PACKING PAPER

Abstract

Packaging paper consisting of an unbleached kraft paper with a kappa value according to ISO 302:2015 between 38 and 60, preferably between 40 and 58 as base paper, which is optionally coated on at least one side, wherein the kraft paper is made of at least 90% primary pulp, has a basis weight according to ISO 536:2019 between 60 g/m.sup.2 and 150 g/m.sup.2 and an air resistance according to ISO 5636-5:2013 (Gurley) between 5 and 30 seconds, wherein the base paper has an elongation at break in the machine direction according to ISO 1924-3:2005 between 2.5% and 8.5% and has a Bendtsen roughness according to ISO 8791-2:2013 between 70 ml/min and 600 ml/min, preferably between 150 ml/min to 550 ml/min, more preferably 200 ml/min to 500 ml/min, and process for its production.

Claims

1. Packaging paper consisting of an unbleached kraft paper with a kappa value according to ISO 302:2015 of between 38 and 60, as base paper, which is optionally coated on at least one side, the kraft paper being made of at least 90% primary pulp, having a basis weight according to ISO 536:2019 of between 60 g/m.sup.2 and 150 g/m.sup.2 and an air resistance according to ISO 5636-5:2013 (Gurley) of between 5 and 30 seconds, wherein the primary pulp contained in the base paper comprises at least 80% pulp with an average length-weighted fiber length according to ISO 16065-2:2014 of between 2.0 mm and 2.9 mm and less than 4.5% fillers as well as cationic starch in an amount of 0.5% by weight.-% to 1.5% by weight of the base paper, and contains other processing agents, that the base paper has an elongation at break in the machine direction according to ISO 1924-3:2005 of between 2.5% and 8.5%, and in that the packaging paper has a Bendtsen roughness according to ISO 8791-2:2013 of between 70 ml/min and 600 ml/min.

2. The packaging paper according to claim 1, wherein the base paper is coated on at least one side with a coating material selected from the group consisting of Polyethylene, Polypropylene, Polyolefin-based Copolymers and Terpolymers, and Ionomers or from the group of Polyolefin-free coating materials.

3. The packaging paper according to claim 1, wherein the coating is applied to each side of the base paper in an amount between 1% and 7% by weight of the basis weight of the base paper.

4. The packaging paper according to claim 1, wherein it contains 100% primary pulp.

5. The packaging paper according to claim 1, wherein the primary pulp consists of a mixture consisting of at least 80% softwood pulp with an average length-weighted fiber length according to ISO 16065-2:2014 of at least 2.0 mm, and the remainder hardwood pulp with an average length-weighted fiber length according to ISO 16065-2:2014 of at least 1.0 mm.

6. The packaging paper according to claim 1, wherein the primary pulp is contained as refined pulp with a Schopper-Riegler freeness according to ISO 5267-1:1999 between 13° SR to 20°SR.

7. A process for the production of a packaging paper, in which an unbleached kraft pulp consisting of at least 90% of primary pulp, containing at least 80% pulp with an average length-weighted fiber length according to ISO 16065-2:2014 of between 2.0 mm and 2.9 mm and less than 4.5% fillers as well as cationic starch in an amount of 0.5% by weight to 1.5% by weight of the base paper, and other processing agents, with a kappa value according to ISO 302:2015 of between 38 and 60 is used as the base material, wherein the base material is creped in a Clupak plant until an elongation at break in the machine direction according to ISO 1924-3:2005 of between 2.5% and 8.5% is achieved, dried to a moisture content of at most 14% and subjected to a calendering step, that a packaging paper with a Bendtsen roughness according to ISO 8791-2: 2013 of between 70 ml/min and 600 ml/min, a basis weight according to ISO 536:2019 of between 60 g/m2 and 150 g/m2 and an air resistance according to ISO 5636-5:2013 (Gurley) of between 5 and 30 seconds is formed, and that optionally at least one one-sided coating of the packaging paper is carried out.

8. The process according to claim 7, wherein the calendering step is carried out in a shoe calender with a line load between 200 and 1000 kN/m and a shoe length of 50 mm-270 mm or a soft-nip calender with a line load of 18 to 80 kN/m.

9. The process according to claim 7, wherein the calendered base paper is subjected to a coating step in which at least one side of the base paper is coated, with a coating material selected from the group consisting of Polyethylene, Polypropylene, Polyolefin-based Copolymers and Terpolymers, and Ionomers or from the group of Polyolefin-free coating materials.

