Method for manufacturing containerboard

Abstract

The present invention relates to a method for manufacturing containerboard in a paper machine comprising a wire section, a press section, and a drying section, the method comprising the steps of: a) forming a web from at least one pulp suspension comprising at least 50 wt% of recycled cellulose fibers based on dry weight on a wire in the wire section; b) dewatering the formed web layer in the press section; and c) drying the dewatered web layer in the drying section to obtain the containerboard; wherein the web speed in the drying section is at most 3.5 % higher, preferably at most 2.5 % higher, and more preferably at most 1.5 % higher, than the web speed in the wire section.

Description

[0001] METHOD FOR MANUFACTURING CONTAINERBOARD

[0002] Technical field

[0003] The present invention relates to a method for manufacturing containerboard for use in corrugated board.

[0004] Corrugated board (sometimes referred to as corrugated cardboard or corrugated fiberboard) is a packaging material which can be converted to different types of packaging solutions. Corrugated board is a fiber based material made from cellulose fibers. The fibers can be virgin fibers or recycled fibers, mainly fibers from old corrugated cardboard (OCC), but used beverage cartons (UBC), recycled food service board (FSB), and other recycled fiber materials may also be used.

[0005] The corrugated board comprises at least one corrugated medium (fluting) and at least one non-corrugated medium (liner or linerboard) glued onto a surface of the corrugated medium. For example, the corrugated board may consist of a layer of fluting glued between two layers of liner to form a sandwich structure. The sandwich structure can be formed in different ways such as in single, double, and triple walls as described, e.g., in Kirwan M., J., Paper and Paperboard. Packaging Technology, Blackwell Publishing 2005.

[0006] Containerboard (also known as CCM or corrugated case material) is a type of paperboard especially manufactured for the production of corrugated board. It includes both linerboard and corrugating medium (or fluting), the two types of paper that make up corrugated board. Since containerboard is made mainly out of natural unbleached wood fibers, it is generally brown, although its shade may vary depending on the type of wood, pulping process, recycling rate and impurity content. Containerboard is manufactured in a paper machine comprising a wire section, a press section and a drying section. In conventional paper machines for board manufacturing, there are draws where the web is unsupported (i.e. not in contact with a wire or press felt) at least at some points in the press section. A certain speed difference between the different sections is then required in order to maintain tension of the web and ensure runnability of the machine. The speed difference will typically be at least 4 % between the wire section and the drying section. However, such a speed difference in machine direction (MD) leads to a shrinkage of the web in cross direction (CD) whereby the CD compression strength of the manufactured board is decreased.

[0007] Containerboard comprising a high content of recycled cellulose fiber (RCF) has limited mechanical properties and especially stretchability in the machine direction (MD stretchability) and compression strength in the cross direction (CD compression strength) as compared to board manufactured from virgin fiber. This is partly due to that the RCF has lost part of its mechanical properties as a result of changes in chemical composition, but it is also due to hornification and reduced ability to form hydrogen bonds and fiber-fiber and fibril-fiber bonds. Mechanical properties and particularly MD stretchability and CD compression strength are needed e.g. to avoid cracking during converting.

[0008] In the art, stretchability has previously been improved by:

[0009] - Controlling the jet-to-wire speed ratio whereby the fiber orientation is controlled. However, this may also involve compromising when it comes to tear strength and formation.

[0010] - Using a higher amount of long fibers. However, this may also involve compromising when it comes to fiber floc formation in the pulp suspension and web formation.

[0011] - Adding chemicals to the pulp suspension in the wet end. However, such chemicals may lead to other problems such as problems with drainage or retention. Adding chemicals also adds significant costs, and may be inefficient due to high contents of impurities in the pulp suspensions. There remains a need for new and improved methods for manufacturing containerboard that combine high stretchability, high strength, low cost, and low chemical consumption while allowing for increased machine speeds and source reduction.

[0012] Description of the invention

[0013] It is an object of the present disclosure to provide an improved method for manufacturing containerboard, which solves or ameliorates at least some of the above mentioned problems.

