WO2025008746A1

WO2025008746A1 - A method for manufacturing a multi-ply paperboard

Info

Publication number: WO2025008746A1
Application number: PCT/IB2024/056456
Authority: WO
Inventors: Kaj Backfolk; Anders Moberg
Original assignee: Stora Enso Oyj
Current assignee: Stora Enso Oyj
Priority date: 2023-07-05
Filing date: 2024-07-02
Publication date: 2025-01-09
Anticipated expiration: 2026-01-05
Also published as: SE2330311A1; SE546839C2

Abstract

The invention discloses a method for manufacturing a multiply paperboard comprising the steps of: - forming a web comprising at least a top ply, a back ply, and a middle ply arranged between the top ply and the back ply, wherein the middle ply is formed from a first furnish comprising at least 50 wt% of a HT-CTMP and 0.1 – 10 wt% of glue pulp based on the total dry weight of said first furnish, wherein said glue pulp has a Schopper Riegler (SR) value in the range of 55- 84 as measured according to standard ISO 5267-1 and a mass fraction of fines of less than 25% as measured according to standard ISO 10376:2011, - subjecting the thereof formed three-ply web to pressing in at least one shoe press, and - drying the web. It has been found that the combination of using the said furnish mixture including HT-CTMP and glue pulp with an SR value within said range enables efficient dewatering by use of a shoe press and gives rise to a paperboard with high bulk but maintained or improved strength properties.

Description

A METHOD FOR MANUFACTURING A MULTI-PLY PAPERBOARD

Technical field

The present disclosure relates to a method for manufacturing a multiply paperboard.

Background

Paperboard intended for conversion into packages using fast-running automatic machines must possess the requisite strength to withstand the strain and stress associated with converting processes. Additionally, it must exhibit high bending resistance, not only to facilitate smooth converting operations but also to ensure optimal package performance. For products with extended shelf life, the package must also possess excellent barrier properties against light, oxygen, and moisture.

The bulk of paperboard (inverse of density) is a significant property contributing to its thickness. Increased thickness enhances the bending stiffness of the board and enables the papermaker to reduce the amount of fibers used, resulting in cost savings. However, higher bulk often leads to a decrease in internal strength. One of the challenges faced by papermakers is to increase the bulk of the paperboard while maintaining its strength and to ensure for the convertability (folding and creasing) of the paperboard.

Typically, paperboard consists of 1-5 plies (layers). Paperboard intended for conversion usually comprises multiple plies, exhibiting higher bending resistance index compared to single-ply paperboard. Multi-ply paperboard generally consists of top and back plies, along with one or more middle plies. The middle plies provide bulk to the paperboard. Optionally, one or several layers of bonding agents are added between the plies to improve ply bond strength

To provide strength and excellent printing properties, chemical pulp is commonly used in the top and back plies of the board. The middle ply may contain both mechanical pulp and/or chemical pulp. Mechanical pulp or semimechanical pulp, such as bleached or unbleached CTMP (chemi-thermomechanical pulp), is oftentimes preferred due to its lower cost compared to chemical pulp and its bulk inducing properties. Mechanical or semi-mechanical pulp also offers higher raw material efficiency and yield. Softwood CTMP is frequently employed in the middle ply or bulk layer in high-quality boards, as it provides high bulk and comprises a low content of shives. Chemical pulp is typically used in conjunction with mechanical pulp in the middle ply to enhance strength.

In recent years, high-temperature chemi-thermomechanical pulp (HT-CTMP) has been preferred in certain applications when forming the bulk layer. HT-CTMP refers to CTMP that has undergone pre-heating before the refining step in the manufacturing process, resulting in a pulp with a higher opacity and/or higher content of longer fibers, which further improves the bulk and the stiffness of a paperboard made thereof. In addition, less refining energy is needed. On the other hand, a higher content of longer fibers or bulky fibers may affect formation and the flocculation behavior of the fibers negatively. Moreover, high yield pulp based on for example CTMP and HT-CTMP will require dry strength bonding agents, especially when targeting higher bulk.

Dry bond strength can be improved with natural polysaccharides such as starch as well as synthetic polymers. Recently, nanocellulose or fine microfibrillated cellulose has been used to improve strength properties such as tensile strength, burst strength and compression strength of the paperboard.

