CN117337237A

CN117337237A - Corrugated medium or liner paper comprising NSSC pulp

Info

Publication number: CN117337237A
Application number: CN202280035486.5A
Authority: CN
Inventors: I·海斯卡宁; K·巴克福克; J·坎库宁; T·西普斯
Original assignee: Stora Enso Oyj
Current assignee: Stora Enso Oyj
Priority date: 2021-05-17
Filing date: 2022-05-13
Publication date: 2024-01-02
Also published as: EP4341089A1; AU2022276166A1; WO2022243820A1; BR112023024100A2

Abstract

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

Description

Corrugated medium or liner paper comprising NSSC pulp

Technical Field

The present invention relates to a corrugated medium or linerboard comprising neutral sulfite semi-chemical (NSSC) pulp.

Background

Corrugated board (sometimes also referred to as corrugated cardboard or corrugated fiberboard) is a packaging material that can be converted into different types of packaging schemes. Corrugated board is a fiber-based material made from cellulosic fibers that are virgin or recycled from used corrugated cardboard or other materials.

The corrugated board comprises corrugated base (corrugated medium) (fluting) and at least one non-corrugated base (linerboard or linerboard) glued to the surface of the corrugated base. For example, corrugated board may be composed of a layer of corrugated medium glued between two layers of linerboard to form a sandwich. The sandwich structure may be formed in different ways, such as in single, double and triple walls, as described in Kirwan m, j.

One difficulty in the production of corrugated board is the adhesion of liner paper to corrugated medium. Too low an adhesion may lead to delamination and the addition of too much adhesive to ensure adequate adhesion may lead to shrinkage (washing) and curling of the corrugated board. Importantly, the adsorption of the added glue into the liner paper and/or corrugated base paper is optimal. Delamination occurs if the adhesive is not absorbed by the corrugated medium/linerboard, and the same occurs if it is absorbed too much into the corrugated medium/linerboard.

Examples of different types of linerboards are kraft linerboards (kraftliner) and recycled linerboards (testliner). Kraft liner paper is typically produced from kraft pulp which may be bleached or unbleached and may include one or more layers/plies (ply), wherein the top layer/ply is typically optimized to provide a good printed surface and good moisture resistance. Recycled linerboard is produced primarily from recycled corrugated board and is typically manufactured in two layers/plies. Recycled linerboard may generally have lower mechanical strength, particularly lower burst strength, than kraft linerboard due to the presence of recycled fibers. Kraft liner paper is often used in packaging boxes where there is a higher demand for strength properties.

Corrugated medium is formed from paper or paperboard corrugated by heat, moisture and pressure using a corrugator.

Corrugated medium is often made from neutral sulfite semi-chemicalNSSC) slurry preparation. NSSC pulp (which is typically made of hardwood species) is known for its special stiffness and high hardness, making it suitable for use in corrugated medium. Neutral sulfite semi-chemical (NSSC) pulping is an old process well known in the paper pulping art. One of the reasons for using NSSC pulping is the high yield, typically above 60%. In NSSC pulping, the cooking liquor contains sulphites such as Na ₂ SO ₃ Or (NH) ₄ ) ₂ SO ₃ And a base such as NaOH or Na ₂ CO ₃ . By "neutral" is meant that the NSSC cooking liquor typically has a pH between 6 and 10. The pulp may be cooked in a batch or continuous digester. Typically, the cooking time is between 5 minutes and 3 hours and the cooking temperature is 160-200 ℃. The NSSC slurry contains a relatively high amount of residual lignin, such as 15-20%, which stiffens the NSSC slurry. The Kappa number of NSSC slurries is typically above 70. NSSC pulping is "semi-chemical" in that it also includes mechanical refining of the pulp. The refining may be performed, for example, at digester pressure or at atmospheric pressure using a disc refiner.