[0014] Specifically, it is an object of the present disclosure to provide an improved method for manufacturing containerboard comprising a high content of recycled cellulose fiber (RCF), which solves or ameliorates at least some of the above mentioned problems.

[0015] The above-mentioned objects, as well as other objects as will be realized by the skilled person in the light of the present disclosure, are achieved by the various aspects of the present disclosure.

[0016] The present disclosure is based on the inventive realization that in the production of containerboard comprising a high amount of recycled cellulose fiber (RCF), it is beneficial to have a very small web speed increase between the wire section and the drying section. This has been found to improve the both the MD stretchability (as determined by ISO 1924-3) and the CD compression strength (CD SCT index as determined by ISO 9895) of the containerboard. It has also been found to improve the burst strength of the containerboard.

[0017] The present disclosure thus relates to a method for manufacturing containerboard from a furnish comprising at least 50 wt% recycled fibers in a paper machine comprising a wire section, a press section and a drying section, wherein the speed of the web (m / min) in the drying section is at most 3.5 % higher than the speed of the web in the wire section. This means that the speed of the web, when the web is in contact with the last drying element in the dryer section is at most 3.5% higher than the speed of the web when it leaves the wire in the wire section. Preferably, the speed of the web in the drying section is at most 2.5 % higher, and more preferably at most 1 .5 % higher, than the speed of the web in the wire section. The speed difference is preferably in the range from > - 0.5 % to < 3.5 %, more preferably from > 0 % to < 2.5 wt% and most preferably from > 0.1 % to < 1 .5 %. To facilitate this low speed increase, the web is preferably supported, e.g. by a wire, by a belt, or by a press felt, throughout the wire section and the press section. Thus, the web is preferably not subjected to any free draws between the wire section and the press section. The term “free draw” as used herein refers generally to a section in the paper machine where the web is unsupported for a distance of 20 cm or more in the machine direction.

[0018] According to a first aspect illustrated herein, there is provided a method for manufacturing containerboard in a paper machine comprising a wire section, a press section, and a drying section, the method comprising the steps of: a) forming a web from at least one pulp suspension comprising at least 50 wt% of recycled cellulose fibers based on dry weight on a wire in the wire section; b) dewatering the formed web layer in the press section; and c) drying the dewatered web layer in the drying section to obtain the containerboard; wherein the web speed in the drying section is at most 3.5 % higher, preferably at most 2.5 % higher, and more preferably at most 1 .5 % higher, than the web speed in the wire section.

[0019] Containerboard is a type of paperboard especially manufactured for the production of corrugated board. The term containerboard includes both linerboard and corrugating medium (or fluting), the two types of paper that make up corrugated board. The containerboard manufactured according to the inventive method may thus be either linerboard or corrugating medium.

[0020] The containerboard is manufactured in a paper machine comprising a wire section, a press section and a drying section. The paper machine is designed to continuously process cellulose based pulp in the form of a pulp suspension into a final containerboard product.

[0021] The paper machine includes a wire section for the initial formation of the cellulose based web from the pulp suspension. The wire section comprises a continuous, permeable wire or mesh through which the pulp suspension is conveyed such that a fibrous web is formed from the pulp. The wire section may further incorporate mechanisms for the removal of excess water, including suction devices and rollers, to facilitate the formation of a uniform and well-structured web. The wire section may also comprise two or more wire sub-sections, wherein the web speed in each wire sub-section can be adjusted individually.

