Fluting or liner containing NSSC pulp

Abstract

The present invention relates to a flute or liner for corrugated board comprising neutral sulfite semi-chemical (NSSC) pulp, the NSSC pulp having an ash content of less than 1.8 wt.% as determined according to ISO standard 1762: 2019. The present invention further relates to a corrugated board comprising the flute and / or liner.

Description

[Technical field]

[0001] The present invention relates to fluting or liners comprising neutral sulfite semi-chemical (NSSC) pulp. [Background technology]

[0002] Corrugated board (sometimes called corrugated cardboard or corrugated fiberboard) is a packaging material that can be converted into many different types of packaging solutions. Corrugated board is a fibrous substrate made from regenerated cellulose fibers derived from virgin or post-consumer cardboard or other materials.

[0003] Corrugated board comprises a medium (fluting) and at least a flat base paper (liner or linerboard) bonded to the surface of the medium. For example, corrugated board may consist of a layer of fluting bonded between two layers of liner to form a sandwich structure. The sandwich structure can be formed in various formats such as single, double, and triple wall, as described for example in Kirwan M., J., Paper and Paperboard. Packaging Technology, Blackwell Publishing 2005.

[0004] One challenge when producing corrugated board is the adhesion between the liner and the fluting. Too little adhesion can cause delamination, and adding too much adhesive to ensure adequate adhesion can cause washboarding and curling of the board. It is important that the glue added is optimally absorbed into the liner and / or corrugating medium. If the adhesive does not adhere to the fluting / liner, delamination will occur, and if too much is absorbed into the fluting / liner, the same can happen.

[0005] Examples of different types of liners are kraftliners and testliners. Kraftliners are typically produced from kraft pulp, which can be bleached or unbleached, and may contain one or more layers / plies, where the top layer / ply is often optimized to provide a good print surface and good moisture resistance. Testliners are primarily produced from recycled corrugated cardboard and are usually manufactured with two layers / plies. Due to the presence of recycled fibers, testliners may typically have lower mechanical strength than kraftliners, especially lower burst strength. Kraftliners are often used for packaging boxes with higher demands on strength properties.

[0006] Fluting is formed from paper or paperboard that has been corrugated using a corrugator with the application of heat, moisture and pressure.

[0007] Fluting is often prepared from Neutral Sulfite Semi-Chemical (NSSC) pulp. NSSC pulp, usually made from hardwood species, is noted for its exceptional stiffness and high stiffness, making it suitable for use in fluting. Neutral Sulfite Semi-Chemical (NSSC) pulping is an old process well known in the field of paper pulping. One of the reasons for using NSSC pulping is the high yield, usually above 60%. In NSSC pulping, the cooking liquor contains a sulfite salt such as Na2SO3 or (NH4)2SO3 and a base such as NaOH or Na2CO3. By "neutral" we mean that the pH of the NSSC cooking liquor is generally between 6 and 10. The pulp can be cooked in a batch or continuous cooker. Typically, the cooking time is between 5 minutes and 3 hours, and the cooking temperature is between 160 and 200°C. NSSC pulp contains a relatively high amount of residual lignin, such as 15-20%, which makes NSSC pulp hard. The Kappa number of NSSC pulp is typically above 70. NSSC pulping is "semi-chemical" in the sense that it also includes mechanical refining of the pulp. Refining can be done, for example, using a disc refiner at digester pressure or atmospheric pressure.

[0008] Currently, the strength and mechanical properties of the fluting and medium are improved by adding small amounts of chemical pulp to the mechanical pulp. Typically, 5-15% chemical pulp is added, which of course increases the cost but slows down the dewatering rate. One possible method is to mix a semi-chemical pulp such as NSSC with unbleached kraft pulp, but this can result in undesirable light mottling and color changes, as well as changes in organoleptic properties.

[0009] The fluting and liner are attached to one another by placing an adhesive between the core and the liner. The liner is attached to at least one surface of the core by the adhesive. The adhesive is preferably applied to at least one surface of the fluted core, and then the liner is attached to said surface. Any adhesive conventional in the art can be used. The adhesive can be, for example, a starch-based glue that can be extracted from a wide variety of plants. Some of the most common plants are corn, wheat, barley, rice, potato, tapioca, and pea. The starch is preferably natural, i.e., the starch is not modified. The adhesive can also include water, sodium hydroxide, and boric acid. Other additives may be added, such as additives that improve wet strength or adhesive bond strength. Also, other functional chemicals, such as borax, glyoxal, or mixtures thereof, can be added, for example to improve moisture resistance or gelling behavior.