Currently, the strength and mechanical properties of corrugated medium and corrugated base paper are improved by adding small amounts of chemical pulp to the mechanical pulp. Typically, 5-15% chemical pulp is added. This of course not only increases the cost, but also results in a reduced dewatering rate. One potential approach is to mix semi-chemical pulps such as NSSC with unbleached kraft pulp, although this may lead to undesirable optical speckle and shading changes, as well as changes in organoleptic properties.

The corrugated medium and the linerboard are attached to each other by disposing an adhesive between the corrugated medium and the linerboard. The linerboard is attached to at least one surface of the corrugated base paper by an adhesive. The adhesive is preferably applied to at least one surface of the fluted corrugated base paper and then the linerboard is attached to the surface. Any conventional adhesive in the art may be used. The binder may be, for example, a gum based on starch extractable from a variety of plants. Some of the most common plants are corn, wheat, barley, rice, potato, tapioca, and pea. The starch is preferably native, i.e. not modified. The binder may also include water, sodium hydroxide, and boric acid. Other additives, such as additives that improve wet strength or adhesive bond strength, may also be added. Also, other functional chemicals, such as borax, glyoxal or mixtures thereof, may be added to improve, for example, moisture resistance or gel behaviour.

An important challenge in making corrugated base paper and corrugated board is moisture resistance. When corrugated board is exposed to moisture, water and water vapor can diffuse through the linerboard and soften the corrugated base paper. A common solution to this problem is to increase the grammage of the corrugated medium and/or linerboard, but this conflicts with the environmental requirement for lower grammage materials that require less raw material to be consumed.

Another solution is to provide a barrier layer on the linerboard to reduce the penetration of water and water vapor. However, this is only a partial solution, since moisture diffusion can still occur on the opposite side or via the edges and thus affect the mechanical stability of the corrugated board. The barrier layer also increases cost and generally reduces the recycling ability of the material.

The corrugated medium or corrugated base paper may also be treated or coated with a hydrophobic chemical, but this generally increases costs and may also negatively impact the mechanical properties of the corrugated medium. High levels of hydrophobic chemicals can also impair the adhesion between the corrugated medium and the linerboard. In particular, NSSC pulp requires high levels of hydrophobic chemicals to achieve the desired level of water repellency in the finished corrugated medium.

New machine concepts and increased machine speeds, coupled with increased demands for source curtailment, further increase the demand for pulps with improved properties.

There remains a need for new and improved corrugated medium and linerboard materials that combine strength, low grammage, water/moisture resistance, low chemical consumption, low cost, and/or high recyclability.

Detailed Description

It is an object of the present invention to provide a corrugated medium or linerboard which solves or ameliorates at least some of the abovementioned problems.

It is a further object of the present invention to provide a corrugated medium or linerboard having improved water repellency properties which can reduce the amount of hydrophobic internal sizing agent required to achieve a desired level of water repellency in the finished corrugated medium or linerboard.

It is a further object of the present invention to provide a corrugated board comprising improved corrugated medium and/or linerboard.

The above objects, as well as other objects that will be recognized by those skilled in the art in light of the present disclosure, are accomplished by various aspects of the present disclosure.

The invention is based on the following inventive recognition: if the ash content of the NSSC pulp used in the corrugated medium or linerboard is reduced, the amount of hydrophobic internal sizing agent required to achieve the desired level of water repellency in the finished corrugated medium or linerboard can be significantly reduced. It has also been found that reducing the ash content of the pulp reduces the required amount of other wet end chemicals, such as drainage in corrugated medium or linerboard.

The reduction of ash content can be achieved by washing the pulp. Ash content can also be reduced by more efficient removal of bark prior to the pulping process.

According to a first aspect shown herein, there is provided corrugated medium or linerboard for corrugated board comprising a neutral sulfite semi-chemical (NSSC) pulp, wherein the NSSC pulp has an ash content of less than 1.8 wt% as determined according to standard ISO 1762:2019.

