SE2051168A1

SE2051168A1 - High yield containerboard

Info

Publication number: SE2051168A1
Application number: SE2051168A
Authority: SE
Inventors: Christer Sandberg; Jan Andersson; Jonas Jonsson; Tommy Wiksand
Original assignee: Holmen Ab
Priority date: 2020-10-02
Filing date: 2020-10-02
Publication date: 2022-04-03
Also published as: WO2022071871A1; SE546114C2; EP4222311A1

Abstract

A high yield containerboard (1) comprising a first group of mechanical pulp cellulose fibres. The high yield containerboard having a content of at least 16 dry weight % of the first group of fibres. The disclosure also comprises a method for producing the high yield containerboard. The disclosure further comprises a containerboard product (100), a packaging material and a container (1000) produced with the high yield containerboard.

Description

HIGH YIELD CONTAINERBOARD The present application relates to a high yield containerboard, a method of producing such a highyield containerboard, a containerboard product, a packaging material, a container and a high yield liner or high yield fluting according to the annexed claims.

BACKGROUND Transporting, storing, displaying, and protection of goods are important factors in today's businessworld. The increasing e-market requires well-functioning packaging material and containers. lt istoday possible to provide packaging material and containers that are highly protective of the goodsthey are intended to transport. However, it has become equally important to provide packagingsolutions that are also environmentally friendly. This means in turn low impact on nature as well as an aim to minimize the waste in the manufacturing process and have a low carbon footprint as well.

SHORT DESCRIPTION OF THE INVENTION Thus it is an aim of the present invention to minimize wood consumption for production of a packaging product.

Thus it is a problem to be solved to achieve a packaging material that is both sufficiently strong but atthe same time optimizes the environmental footprint. A solution to this is presented in a high yieldcontainerboard for use as a layer in a board product. lt is preferred that the board product iscomprising at least two layers glued together. lt may also be at least three layers glued together. Oneof said at least two or at least three layers may be a corrugated layer. The containerboard comprises,a first group of high yield cellulose fibres produced by mechanical defibration of wood chips. The firstgroup may comprise cellulose fibres chosen from a group consisting of: any kind of mechanical pulp(MP) fibres e.g. refiner mechanical pulp (RMP) cellulose fibres, pressurized refiner mechanical pulp(PRMP) cellulose fibres, thermomechanical pulp (TMP) cellulose fibres, chemithermomechanical pulp(CTMP) cellulose fibres, all kinds of alkaline peroxide mechanical pulp (APMP) cellulose fibres,pressure groundwood (PGW) cellulose fibres ; and PRC-APMP cellulose fibres, and/ orchemimechanical pulp (CMP) cellulose fibres. The high yield containerboard may comprise anoptional second group of cellulose fibres. The second group of cellulose fibres are chosen from agroup consisting of chemical cellulose fibres, sulphate cellulose fibres, sulphite cellulose fibres, OCC and/or recycled chemical cellulose fibres. The high yield containerboard comprises at least 16 dry weight % of the first group of cellulose fibres. The cellulose fibres in the first group may comprisevirgin cellulose fibres. The optional second group may comprise virgin cellulose fibres. lt may be sothat the first group consists of only virgin cellulose fibres. lt may be so that the optional second group only consists of virgin cellulose fibres.

The advantage of the high yield containerboard is that the wood material put into the process will beefficiently used in the ensuing high yield containerboard. ln particular the first group of cellulosefibres provides excellent yield in producing the high yield containerboard. And by having at least 16 %of the high yield containerboard coming from the first group of cellulose fibres gives both a high yieldrequiring less wood chips as starting material per unit of needed high yield, and also a sufficiently strong high yield containerboard.

By applying virgin cellulose fibres several advantages are achieved. This in turn decreases theenvironmental impact, carbon footprint etc. Also, with virgin cellulose fibres a more homogenousstructure of the high yield containerboard is achieved. lt is possible to design it more precisely for the intended use.

According to a further aspect there is disclosed a high yield containerboard, wherein the productionof the high yield containerboard comprises the use of NaHSOg, and NaOH. Preferably the amounts of 40-60 kg of NaHSOg, and 25-45 kg of NaOH per ton of chips, are used.