[0010] One significant challenge when making corrugated board and medium is resistance to moisture. When corrugated board is exposed to moisture, water and water vapor can diffuse through the liner and soften the medium. Common solutions to this problem are fluting and / or increasing the basis weight of the liner, but this conflicts with environmental imperatives that call for lower basis weight materials that consume less raw materials.

[0011] Another solution is to provide a barrier layer in the liner to reduce water and water vapor transmission. However, this is only an incomplete solution, since moisture diffusion can still occur on the other side or through the edges, thus affecting the mechanical stability of the board. Barrier layers also increase costs and usually reduce the recyclability of the material.

[0012] The flutings or medium may also be treated or coated with hydrophobizing chemicals, but this generally increases cost and may also have a negative effect on the mechanical properties of the fluting. High levels of hydrophobizing chemicals may also impair the adhesion of the fluting to the liner. In particular, NSSC pulp requires high levels of hydrophobizing chemicals to obtain the required level of water resistance in the finished fluting.

[0013] New machine concepts and increased machine speeds coupled with an increased desire to conserve resources have further increased the need for pulps with improved properties.

[0014] There remains a need for new and improved fluting and liner materials that combine strength, low basis weight, water / moisture resistance, low chemical consumption, low cost, and / or high recyclability. Summary of the Invention

[0015] It is an object of the present disclosure to provide a fluting or liner that overcomes or ameliorates at least some of the problems mentioned above.

[0016] It is a further object of the present disclosure to provide a flute or liner having improved water resistance properties that can reduce the amount of hydrophobizing internal sizing agent required to obtain a required level of water resistance in the finished flute or liner.

[0017] It is a further object of the present disclosure to provide corrugated board containing improved fluting and / or liners.

[0018] The above objectives, as well as other objectives that will be appreciated by those skilled in the art in light of this disclosure, are accomplished by various aspects of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention is based on the inventive recognition that reducing the ash content of the NSSC pulp used in the fluting or liner can significantly reduce the amount of hydrophobizing internal sizing agent required to achieve the required level of water resistance in the finished fluting or liner. It has been found that reducing the ash content of the pulp also reduces the required amount of other wet end chemicals in the fluting or liner, such as drainage / retention agents.

[0020] A reduction in the ash content can be achieved by washing the pulp. The ash content can also be reduced by more efficient removal of the bark prior to the pulping process.

[0021] According to a first aspect presented herein, there is provided a flute or liner for corrugated board comprising neutral sulfite semi-chemical (NSSC) pulp, the NSSC pulp having an ash content of less than 1.8 wt.% as determined in accordance with ISO Standard 1762:2019.

[0022] "NSSC pulp" is obtained by "NSSC pulping", as such is defined in the Background section. NSSC pulp can be hardwood pulp or softwood pulp, or a mixture thereof. NSSC pulp is preferably hardwood pulp or a hardwood / softwood pulp mixture containing less than 15 wt% softwood, preferably less than 10 wt% softwood, more preferably less than 5 wt% softwood. Hardwood can be, for example, aspen, alder, poplar, eucalyptus, birch, acacia, or beech. NSSC pulp is preferably prepared by cooking with a cooking liquor containing sulfite, preferably Na2SO3 or (NH4)2SO3, and a base, preferably NaOH or Na2CO3. In some embodiments, the yield from NSSC pulping is greater than 60%, preferably greater than 65%, preferably greater than 70%, more preferably greater than 75%. The term "neutral" means that the pH of the NSSC cooking liquor is in the range of 6 to 10. Cooking time is preferably in the range of 5 minutes to 3 hours. The cooking temperature is preferably in the range of 160-200°C. NSSC pulp may contain a relatively high amount of residual lignin, such as 15-20%. The Kappa number of NSSC pulp is typically above 70 according to ISO 3260, preferably above 80, preferably above 95, more preferably above 100. NSSC pulping is "semi-chemical" in the sense that it also includes mechanical refining of the pulp. Refining may be carried out, for example, using a disc refiner at digester pressure or at atmospheric pressure. Refining may be carried out in one or more steps at the same or different pulp consistencies. The first refining step may preferably be carried out at a higher consistency, such as 5-35%, and the second refining step may preferably be carried out at a lower consistency, <5%.