"NSSC pulp" is obtained from "NSSC pulping", which is in turn defined in the background section. The NSSC pulp may be hardwood pulp or softwood pulp, or a mixture thereof. The NSSC pulp is preferably hardwood pulp or a hardwood/softwood pulp mixture having less than 15 wt% softwood, preferably less than 10 wt% softwood, and more preferably less than 5 wt% softwood. The hardwood may be, for example, aspen, alder, aspen, eucalyptus, birch, acacia (acacia) or beech. The NSSC slurry preferably contains sulfite (preferably Na ₂ SO ₃ Or (NH) ₄ ) ₂ SO ₃ ) And a base (preferably NaOH or Na) ₂ CO ₃ ) Is a cooking liquid of (2)And (5) cooking to prepare. In some embodiments, the NSSC pulping yield is above 60%, preferably above 65%, preferably above 70%, and more preferably above 75%. The term "neutral" means that the NSSC cooking liquor has a pH in the range of 6-10. The cooking time is preferably in the range of 5 minutes to 3 hours. The cooking temperature is preferably in the range of 160-200 ℃. NSSC pulp may contain relatively high amounts of residual lignin, such as 15-20%. The nssc pulp typically has a kappa number of above 70, preferably above 80, preferably above 95, and more preferably above 100 according to ISO 3260. NSSC pulping is "semi-chemical" in that it also includes mechanical refining of the pulp. The refining may be performed, for example, at digester pressure or at atmospheric pressure using a disc refiner. Refining may be performed in one or more steps at the same or different pulp consistencies. The first refining step may preferably be performed at a higher consistency, such as 5-35%, and the second refining step may be performed at a lower consistency of < 5%.

In some embodiments, the NSSC pulp in corrugated medium or linerboard has been subjected to washing to reduce ash content. The purpose of the washing is to separate the pulp from the black liquor, to wash away residual substances such as alkali lignin generated during the digestion process, and to purify the pulp. Washing may 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 equipment. Washing involves dilution of NSSC slurry with water, followed by removal of the water through a wire mesh along with diluted colloidal materials, salts, impurities and fines.

In some embodiments, NSSC pulp is prepared from wood comprising 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.

The reduction in ash content can be measured by measuring ash content according to standard ISO 1762:2019. In some embodiments, the NSSC pulp has an ash content of less than 1.6 wt%, preferably less than 1.4 wt%, and more preferably less than 1.2 wt% or less than 1.0 wt% or less than 0.9 wt%, as determined according to standard ISO 1762:2019. In some embodiments, the corrugated medium or linerboard has an ash content of less than 1.6 wt%, preferably less than 1.4 wt%, and more preferably less than 1.2 wt% or less than 1.0 wt% or less than 0.9 wt%, as determined according to standard ISO 1762:2019.

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

In some embodiments, the NSSC pulp used in corrugated medium or linerboard has a conductivity of less than 1200, less than 1000, less than 800, or less than 600, and more preferably less than 500, less than 450, less than 400, less than 350, or less than 300mS/m when decomposed at 3.5 wt% in distilled water.

In some embodiments, the NSSC pulp comprises less than 2%, preferably less than 1.8%, more preferably less than 1.6% of Pulmac pulp mass (shives) (mesh size 0.1 mm). It has been found to be advantageous to use pulp with a lower amount of pulp cake.

In addition to reducing ash content, washing can also result in a reduction in the content of cellulosic fines in the NSSC pulp. The term cellulosic 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 are capable of passing through a 200 mesh screen (equivalent pore diameter 76 μm) of a conventional laboratory fractionation device (SCAN-CM 66:05). The reduction of fines in the NSSC slurry may be, for example, in the range of 0.1-10 wt.%, or in the range of 0.5-7 wt.%.

The inventors have found that by reducing the ash content of the NSSC pulp, the amount of hydrophobic internal sizing agent required to achieve the desired level of water repellency in the finished corrugated medium or linerboard can be significantly reduced.

Thus, NSSC pulp is used in a pulp composition in corrugated medium or linerboard, wherein 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 furnish in the manufacture of paper or board in a paper machine.