By applying a certain amount of NaHSOg, and NaOH in the production of the high yieldcontainerboard, a particularly good balance between the strength properties and the yield of the high yield containerboard is attained.

According to a further aspect there is disclosed a high yield containerboard wherein the cellulosefibres of the first group and/or the second group comprise softwood fibres. I may be preferred thatthe cellulose fibres consists of softwood fibres. lt may as well be preferred that the cellulose fibrescomprises spruce fibres, for example from picea abies. The cellulose fibres may also comprises pine cellulose fibres, for example from pinus sylvestris.

The advantage of using softwood fibres is that they give a strong high yield containerboard, forexample due to longer fibres than hardwood fibres. Spruce fibres, in particular picea abies grows inforests that are easy to regrow and gives very little impact to the environment when farmed. Pine fibres have the same advantages and pinus sylvestris is easy to regrow as well.

According to a further aspect there is disclosed a high yield containerboard wherein the surfaceweight of the high yield containerboard is comprised in the range of 40-140 g/mz, preferably 50-130 g/mz, even more preferred in the range of 60-120 g/mz, most preferred 60-100 g/mz. ln a particular range of surface weights the high yield containerboard is particularly favourable for the balance between strength and amount of cellulose fibres used for the high yield.

According to a further aspect there is disclosed a high yield containerboard wherein the high yieldcontainerboard comprises at least 20 dry weight % of the first group of cellulose fibres in the highyield containerboard, preferably at least 40 % or at least 60 %, or at least 70 %, or at least 80 %, or at least 90 % or at least 95 % or 100 %, in dry weight of the cellulose fibres of the first group.

The advantage with increased amount of the first group of fibres is that each advantage mentionedabove is improved. More high yield cellulose fibres will be in the high yield containerboard. This willin turn improve the overall yield for the high yield containerboard, as compared with the amount ofwood start material. Also there can be advantages in terms of reduction of the use of chemicals for providing the free cellulose fibres.

According to a further aspect there is disclosed a high yield containerboard, wherein the tensilestrength is comprised in the range of 3-20 kN/m, preferably 3-15 kN/m in machine direction and/or3-7 kN/m, preferably 1-7 kN/m in cross machine direction. According to yet a further aspect there isdisclosed a high yield container board wherein the burst index is comprised in the range of 1-500 kPa*m2/g, preferably 1-450 kPa*m2/g, even more preferred 1-430 kPa*m2/g. lt has been found that increasing the amount of the high yield fibres will affect the strengthproperties of the high yield containerboard, in that compared with fibres of group 2, the strengthproperties can decrease. However it has at the same time been found that the high yield containerboard will have sufficient strength for a proper function as a liner.

According to a further aspect there is disclosed a high yield containerboard wherein the high yield containerboard comprises surface sizing applied on at least on side.

By adding surface sizing it is possible to despite using first group cellulose fibres to have very good strength properties of the high yield containerboard.

According to a further aspect there is disclosed a high yield containerboard wherein it further comprises micro fibrillated cellulose and/or nano fibrillated cellulose.

When adding MFC/NFC the properties of the micro/nano fibrillated cellulose, can help improve bonding in the high yield containerboard, in particular bonding can be improved at a high share of the first group of cellulose fibres together. This means improved mechanical properties, with lesscellulose fibres needed for the same properties. Thus if it is desired to improve the strength properties it is possible to add MFC/NFC.

According to a further aspect there is disc|osed a high yield containerboard, wherein the cellulosefibres of the first group has a yield when compared with the starting material, preferably wood chips, of above 80 dry weight %. lt is an advantage if the yield of the cellulose fibres of the first group is high, this improves the overallenvironmental impact. i.e. less wood chips is needed for the same amount of produced high yield containerboard.

According to a further aspect there is disc|osed a high yield containerboard wherein the SCT inmachine direction is comprised in the range of 1,5 -15 kN/m, and/or the SCT in cross direction is comprised in the range of 1-10 kN/m.

The range of SCT values of the high yield containerboard has been found to characterize a well- functioning high yield liner.