[0023] In some embodiments, the NSSC pulp in the flutes or liners is subjected to washing to reduce the ash content. The purpose of washing is to separate the pulp from the black liquor and to wash away residual materials, such as alkaline lignin, produced during the cooking process, and to purify the pulp. Washing can be performed using one or more conventional pulp washing methods and washing equipment, including, but not limited to, rotary vacuum washers, rotary pressure washers, pressure and atmospheric diffusion washers, horizontal belt washers, and / or dilution / extraction machines. Washing involves diluting the NSSC pulp with water, followed by wire removal of the diluted colloidal materials, salts, impurities, and fines along with the water.

[0024] In some embodiments, the NSSC pulp is prepared from wood containing less than 3 wt%, less than 2.5 wt%, less than 2 wt%, or preferably less than 1 wt% or less than 0.8 wt% bark.

[0025] The reduction in ash content can be measured by measuring the ash content according to ISO Standard 1762:2019. In some embodiments, the NSSC pulp has an ash content of less than 1.6 wt%, preferably less than 1.4 wt%, more preferably less than 1.2 wt% or less than 1.0 wt% or less than 0.9 wt%, as determined according to ISO Standard 1762:2019. In some embodiments, the fluting or liner has an ash content of less than 1.6 wt%, preferably less than 1.4 wt%, more preferably less than 1.2 wt% or less than 1.0 wt% or less than 0.9 wt%, as determined according to ISO Standard 1762:2019.

[0026] The reduction in ash content can also be measured by measuring the hot water extract conductivity of the NSSC pulp according to ISO 6587. In some embodiments, the NSSC pulp has a hot water extract conductivity determined according to ISO 6587 of less than 15 mS / cm, preferably less than 10 mS / cm, and more preferably less than 8 mS / cm. In some embodiments, the fluting or liner has a hot water extract conductivity determined according to ISO 6587 of less than 15 mS / cm, preferably less than 10 mS / cm, and more preferably less than 8 mS / cm.

[0027] In some embodiments, the conductivity of the NSSC pulp used for the fluting or liner when disintegrated at 3.5 wt % in distilled water is less than 1200, less than 1000, less than 800, or less than 600, more preferably less than 500, less than 450, less than 400, less than 350, or less than 300 mS / m.

[0028] In some embodiments, the NSSC pulp contains less than 2%, preferably less than 1.8%, more preferably less than 1.6% Pulmac shives (slot size 0.1 mm). It has been found advantageous to use pulps with a low amount of shives.

[0029] In addition to reducing the ash content, washing may also result in a reduction in the content of cellulose fines in the NSSC pulp. The term cellulose fines as used herein generally refers to cellulose particles that are significantly smaller in size than cellulose fibers. In some embodiments, the term fines as used herein refers to fine cellulose particles that can pass through a 200 mesh screen (76 μm equivalent hole diameter) of a conventional laboratory fractionator (SCAN-CM 66:05). The reduction in fines in the NSSC pulp may be, for example, in the range of 0.1-10 wt%, or in the range of 0.5-7 wt%.

[0030] The inventors have found that by reducing the ash content of the NSSC pulp, the amount of hydrophobizing internal size required to obtain the required level of water resistance in the finished fluting or liner can be significantly reduced.

[0031] Thus, NSSC pulp is used in pulp compositions used in fluting or liners for corrugated board, where the pulp composition further comprises at least one internal sizing agent. The term "pulp composition" refers to an aqueous dispersion of cellulosic fibers and non-fibrous additives used as a furnish for making paper or paperboard on a paper machine.

[0032] The pulp of the fluting or liner pulp composition preferably consists primarily of NSSC pulp. Preferably, at least 50 wt%, based on the dry weight of the pulp in the pulp composition, is NSSC pulp. In other examples, at least 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt% or 98 wt% is NSSC pulp, based on the dry weight of the pulp.