[0022] Subsequent to the wire section, the paper machine comprises a press section for the mechanical dewatering of the web. The press section is designed to enhance the dryness and density of the web. The press section comprises one or more press units or rollers that apply pressure to the web, thereby removing additional moisture. The removed water is typically received by a fabric or felt. The press section may comprise traditional nip press units and / or with one or more shoe press units or extended dewatering nip press units. These units can be run at various nip or press loads, temperatures, and delays times. The nip or press load of the nip or press units is preferably in the range of 450-1800 kN / m. The temperature of the nip or press units is preferably in the range of 35-105 °C. In some embodiments, the temperature of the nip or press units is in the range of 35- 75 °C. In some embodiments, the nip or press units are heated such that the temperature of the nip or press units is in the range of 55-105 °C, preferably in the range of 65-95 °C. By heating the nip or press units, it is possible to further improve the tensile strength and stretchability of the web. The press section may also comprise a series 2-5 press sub-sections, wherein the web speed in each press sub-section can be adjusted individually.

[0023] Following the press section, the paper machine comprises a drying section. The drying section comprises a series of drying elements, such as heated drying cylinders, drying cans, or hot air dryers, which are arranged to progressively dry the web as it passes through the drying section. The drying section may also comprise a series 2-5 drying sub-sections The drying section may further comprise temperature and humidity control systems to optimize the drying process and ensure the web reaches the desired moisture content. Drying may typically reduce the water content of the web down to a level of about 1-15 wt%, preferably to about 2-10 wt%.

[0024] The present invention is based on the inventive realization that in the production of containerboard comprising a high amount of recycled cellulose fiber (RCF), it is beneficial to have a very small web speed increase between the wire section and the drying section.

[0025] The web average web speed in the paper machine is typically at least 300 m / min, such as 350-2150 m / min or 400-1850 m / min. In some embodiments of the inventive method, the web speed in in the wire section is at least 300 m / min, preferably in the range of 350-2150 m / min, and more preferably in the range of 400-1850 m / min. In some embodiments of the inventive method, the web speed in in the drying section is at least 300 m / min, preferably in the range of 350-2150 m / min, and more preferably in the range of 400-1850 m / min. In some embodiments of the inventive method, the web speed is lower. In some embodiments of the inventive method, the web speed in in the drying section is in the range of 350-1200 m / min, and more preferably in the range of 400-1200 m / min. The lower web speed allows for having a low speed increase from the wire section to the drying section without runnability problems caused by low web tension or sagging of the web.

[0026] The web speed in the drying section is at most 3.5 % higher, preferably at most 2.5 % higher, and more preferably at most 1.5 % higher, than the web speed in the wire section. In some embodiments, the web speed in the drying section is at most 2.5 % higher, at most 2 % higher, or at most 1.5 % higher, than the web speed in the wire section. In some embodiments the web speed in the drying section is at least 0.1 % higher, at least 0.3 % higher, at least 0.5 % higher, at least 0.7 % higher, or at least 0.9 % higher, than the web speed in the wire section. In some embodiments it is also possible to have a slightly negative speed difference. Thus, in some embodiments the web speed in the drying section is up to 0.5 % lower, up to 0.3 % lower, or up to 0.1 % lower, than the web speed in the wire section. It is understood that any combination of the listed end-points is encompassed by the present disclosure. In some embodiments, the web speed in the drying section is in the range from 99.5 % to 103.5 %, preferably in the range from 100 % to 102.5 %, and more preferably in the range from 100.1 % to 101.5 %, of the web speed in the wire section. In some embodiments, the web speed in the drying section is in the range from 99.5 % to 102.5 %, preferably in the range from 99.5 % to 102 %, and more preferably in the range from 99.5 % to 101.5 %, of the web speed in the wire section. In some embodiments, the web speed in the drying section is in the range from 100 % to 102.5 %, preferably in the range from 100 % to 102 %, and more preferably in the range from 100 % to 101.5 %, of the web speed in the wire section. In some embodiments, the web speed in the drying section is in the range from 100.1 % to 102.5 %, preferably in the range from 100.1 % to 102 %, and more preferably in the range from 100.1 % to 101.5 %, of the web speed in the wire section. In some embodiments, the web speed in the drying section is in the range from 100.5 % to 102.5 %, preferably in the range from 100.5 % to 102 %, and more preferably in the range from 100.5 % to 101.5 %, of the web speed in the wire section. In some embodiments, the web speed in the drying section is in the range from 101 % to 102.5 %, preferably in the range from 101 % to 102 %, and more preferably in the range from 101 % to 101 .5 %, of the web speed in the wire section.