10. The process according to claim 7, wherein in the coating step an amount between 2% and 7%, of the basis weight of the base paper is applied to each side of the base paper to be coated.

11. The process according to claim 7, wherein the coating is applied to at least one side creped in the Clupak unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0024] The invention is explained in more detail below with reference to exemplary embodiments.

Example 1: Production of a Packaging Paper with a Basis Weight (Grammage) of 60 g/m.SUP.2

Process Description:

[0025] An unbleached pulp consisting of 95% softwood (spruce) primary pulp having a kappa number of 42 and 5% hardwood (birch) primary pulp having a kappa number of 40, which was first subjected to high consistency refining with a refining power of 190 to 210 kWh/t, wherein a freeness of the pulp after the high consistency refining was 17° SR and subsequently this pulp was subjected to a low consistency refining with a refining power of 75 kWh/t, wherein the freeness of the pulp after the high consistency refining and the low consistency refining was 22° SR, was used.

[0026] In the approach flow system, the agents (Aluminum Sulfate, cationic starch, and a mixture of Alkenyl Succinic Anhydride (ASA) and Alkylated Ketene Dimers (AKD)) are added. Here, the pH was adjusted with Aluminum Sulfate to a pH of 6.8 to 7.1, cationic starch, with a cationization degree DS of 0.03, was added in an amount of 10 kg/t paper absolutely dry as well as 1 kg/t of a dry strengthener (Glyoxylated Polyacrylamide (G-PAM)), and a mixture of ASA and AKD in an amount of 0.4 kg/t paper adry (absolutely dry) [atro—absolut trocken] was used as a sizing agent. The pulp did not contain any fillers. The consistency of the pulp at the headbox was 0.21%. Dewatering was carried out on a Fourdrinier section, and with a press section with three nips, with line pressures at the three nips being 55 kN/m, 80 kN/m, and again 80 kN/m. Before the still moist paper was fed to the Clupak system, it was pre-dried in a slalom dryer section and treated and micro creped in a Clupak system at a differential speed of −5.2%. The paper was dried to a residual moisture content of 9% before being calendered and finally wound up in a soft nip calender with a line load of 45 kN/m and a temperature of 100° C. The paper can be used as such.

[0027] The paper had the paper properties described in Table 1 below:

TABLE-US-00001 TABLE 1 Paper Property Norm Unit Direction Result Grammage ISO 536: 2019 g/m.sup.2 60 Tensile Strength ISO 1924-3: 2005 kN/m MD 4.9 Tensile Strength Index ISO 1924-3: 2005 Nm/g MD 81.7 Tensile Strength ISO 1924-3: 2005 kN/m CD 3.3 Tensile Strength Index ISO 1924-3: 2005 Nm/g CD 55 Elongation at break ISO 1924-3: 2005 % MD 6.7 Elongation at break ISO 1924-3: 2005 % CD 7.3 Tensile fracture work ISO 1924-3: 2005 J/g MD 3.4 index Tensile fracture work ISO 1924-3: 2005 J/g CD 2.9 index Air Permeability ISO 5636-5: 2013 s 14.3 Gurley Cobb Value 60 s ISO 535: 2014 g/m.sup.2 32 Bendtsen Roughness ISO 8791-2: 2013 ml/min smooth 298 side Bendtsen Roughness ISO 8791-2: 2013 ml/min rough side 819

[0028] Needless to say, the paper can additionally be subjected to a coating treatment, such as extrusion coating with polyethylene (e.g., 4.0 g/m.sup.2) or, after a pigmenting precoat with kaolin, a dispersion coating (1.8 g/m.sup.2), which can further modify the properties, especially roughness and air permeability.

Example 2: Production of a Packaging Paper with a Basis Weight of 81 g/m.SUP.2

Process Description:

[0029] An unbleached pulp consisting of 100% softwood primary pulp (mixture of spruce and pine) with a kappa number of 47, which was first subjected to high consistency refining with a refining power of 210 to 220 kWh/t, wherein a freeness of the pulp after the high consistency refining was 18° SR and subsequently this pulp was subjected to low consistency refining with a refining power of 80 kWh/t, wherein the freeness of the pulp after the high consistency refining and the low consistency refining was 24° SR was used.