Unfortunately, many of the available strength enhancing additives increases the density of the paperboard, which in turn may impact e.g. stiffness and mechanical behavior. Moreover, the use of a high content of water soluble polysaccharides or/and nanocellulose increases the risk of low (self-) retention and may further consume a higher content of retention and drainage aids. It is a challenge to improve the retention of strength chemicals when using a high content of nanocellulose.

The patent publication WO15087293 discloses a paperboard comprising HT- CTMP and strength additives, such as MFC and starch. The addition of MFC to paperboard may however increase the density of the paperboard, whereby the bulk is reduced. To control sheet density and especially the density profile (z- direction) and to increase or maintain high bulk, it is common to optimize dewatering and wet pressing by using extended nips, such as shoe-presses, in the pressing section in combination with low nip loads. However, the utilization of shoe presses for preserving bulk in MFC-containing paperboard poses challenges due to the difficulty in dewatering the board effectively, resulting in the requirement of high nip loads. This might lead to uneven (z-)distribution of strength additives, which may result in delamination, reduced strength and problems with dimensional stability.

There thus remains a need for a method for manufacturing a paperboard with high bulk and yet excellent strength properties, which method further enables high retention and an even distribution of strength chemicals.

Description of the invention

It is an object of the present invention to provide a method for manufacturing a paperboard with a high bulk while maintaining excellent strength properties.

Another object of the present invention is to provide a method for manufacturing paperboard that is energy-efficient and yields high-quality paperboard with exceptional strength properties.

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.

According to a first aspect illustrated herein, there is provided a method for manufacturing a multiply paperboard comprising the steps of:

- forming a web comprising at least a top ply, a back ply, and a middle ply arranged between the top ply and the back ply, wherein the middle ply is formed from a first furnish comprising at least 50 wt% of a HT-CTMP and 0.1 - 10 wt% of glue pulp based on the total dry weight of said first furnish, wherein said glue pulp has a Schopper Riegler (SR) value in the range of 55- 84 as measured according to standard ISO 5267-1 and a mass fraction of fines of less than 25%, more preferably less than 20 and most preferably less than 10 % as measured according to standard ISO 10376:2011

- subjecting the thereof formed three-ply web to pressing in at least one shoe press, and

- drying the web.

It has been found that utilizing the aforementioned furnish mixture, which includes HT-CTMP, along with glue pulp having an SR value within the specified range and such low mass fraction of fines, enables efficient formation and/or dewatering using a shoe press and results in a paperboard with enhanced bulk while maintaining or improving its strength properties. Moreover, the inventive method has shown to improve the retention of strength additives and result in a more even distribution of the strength additives in the z-direction of the middle ply. It further enables a higher content of HT-CTMP in the middle ply of the paperboard, although HT-CTMP comprises quite bulk and/or long fibers, without affecting the formation and dimensional stability negatively.

The term “mass fraction of fines” refers to the total mass fraction of fines in the glue pulp, as defined in the standard ISO 10376:2011. As defined in the standard, fines refer to a fraction of the pulp which passes a screen with a nominal aperature of 76 pm or a perforated plate with holes of 76 pm.

The term “high-temperature chemi-thermomechanical pulp (HT-CTMP)” as used herein refers to pulp that has been pre-heated to a temperature of at least 140 °C, preferably of at least 150 °C, or even more preferably of at least 160 °C prior to the refining step. The HT-CTMP may be produced from hardwood or softwood or a combination thereof. The HT-CTMP can be bleached or unbleached or delignified pulp. Preferably, the fibers of the HT-CTMP have a length-weighted mean fiber length of at least 0.7 mm and more preferably of at least 0.8 mm, such as between 0.7 - 2.5 mm or between 0.8 - 2.5 mm, as measured according to standard ISO 16065-2 and/or a mass fraction of fines of less than 15%, more preferably less than 10% and most preferably less than 8% as measured according to standard ISO 10376:2011. The freeness (CSF) of the HT-CTMP pulp is preferably at least 550 ml, more preferably at least 600 and most preferably at least 650 ml as measured according to standard ISO 5367-2. The HT-CTMP pulp may be made from hardwood or softwood but is preferably made from birch. The HT-CTMP may further be made from a mixture of hardwood and softwood, such as birch-HT- CTMP and spruce HT-CTMP, preferably with a ratio birch:spruce of 100:0 to 50:50, such as 90:10, 80:20, 70:30 and/or 60:40. Preferably, the HT-CTMP has a shape factor of at least 80%, more preferably at least 85% and most preferably at least 88%. The shape factor defines the straightness of the fibers is defined as the maximum extension length of the fiber (projected length) divided by the true length of the fiber (along the fiber contour). The shape factor can be calculated according to the formula S = 10Oxl/L, wherein I = the projected length and L = the true length. In the manufacturing of the HT-CTMP, the fibers have preferably been subjected to gentle refining, preferably by high-consistency (HC) refining, and optionally to treatment in at least one latency chest. The fibers may further have been subjected to at least one washing step. In this way, the shape factor, the permeability and the bulk of the pulp are improved.

