Packaging material made of unbleached kraft paper, sleeve produced therefrom, and method for manufacturing same

Abstract

A packaging material consisting of an unbleached kraft paper as a base paper, —the kraft paper has at least 90% primary cellulose and a grammage of between 65 g/m2 and 170 g/m2; —the primary cellulose, containing at least 80% cellulose with a length-weighted mean fiber length of between 2.0 mm and 2.9 mm, and less than 5% fillers, —the primary cellulose is cellulose beaten with high consistency, —the packaging material has a strain ratio break of >1.1, a tear length in the machine direction of >10 km, and a tear index in the cross direction of >16.0 mN·m2/g. The invention also relates to a method for manufacturing the packaging material, to a sleeve produced from the packaging material, and to a use of the packaging material.

1 . A packaging material consisting of an unbleached kraft paper with a Kappa number according to ISO 302:2015 between 38 and 60, as base paper, wherein the kraft paper is manufactured from at least 90% primary cellulose and has a grammage according to ISO 536:2019 between 65 g/m 2  and 170 g/m 2 , wherein the kraft paper contains at least 90% primary cellulose, containing at least 80% of cellulose with a length-weighted mean fibre length according to ISO 16065-2:2014 between 2.0 mm and 2.9 mm and less than 5%, fillers as well as cationic starch, that the primary cellulose is contained in the form of high-consistency beaten cellulose having a Schopper-Riegler degree of beating according to ISO 5267-1:1999 between 13° SR and 20° SR, that the packaging material has a strain ratio MD/CD of the kraft paper at break according to ISO 1924-3:2005 of >1.1, a tear length in the machine direction according to ISO 1924-3:2005 of >10 km, a tear index in the cross direction of the kraft paper according to ISO 1974:2012 is >16.0 mN·m 2 /g and that the kraft paper is coated on at least one side with a coating material. 
     
     
         2 . The packaging material according to  claim 1 , wherein the primary cellulose consists of a mixture consisting of at least 80% softwood cellulose, with a length-weighted mean fibre length according to ISO 16065-2:2014 of at least 2.0 mm, and the substantial remainder of softwood cellulose with a length-weighted mean fibre length according to ISO 16065-2:2014 of at least 1.0 mm. 
     
     
         3 . The packaging material according to  claim 2 , wherein the packaging material it has a starch content of 0.5% to 2.2% of the paper. 
     
     
         4 . The packaging material according to  claim 1 , wherein the packaging material has a tensile strength index in the machine direction according to ISO 1924:3-2005 of >105 Nm/g. 
     
     
         5 . The packaging material according to  claim 1 , wherein the packaging material has a TEA index in the longitudinal direction according to ISO 1924-3:2005 greater than 5.0 J/g. 
     
     
         6 . The packaging material according to  claim 1 , wherein the packaging material has a bursting strength according to ISO 2758:2014 of greater than 750 kPa. 
     
     
         7 . The packaging material according to  claim 1 , wherein the packaging material has a wet strength index according to ISO 3781:2011 in the machine direction of the kraft paper of at least 14.0 Nm/g. 
     
     
         8 . The packaging material according to  claim 1 , wherein on at least one side a coating material selected from a polyolefin or polylactic acid (PLA) in an amount corresponding to 1/15 to ⅙ of the grammage of the kraft paper, is applied. 
     
     
         9 . The packaging material according to  claim 8 , wherein the polyolefin is selected from high-density polyethylene (HDPE), low-density polyethylene (LDPE), or polypropylene (PP). 
     
     
         10 . The packaging material according to  claim 1 , wherein the packaging material forms a laminate consisting of several layers of kraft paper and several layers of coating material. 
     
     
         11 . (canceled) 
     
     
         12 . The packaging material according to  claim 10 , wherein the laminate has at most 5 layers of the kraft paper, and at most 6 layers of the coating material. 
     
     
         13 . The packaging material according to  claim 12 , wherein each layer of the coating material located between two layers of kraft paper has an amount corresponding to 1/15 to 1/9 of the grammage of the kraft paper and a layer forming an outer side of the laminate of the coating material has an amount that corresponds to 1/11 to ⅙ of the grammage of the kraft paper. 
     
     
         14 . A sleeve made from a packaging material according to  claim 1 , wherein the packaging material is formed from a coated, at least single-layer web of the packaging material, that is closed, in the cross direction, substantially made of unbleached kraft paper, and that a machine direction of the paper web of the packaging material forms a circumferential direction of the sleeve. 
     
     
         15 . The sleeve according to  claim 14 , wherein the sleeve is subjected to tension by enclosed objects with a tensile stress which is smaller than an elongation at break in the machine direction (MD) measured in accordance with ISO 1924-3:2005 of the coated paper web. 
     
     
         16 . The sleeve according to  claim 15 , wherein the elongation at break in the machine direction (MD) measured according to ISO 1924-3:2005 of the packaging material is >8%. 
     
     
         17 . The sleeve according to  claim 14 , wherein the sleeve is formed from a laminate consisting of several layers of kraft paper and several layers of coating material, such as at most 5 layers of kraft paper, and at most 6 layers of the coating material. 
     
     
         18 . Method A method for forming the sleeve from a packaging material according to  claim 14 , wherein a length of the packaging material slightly exceeding the circumference of the sleeve to be formed is cut off from a web of the packaging material substantially consisting of unbleached kraft paper that is unrolled in the machine longitudinal direction, the cut length of the packaging material is pivoted by 90°, two free edges of the cut length, which run in the cross-machine direction when the web of packaging material is unrolled, are folded over one another and closed to form a tube and that a plurality of sleeves are separated from the closed tube or prepared for separation, in particular perforated, scored or marked. 
     
     
         19 . The method according to  claim 18 , wherein pivoting the cut length of the packaging material by 90° is performed before or after folding over and closing the two free edges of the cut length which run in the cross-machine direction when the web of packaging material is unrolled. 
     
     
         20 . Use of the sleeve produced from the packaging material according to  claim 14  for tightly enclosing a plurality of objects that are the same or different from one another.