[0033] The non-NSSC pulp portion of the pulp composition may include any type of fiber, such as hardwood and / or softwood fibers, e.g., chemical pulp, mechanical pulp, thermomechanical pulp, or chemi-thermomechanical pulp (CTMP). The non-NSSC pulp portion of the pulp composition may also include, e.g., recycled fibers. For example, the pulp of the present disclosure may consist essentially of NSSC pulp or a mixture of NSSC pulp and recycled fibers. By "recycled fibers" it is meant fibrous material that has previously been incorporated into some paper or board product. Alternatively, or as a complement, the non-NSSC pulp portion may include, e.g., reject pulp. For example, the pulp of the present disclosure may consist essentially of NSSC pulp and reject pulp. By "reject pulp" it is meant pulp prepared by refining screen rejects from a pulping process.

[0034] In some embodiments, the pulp of the pulp composition comprises less than 10 wt%, preferably less than 5 wt%, more preferably less than 2 wt% recycled fibers. Since high amounts of inorganic materials are typically added via recycled fibers, low amounts of recycled fibers are preferred. In some embodiments, the fluting comprises less than 10 wt%, preferably less than 5 wt%, more preferably less than 2 wt% recycled fibers.

[0035] The fluting and / or liner may further comprise an internal size. The internal size is preferably a hydrophobizing size. In some embodiments, the internal size is selected from the group consisting of alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), rosin size, and mixtures thereof. In a preferred embodiment, the internal size is alkyl ketene dimer (AKD).

[0036] In some embodiments, the amount of internal sizing agent in the flutes or liners is in the range of 0.5-6 kg / tn, preferably in the range of 0.5-4 kg / tn, preferably in the range of 0.5-3 kg / tn, more preferably in the range of 1-2 kg / tn, based on dry weight. As a result, the amount of sizing agent in the flutes or liners is extremely low.

[0037] At least one face of the flutes or liner preferably has a Cobb 30s value as determined according to ISO Standard 535 of less than 30, preferably less than 25, more preferably less than 22. It would be preferred for both faces of the flutes or liner to have a Cobb 30s value as determined according to ISO Standard 535 of less than 30, preferably less than 25, more preferably less than 22. Surprisingly, it has been found that the addition of clean NSSC pulp to the bottom or top ply of the liner or flutes does not negatively affect the Cobb value. As a result, the face of the liner or flutes containing clean NSSC pulp preferably has a Cobb 30s value as determined according to ISO Standard 535 of less than 30, preferably less than 25, more preferably less than 22. NSSC pulp is often used in the back ply of the flutes or liner, so that the back side of the flutes or liner preferably has a Cobb 30s value as determined according to ISO Standard 535 of less than 30, preferably less than 25, more preferably less than 22.

[0038] To produce quality paper, such as high volume NSSC pulp flutings or liners, at high machine speeds, it is important that inorganic fillers and fiber fines are effectively retained while at the same time achieving high dewatering rates. To help address these challenges, microparticle retention aid systems have been developed that utilize typically anionic colloidal silica and / or clay based particles in combination with cationic polymers. Generally, microparticle retention aid systems exhibit better retention and dewatering performance compared to classical single or binary polymer retention aid systems. In some embodiments, the flutings or liners further comprise a microparticle retention aid system, preferably a multicomponent microparticle retention aid system.

[0039] In some embodiments, the microparticles of the microparticle retention assistance system are selected from the group consisting of silica microparticles, bentonite microparticles, and cellulose nanoparticles.

[0040] In some embodiments, the microparticle retention assist system comprises a water soluble polymer, preferably a cationic polymer.

[0041] In some embodiments, the amount of microparticle retention aid system in the flutes or liners ranges from 50 g / tn to 5 kg / tn, more preferably from 100 g / tn to 2 kg / tn, on a dry weight basis.

[0042] The fluting or liner may further comprise additional ingredients commonly used in fluting or liner production, such as natural starch or starch derivatives, microfibrillated cellulose (MFC), cellulose derivatives such as sodium carboxymethyl cellulose, fillers, retention and / or drainage aids, flocculating additives, deflocculating additives, dry strength additives, softeners, crosslinking aids, sizing agents, dyes and colorants, wet strength resins, solidifying agents, defoaming aids, microbial and slime control aids, or mixtures thereof.

[0043] The fluting or liner is typically a single ply product, but may be a multi-ply product. The fluting or liner is typically formed on a gap former, but may also be formed on a Fourdrinier type former. The press section may include a shoe press to maximize production.

[0044] The basis weight of the fluting or liner may preferably range from 80 to 300 gsm.