[0030] In the approach flow system of the paper machine, the additives are metered in. Here, the pH was adjusted with Aluminum Sulfate to a pH of 6.6 to 7.1, cationic starch, with a cationization degree DS of 0.03, was added in an amount of 13 kg/t paper adry, and alkenyl succinic anhydride was used as a sizing agent in an amount of 0.5 kg/t paper adry. 2% filler in the form of talc was added. The consistency of the pulp at the headbox was 0.19%. Dewatering was carried out on a Fourdrinier section, and with a press section with three nips, with line pressures at the three nips being 60 kN/m, 80 kN/m, and again 80 kN/m. Before the still moist paper was fed to the Clupak system, it was pre-dried in a slalom dryer section and treated and (micro)creped in a Clupak system at a differential speed of −6.1%. The paper was dried to a residual moisture content of 10.5% before calendering and final rewinding in a soft-nip calender with a line load of 57 kN/m at a temperature of 110° C. The paper can be used as such.

[0031] The paper had the paper properties described in Table 2 below:

TABLE-US-00002 TABLE 2 Paper Property Norm Unit Direction Result Grammage ISO 536: 2019 g/m.sup.2 81 Tensile Strength ISO 1924-3: 2005 kN/m MD 6.5 Tensile Strength Index ISO 1924-3: 2005 Nm/g MD 80.2 Tensile Strength ISO 1924-3: 2005 kN/m CD 4.7 Tensile Strength Index ISO 1924-3: 2005 Nm/g CD 58.0 Elongation at break ISO 1924-3: 2005 % MD 8.0 Elongation at break ISO 1924-3: 2005 % CD 7.1 Tensile fracture work ISO 1924-3: 2005 J/g MD 3.4 index Tensile fracture work ISO 1924-3: 2005 J/g CD 2.8 index Air Permeability ISO 5636-5: 2013 s 18.7 Gurley Cobb Value 60 s ISO 535: 2014 g/m.sup.2 30 Bendtsen Roughness ISO 8791-2: 2013 ml/min smooth 241 side Bendtsen Roughness ISO 8791-2: 2013 ml/min rough side 857

[0032] The paper can additionally be subjected to a coating treatment, such as extrusion coating with polyethylene (e.g., 4.0 g/m.sup.2 on the smoothed side or e.g., 6.0 g/m.sup.2 on at least one side), whereby the properties, in particular roughness and air permeability, can be changed.

[0033] Such a paper was printed in a flexographic printing process with a multicolor print. The colors showed a high brilliance and bleeding of the same could not be observed.

[0034] In two further tests, sample packages were made from the paper, one batch in which the coated side of the paper formed the inside of the package and one batch in which the coated side of the paper formed the outside of the package. Both batches of packages were filled with sand, 25 kg, gravel, 25 kg, rice 15 kg, children's play stones, wood chips 10 kg, and 2 kg of nails, sealed, and subjected to load tests in each case. The load tests here consisted of drop tests from a constant drop height of 0.8 meters with a flat drop in accordance with ISO 7965-1:1984.

[0035] In the case of packages where the coated side of the paper forms the inside of package, packaging I, the closing was performed by heat sealing and in cases where the coated side of the paper forms the outside of the package, packaging II, the closing was performed by means of a conventional adhesive.

[0036] These tests showed that the packaging I and II made from the packaging paper according to the present invention did not break even after 9 to 10 drops, and the pointed or sharp-edged filling materials also did not pierce the paper.

[0037] Both groups of packages, packaging I and II, were also printed in multiple colors on the outside using flexographic printing. The packaging I could be printed on well, the colors did not run out and did not flow into each other, the color brilliance was sufficient. The feel of packaging I corresponded to that of, for example, natural brown paper bags. Significantly less ink was required for printing packaging II compared to packaging I, the color brilliance was excellent, and no merging or bleeding of colors was observed. The drying time of the inks was somewhat prolonged compared to packaging I. After drying and after the drop tests as described above, it was found that the color print on both packaging I and II was neither chipped nor smudged or damaged in any way.

[0038] Thus, these tests show that, depending on the desired feel of the packaging and the brilliance of the print applied to it, as well as possibly the goods to be packaged in it, the packaging paper can be used with its coated side facing both inwards and outwards.