The pulp of the pulp composition of the corrugated medium or linerboard preferably comprises primarily NSSC pulp. Preferably, at least 50 wt% of the pulp composition is NSSC pulp on a dry weight basis. 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% of the slurry is NSSC slurry on a dry weight basis.

The portion of the pulp composition that is not NSSC pulp may comprise any kind of fibers, such as hardwood and/or softwood fibers, and may include, for example, chemical pulp, mechanical pulp, thermomechanical pulp, or chemical-thermomechanical pulp (CTMP). The portion of the pulp composition that is not NSSC pulp may also, for example, comprise 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. "recycled fibers" refer to fibrous materials that have been previously incorporated into certain paper or paperboard products. Alternatively, or in addition, the portion of the slurry other than NSSC slurry may, for example, comprise reject slurry (reject slurry). For example, the slurries of the present disclosure may consist essentially of NSSC slurries and slag slurries. "pulp" refers to pulp produced by refining the screen reject from the pulping process.

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. A small amount of recycled fiber is preferred because a large amount of inorganic material is typically added via the recycled fiber. In some embodiments, the corrugated medium comprises less than 10 wt%, preferably less than 5 wt%, more preferably less than 2 wt% recycled fibers.

The corrugated medium and/or the linerboard may further comprise an internal sizing agent. The internal sizing agent is preferably a hydrophobic sizing agent. In some embodiments, the internal sizing agent 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 sizing agent is Alkyl Ketene Dimer (AKD).

In some embodiments, the amount of internal sizing agent in the corrugated medium or linerboard is in the range of 0.5 to 6kg/tn, preferably in the range of 0.5 to 4kg/tn, preferably in the range of 0.5 to 3kg/tn, and more preferably in the range of 1 to 2kg/tn on a dry weight basis. Thus, the amount of sizing agent in the corrugated medium or linerboard is quite low.

At least one side of the corrugated medium or linerboard preferably has a Cobb 30s value of less than 30, preferably less than 25, and more preferably less than 22, as measured according to standard ISO 535. It may be preferred that both sides of the corrugated medium or linerboard have Cobb 30s values of below 30, preferably below 25, and more preferably below 22 as determined according to standard ISO 535. It has surprisingly been found that the addition of a clean NSSC pulp to the backsheet layer or the topsheet layer of a linerboard or corrugated medium does not negatively affect Cobb values. Thus, one or both sides of the liner paper or corrugated medium comprising the clean NSSC pulp preferably have Cobb 30s values of below 30, preferably below 25, and more preferably below 22, as determined according to standard ISO 535. NSSC pulp is typically used for the back sheet layer of corrugated medium or linerboard and then it is preferred that the back side of the corrugated medium or linerboard has a Cobb 30s value of below 30, preferably below 25, and more preferably below 22 as determined according to standard ISO 535.

In order to produce high quality papers such as corrugated medium or linerboard with high quantities of NSSC pulp at high machine speeds, it is important to effectively retain mineral fillers and fibrous fines while achieving high dewatering rates. Microparticle retention systems, which typically utilize anionic colloidal silica and/or clay-based particles in combination with cationic polymers, have been developed to help address these challenges. Generally, microparticle retention systems exhibit better retention and dewatering properties than classical single or dual polymer retention systems. In some embodiments, the corrugated medium or linerboard further comprises a particulate retention system, preferably a multicomponent particulate retention system.

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

In some embodiments, the microparticle retention aid system comprises a water soluble polymer, preferably a cationic polymer.

In some embodiments, the amount of particulate retention system in the corrugated medium or linerboard is in the range of 50g/tn to 5kg/tn on a dry weight basis, and more preferably in the range of 100g/tn to 2 kg/tn.