The first furnish comprises at least 50 wt% of HT-CTMP. Preferably, the first furnish comprises HT-CTMP in the range of 50 - 99.1 wt%, more preferably in the range of 60 - 90 wt%, or in the range of 70 - 85 wt%, and glue pulp in the range of 0.1 - 10 wt%, preferably in the range of 0.1 - 5 wt%. The remaining pulp in the first furnish may be kraft pulp, preferably bleached or unbleached kraft pulp from hardwood, and preferably originating from broke.

Paperboard generally refers to strong, thick paper or cardboard comprising cellulose fibers used for boxes and other types of packaging. Typically, uncoated paperboard has a grammage of between 150 - 400 gsm, preferably 180 - 400 gsm, or 200 - 350 gsm and a density of between 500 - 900 kg/m³ , preferably 600 - 850 kg/m³. The process of the invention is particularly advantageous for the production of Folding Boxboard (FBB) used for e.g. food packaging applications such as cereal boxes, frozen food packaging and confectionery boxes, or for the production of Solid Bleached Sulphate board (SBS) used for e.g. packaging of premium food items, cosmetics and pharmaceutical products. Other suitable enduses include Clay Coated News Back (CCNB), which is a recycled paperboard coated with a layer of clay on the top side and often has a grey or brown backside and is used for e.g. food packaging boxes, takeout containers and retail packaging and greaseproof paperboard, which has a special treatment that provides resistance to grease and oil used for packaging of fatty and greasy food items like bakery products, fast food and fried snacks.

In embodiments, the first furnish further comprises a strength additive selected from the group consisting of cationic starch, anionic polymers, microfibril lated cellulose (MFC), polyvinylamine, chitosan, primary and secondary amines, polyethylene amines and modified polyacrylamides and combinations thereof. The first furnish may comprise such additional strength additives in an amount of 1 - 5 % dry weight. The anionic polymer may be e.g. carboxymethyl cellulose (CMC) and/or anionic polyacrylamide (A-PAM). In embodiments, the first furnish comprises less than 3 wt%, preferably less than 2 wt% or less than 1.5 wt% of MFC, such as in the range of 0.1 - 3 wt%, or 0.1 - 2 wt% or 0.1 - 1.5 wt% of MFC, based on the dry weight of the first furnish.

Microfibrillated cellulose (MFC) shall in the context of this patent application mean a cellulose particle, fiber or fibril having a width or diameter of from 20 nm to 1000 nm.

In embodiments, the first furnish comprises an anionic strength additive and a cationic strength additive. The anionic additive is preferably an anionic polysaccharide selected from nanocrystalline cellulose, MFC, CMC, anionic starch, alginate, and hemicellulose, whereas the catanionic additive is preferably a cationic polysaccharide, such as cationic starch.

Most preferable, the cationic starch is a high Mw starch made from potato or a crosslinked or branched starch comprising a high content of amylopectin. The starch may also be an amphoteric starch. The invention allows for a low amount of starch dosing, such as 0.1 - 3 wt%, or preferably 0.1 - 2 wt% since the retention of starch is improved.

The first furnish may further comprise internal sizing agents, preferably chosen from the group of alkyl ketene dimer (AKD), alkyl succinic anhydride (ASA), styrene acrylate or styrene maleic anhydride, waxes, and rosin resin, or a combination thereof, preferably added to the first furnish in an amount of in the range of 0.02 - 1.5 wt%, or preferably in an amount in the range of 0.1 - 0.5 wt%. When internal sizing agents are used in combination with glue pulp as an additive, the internal sizing agents are retained on the surface of the glue pulp, whereby the retention of the sizing agents is improved. In this way, less amount of sizing agents may be added to the furnish. In embodiments, the first furnish is formed by adding glue pulp and at least part of the internal sizing agents as a pre-mixture to a furnish comprising HT-CTMP. When at least a part of the surface sizing agents is added as a pre-mixture with the glue pulp the retention of the surface sizing agents is further improved.

