Stretchable high-density paper

Abstract

A paper having: —a density measured according to ISO 534:2011 above 1000 kg/m3; —a strain at break measured according to ISO 1924-3:2005 in the machine direction above 3%; —a basis weight measured according to ISO 536:2012 below 100 g/m2, such as below 70 g/m2; and—a Bendtsen surface roughness on at least one side below 150 ml/min when measured according to ISO 8791-2:2013.

1 . A paper having:
 a density measured according to ISO 534:2011 above 1000 kg/m 3 ;   a strain at break measured according to ISO 1924-3:2005 in the machine direction above 3%;   a basis weight measured according to ISO 536:2012 below 100 g/m 2 ; and   a Bendtsen surface roughness on at least one side below 150 ml/min when measured according to ISO 8791-2:2013.   
     
     
         2 . The paper of  claim 1 , wherein the strain at break in the machine direction is in the range of 3.5%-9.0%. 
     
     
         3 . The paper of  claim 1 , wherein the strain at break measured according to ISO 1924-3:2005 in the cross direction is above 5.0%. 
     
     
         4 . The paper of  claim 1 , wherein the basis weight of the paper is 66 g/m 2  or lower. 
     
     
         5 . The paper of  claim 1 , wherein cellulose fibers constitute at least 90% of the dry weight of the paper. 
     
     
         6 . The paper of  claim 1 , wherein the Bendtsen surface roughness on at least one side is below 100 ml/min. 
     
     
         7 . The paper of  claim 1 , wherein at least one side of the paper is coated or impregnated with a polymer. 
     
     
         8 . The paper of  claim 1 , wherein both sides of the paper is coated or impregnated with a polymer. 
     
     
         9 . The paper of  claim 1 , which is a kraft paper. 
     
     
         10 . A method of producing a high-density paper having a density above 1000 kg/m 3 , a strain at break in the machine direction above 3% and a basis weight below 100 g/m 2 , said method comprising the steps of:
 forming a paper web;   drying the paper web in a drying section to obtain a paper, said drying section comprising an extensible unit that compacts the paper web in the machine direction; and   supercalendering the paper to obtain the high-density paper.   
     
     
         11 . The method of  claim 10 , wherein the method further comprises the step coating or impregnating at least one side of the paper with a composition comprising PVOH, EVOH, starch and/or CMC, which coating or impregnating step is carried out between the drying step and the supercalendering step. 
     
     
         12 . The method of  claim 11 , wherein both sides of the paper is coated or impregnated with the composition comprising PVOH, EVOH, starch and/or CMC. 
     
     
         13 . The method of  claim 10 , wherein the extensible unit is an Expanda unit or a Clupak unit. 
     
     
         14 . A coated paper comprising a paper according to  claim 1 , wherein a surface of the paper is provided with a barrier coating. 
     
     
         15 . (canceled) 
     
     
         16 . The paper according to  claim 1 , wherein the basis weight is below 70 g/m 2 . 
     
     
         17 . The paper of  claim 2 , wherein the strain at break in the machine direction is in the range of 4.0%-8.0%. 
     
     
         18 . The paper of  claim 4 , wherein the basis weight of the paper is 35-66 g/m 2 . 
     
     
         19 . The paper of  claim 7 , wherein the polymer is PVOH, EVOH, starch and/or CMC. 
     
     
         20 . The paper of  claim 14 , wherein the barrier coating comprises polyvinyl alcohol (PVOH), ethylene vinyl alcohol (EVOH), a starch or starch derivative, a nano or micro-fibrillar cellulose, polyvinylidene chloride (PVDC) or a polyamide.