The corrugated medium or linerboard may also contain additional components commonly used in the manufacture of corrugated medium or linerboard such as natural starch or starch derivatives, microfibrillated cellulose (MFC), cellulose derivatives such as sodium carboxymethyl cellulose, fillers, retention and/or drainage chemicals, flocculation additives, deflocculating additives, dry strength additives, softeners, crosslinking aids, sizing agents, dyes and colorants, wet strength resins, fixatives, defoamers aids, microbial and slime control aids, or mixtures thereof.

The corrugated medium or linerboard is typically a single ply product, but it may also be a multi-ply product. Corrugated medium or linerboard is typically formed in a gap former, but it may also be formed in a fourdrinier-type former. The press section may be provided with a shoe press to maximize production.

The basis weight of the corrugated medium or linerboard may preferably be in the range of 80-300 gsm.

In some embodiments, the corrugated medium or linerboard has an Equilibrium Moisture Content (EMC) at 50% RH of less than 10% by weight, preferably less than 8% by weight, as determined according to standard ISO 287.

In some embodiments, the corrugated medium or linerboard has a cd/md elongation value of greater than 1.8, preferably greater than 1.9, and more preferably greater than 2.0 as determined according to standard ISO 1924-3.

In some embodiments, the corrugated medium or linerboard has a dynamic friction of less than 0.5, preferably less than 0.45, and more preferably less than 0.4 as determined according to standard astm d 1894-63.

According to a second aspect shown herein, there is provided corrugated board comprising the corrugated medium and/or linerboard according to the first aspect. The corrugated board includes at least one layer of non-corrugated linerboard and at least one layer of corrugated medium. In normal production of corrugated board, the corrugated medium is corrugated and then glued to linerboard. For example, corrugated board may be comprised of a layer of corrugated medium sandwiched between two layers of linerboard.

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 intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Examples

The examples show that the washed NSSC pulp can be used in sheet manufacture and provides improved mechanical properties and different responses to liquid absorption.

Example 1 (comparative)

NSSC beech pulp was obtained in dry form, then decomposed into ingredients and made 150g/m on a fourdrinier pilot (pilot) paper machine ² Is a single ply web of (c). The production speed was 45m/min and the dosing temperature was 45 ℃.

Example 2 (comparative)

NSSC beech pulp as used in example 1 was refined to a higher SR value and a web was prepared as in example 1. The increased SR due to refining increases in particular the tensile index (Geom).

Example 3

Using Eimco belt wash unit water (40 m per ton of pulp) ³ Fresh water) washing faithfullyNSSC beech pulp used in example 1. 2.7% of the fines are removed along with colloidal material and impurities (including electrolytes) in the liquid phase. As a result of the washing, the pH of the pulp suspension increased, confirming removal of electrolyte and reduction of ash content. A web was prepared as in example 1. A small increase in both tensile strength and elongation was noted.

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 slurries were mixed in a ratio of 50-50. A web was prepared as in example 1. A significant increase in both tensile strength and elongation was observed.

Example 5

In this example, washed NSSC birch broke pulp as used in example 4 was used without using any other fibers. A web was prepared as in example 1. The tensile strength and elongation are further improved.

TABLE 1 slurry composition

TABLE 2 physical Properties of the sheet formed

Example 6

In this example, the washed NSSC pulp was added to a linerboard. The washed pulp has an ash content below 1.8 wt%.

Unwashed NSSC pulp was added to another linerboard for comparison. Unwashed NSSC slurries have ash contents of greater than 1.8 wt.%.

All linerboards produced included unbleached kraft pulp (100%) in the top sheet layer and recycled fiber (RCF) pulp in the back sheet layer with or without NSSC pulp added.

TABLE 3 results

From these tests it is clear that the use of clean NSSC pulp in the linerboard provides linerboard with a very good Cobb value even on the backside of the linerboard as shown in sample 3 (S3) of table 3. Cobb values were at the same level as the reference samples. It is clear that the use of unwashed NSSC pulp will provide a linerboard with a high Cobb value, which means that these samples have a much lower water repellency, as can be seen in samples 1 and 2 (S1 and S2). Thus, by the present invention, a fine (high) water-repellent fine paper can be produced even with a small amount of an internal sizing additive.