In embodiments, the first furnish is formed by adding a pre-mixture of glue pulp and CMC having a degree of substitution of less than 0.4, preferably of less than 0.3, and most preferably of between 0.05 - 0.28, to a furnish comprising HT- CTMP. Such a CMC quality stabilize the glue pulp, but has lower solubility in water whereby the retention of glue pulp is enhanced. Moreover, this has also a positive effect on the formation of the produced paperboard.

In embodiments, the first furnish is formed by adding a pre-mixture of glue pulp and CMC having an ash content of higher than 1wt%, preferably higher than 5 wt%, most preferably higher than 10 wt%, such as in the range of 1 - 60 wt%, or 5 - 60 wt% or 10 - 40 wt%. In this way, the affinity of CMC to the fiber is improved. The term “ash” as used herein refers to inorganic material, for example added electrolytes and residuals from the CMC manufacturing process.

The glue pulp, having the claimed SR value and mass fraction of fines, may be produced by fibrillating cellulose containing pulp, preferably softwood pulp and most preferably never dried softwood kraft pulp. The fibrillation can be accomplished in one or several steps. In embodiments, the glue pulp may be fractionized prior to or after a fibrillation step. In other embodiments, the glue pulp is subjected to refining to exhibit the claimed SR value and mass fraction of fines. In these embodiments, the refining step is optimized to achieve the desired properties and the glue pulp is not fractionated. Preferably, the glue pulp comprises at least 50 wt%, or 80 wt% or 90 wt% or 95 wt% of fibrillated cellulose fibers as calculated on the total dry weight of the glue pulp. In embodiments, the SR value of the glue pulp is between 55 - 80, preferably between 55 - 75 and most preferably between 55 - 60. In embodiments, the glue pulp has a mean fibril area of fibers having a length of at least 0.2 mm (ISO 16065-2) of at least 10%, preferably of at least 15, and more preferably at least 20%, such as 20-60%. The term “mean fibril area” as used herein refers to the length weighted mean fibril are and can be determined using a Fiber Test + (plus) device.

In embodiments, the glue pulp is fibrillated broke. The broke may comprise surface sized broke, preferably uncoated broke. Uncoated broke as used herein refers to broke that is substantially free from pigments or fillers, such that the amount of pigments or fillers is less than 10 wt%, preferably less than 5 wt% or less than 1wt%. The use of surface-sized broke improves the fibrillation and enhances the glue effect. In embodiments, the fibrillated broke is manufactured by fibrillating broke in the presence of MFC, CMC and/or starch. Preferably, the fibrillated broke is manufactured by fibrillating broke in the presence of CMC, wherein the CMC has a degree of substitution of less than 0.4, preferably of less than 0.3, and most preferably of between 0.05 - 0.28. In embodiments, the broke comprises at least 10 wt% HT-CTMP.

The uncoated broke is optionally subjected to an activation step before the fibrillation step. Such an activation step is preferably selected from oxidation (e.g. using hydrogen peroxide, peracetic acid, NaOH, hypochlorite, potassium permanganate), ozone - or oxygen treatment, treatment with electrolysed water or with pulsed corona discharge. Without wishing to be bound to any theory, it is believed that such a deactivation step can effectively decrease microbial activity in the pulp. This, in turn, helps prevent or minimize microbial degradation of polysaccharides and fines, resulting in lower levels of COD and BOD levels in the wet end. Moreover, the activation treatment further reduces the required refining energy levels to make glue pulp, enhances the runnability and improves the dispersability of the glue pulp. The paperboard may comprise further bulk providing middle plies, such as a first and a second middle ply or a first, a second and a third middle ply. Such additional middle plies may be formed from the first furnish.