According to a further aspect there is disc|osed a method for producing a high yield containerboard comprising the steps of:-providing wood material, -treating said wood chips with a mechanical defibration device to receive a first group of cellulose fibres, -producing a pulp furnish comprising at least 16 dry weight % of the first group of cellulose fibres in the furnish,-providing said pulp furnish to a containerboard machine to produce a high yield containerboard, preferably the high yield containerboard produced is a high yield containerboard according to the aspects above.

The advantages of the method follows the advantages mentioned above in line with the high yield containerboard.

According to a further aspect there is disc|osed a containerboard product according to claim 13, packaging material according to claim 14 and a container for goods according to claim 15.

When producing a containerboard product, a packaging material or a container, the advantages with the high yield containerboard will also incorporated into these products.

According to a further aspect there is disc|osed a High yield liner product or a High yield fluting product according to claim 16.

LIST OF DRAWINGSFig. 1 disc|oses a high yield containerboard according to an aspect of the disclosure.

Fig. 2 A high yield containerboard according to one aspect of the disclosure included into a corrugated containerboard.Fig. 3 A container including the high yield containerboard according to the present disclosure.

Fig. 4 Example of a process for producing the cellulose fibres of group 1.

DETAILED DESCRIPTION The present disclosure is related to a high yield containerboard. The high yield containerboard is acellulose fibre product that is entirely intended to be used as a liner and/or a fluting, for example in acorrugated containerboard product. The corrugated containerboard product, can be made in variousways. ln general the high yield containerboard is applied as one layer in a containerboard product.Even if the preferred use is in a corrugated containerboard product, it can be used also in amultilayer product where the corrugated medium is replaced with another layer. Other layers can bemade of any material, for example a resin material or a layer contain metal. There may be added afluting layer to the containerboard product, i.e. a corrugated layer of cellulose fibres. meaning a layerof undulating containerboard. The fluting layer can be glued directly onto the high yieldcontainerboard. The corrugated containerboard product can be a multilayer product. ln general atleast two layers is provided in a containerboard product, that is at least one liner layer and oneundulating fluting layer. But in general it is suitable to have all liner layers of a containerboard product or packaging material to be made from the high yield containerboard.Containerboard being defined as a raw material intended to be used in a corrugated board product.

Figure 1 disc|oses a high yield containerboard 1 according to the disclosure. ln Fig. 2 the liner 1a is made of the high yield containerboard 1. This liner 1a is glued to an undulating fluting layer 20 of fluting material. The high yield containerboard 1 has two sides 2, 3. The high yield containerboard 1may be homogenous in the direction from the first side 2 to the second side 3, i.e. with normalvariations in the cellulose fibre formation. High yield in high yield containerboard, means that thehigh yield containerboard 1 comprises cellulose fibres that has not had the |ignin removed to anygreater extent. |.e. the major part of the defibration, where the cellulose fibres are separated fromeach other, is made through mechanica| processes. ln producing a pulp with this type of cellulose fibres the basic material is wood chips.

Also in Figure 2 the undulating layer 20 may be made with the high yield containerboard 1. Thus thesame figure 2 is relevant for a fluting 20 made from the containerboard 1. ln general thecontainerboard 1 when used for fluting should be adapted for the undulating application. A lower basis weight may apply than for the corresponding liner 1a, 1b.

The high yield containerboard 1 comprises a first group of cellulose fibres. The first group of fibresthus being produced by mechanica| defibration of wood chips. Mechanical defibration is achieved through a mill, a refiner or the like. ln particular the first group is comprising cellulose fibres chosen from a group consisting of: any kindof mechanica| pulp MP fibres e.g. refiner mechanica| pulp RMP cellulose fibres, pressurized refinermechanica| pulp PRMP cellulose fibres, thermomechanical pulp TMP cellulose fibres,chemithermomechanical pulp CTMP cellulose fibres, all kinds of alkaline peroxide mechanica| pulpAPMP cellulose fibres, pressure groundwood PGW cellulose fibres and PRC-APMP cellulose fibres, and/or chemimechanical pulp CMP cellulose fibres, ln order to achieve the required yield improvement of the percent disclosure and the desired highyield containerboard 1, at least 16 % of dry weight of the cellulose fibres of the high yield liner aremade according to any of the mechanica| processes above. That is 16 % dry weight compared withtotal dry weight of cellulose fibres. Any amount, below 16 % of the first group of fibres is not enoughto achieve the desired advantages for the present disclosure, and would have disadvantageouseffects in terms of the amount of wood material (chips) needed for same the desired amount of cellulose fibres (in weight).