Unless otherwise indicated, the physical properties discussed in this disclosure are determined according to the following criteria:

unless otherwise indicated, standard methods can then be used to determine physical and mechanical properties in the cross-machine direction (cd) and machine direction (md).

Claims

1. Corrugated medium or linerboard for corrugated board comprising a neutral sulfite semi-chemical (NSSC) pulp, wherein the NSSC pulp has an ash content of less than 1.8 wt% as determined according to standard ISO 1762:2019.

2. The corrugated medium or linerboard according to claim 1 wherein the NSSC pulp has been subjected to washing to reduce ash content.

3. The corrugated medium or linerboard according to any preceding claim wherein the NSSC pulp has an ash content of less than 1.6 wt%, preferably less than 1.4 wt%, and more preferably less than 1.2 wt% or less than 1.0 wt% or less than 0.9 wt%, as determined according to standard ISO 1762:2019.

4. The corrugated medium or linerboard according to any preceding claim wherein the NSSC pulp has a hot water extract conductivity of less than 5mS/cm, preferably less than 10mS/cm, and more preferably less than 8mS/cm, as determined according to ISO 6587.

5. The corrugated medium or linerboard according to any preceding claim wherein the corrugated medium or linerboard comprises at least one internal sizing agent.

6. Corrugated medium or linerboard according to claim 5 wherein the internal sizing agent is selected from Alkyl Ketene Dimer (AKD), alkenyl Succinic Anhydride (ASA), rosin size and mixtures thereof, preferably the internal sizing agent is Alkyl Ketene Dimer (AKD).

7. The corrugated medium or linerboard according to any one of claims 5 to 6 wherein the amount of the internal sizing agent in the corrugated medium or linerboard is in the range of 0.5 to 6kg/tn, preferably in the range of 0.8 to 4kg/tn, and more preferably in the range of 1 to 3kg/tn on a dry weight basis.

8. A corrugated medium or linerboard according to any preceding claim further comprising a particulate retention system, preferably a multicomponent particulate retention system.

9. The corrugated medium or linerboard according to claim 8 wherein the particulates of the particulate retention system are selected from the group consisting of silica particulates, bentonite particulates, and cellulose nanoparticles.

10. The corrugated medium or linerboard according to any one of claims 8 to 9 wherein the particulate retention system comprises a water soluble polymer, preferably a cationic polymer.

11. The corrugated medium or linerboard according to any one of the preceding claims wherein at least one side of the corrugated medium or linerboard has a Cobb (60 s) value of 40gsm or less, preferably 35gsm or less, and even more preferably 30gsm or less, as determined according to standard ISO 535.

12. The corrugated medium or linerboard according to any one of the preceding claims wherein the corrugated medium or linerboard comprises less than 10 wt%, preferably less than 5 wt%, more preferably less than 2 wt% recycled fibers.

13. The corrugated medium or linerboard according to any preceding claim wherein the corrugated medium or linerboard has a hot water extract conductivity of less than 15mS/cm, preferably less than 10mS/cm, and more preferably less than 8mS/cm, as determined according to ISO 6587.

14. The corrugated medium or linerboard according to any one of the preceding claims, wherein the corrugated medium has an Equilibrium Moisture Content (EMC) of less than 10 wt%, preferably less than 8 wt%, at 50% rh as determined according to standard ISO 287.

15. The corrugated medium or linerboard according to any preceding claim wherein the corrugated medium or linerboard has a cd/md elongation value of greater than 1.8, preferably greater than 1.9, and more preferably greater than 2.0 as determined according to standard ISO 1924-3.

16. The corrugated medium or linerboard of any preceding claim wherein the corrugated medium has a dynamic friction of less than 0.5, preferably less than 0.45, and more preferably less than 0.4 as determined according to standard astm d 1894-63.

17. Corrugated board comprising a corrugated medium and/or linerboard according to any of the preceding claims.