[0045] In some embodiments, the fluting or liner has an equilibrium moisture content (EMC) of less than 10 wt.%, preferably less than 8 wt.%, at 50% RH as determined according to ISO standard 287.

[0046] In some embodiments, the fluting or liner has a cd / md elongation value greater than 1.8, preferably greater than 1.9, and more preferably greater than 2.0, as determined according to ISO standard 1924-3.

[0047] In some embodiments, the fluting or liner has a dynamic friction determined according to standard ASTM D 1894-63 of less than 0.5, preferably less than 0.45, and more preferably less than 0.4.

[0048] According to a second embodiment shown herein, there is provided a corrugated board comprising fluting and / or a liner according to the first embodiment. The corrugated board comprises at least one layer of uncorrugated liner and at least one layer of fluting. In normal corrugated board production, the flutes are corrugated and then bonded to a linerboard. For example, the corrugated board may consist of a layer of fluting sandwiched between two layers of liner.

[0049] While the invention has been described with reference to various exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is not intended that the invention be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but the invention is intended to include all embodiments falling within the scope of the appended claims. EXAMPLES

[0050] The examples show that washed NSSC pulp can be used in sheet making and provides improved mechanical properties and a different response to liquid absorption.

[0051] Example 1 (Comparison) NSSC beech pulp was obtained in a dry form and then broken down into furnish and compressed to 150 g / m on a Fourdrinier type pilot paper machine. 2 The production speed was 45 m / min and the furnish temperature was 45° C.

[0052] Example 2 (Comparison) NSSC beech pulp as used in Example 1 was refined to higher SR values ​​and webs were prepared as in Example 1. The increased SR due to refining notably increased the tensile index (Geom).

[0053] Example 3 NSSC beech pulp as used in Example 1 was washed with water (40 m per tonne of pulp) using an Eimco belt washer. 3 The pulp was washed with 100 ml of fresh water (100 ml of fresh water). 2.7% of the fines were removed along with colloidal matter and impurities in the liquid phase, including the electrolyte. As a result of the washing, the pH of the pulp suspension increased, confirming the removal of the electrolyte and the reduction in the ash content. Webs were prepared as in Example 1. Small improvements were observed in both tensile strength and elongation.

[0054] Example 4 NSSC beech pulp as used in Example 1 was mixed with washed NSSC birch broke pulp (washed as described in Example 3). The pulps were mixed in a 50-50 ratio. Webs were prepared as in Example 1. Significant improvements in both tensile strength and elongation were observed.

[0055] Example 5 In this example, washed NSSC birch broke pulp as used in Example 4 was used without any other fibers. Webs were prepared similar to Example 1. Tensile strength properties and elongation were further improved. TIFF2024519007000001.tif76170TIFF2024519007000002.tif93170

[0056] Example 6 In this example, washed NSSC pulp was added to the liner. The washed pulp has an ash content of less than 1.8 wt%.

[0057] For comparison, unwashed NSSC pulp was added to another liner. The unwashed NSSC pulp has an ash content higher than 1.8 wt%.

[0058] All the liners produced contained unbleached kraft pulp (100%) in the top ply and recycled fiber (RCF) pulp in the back ply, with or without NSSC pulp addition. TIFF2024519007000003.tif101170

[0059] From these tests, it is clear that the use of clean NSSC pulp in the liner provides a liner with a very good Cobb value even on the back side of the liner, as shown in sample 3 (S3) in Table 3. The Cobb value is at the same level as the reference sample. It is clear that the use of unwashed NSSC pulp, as seen in samples 1 and 2 (S1 and S2), results in a high Cobb value for the liner, which means that these samples have a much lower water resistance. As a result, the present invention makes it possible to produce liners with good (high) water resistance even with low amounts of internal sizing agent added.