There is an optional second group of cellulose fibres that may be comprised in the high yieldcontainerboard 1. This group of cellulose fibres that primarily are not separated by means ofmechanica| processes. |nstead the main process step for separation of the cellulose fibres from each other is based on partial chemical dissolution of the wood material, that is comprised in wood. ln the second group the cellulose fibres are chosen from a group consisting of chemical cellulose fibres, sulphate cellulose fibres, sulphite cellulose fibres, OCC and/or recycled chemical cellulose fibres.

All through the disclosure the amount sums up to a total dry weight of 100 % of cellulose fibres. lfthe amount of fibres of the first group is below 100 % dry weight, the remainder of fibres are eithercoming from the second group of fibres, or from both the second group of fibres and other fibresthat not belong to the first or second group. lt is also thinkable that only first group fibres and other fibres are mixed.

All along the disclosure fibres of first and second groups are discussed. With fibres is meant ingeneral wood material, thus both long fibres and shorter fibre fragments and preferably fines of the particular group should be included in this wording. lt is an important aspect that the cellulose fibres of the first group may come from virgin cellulosefibres. With virgin it is to be defined fibres that have their origin from wood chips. Thus any recycledcellulose fibre should not be construed as belonging to the group of virgin cellulose fibres. The virginfibres need not come from wood chips per se. lt is thinkable that the cellulose fibres is not comingfrom what would be termed wood chips. There could be other forms of virgin, new, fresh woods thatis used to provide the cellulose fibres of the first group of cellulose fibres, i.e. for example in the form of log, sawdust, planks or the like.

The cellulose fibres may be softwood cellulose fibres. Softwood provides good properties in the highyield containerboard of the present disclosure. As compared with hardwood fibres, softwood fibresprovide better strength properties due to longer fibres on average. The soft wood cellulose fibresmay for example come from Nordic Softwood. One particular fibre may be spruce fibres. The type ofspruce could be picea abies, which grows well in colder climates. The softwood cellulose fibres may also for example be pine cellulose fibres. The pine cellulose fibres may come from pinus sylvestris. ln order to achieve a well-functioning high yield containerboard the surface weight may becomprised within the range of 40-140 g/mz. The aim of the disclosure is to present an effective usageof the wood material put into the production of a high yield liner. ln this regard unnecessary highsurface weights of the high yield liner is preferred to be avoided, as this will mean that anunnecessary large amount of cellulose fibres are used. lt is equally important not apply a too lowsurface weight as this will give very poor strength properties. ln a more narrow range 50-130, or 60-120 g/mz. A good range that applies for many applications would be 60-100 g/mz. Looking at singularsurface weights the weight 100 g/mz has been found to be very satisfactory in terms of the amount of fibres used and the sufficient strength properties for the high yield containerboard 1. ln particular the lower end of the range of the basis weight is better for a high yield fluting product 20, and the upper range of the basis weight is better for a high yield liner 1a.

The first group of cellulose fibres may be increased. For example 20 % of cellulose fibres of the firstgroup gives less use of the input wood material for a given weight of high yield containerboard, i.e.yield increases. Other amounts can be 40, 50, 60, 70, 80, 90, 95 or 100 % of fibres of the first groupwith an increased yield and an excellent yield, despite using mechanical pulp fibres that are generallyknown as not to give sufficiently good strength properties, compared with the second group of cellulose fibres. ln order to solve the assignments needed for the high yield containerboard a machine directiontensile strength is preferred to be in the range of 3-20 kN/m, or more narrow ranges, 3-15, 3-7, 1-7 kN/m and a tensile strength in cross machine direction 3-7 kN/m, preferably 1-7 kN/m is preferred.

