New substrate

Abstract

There is provided a high-density paper having a grammage measured according to ISO 536:2012 of 30-75 g/m 2 and a density measured according to ISO 534:2011 above 1000 kg/m 3 and wherein the high-density paper is impregnated on each side with 0.3-4.0 g/m 2 , such as 0.5-3.0 g/m 2 , of a polymer selected from the group consisting of polyvinyl alcohol (PVOH), ethylene vinyl alcohol (EVOH), carboxymethylated cellulose (CMC), nanocrystalline cellulose (NCC) and carboxy methyl starch (CMS).

1 . A high-density paper having a grammage measured according to ISO 536:2012 of 30-75 g/m 2  and a density measured according to ISO 534:2011 above 1000 kg/m 3  and
 wherein the high-density paper is impregnated on each side with 0.3-4.0 g/m 2  of a polymer selected from the group consisting of polyvinyl alcohol (PVOH), ethylene vinyl alcohol (EVOH), carboxymethylated cellulose (CMC), nanocrystalline cellulose (NCC) and carboxy methyl starch (CMS).   
     
     
         2 . The high-density paper of  claim 1 , which is formed from at least 50% by dry weight kraft pulp. 
     
     
         3 . The high-density paper of  claim 1 , wherein 20-65% by dry weight of the pulp used to form the high-density paper is hardwood pulp. 
     
     
         4 . The high-density paper of  claim 1 , wherein 35-80% by dry weight of the pulp used to form the high-density paper is softwood pulp. 
     
     
         5 . The high-density paper of  claim 1 , having a top ply and a bottom ply. 
     
     
         6 . The high-density paper of  claim 1 , wherein the grammage measured according to ISO 536:2012 is 35-65 g/m 2 . 
     
     
         7 . The high-density paper of  claim 1 , which has a Schopper-Riegler (° SR) number measured according to ISO 5267-1:1999 of 33-50 after repulping according to ISO 5263-1:2004. 
     
     
         8 . The high-density paper of  claim 1 , which has a fines content measured with a L&W Fibretester+(ABB, Lorentzen & Wettre, Sweden) of less than 40% after repulping according to ISO 5263-1:2004, wherein fines are defined as fibrous particles shorter than 0.2 mm. 
     
     
         9 . A method of forming a high-density paper having a grammage measured according to ISO 536:2012 of 30-75 g/m 2 , said method comprising the steps of:
 impregnating each side of a paper substrate with 0.3-4.0 g/m 2  of a polymer selected from the group consisting of polyvinyl alcohol (PVOH), ethylene vinyl alcohol (EVOH), carboxymethylated cellulose (CMC), nanocrystalline cellulose (NCC) and carboxy methyl starch (CMS) to obtain an impregnated substrate; and   supercalendering the impregnated substrate to obtain the high-density paper.   
     
     
         10 . The method of  claim 9 , wherein the polymer is PVOH having a weight average molecular weight (M w ) below 100,000 g/mol. 
     
     
         11 . The method of  claim 9 , wherein the impregnating step comprises adding an aqueous composition comprising the polymer to each side of the paper substrate and the viscosity measured at 60° C. of the aqueous composition is 55-90 mPa*s. 
     
     
         12 . The method of  claim 9 , wherein the impregnated substrate entering the supercalendering step has a moisture content of 11.0%-20.0%. 
     
     
         13 . The method of  claim 9 , wherein the impregnating step is carried out by means of a film press. 
     
     
         14 . A coated paper comprising a high-density paper according to  claim 1 , wherein a surface of the high density paper is provided with a barrier coating comprising polyvinyl alcohol (PVOH), ethylene vinyl alcohol (EVOH), a starch or starch derivative, a nano or micro-fibrillar cellulose, polyvinylidene chloride (PVDC) or a polyamide. 
     
     
         15 . (canceled) 
     
     
         16 . The high-density paper of  claim 2 , which is formed from at least 85% by dry weight kraft pulp. 
     
     
         17 . The high-density paper of  claim 4 , wherein the softwood pulp has been subjected to high consistency (HC) refining.