[0027] In some embodiments, the drying section comprises a series of drying elements and the web speed in the drying section refers to the speed of the last drying element. In some embodiments, the web speed in the drying section refers to the speed of the web where the web leaves the drying section The drying section may also comprise a series 2-5 drying sub-sections, wherein the web speed in each drying sub-section can be adjusted individually.

[0028] The web speed in the wire section refers to the speed of the web where the web leaves the wire in the wire section.

[0029] In preferred embodiments, the web is not subjected to any free draws throughout or between the wire section and the press section. In other words, the web is preferably not unsupported for a distance of 20 cm or more in the machine direction at any point throughout or between the wire section and the press section. This allows for having a low speed increase from the wire section to the drying section without runnability problems caused by low web tension or sagging of the web.

[0030] In some embodiments, the web is supported, for example by a wire, by a belt or by a press felt, between the wire section and the press section.

[0031] The present invention has been identified as especially useful in the manufacturing of containerboard comprising significant amounts of recycled cellulose fibers (RCF). Containerboard comprising a high content of recycled cellulose fiber (RCF) typically has limited mechanical properties and especially MD stretchability and CD compression strength as compared to board manufactured from virgin fiber. Thus, the at least one pulp suspension used for forming the web in step a) of the method comprises at least 50 wt% of recycled cellulose fibers based on dry weight. Examples of recycled cellulose fibers include old corrugated cardboard (OCC), used beverage cartons (UBC), and recycled food service board (FSB), and mixtures thereof. In some embodiments, the at least one pulp suspension comprises at least 60 wt%, preferably at least 70 wt%, and more preferably at least 80 wt%, of recycled cellulose fibers based on dry weight.

[0032] The recycled cellulose fibers preferably have an ash content of less than 15 wt%, preferably less than 10 wt% and more preferably less than 8 wt%, upon combustion at 525 °C or 900 °C in accordance with Tappi standard T211 or T413 respectively. The ash content of the recycled cellulose fibers may be reduced to less than 15 wt%, preferably less than 10 wt% and more preferably less than 8 wt%, by subjecting the recycled cellulose fibers to size fractionation, such as using pressure screens or VarioSplit (Voith GmbH) technology, or cleaning, such as low or high consistency reverse or forward cleaning, prior to their use in the inventive method. Forward cleaning removes contaminants that are heavier or more dense than the cellulose fibers. Reverse cleaning removes contaminants that are less dense or lighter than the cellulose fibers. The recycled cellulose fibers may further be treated by for example sterilization, delignification or oxidation. The recycled cellulose fibers may be dried or neverdried. Neverdried as used in this context means that the recycled cellulose fibers have not been dried after being recycled and optionally fractionated or cleaned. The term "dried” in this context means that the recycled material has been subjected to dewatering and drying to a moisture content of less than 10 wt%. In preferred embodiments the recycled cellulose fibers are neverdried.

[0033] In some embodiments, the web is formed by applying the at least one pulp suspension onto the wire from a headbox. The function of the headbox is to dose and distribute the pulp suspension uniformly across the width of the wire. In the headbox, the pulp suspension pumped in a pipe is converted to a uniform rectangular flow with the same flow direction and essentially the same flow rate across the width of the wire. The headbox typically consists of a manifold distributor, which converts the pipe flow into a rectangular flow through a slice opening with same velocity, quantity and jet thickness across the width of the wire.

[0034] In some embodiments, the web is a multilayer web formed by applying at least two pulp suspensions onto the wire using a multilayer headbox. A pulp suspension comprising at least 50 wt% of recycled cellulose fibers based on dry weight is used for forming at least one layer of the multilayer web.