In embodiments, the top ply is formed from a second furnish comprising 80 - 100 wt% of hardwood kraft pulp, preferably bleached hardwood kraft pulp, based on the total dry weight of said second furnish. Such a composition of the top ply improves the formation, surface smoothness and the print quality of the paperboard. In embodiments, the second furnish comprises 80 - 99.9 wt% of hardwood kraft pulp and 0.1 - 10 wt%, preferably 0.1 - 8 wt% and most preferably 0.1 - 5 wt% of glue pulp having a Schopper Riegler (SR) value in the range of 55 - 84, preferably 55 - 80 or 55 - 60, as measured according to standard ISO 5267- 1, based on the total dry weight of said second furnish. The remaining pulp may be e.g. softwood kraft pulp. The said glue pulp may preferably be fibrillated broke and most preferably surface sized fibrillated broke. The surface sizing agents, such as starch, may improve the fibrillation process and stabilize the gel formed.

In embodiments, the back ply is formed from a third furnish comprising 80 - 100 wt% of unbleached kraft pulp from hardwood based on the total dry weight of said third furnish.

In embodiments, at least one of the top-, middle- and back ply is formed by foam forming. Foam forming further improves the bulk of the thereof formed paperboard.

The top ply, middle ply and back ply may be formed by use of a multi-layer headbox. The method may further comprise forming a central layer in-between the top ply and the middle ply or in-between the middle ply and the back ply, using the multi-layer headbox. The multi-layer headbox preferably includes separate guide devices, such as guiding tubes, for guiding the furnishes and an aqueous composition forming the central layer to a nozzle, from which the furnishes and the central layer composition emerge via a gap onto a forming wire. The central layer composition may comprise at least 80 wt% glue pulp having an SR in the range of the range of 55- 84, preferably in the range of 55 - 80 or 55 - 60, as measured according to standard ISO 5267-1 and as calculated on the total dry weight of the central layer composition. The central layer composition is preferably an aqueous suspension of the glue pulp and optional additives and has preferably a solid content of 10 - 50 wt%.

In alternative embodiments, the top ply, middle ply and back ply may be formed as separate webs on separate wires, wherein the method includes the step of coaching said webs to form the multi-ply web. In the embodiment wherein the paperboard comprises more than one middle ply, the middle plies may be formed by use of a multilayer headbox.

The web comprising the top-, middle- and back ply may be dewatered on a dewatering wire by use of a sleeve roll prior to the step of pressing the web. The sleeve roll may be curved to change the wrap angle of the dewatering wire on the sleeve roll, thereby increasing the dewatering capacity. It has been found that the furnish mixture of the invention facilitates the use of such a sleeve roll in the dewatering without causing problems with two-sidedness. Two-sidedness of paperboard may induce problems with curl, formation, uneven distribution of fines, delamination at the converting of the paperboard etc.

The multilayer web is preferably subjected to pressing in at least a first and a second shoe press. The invention enables higher line loads in the shoe presses compared to using MFC as a strength additive, while preserving the bulk. In embodiments, the line load of the first and the second shoe press is between 200 - 1100 kN/m, preferably in the range of 200 - 800 kN/m. The line load of the first shoe press may e.g. be between 200 - 450 kN/m and the line load of the second shoe press may be between 600 - 800 kN/m. In embodiments, the web is subjected to pressing in a first, a second and a third shoe press nip. In these embodiments, the the line load of the first shoe press may e.g. be in the range of 500 - 800 kN/m and the line load of the second shoe press may e.g. be in the range of 700 kN/m - 1500 kN/M, preferably in the range of 800 - 1200 kN/m, and the line load of the third shoe press nip may e.g. be in the range of 600 - 1500 kN/m, preferably in the range of 700 - 1200 kN/m. The use of the claimed furnish mixture in the middle ply reduces the risk of migration of the strength additives at the pressing of the paperboard. Migration of strength additives may cause undesired two-sidedness. The web speed in the press section is preferably between 450 - 1200 m/min, more preferably around 800 - 1000 m/min. In embodiments, the at least one shoe press forms a shoe press nip and the temperature of the web in the shoe press nip is in the range of 20 - 75 °C, preferably in the range of 35 - 75 °C and most preferably in the range of 40 - 75 °C. It has been found that the addition of glue pulp to the furnish in accordance with the invention enhances the positive influence of temperature on water removal.

In embodiments, the method further comprises the step of reeling the web (after the step of drying the web) on a reel spool to form a paperboard roll, wherein the paperboard roll is loaded with two rider rolls during the reeling. In this way, the bulk is maintained, and issues related to two-sidedness is reduced.