Example 3: Production of a Packaging Paper with a Basis Weight (Grammage) of 138 g/m.SUP.2

Process Description:

[0039] An unbleached pulp consisting of 80% softwood primary pulp (spruce and pine) with a kappa number of 45 and 15% hardwood primary pulp (birch and beech) with a kappa number of 40, which was first subjected to high consistency refining with a refining power of 190 to 210 kWh/t, where a freeness of the pulp after the high consistency refining was 17° SR, and subsequently this pulp was subjected to low consistency refining with a refining power of 75 kWh/t, where the freeness of the pulp after the high consistency refining and the low consistency refining was 23° SR, was used. Likewise, 5% recovered paper was used, but this was only added to the stock stream after refining.

[0040] In the approach flow system of the paper machine, the additives were metered in. Here, the pH was adjusted with Aluminum Sulfate to a pH of 7.0 to 7.2, cationic starch, with a cationization degree DS of 0.04, was added in an amount of 13 kg/t paper adry, and Alkenyl Succinic Anhydrides were used as sizing agents in an amount of 0.7 kg/t paper adry (absolutely dry). Furthermore, no fillers were added. The consistency of the pulp at the headbox was 0.25%. Dewatering was carried out on a Fourdrinier wire section and with a press section with three nips, one of which may be a shoe press, where the line pressure at the three nips was 60 kN/m, 90 kN/m and 500 kN/m (in the shoe press), respectively.

[0041] Before the still moist paper was fed to the Clupak system, it was pre-dried in a slalom dryer section and treated and (micro)creped in a Clupak system at a differential speed of −4.2%. The paper was dried to a residual moisture content of 9% before calendering and final rewinding in a soft-nip calender with a line load of 37 kN/m and a temperature of 110° C. The paper can be used as such.

[0042] The paper had the paper properties described in Table 3 below:

TABLE-US-00003 TABLE 3 Paper Property Norm Unit Direction Result Grammage ISO 536: 2019 g/m.sup.2 138 Tensile Strength ISO 1924-3: 2005 kN/m MD 11.5 Tensile Strength Index ISO 1924-3: 2005 Nm/g MD 83.3 Tensile Strength ISO 1924-3: 2005 kN/m CD 8.2 Tensile Strength Index ISO 1924-3: 2005 Nm/g CD 59.4 Elongation at break ISO 1924-3: 2005 % MD 5.9 Elongation at break ISO 1924-3: 2005 % CD 6.1 Tensile fracture work ISO 1924-3: 2005 J/g MD 3.0 index Tensile fracture work ISO 1924-3: 2005 J/g CD 2.6 index Air Permeability ISO 5636-5: 2013 s 26.9 Gurley Cobb Value 60 s ISO 535: 2014 g/m.sup.2 28 Bendtsen Roughness ISO 8791-2: 2013 ml/min smooth 334 side Bendtsen Roughness ISO 8791-2: 2013 ml/min rough side 1264

[0043] The paper thus obtained was extrusion coated on one side with 7 g/m.sup.2 polyethylene on the smooth side (the side facing the calender roll). After coating, the Bendtsen roughness of the smooth side was 78 ml/min and the air permeability has decreased to 15400 seconds according to ISO 5636-5:2013 (Gurley).

[0044] Such a paper was printed using a flexographic printing process with a multicolor print. The colors showed a high brilliance and bleeding of the same could not be observed.

[0045] In another test, test packages such as bags, sacks or pouches were made from the paper and filled with sand, 25 kg, gravel, 25 kg, rice 15 kg, children's play stones, wood chips 10 kg, and 2 kg of nails, heat-sealed and subjected to load tests in each case. The load tests here consisted of drop tests from a constant drop height of 0.8 meters with a flat drop in accordance with ISO 7965-1:1984

[0046] These tests showed that the packages made from the packaging paper according to the present invention did not break even after 9 to 10 drops, nor did the pointed or sharp-edged filling materials pierce through the paper, and finally the color printing did not flake off or become smudged or damaged in any other way.

Example 4: Production of a Packaging Paper with a Basis Weight of 80 g/m.SUP.2

Process Description:

[0047] An unbleached pulp consisting of 100% softwood primary pulp (mixture of spruce and pine) with a kappa number of 52, which was first subjected to high consistency refining with a refining power of 220 to 230 kWh/t, wherein a freeness of the pulp after the high consistency refining was 17° SR and subsequently this pulp was subjected to low consistency refining with a refining power of 90 kWh/t, wherein the freeness of the pulp after the high consistency refining and the low consistency refining was 22° SR was used.