[0035] In some embodiments, the web is a multilayer web formed by applying at least three pulp suspensions onto the wire using a multilayer headbox. A pulp suspension comprising at least 50 wt% of recycled cellulose fibers based on dry weight is used for forming at least one layer of the multilayer web. Preferably a pulp suspension comprising at least 50 wt% of recycled cellulose fibers based on dry weight is used for forming at least a mid-layer of the multilayer web.

[0036] In some embodiments, the recycled cellulose fibers have a water retention value (WRV) in the range of 80-200 %, preferably in the range of 120-160 %, as determined by standard ISO 23714:2014. In some embodiments the water retention value of the recycled cellulose fibers is low. In some embodiments, the recycled cellulose fibers have a water retention value (WRV) in the range of 80- 160 %, preferably in the range of 100-160 %, as determined by standard ISO 23714:2014. In some embodiments, the recycled cellulose fibers have a water retention value (WRV) in the range of 80-140 %, preferably in the range of 100- 140 %, as determined by standard ISO 23714:2014. A low WRV allows for rapid dewatering and may lead to a relatively low water content in the web formed in the wire section. This in turn allows for having a low speed increase from the wire section to the drying section without runnability problems caused by low web tension or sagging of the web.

[0037] In some embodiments, the at least one pulp suspension has a water retention value (WRV) in the range of 80-200 %, preferably in the range of 120-160 %, as determined by standard ISO 23714:2014. In some embodiments the water retention value of the at least one pulp suspension is low. In some embodiments, the at least one pulp suspension has a water retention value (WRV) in the range of 80-160 %, preferably in the range of 100-160 %, as determined by standard ISO 23714:2014. In some embodiments, the at least one pulp suspension has a water retention value (WRV) in the range of 80-140 %, preferably in the range of 100- 140 %, as determined by standard ISO 23714:2014. A low WRV allows for rapid dewatering and may lead to a relatively low water content in the web formed in the wire section. This in turn allows for having a low speed increase from the wire section to the drying section without runnability problems caused by low web tension or sagging of the web.

[0038] In some embodiments, the at least one pulp suspension further comprises 0.1 - 10 wt%, preferably 0.5 - 10 wt%, and more preferably 1 - 5 wt%, of highly refined cellulose or m icrofi brillated cellulose (MFC) based on dry weight. The highly refined cellulose or microfibrillated cellulose (MFC) may be obtained from recycled cellulose fibers, for example recycled cellulose fibers from used beverage cartons (UBC) or recycled food service board (FSB).

[0039] In some embodiments, wherein the at least one pulp suspension further comprises highly refined cellulose or microfibrillated cellulose (MFC), the at least one pulp suspension has a water retention value (WRV) in the range of 120-200 % as determined by standard ISO 23714:2014. In some embodiments, wherein the at least one pulp suspension further comprises highly refined cellulose or microfibri Hated cellulose (MFC), the water retention value of the at least one pulp suspension is low. In some embodiments, wherein the at least one pulp suspension further comprises highly refined cellulose or microfibrillated cellulose (MFC), the at least one pulp suspension has a water retention value (WRV) in the range of 100-160 %, preferably in the range of 120-160 %, as determined by standard ISO 23714:2014. In some embodiments, wherein the at least one pulp suspension further comprises highly refined cellulose or microfibrillated cellulose (MFC), the at least one pulp suspension has a water retention value (WRV) in the range of 100-140 %, preferably in the range of 120-140 %, as determined by standard ISO 23714:2014. A low WRV allows for rapid dewatering and may lead to a relatively low water content in the web formed in the wire section. This in turn allows for having a low speed increase from the wire section to the drying section without runnability problems caused by low web tension or sagging of the web.

[0040] In some embodiments, an interfacial layer comprising an additive, for example a strength enhancement agent or fines or reject obtained in a size fractionation or cleaning process, is formed at the interface between at least two adjacent layers of a multilayer web. In some embodiments, the interfacial layer is applied using a separate water layer between the first and second outer ply using a multiply headbox. Applying additives in a water layer using a multiply headbox is well known to the skilled person.