[0060] Unless otherwise specified, the physical properties discussed in this disclosure are determined according to the following standards: Whiteness C / 2°+UV ISO 2470-1 L* C / 2°+UV ISO 5631-1 a* C / 2°+UV ISO 5631-1 b* C / 2°+UV ISO 5631-1 Basis weight ISO 536 Thickness, single sheet ISO 534 Umbrella, single sheet ISO 534 Air permeability GH ISO 5636-5 Cobb 60s ISO 535 Moisture content 50%rh ISO 287 Scott-Bond TAPPI T569 Tensile strength ISO 1924-3 Tensile Index ISO 1924-3 Tensile strength md / cd ISO 1924-3 Elongation ISO 1924-3 Tensile stiffness ISO 1924-3 Tensile stiffness index ISO 1924-3 E-Module ISO 1924-3 TEA ISO 1924-3 TEA index ISO 1924-3 TEA index ISO 1924-3 Fracture toughness ISO / TS 17958 Fracture toughness index ISO / TS 17958 Tear resistance ISO 1974 Tear index ISO 1974 SCT ISO 9895 SCT index ISO 9895 RCT ISO 12192 RCT index ISO 12192 Rupture Index ISO 2759 Bursting strength ISO 2759

[0061] Unless otherwise specified, standard methods may be applied to determine the physical and mechanical properties in both the cross direction (cd) and machine direction (md).

Claims

1. 1. A fluting or liner for corrugated board comprising neutral sulfite semi-chemical (NSSC) pulp, the NSSC pulp having an ash content of less than 1.8 wt. % as determined in accordance with ISO Standard 1762:2019.

2. 2. The fluting or liner of claim 1, wherein the NSSC pulp is a washed NSSC pulp having a reduced ash content.

3. 3. The fluting or liner of claim 1 or 2, wherein the NSSC pulp has an ash content, determined according to ISO Standard 1762:2019, of less than 1.6 wt.%, preferably less than 1.4 wt.%, more preferably less than 1.2 wt.% or less than 1.0 wt.% or less than 0.9 wt.%.

4. 3. The fluting or liner of claim 1 or 2, wherein the NSSC pulp has a hot water extractable conductivity, determined in accordance with ISO 6587, of less than 5 mS / cm, preferably less than 10 mS / cm, more preferably less than 8 mS / cm.

5. 3. The flute or liner of claim 1 or 2, wherein the flute or liner comprises at least one internal size.

6. 6. The fluting or liner of claim 5, wherein the internal size is selected from the group consisting of alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), rosin size, and mixtures thereof, preferably the internal size is alkyl ketene dimer (AKD).

7. 6. The fluting or liner according to claim 5, wherein the amount of internal sizing agent in the fluting or liner is in the range of 0.5 to 6 kg / tn, preferably in the range of 0.8 to 4 kg / tn, more preferably in the range of 1 to 3 kg / tn, based on dry weight.

8. 3. A fluting or liner according to claim 1 or 2, further comprising a microparticle retention aid system, preferably a multi-component microparticle retention aid system.

9. 9. The fluting or liner of claim 8, wherein the microparticles of the microparticle retention aid system are selected from the group consisting of silica microparticles, bentonite microparticles and cellulose nanoparticles.

10. 9. The fluting or liner of claim 8, wherein the microparticle retention aid system comprises a water-soluble polymer, preferably a cationic polymer.

11. 3. A fluting or liner according to claim 1 or 2, wherein at least one surface of the flute or liner has a Cobb (60s) value, determined according to ISO standard 535, of less than 40 gsm, preferably less than 35 gsm, even more preferably less than 30 gsm.

12. 3. A fluting or liner according to claim 1 or 2, wherein the fluting or liner comprises less than 10 wt%, preferably less than 5 wt%, more preferably less than 2 wt% recycled fibres.

13. 3. A fluting or liner according to claim 1 or 2, wherein the fluting or liner has a hot water extract conductivity determined in accordance with ISO 6587 of less than 15 mS / cm, preferably less than 10 mS / cm, more preferably less than 8 mS / cm.

14. 3. A fluting or liner according to claim 1 or 2, wherein the fluting has an equilibrium moisture content (EMC) of less than 10 wt. %, preferably less than 8 wt. %, at 50% RH, determined according to ISO standard 287.

15. A fluting or liner according to claim 1 or 2, wherein the flute or liner has a cd / md elongation value determined according to ISO standard 1924-3 of greater than 1.8, preferably greater than 1.9, more preferably greater than 2.

0.

16. A fluting or liner according to claim 1 or 2, wherein said fluting has a dynamic friction determined according to standard ASTM D 1894-63 of less than 0.5, preferably less than 0.45, more preferably less than 0.

4.

17. 3. A corrugated board comprising the fluting and / or liner of claim 1 or 2.