A method, a paperboard product and use of a foam coater and a subsequent high-consistency metering size press

Abstract

According to an example aspect of the present invention, there is provided a method comprising: providing a web comprising fibrous material; applying a first binder composition in the form of a foamed composition onto the web; and subsequently applying a second binder composition onto the web; wherein the second binder composition has a higher solids content than the first binder composition.

1 . A method comprising:
 providing a web comprising fibrous material;   applying a first binder composition in the form of a foamed composition onto the web; and subsequently   applying a second binder composition onto the web;   wherein the second binder composition has a higher solids content than the first binder composition.   
     
     
         2 . The method according to  claim 1 , wherein said providing of a web comprises forming a fibrous slush on a wire to obtain a wet web. 
     
     
         3 . The method according to  claim 1 , wherein:
 between said applying of the first binder and said applying of the second binder, the solids content of the web is increased, by removing water by suction, by pressing, and/or by heating.   
     
     
         4 . The method according to  claim 1 , wherein the first binder composition is applied onto a web having a solids content in the range 4 to 45 wt %, calculated from the total weight of the web. 
     
     
         5 . The method according to  claim 1 , wherein said first binder composition has a solids content of from 0.1 to 20 wt-%. 
     
     
         6 . The method according to  claim 1 , wherein the first binder composition comprises a binder that is at least partly in a particulate form. 
     
     
         7 . The method according to  claim 1 , wherein the first binder composition comprises nanostructured cellulose or microstructured cellulose, having an average fibre diameter smaller than 1 μm. 
     
     
         8 . The method according to  claim 1 , wherein the first binder composition comprises a binder that is at least partly in the form of an aqueous dispersion. 
     
     
         9 . The method according to  claim 2 , wherein at least a part of the first binder composition is retained in a surface part of the wet web. 
     
     
         10 . The method according to  claim 2 , wherein at least a part of the first binder composition penetrates into the wet web, preferably to a depth of at least 10% of the total thickness of the wet web. 
     
     
         11 . The method according to  claim 1 , wherein said first binder composition comprises starch, at least a part of said starch being in a gelatinized form, and optionally comprising a dry strength resin. 
     
     
         12 . The method according to  claim 1 , wherein said first binder composition comprises polyvinylamine and/or starch. 
     
     
         13 . (canceled) 
     
     
         14 . (canceled) 
     
     
         15 . The method according to  claim 1 , wherein said applying of the first binder composition is carried out in a wire section of a paperboard manufacturing process. 
     
     
         16 . The method according to  claim 2 , wherein said applying of the first binder composition comprises applying the first binder composition onto one side of the wet web and providing suction from an opposite side of the wet web to make the first binder composition penetrate into the wet web. 
     
     
         17 . The method according to  claim 1 , wherein after applying a first binder composition on a surface of the web, said web is combined with other webs, one or more of which have been optionally also treated with the first binder composition, to form a multi-ply structure, and subsequently water is removed from the multi-ply structure. 
     
     
         18 . (canceled) 
     
     
         19 . The method according to  claim 1 , wherein:
 the method is for manufacturing of a multi-ply paperboard product, and   said applying of the first binder composition is carried out separately onto one or more wet webs, which are then combined with each other and/or with further wet webs to form a multi-ply board, and   any application of the first hinder composition is carried out before said combining of the webs.   
     
     
         20 . The method according to  claim 1 , wherein:
 said applying of the first binder composition is carried out as a foamed composition by a foam applicator or a foam coater,   said applying of the first binder composition is carried out in a wire section of a paperboard manufacturing process, and   the first binder composition is applied onto a web having a solids content in the range 8 to 15 wt-%.   
     
     
         21 . The method according to  claim 1 , wherein said second binder composition has a different composition from that of the first binder composition by comprising a different binder or binders. 
     
     
         22 . The method according to  claim 1 , wherein said second binder composition is applied in a non-foamed form and has a higher solids content than the first binder composition. 
     
     
         23 . The method according to  claim 1 , wherein said second binder composition has a solids content of at least 5 wt-%. 
     
     
         24 . The method according to  claim 1 , wherein said second binder composition comprises a cationic starch. 
     
     
         25 . (canceled) 
     
     
         26 . The method according to  claim 1 , wherein the method is for manufacturing of a multi-ply paperboard product, and the second binder composition is applied on a surface of a dried multi-ply board which comprises one or more plies treated with the first binder composition. 
     
     
         27 . The method according to  claim 1 , wherein said applying of the second binder composition is carried out by a size press suitable for high-consistency surface sizing. 
     
     
         28 . The method according to  claim 1 , wherein:
 said second binder composition has a solids content of at least 10 wt-%,   said applying of the second binder composition is carried out by a high-consistency metering size press, and   said applying of the second binder composition is carried out on a web having a dryness in the range 85 to 100%.   
     
     
         29 . The method according to  claim 1 , wherein:
 said applying of the first binder composition is carried out as a foamed composition by a foam applicator or a foam coater,   said applying of the first binder composition is carried out in a wire section of a paperboard manufacturing process,   the first binder composition is applied onto a web having a solids content in the range 8 to 15 wt-%,   said second binder composition has a solids content of at least 10 wt-%,   said applying of the second binder composition is carried out by a high-consistency metering size press, and   said applying of the second binder composition is carried out on a web having a dryness in the range 85 to 100%.   
     
     
         30 . The method according to  claim 1 , wherein said method is carried out in the course of a paper or paperboard manufacturing process. 
     
     
         31 . The method according to  claim 30 , wherein said paper or paperboard manufacturing process does not include any step in which starch is sprayed in a non-foamed form on the web. 
     
     
         32 . A paperboard product obtained by the method according to  claim 1 . 
     
     
         33 - 38 . (canceled)