For any high yield containerboard 1 burst strength is important. The high yield containerboard may aburst strength is comprised in the range of 1-500 kPa*m2/g, preferably 1-450 kPa*m2/g, even morepreferred 1-430 kPa*m2/g. A higher burst strength is important when a container is made, as shownin fig.2. lt should be understood that burst strength preferably should be in the upper part of the range for a high yield liner product 1a, than for a high yield fluting product 20. ln order to be able to use an amount of 16 % or more of the first group of cellulose fibres for the highyield containerboard, a surface sizing layer 10, Fig. 2, may be applied. The surface sizing layer 10 maycomprise starch. By using surface sizing it is possible to increase the amount of first group of cellulosefibres without too much of reduction of strength properties to the high yield containerboard 1. Also for surface sizing purposes a high yield liner 1a may have only surface sizing applied to one side, but a high yield fluting product 20 is preferred to have surface size applied to both sides.

The high yield containerboard 1 can also comprise an amount of MFC, micro fibrillated cellulose, i.e.NFC nano fibrillated cellulose. Addition of MFC/NFC will further increase the strength of the high yield containerboard 1, i.e. it will function as a glue and adhere the cellulose fibres to each other.

The yield of the cellulose fibres of the first group may be 80 dry weight % or more compared with thedry weight of the wood chips starting material. This is a high yield in terms of the present disclosure.

Also higher yield as 90 % or 95 % or close to 100 % is thinkable.

The present disclosure is also related to a method for producing a high yield containerboard comprising the steps of: -providing wood material, -treating said wood chips with a mechanical defibration device to receive a first group of cellulose fibres, -producing a pulp furnish comprising at least 16 dry weight % of the first group of cellulose fibres the in the furnish,-providing said pulp furnish to a containerboard machine to produce a high yield containerboard. lt is also comprised in the present disc|osure a containerboard product comprising the high yield containerboards. Such a containerboard product is disc|osed in Figure 2.

The containerboard product 100 has in this case two liner layers 1a, 1b. The liner layers 1a, 1b aremade from the high yield containerboard 1 as described above. The middle layer 20 is a corrugatedfluting layer. The second liner layer 1b need not be the high yield containerboard, it could be anotherliner made according to traditional technology. I should be understood that the containerboardproduct 100 could be made in numerous ways, i.e. with only one liner layer and one fluting layer. ltcould also be a sandwich design with a group of liner layers, and a group of fluting layers 20. lf thereare a group of fluting layers, it is preferred that all layers are made from the containerboard product1, but of the group at least one fluting layer made from the high yield container product 1 issufficient for the present disc|osure. Also it is thinkable that the fluting layer of a containerboardproduct is made from a different containerboard, but at least one liner comprised in thecontainerboard product is made from the containerboard 1 of the present disc|osure, the reversedbeing also thinkable, i.e. that only a corrugated fluting layer 20 is made from the high yield containerboard 1 of the present disc|osure. lt is also comprised in the present disc|osure a packaging material. The packaging material comprising the high yield containerboard 1 as described above.

Figure 3 discloses a container 1000, which comprises the high yield containerboard of the presentdisc|osure. Such a container 1000 will be very efficient in terms of yield of the input wood materialinto the process of producing a container for transporting, storing, displaying and/or protection of goods.

The following examples discloses production of a high yield containerboard according to the present disc|osure.