[0041] In some embodiments, the interfacial layer comprises a strength enhancement agent. The strength enhancement agent may for example comprise a polysaccharide or a combination of polysaccharides, such as starch, cellulose or derivatives thereof, hemicellulose, or natural gums, such as guar gum or alginate. The polysaccharide or combination of polysaccharides may also comprise highly refined cellulose, microfibrillated cellulose (MFC), or nanocrystalline cellulose (NCC). The strength enhancement agent is preferably selected form the group consisting of a starch based strength enhancement agent, a cellulose based strength enhancement agent, and mixtures thereof. In some embodiments, the strength enhancement agent is a cellulose based strength enhancement agent. The cellulose based strength enhancement agent preferably comprises, or consists of, a fine cellulosic material such as highly refined cellulose or microfibri Hated cellulose.

[0042] A paper machine variable that can affect formation of the web is the jet-to-wire speed ratio, i.e. the ratio between the jet speed of the pulp suspension as it leaves the headbox and the wire speed. Jet-to-wire speed ratio is applicable to all paper machines where a headbox is used to apply the pulp suspension to a wire. Although it is preferred that the jet speed is the same across the width of the wire, minor variations in jet speed may occur. Jet speed discussed herein thus refers to the average jet speed across the width of the wire. Jet speed can be calculated based on headbox parameters (e.g. pressure and slice opening dimensions), or measured using measuring techniques known in the art.

[0043] If the jet-to-wire speed ratio is 1 the speed of the pulp suspension matches the speed of the wire and there is relatively little shear imposed on the suspension. Typically, in conventional papermaking, a jet-to-wire speed ratio above 1 is preferred because this has been found to provide improved edge profile and mechanical properties such as tensile stiffness index and elastic modulus ratio.

[0044] It is known that by controlling the jet-to-wire speed ratio, the fiber orientation of the web can be controlled. However, the effect of the fiber orientation alone on the MD stretchability of the obtained containerboard is typically low. The fiber orientation may be expressed as tensile stiffness index ratio, and the lowest tensile stiffness index ratio is typically obtained when the jet-to-wire-ratio is close to 1. The present inventors have found that the improvement of the MD stretchability of the obtained containerboard is especially high when the low web speed increase is also combined with a jet-to-wire speed ratio in the range of 0.88-1.15. Thus, in some embodiments, web in step a) of the method is formed with a jet-to-wire speed ratio in the range of 0.88-1.15, preferably in the range of 0.9-1.10. In some embodiments the speed difference between the jet and the wire is less than 40 m / min, and preferably less than 30 m / min. In some embodiments, the tensile stiffness index ratio of the obtained containerboard is below 2.7, preferably below 2.5, and more preferably below 2.2 or below 1.8, as determined by ISO 1924-3. In some embodiments, the obtained containerboard has a grammage in the range of 80-300 g / m2, preferably in the range of 90-260 g / m2.

[0045] In some embodiments, the obtained containerboard has a stretchability in the machine direction (MD) of at least 1 .5 %, preferably at least 3 %, and more preferably at least 5 % as determined by ISO 1924-3.

[0046] In some embodiments, the obtained containerboard has a stretchability in the cross direction (CD) of at least 2 %, preferably at least 3 %, and more preferably at least 4 % as determined by ISO 1924-3.

[0047] In some embodiments, the obtained containerboard has a compression strength in the cross direction (CD) of at least 12 Nm / g, preferably at least 15 Nm / g, and more preferably at least 18 Nm / g as determined by ISO 9895. The compression strength in the cross direction (CD) is also referred to as SCT index CD.