[0048] In the approach flow system of the paper machine, the additives are metered in. Here, the pH was adjusted with Aluminum Sulfate to a pH of 6.6 to 7.1, cationic starch, with a cationization degree DS of 0.03, was added in an amount of 13 kg/t paper adry, and Alkenyl Succinic Anhydride was used as a sizing agent in an amount of 0.5 kg/t paper adry. 2% filler in the form of talc was added. The consistency of the pulp at the headbox was 0.19%. Dewatering was carried out on a Fourdrinier section, and with a press section with three nips, with line pressures at the three nips being 60 kN/m, 80 kN/m, and again 80 kN/m. Before the still moist paper was fed to the Clupak system, it was pre-dried in a slalom dryer section and treated and (micro)creped in a Clupak system at a differential speed of −6.1%. The paper was dried to a residual moisture content of 10.5% before being calendered and finally wound up in a soft-nip calender with a top roll having an Ra value of 0.03 μm with a line load of 65 kN/m and a temperature of 120° C. The paper can be used as such.

[0049] The paper had the paper properties described in Table 4 below:

TABLE-US-00004 TABLE 4 Paper Property Norm Unit Direction Result Grammage ISO 536: 2019 g/m.sup.2 80 Tensile Strength ISO 1924-3: 2005 kN/m MD 6.5 Tensile Strength Index ISO 1924-3: 2005 Nm/g MD 80.2 Tensile Strength ISO 1924-3: 2005 kN/m CD 4.7 Tensile Strength Index ISO 1924-3: 2005 Nm/g CD 58.0 Elongation at break ISO 1924-3: 2005 % MD 7.9 Elongation at break ISO 1924-3: 2005 % CD 7.0 Tensile fracture work ISO 1924-3: 2005 J/g MD 3.4 index Tensile fracture work ISO 1924-3: 2005 J/g CD 2.8 index Air Permeability ISO 5636-5: 2013 s 20.2 Gurley Cobb Value 60 s ISO 535: 2014 g/m2 28 Bendtsen Roughness ISO 8791-2: 2013 ml/min smooth 93 side Bendtsen Roughness ISO 8791-2: 2013 ml/min rough side 790

[0050] The paper can additionally be subjected to a coating treatment, such as extrusion coating with Polyethylene (e.g., 3.8 g/m.sup.2 on the smoothed side or e.g., 6.0 g/m.sup.2 on at least one side), whereby the properties, in particular roughness and air permeability, can be changed.

Example 5: Production of a Packaging Paper with a Basis Weight of 100 g/m.SUP.2

Process Description:

[0051] An unbleached pulp consisting of 100% softwood primary pulp (mixture of spruce and pine) with a kappa number of 53, which was first subjected to high consistency refining with a refining power of 220 to 230 kWh/t, wherein a freeness of the pulp after the high consistency refining was 17° SR and subsequently this pulp was subjected to low consistency refining with a refining power of 90 kWh/t, wherein the freeness of the pulp after the high consistency refining and the low consistency refining was 22° SR was used.

[0052] In the approach flow system of the paper machine, the additives are metered in. Here, the pH was adjusted with Aluminum Sulfate to a pH of 6.6 to 7.1, cationic starch, with a cationization degree DS of 0.03, was added in an amount of 13 kg/t paper adry, and Alkenyl Succinic Anhydride was used as a sizing agent in an amount of 0.5 kg/t paper adry. 2% filler in the form of talc was added. The consistency of the pulp at the headbox was 0.2%. Dewatering was carried out on a Fourdrinier section, and with a press section with three nips, with line pressures at the three nips being 60 kN/m, 80 kN/m, and again 80 kN/m. Before the still moist paper was fed to the Clupak system, it was pre-dried in a slalom dryer section and treated and (micro)creped in a Clupak system at a differential speed of −6.1%. The paper was dried to a residual moisture content of 10.5% before being calendered and finally wound up in a soft-nip calender with a top roll having an Ra value of 0.03 μm with a line load of 25 kN/m and a temperature of 120° C. The paper can be used as such.