EXAMPLE 1 PULP PRODUCTION FOR HIGH YIELD CONTAINERBOARDProduction of pulp of group 1 was made according to process seen in Fig. 4 Spruce chips were heated in a bin 33 with steam 21 for two minutes at atmospheric pressure andthereafter introduced to a pressurized heating screw 22 and heated with steam 21 at 1.5 bar for 15seconds. After the preheating, the chips were compressed in an lmpressafiner 30 and after thecompression, chips were submerged in a solution of sodium bisulphite (NaHSOg) and caustic (NaOH)at 23 with the doses 50 kg bisulphite and 35 kg caustic per ton of chips. The impregnated chips werefed through a rotary valve 24 into a steam heated screw conveyor (digester) 25. The temperature inthe digester was 175 °C and the retention time was 10 minutes. After the digester 25 chips were fedto a pressurized DD-refiner 26 (Bauer 418) and refined with 400 kWh/t specific energy at around 25% consistency. After the pressurized refiner, and steam out|et 27, the pulp was refined in a secondatmospheric refiner 28 (Bauer DD 401) with 600 kWh/t specific energy at around 25 % consistency.Both refiners 26, 28 were equipped with plate patterns 36104. Directly after the second refiner 28the pulp was diluted with water 35 to 3 % in a chest 32 and agitated for 15 minutes. The diluted pulpwas pressed on a wire press 34 to 30 % consistency and afterwards refined in two passes with theatmospheric refiners 29 (Bauer DD 401) with 500 kWh/t specific energy per pass at around 25 % consistency.

EXAMPLE 2 PRODUCTION OF HIGH YIELD CONTAINERBOARD The thick stock of EXAMPLE 1 was post-refined in a JC01 low consistency refiner at around 3.5 %consistency to around 350 ml freeness. The refiner was equipped with PSED segments. Directly afterthe post refining the stock was diluted to 2.5 % consistency in the machine chest. The high yield containerboard was produced in a containerboard machine equipped as follows: Headbox: Metso OptiFlo (No vanes, 5 rows) Forming section: Metso OptiFormer Gap with loadable blades (forming roll gap angle: 20°).Press section: Metso OptiPress. Shoe width 250 mm 1st press roll load: 1000 kN/m, tilt 1.5 2nd press roll load: 1200 kN/m, tilt 1.4 Basis weight: 65 - 110 gsm 11 Retention aid: Fennopol K3400, dosage 150 g/tMachine speed: 800 m/minHeadbox flow: 181l/s/m Strength properties of the high yield containerboard in Table I TABLE I Properties Test method Unit ValueBasis Weight ISO -536 g/mz 108.0Tensile Strength *MD ISO-1924-3 kN/m 11.07Tensile Strength *CD ISO-1924-3 kN/m 3.03Burst Strength ISO 2758 kPa 333SCT *MD ISO 9895 kN/m 4.99SCT *CD ISO 9895 kN/m 2.75 Test conditions: ISO 554 - 1976 (23 i 1°C / 50: 2%) As can be seen in the results, the strength properties fulfils a sufficiently good criterion or use as ahigh yield containerboard. I.e. we have a reasonable good tensile strength in machine direction and somewhat lower in cross direction, but still sufficient.

EXAMPLE 3 SURFACE SIZING OF THE HIGH YIELD CONTAINERBOARD OF EXAMPLE 2Materials: Metso OptiSizer Film Starch: Raisamyl 01121 Metering unit: Grooved rod ø10 mm D10 VMR 0,40/37Sealing blade 1.5x15 mm slotRoll covers: Rayflex 5000 20 P&J Nip load 40 kN/m 12 Machine speed: 700 m/min High yield Containerboard: CMP containerboardSolid starch: 14% Starch temperature: 58 °C Viscosity: 39 mPas Total amount starch applied: 7.0 gsm Strength properties of surface sized containerboard: TABLE llProperties Test method Unit ValueBasis Weight ISO -536 g/mz 117.2 TensileStrength*MD ISO-1924-3 kN/m 14.1TensiIeStrength*CD ISO-1924-3 kN/m 3.27 Burst Strength ISO 2758 kPa 426SCT *MD ISO 9895 kN/m 7.02SCT *CD ISO 9895 kN/m 3.02 Test conditions: ISO 554 - 1976 (23 i 1°C / 50 i 2%)MD-Machine Direction; CD-Cross Direction As can be seen in Table II the tensile strength has increased in both MD and CD direction. Burst strength is also higher after surface sizing.