The paperboard manufactured by the method of the invention preferably exhibits a Scott Bond of at least 180 J/m², or preferably at least 200 J/m² or at least 220 J/m² as measured according to standard TAPPI 569 and/or a tensile stiffness index (GM) of at least 5 kNm/g, or preferably at least 6 kNm/g or at least 10 kNm/g, as measured according to standard ISO 1924-3, and/or a thickness of between 250 and 800 pm, and/or a PTS recyclability of the base board defining a reject level of less than 10%, or less than 5% according to PTS RH 021/97 test method for Category II . In one embodiment, the paperboard manufactured by the method of the invention exhibit a taint value of less than 0.5 according to the Robinson chocolate test as measured using standard EN 1230-2-2009, the multicomparison test.

In view of the above detailed description of the present invention, other modifications and variations will become apparent to those skilled in the art. However, it should be apparent that such other modifications and variations may be effected without departing from the spirit and scope of the invention.

Claims

1. A method for manufacturing a multiply paperboard comprising the steps of:

- forming a web comprising at least a top ply, a back ply, and a middle ply arranged between the top ply and the back ply, wherein the middle ply is formed from a first furnish comprising at least 50 wt% of a HT-CTMP and 0.1 - 10 wt% of glue pulp based on the total dry weight of said first furnish, wherein said glue pulp has a Schopper Riegler (SR) value in the range of 55 - 84 as measured according to standard ISO 5267-1 and a mass fraction of fines of less than 25% as measured according to standard ISO 10376:2011 ,

- drying the web.

2. A method according to claim 1 , wherein the first furnish further comprises a strength additive selected from the group consisting of cationic starch, anionic polymers, microfibrillated cellulose, polyvinylamine, chitosan, primary and secondary amines, polyethylene amines and modified polyacrylamides and combinations thereof.

3. A method according to anyone of the preceding claims, wherein the HT- CTMP has a freeness (CSF) of at least 600 ml, preferably at least 650 ml, as measured according to ISO 5367-2.

4. A method according to anyone of the preceding claims, wherein the first furnish further comprises internal sizing agents, preferably chosen from the group of alkyl ketene dimer (AKD), alkyl succinic anhydride (ASA) and rosin resin, or a combination thereof.

5. A method according to claim 4, wherein the first furnish is formed by adding a pre-mixture of glue pulp and internal sizing agents to a cellulose containing furnish comprising HT-CTMP.

6. A method according to any one of the preceding claims, wherein the first furnish is formed by adding a pre-mixture of glue pulp and CMC having a degree of substitution of less than 0.4 to a cellulose containing furnish comprising HT-CTMP.

7. A method according to anyone of the preceding claims, wherein the SR value of the glue pulp is between 55 - 75, as measured according to standard ISO 5267-1.

8. A method according to anyone of the preceding claims, wherein the SR value of the glue pulp is between 55 - 60, as measured according to standard ISO 5267-1.

9. A method according to anyone of the preceding claims, wherein the glue pulp is fibrillated broke.

10. A method according to claim 9, wherein the broke at least partly comprises surface sized broke.

11 . A method according to anyone of the preceding claims, wherein the top ply is formed from a second furnish comprising 80 - 100 wt% of hardwood kraft pulp, preferably bleached hardwood kraft pulp, based on the total dry weight of said second furnish.

12. A method according to anyone of the preceding claims, wherein the back ply is formed from a third furnish comprising 80 - 100 wt% of unbleached kraft pulp from hardwood based on the total dry weight of said third furnish.

13. A method according to anyone of the preceding claims, wherein web comprising the top-ply, the middle-ply, and the back-ply is formed by use of a multi-layer headbox and the method further comprises applying a central layer in-between the top ply and the middle ply or in-between the middle ply and the back ply using the multilayer headbox, and wherein the central layer is formed from an aqueous suspension comprising 80 wt% of glue pulp having an SR in the range of 55 - 84, as measured according to standard ISO 5267-1 and based on the total dry weight of the aqueous suspension.

14. A method according to anyone of the preceding claims, wherein the at least one shoe press forms a shoe press nip and wherein the temperature of the web in the shoe press nip is in the range of 20 - 75 °C, preferably in the range of 35 - 75 °C and most preferably in the range of 40 - 75 °C.

15. A method according to anyone of the preceding claims, further comprising the step of reeling the web on a reel spool to form a paperboard roll, wherein the paperboard roll is loaded with two rider rolls during the reeling.