[0053] The paper had the paper properties described in Table 5 below:

TABLE-US-00005 TABLE 5 Paper Property Norm Unit Direction Result Grammage ISO 536: 2019 g/m.sup.2 100 Tensile Strength ISO 1924-3: 2005 kN/m MD 7.9 Tensile Strength Index ISO 1924-3: 2005 Nm/g MD 79 Tensile Strength ISO 1924-3: 2005 kN/m CD 5.9 Tensile Strength Index ISO 1924-3: 2005 Nm/g CD 59 Elongation at break ISO 1924-3: 2005 % MD 8.0 Elongation at break ISO 1924-3: 2005 % CD 7.3 Tensile fracture work ISO 1924-3: 2005 J/g MD 3.4 index Tensile fracture work ISO 1924-3: 2005 J/g CD 2.8 index Air Permeability ISO 5636-5: 2013 s 18.9 Gurley Cobb Value 60 s ISO 535: 2014 g/m.sup.2 27 Bendtsen Roughness ISO 8791-2: 2013 ml/min smooth 421 side Bendtsen Roughness ISO 8791-2: 2013 ml/min rough side 898

[0054] The paper can additionally be subjected to a coating treatment, such as extrusion coating with Polyethylene (e.g., 5.0 g/m.sup.2 on the smoothed side or e.g., 7.0 g/m.sup.2 on at least one side), whereby the properties, in particular roughness and air permeability, can be changed.

Example 6: Production of a Packaging Paper with a Basis Weight (Grammage) of 140 g/m.SUP.2

Process Description:

[0055] An unbleached pulp consisting of 80% softwood primary pulp (spruce and pine) with a kappa number of 40 and 15% hardwood primary pulp (birch and beech) with a kappa number of 40, which was first subjected to high consistency refining with a refining power of 180 to 200 kWh/t, where a freeness of the pulp after the high consistency refining was 17° SR, and subsequently this pulp was subjected to low consistency refining with a refining power of 70 kWh/t, where the freeness of the pulp after the high consistency refining and the low consistency refining was 23° SR, was used.

[0056] In the approach flow system of the paper machine, the additives were metered in. Here, the pH was adjusted with Aluminum Sulfate to a pH of 7.0 to 7.2, cationic starch, with a cationization degree DS of 0.04, was added in an amount of 13 kg/t paper adry, and Alkenyl Succinic Anhydrides were used as sizing agents in an amount of 0.7 kg/t paper adry (absolutely dry). Furthermore, no fillers were added. The consistency of the pulp at the headbox was 0.25%. The Dewatering was carried out on a Fourdrinier wire section and with a press section with three nips, one of which may be a shoe press, where the line pressure at the three nips was 60 kN/m, 90 kN/m and 500 kN/m (in the shoe press), respectively.

[0057] Before the still moist paper was fed to the Clupak system, it was pre-dried in a slalom dryer section and treated and (micro)creped in a Clupak system at a differential speed of −4.2%. The paper was dried to a residual moisture content of 9.5% before calendering and final rewinding in a soft-nip calender with a line load of 20 kN/m and a temperature of 110° C. The paper can be used as such.

[0058] The paper had the paper properties described in Table 3 below:

TABLE-US-00006 TABLE 6 Paper Property Norm Unit Direction Result Grammage ISO 536: 2019 g/m.sup.2 140 Tensile Strength ISO 1924-3: 2005 kN/m MD 11.6 Tensile Strength Index ISO 1924-3: 2005 Nm/g MD 82.9 Tensile Strength ISO 1924-3: 2005 kN/m CD 8.1 Tensile strength index ISO 1924-3: 2005 Nm/g CD 57.9 Elongation at break ISO 1924-3: 2005 % MD 6.0 Elongation at break ISO 1924-3: 2005 % CD 6.4 Tensile fracture work ISO 1924-3: 2005 J/g MD 3.0 index Tensile fracture work ISO 1924-3: 2005 J/g CD 2.7 index Air Permeability ISO 5636-5: 2013 s 25.2 Gurley Cobb Value 60 s ISO 535: 2014 g/m.sup.2 27 Bendtsen Roughness ISO 8791-2: 2013 ml/min smooth 561 side Bendtsen Roughness ISO 8791-2: 2013 ml/min rough side 1242

[0059] The paper thus obtained was extrusion coated on one side with 7 g/m.sup.2 Polyethylene on the smooth side (the side facing the calender roll). After coating, the Bendtsen roughness of the smooth side was 112 ml/min, and the air permeability has decreased to 14900 seconds according to ISO 5636-5:2013 (Gurley).

[0060] Such a paper was printed using a flexographic printing process with a multicolor print. The colors showed a high brilliance and bleeding of the same could not be observed.