EXAMPLE 4 HIGH YIELD CONTAINERBOARD PRODUCTION The thick stock was a blend of 60 % dry weight TMP pulp and 40 % dry weight of NBSK pulp. The Canadian Standard Freeness was 142 ml and the fibre length measured with PQM was 1.68 mm.Machine settings:Machine speed: 786 m/min Head box flow: 105 l/s/m 13 Temperature 53 °CBasis weight: 78.4 g/m2 TABLE III Strength properties of containerboard Properties Test method Unit ValueBasis Weight ISO -536 g/mz 78.4Tensile Strength *MD ISO-1924-3 kN/m 5.68Tensile Strength *CD ISO-1924-3 kN/m 1.75 Burst Strength ISO 2758 kPa 166SCT *MD ISO 9895 kN/m 2.44SCT *CD ISO 9895 kN/m 1.12 Test conditions: ISO 554 - 1976 (23 i 1°C / 50 i 2%)*MD - Machine Direction; CD - Cross Direction The above example discloses a first group pulp, TMP, and a second group pulp NBSK (NorthernBleached Softwood Kraft). The ratio of the mix is 60/40 of TMP/NBSK. Thus the first group pulp was 60 % dry weight and the second group pulp was 40 % dry weight.

We can see that the tensile strength is somewhat lower than the first example. Application of a pulpmade from TMP, affects the strength properties, however sufficient tensile strength is achieved.About half of the decreased tensile strength can be explained by the lower basis weight of Example 4compared with Example 2. The further decrease in Tensile strength is due to the mix of Fibre beingmore unfavourable than in Example 1. I.e. the TMP fibre performs less good than the CMP fibre ofExample 1-2. And the second group fibre of Example 4 does not compensate for this. Still the high yield containerboard performs sufficiently well.

EXAMPLE 5 SURFACE SIZING OF HIGH YIELD CONTAINERBOARD COMPARABLE TO HIGH YIELDCONTAINERBOARD OF EXAMPLE 4 Materials: UMV Twin sizer Gravure Transfer rolls: Metso CoteEagle, RA 1.2 -1.3, Hardness 90 P&J 14 Starch: Roquette STABILYS® A030 Volume Gravure rolls: 43 cm3/m2 Gravure rolls cells: Quadrangal, 30 lines/cm Machine speed: 500 m/min Gravure speed: 100% High yield containerboard: 80 gsm, 60 % TMP and 40 % Kraft fibresSolid starch: 15% Starch temperature: 40 °C Viscosity: 20 cPa Total amount starch applied: 3.5 gsm Strength properties of surface sized high yield containerboard: Properties Testmethod Unit Value Basis Weight ISO -536 g/mz 83.4 TensileStrength *MD ISO-1924-3 kN/m 7.01 Tensile Strength *CD ISO-1924-3 kN/m 1.99 Burst Strength ISO 2758 kPa 197SCT *MD ISO 9895 kN/m 3.21SCT *CD ISO 9895 kN/m 1.5 Test conditions: ISO 554 - 1976 (23 i 1°C / 50 i 2%)*MD - Machine Direction; CD - Cross Direction When surface sizing a high yield containerboard comparable to the Example 4 high yieldcontainerboard, an increase in all strength properties is achieved an increase in strength properties over all parameters. This increase in strength properties gives the possibility to further decrease the amount of group two cellulose fibres in the Example 4 high yield containerboard, thus further improving the yield of cellulose fibres that is achieved from the starting wood material.

Claims

1. 1. High yield containerboard (1) for use as a layer in a board product (100), preferably the boardproduct (100) is comprising at least two layers glued together, preferably at least three layers (1a, 20,1b) glued together, preferably one of said at least two or at least three layers is a corrugated layer (20), wherein the containerboard comprises: - a first group of high yield cellulose fibres produced by mechanical defibration of wood chips,preferably the first group is comprising cellulose fibres chosen from a group consisting of: any kind ofmechanical pulp (MP) fibres e.g. refiner mechanical pulp (RMP) cellulose fibres, pressurized refinermechanical pulp (PRMP) cellulose fibres, thermomechanical pulp (TMP) cellulose fibres,chemithermomechanical pulp (CTMP) cellulose fibres, all kinds of alkaline peroxide mechanical pulp(APMP) cellulose fibres, pressure groundwood (PGW) cellulose fibres and PRC-APMP cellulose fibres, and/or chemimechanical pulp (CMP) cellulose fibres, -an optional second group of cellulose fibres, wherein the second group of cellulose fibres are chosenfrom a group consisting of chemical cellulose fibres, sulphate cellulose fibres, sulphite cellulose fibres, OCC and/or recycled chemical cellulose fibres,characterized in that the high yield containerboard comprises at least 16 dry weight % of the first group of cellulose fibres,preferably the cellulose fibres in the first group comprises virgin cellulose fibres, further preferablythe optional second group comprises virgin cellulose fibres, more preferred the first group consistsonly of virgin cellulose fibres, more preferred the optional second group of fibres consist of only virgin cellulose fibres.

