Barrier layers comprising nanocellulose onto the surface of paper or paperboard substrates at the wet end of a papermaking process

Abstract

Methods of sequentially applying nanocellulose(s) onto the surface of paper and paperboard substrates, paper or paperboard prepared using said methods, and systems for producing paper or paperboard having sequentially applied nanocellulose(s).

1 . A method of applying a nanocellulose-containing composition onto a surface of a paper or paperboard substrate, the method comprising:
 applying a first layer of a first nanocellulose-containing composition to a first surface of a consolidating base sheet of paper or paperboard comprising cellulose fibres after the consolidating base sheet leaves a headbox of a paper machine, thereby forming a consolidating substrate comprising a first layer of nanocellulose on the first surface of the paper or paperboard; wherein the first nanocellulose-containing composition comprises nanocellulose in a range of about 0.2 wt % to about 6 wt %, preferably about 0.5 to about 3 wt. %, based on the total weight of the first nanocellulose-containing composition; wherein the nanocellulose has a d 50  (by Malvern) of about 50 to about 400 μm, a Lc(l) of about 0.1-1 mm, a Lc(w) of about 0.1 to about 1.5 mm by fibre analyzer, a fibre steepness of about 20 to about 50, an FLT between 4 and 17 N m g −1 ; and a Fines B content by fibre analyzer between about 1% and about 80% as a percentage of total measured particle length by fibre analyzer.   
     
     
         2 . The method according to  claim 1 , further comprising applying a second layer of a second nanocellulose-containing composition to the first layer of nanocellulose of the consolidating substrate thereby forming a three layer paper or paperboard; wherein the first nanocellulose-containing composition comprises nanocellulose in a range of about 0.2 wt % to about 6 wt %, preferably about 0.5 to about 3 wt. %, based on the total weight of the first nanocellulose-containing composition; wherein the nanocellulose of the second nanocellulose-containing has a d 50  (by Malvern) of about 50 to about 400 μm, a Lc(l) of about 0.1-1 mm, a Lc(w) of about 0.1 to about 1.5 mm by fibre analyzer, a fibre steepness of about 20 to about 50, an FLT between 4 and 17 N m g −1 ; and a Fines B content by fibre analyzer between about 1% and about 80% as a percentage of total measured particle length by fibre analyzer; and wherein the first nanocellulose-containing composition has a first particle size distribution, and the second nanocellulose-containing composition has a second particle size distribution, and the mean size, of the first particle size distribution, is greater than the mean size of the second particle size distribution. 
     
     
         3 - 7 . (canceled) 
     
     
         8 . The method according to any one of  claim 1 , wherein the first nanocellulose-containing composition comprises one or more of:
 one or more inorganic particulate material;   one or more starches;   one or more sizing agents;   one or more polyacrylamides; and   one or more copolymers.   
     
     
         9 - 20 . (canceled) 
     
     
         21 . The method according to  claim 1 , wherein the layer of the first nanocellulose-containing composition is applied using a slotted applicator or by spraying. 
     
     
         22 - 24 . (canceled) 
     
     
         25 . The method according to  claim 1 , wherein applying the layer of the first nanocellulose-containing composition causes the consolidating substrate to have a heptane vapor transmission rate of about 0 g m −2  day −1  to about 2,500 g m −2  day −1 . 
     
     
         26 - 27 . (canceled) 
     
     
         28 . The method according to  claim 1 , wherein the first nanocellulose-containing composition comprises at least about 0.2 wt % nanocellulose based on the total weight of the first nanocellulose-containing composition. 
     
     
         29 . The method according to  claim 1 , wherein the first nanocellulose-containing composition comprises at most about 6 wt %, at most about 5.5 wt. %, at most about 5 wt. %, at most about 4.5 wt %, at most about 4 wt. %, at most about 3.5 wt. %, or at most about 3 wt. % nanocellulose based on the total weight of the first nanocellulose-containing composition. 
     
     
         30 - 32 . (canceled) 
     
     
         33 . The method according to  claim 2 , wherein the mean size, of the first particle size distribution of the first nanocellulose-containing composition, is from about 50 μm to about 400 μm as measured by Malvern. 
     
     
         34 - 36 . (canceled) 
     
     
         37 . The method according to  claim 2 , wherein the second nanocellulose-containing composition comprises one or more of:
 one or more inorganic particulate material;   one or more starches;   one or more sizing agents;   one or more polyacrylamides; and   one or more copolymers.   
     
     
         38 - 49 . (canceled) 
     
     
         50 . The method according to  claim 2 , wherein the layer of the second nanocellulose-containing composition is applied using a slotted applicator. 
     
     
         51 - 52 . (canceled) 
     
     
         53 . The method according to  claim 2 , wherein the second nanocellulose-containing composition is applied by spraying. 
     
     
         54 . The method according to  claim 2 , wherein applying the second layer of the second nanocellulose-containing composition causes the consolidating substrate to have a heptane vapor transmission rate of about 0 g m −2  day −1  to about 2,500 g m −2  day −1 . 
     
     
         55 - 56 . (canceled) 
     
     
         57 . The method according to  claim 2 , wherein the second nanocellulose-containing composition comprises at least about 0.2 wt % nanocellulose based on the total weight of the second nanocellulose-containing composition. 
     
     
         58 . The method according to  claim 2 , wherein the first nanocellulose-containing composition comprises at most about 6 wt %, at most about 5.5 wt. %, at most about 5 wt. %, at most about 4.5 wt %, at most about 4 wt. %, at most about 3.5 wt. %, or at most about 3 wt. % nanocellulose based on the total weight of the second nanocellulose-containing composition. 
     
     
         59 . (canceled) 
     
     
         60 . The method according to  claim 2 , wherein:
 the layer of the first nanocellulose-containing composition is applied using a first slotted applicator; and   the layer of the second nanocellulose-containing composition is applied using a second slotted applicator.   
     
     
         61 - 64 . (canceled) 
     
     
         65 . The method according to  claim 2 , wherein the first layer of the first nanocellulose-containing composition, and the second layer of the second nanocellulose containing composition, are both applied via spraying. 
     
     
         66 . The method according to  claim 2 , wherein:
 the first layer of the first nanocellulose-containing composition is applied using a slotted applicator; and   the second layer of the second nanocellulose-containing composition is applied via spraying.   
     
     
         67 - 86 . (canceled) 
     
     
         87 . The method according to  claim 2 , wherein the mean size, of the first particle size distribution of the first nanocellulose-containing composition and/or the second particle size distribution of the second nanocellulose-containing composition is from about 50 μm to about 400 μm. 
     
     
         88 - 89 . (canceled) 
     
     
         90 . The method according to  claim 1 , wherein the dry solids of the first nanocellulose-containing composition are about 5% to about 100% nanocellulose. 
     
     
         91 - 93 . (canceled) 
     
     
         94 . A paper or paperboard prepared using the method according to  claim 1 . 
     
     
         95 - 120 . (canceled)