[0048] In some embodiments, the method comprises measuring at least one value characterizing the pulp suspension, the web, or the obtained paperboard, in-line in the paper machine, and adjusting at least one machine parameter based on the measured value. For example, a high drying shrinkage in the cross direction may cause reduced CD compression strength. Therefore, a balance between drying shrinkage and CD compression strength should be maintained. Thus in some embodiments, the drying shrinkage of the web in the cross direction, is be measured, and one or more of the following machine parameters is adjusted in order to maintain the drying shrinkage within a suitable range:

[0049] - Increasing or decreasing the refining of the pulp (higher refining typically leads to higher drying shrinkage).

[0050] - Increasing or decreasing the jet-to-wire speed ratio to modify the fiber orientation in the web (higher fiber orientation typically leads to higher drying shrinkage).

[0051] - Increasing or decreasing the tension of the dryer fabrics in the drying section (higher dryer fabric tension typically leads to lower drying shrinkage). 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.

Claims

CLAIMS1. A method for manufacturing containerboard in a paper machine comprising a wire section, a press section, and a drying section, the method comprising the steps of: a) forming a web from at least one pulp suspension comprising at least 50 wt% of recycled cellulose fibers based on dry weight on a wire in the wire section; b) dewatering the formed web layer in the press section; and c) drying the dewatered web layer in the drying section to obtain the containerboard; wherein the web speed in the drying section is at most 3.5 % higher, preferably at most 2.5 % higher, and more preferably at most 1 .5 % higher, than the web speed in the wire section.

2. The method according to claim 1 , wherein the web speed in the drying section is in the range from 99.5 % to 103.5 %, preferably in the range from 100 % to 102.5 %, and more preferably in the range from 100.1 % to 101.5 %, of the web speed in the wire section.

3. The method according to any one of the preceding claims, wherein the drying section comprises a series of drying elements and the web speed in the drying section refers to the speed of the last drying element.

4. The method according to any one of the preceding claims, wherein the web speed in the wire section refers to the speed of the web where the web leaves the wire.

5. The method according to any one of the preceding claims, wherein the web is not subjected to any free draws throughout or between the wire section and the press section.

6. The method according to any one of the preceding claims, wherein the web is supported, for example by a wire, by a belt, or by a press felt, between the wire section and the press section.

7. The method according to any one of the preceding claims, wherein the at least one pulp suspension comprises at least 60 wt%, preferably at least 70 wt%, and more preferably at least 80 wt%, of recycled cellulose fibers based on dry weight.

8. The method according to any one of the preceding claims, wherein the web is formed by applying at least one pulp suspension onto the wire from a headbox.

9. The method according to any one of the preceding claims, wherein the web is a multilayer web formed by applying at least two pulp suspensions onto the wire using a multilayer headbox.

10. The method according to any one of the preceding claims, wherein the recycled cellulose fibers have a water retention value (WRV) in the range of 80- 200 %, preferably in the range of 120-160 %, as determined by standard ISO 23714:2014.

11. The method according to any one of the preceding claims, wherein the at least one pulp suspension comprises 0.1 - 10 wt%, preferably 0.5 - 10 wt%, and more preferably 1 - 5 wt%, of highly refined cellulose or microfibrillated cellulose (MFC) based on dry weight.

12. The method according to claim 11 , wherein the at least one pulp suspension has a water retention value (WRV) in the range of 120-200 % as determined by standard ISO 23714:2014.

13. The method according to any one of the preceding claims, wherein the obtained containerboard has a grammage in the range of 80-300 g / m2, preferably in the range of 90-260 g / m2.

14. The method according to any one of the preceding claims, wherein the obtained containerboard has a stretchability in the machine direction (MD) of at least 1.5 %, preferably at least 3 %, and more preferably at least 5 % as determined by ISO 1924-3.

15. The method according to any one of the preceding claims, wherein the obtained containerboard has a stretchability in the cross direction (CD) of at least 2 %, preferably at least 3 %, and more preferably at least 4 % as determined by ISO 1924-3.

16. The method according to any one of the preceding claims, wherein the obtained containerboard has a compression strength in the cross direction (CD) of at least 12 Nm / g, preferably at least 15 Nm / g, and more preferably at least 18 Nm / g as determined by ISO 9895.

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