2. High yield containerboard (1) according to claim 1, wherein the production of the high yieldcontainerboard comprises the use of NaHSOg, and NaOH, preferably in the amounts of 40-60 kg of NaHSOg, and 25-45 kg of NaOH per ton of chips.

3. High yield containerboard (1) according to claim 1 or 2, wherein the cellulose fibres of the firstgroup and/or second group comprise softwood fibres, preferably the cellulose fibres consists ofsoftwood fibres, preferably the cellulose fibres comprises spruce fibres, preferably from picea abies, and/or the cellulose fibres comprises pine cellulose fibres, preferably from pinus sylvestris.

4. High yield containerboard (1) according to any of the claims above, wherein the surface weight ofthe high yield containerboard is comprised in the range of 40-140 g/mz, preferably 50-130 g/mz, even more preferred in the range of 60-120 g/mz, most preferred 60-100 g/mz. 17

5. High yield containerboard (1) according to any of the claims above, wherein the high yieldcontainerboard comprises at least 20 dry weight % of the first group of cellulose fibres in the highyield containerboard, preferably at least 40 % or at least 60 %, or at least 70 %, or at least 80 %, or at least 90 % or at least 95 % or 100 %, in dry weight of the cellulose fibres of the first group.

6. High yield containerboard (1) according to any of the claims above, wherein the tensile strength iscomprised in the range of 3-20 kN/m, preferably 3-15 kN/m in machine direction and/or 3-7 kN/m, preferably 1-7 kN/m in cross machine direction.

7. High yield containerboard (1) according to any of the claims above, wherein the burst index iscomprised in the range of 1-500 kPa*m2/g, preferably 1-450 kPa*m2/g, even more preferred 1-430kPa*m2/g.

8. High yield containerboard (1) according to any of the claims above, wherein the high yield containerboard (1) comprises surface sizing applied on at least on side.

9. High yield containerboard (1) according to any of the claims above, wherein it further comprises micro fibrillated cellulose and/or nano fibrillated cellulose.

10. High yield containerboard (1) according to any of the claims above, wherein the cellulose fibres ofthe first group has a yield when compared with the starting material, preferably wood chips, of above 80 dry weight %.

11. High yield containerboard (1) according to any of the claims above, wherein the SCT in machinedirection is comprised in the range of 1,5 -15 kN/m, and/or the SCT in cross direction is comprised in the range of 1-10 kN/m.

12. Method for producing a high yield containerboard (1) comprising the steps of:-providing wood material, -treating said wood chips with a mechanical defibration device to receive a first group of cellulose fibres, -producing a pulp furnish comprising at least 16 dry weight % of the first group of cellulose fibres in the furnish,-providing said pulp furnish to a containerboard machine to produce a high yield containerboard, preferably the high yield containerboard produced is a high yield containerboard according to any of the claims 1-11. 18

13. Containerboard product (100) comprising the high yield containerboard according to any of theclaims 1-11, produced according to the method according to claim 12, and further comprising afluting which is attached to the high yield containerboard to form a corrugated layer in saidcontainerboard product, and/or further comprising a resin layer extruded onto said high yield containerboard.

14. Packaging material, comprising the high yield containerboard according to any of the claims 1-11.

15. Container (1000) for transporting, storing, displaying, and/or protection of goods, wherein the container is comprising the packaging material according to claim 14.

16. High yield liner product (1a) or High yield fluting product (20), comprising the high yield containerboard (1) of any of the claims 1-11.