 . The method of  claim 1 , wherein the action of drying the resulting paper substrate in the post-treatment step includes drying the paper substrate with a drying unit which is maintained at a temperature range of 95-117° C. 
     
     
         15 . The method of  claim 1 , wherein the barrier coating composition is in the form of aqueous dispersions, preferably aqueous polymer dispersions. 
     
     
         16 . The method of  claim 15 , wherein said polymers of the barrier coating composition are biodegradable/renewable polymers. 
     
     
         17 . The method of  claim 1 , further comprising a finishing step after the post-treatment step,
 wherein the finishing step includes   cooling the paper substrate being the result of the post-treatment step; and   winding the coated paper substrate into rolls.   
     
     
         18 . A system of manufacturing paper board, the system comprising:
 an internal sizer;   a surface sizer;   a spraying unit;   at least one coating unit configured to apply   a base barrier coating;   a barrier coating;   a heat-sealing coating; and   a shield coating;   at least one drying unit;   at least one cooling unit;   at least one calendaring unit; and   a paperboard roll winding unit.