Multilayer sheet liner with washed NSSC pulp

Abstract

The present invention relates to a multilayer sheet liner for a food or beverage packaging material, the multilayer sheet liner comprising: a first ply comprising at least 70% by weight of unbleached kraft pulp and less than 30% by weight of neutral sulfite semi-chemical (NSSC) pulp, based on dry weight, and a second ply comprising at least 70% by weight of unbleached kraft pulp and less than 30% by weight of neutral sulfite semi-chemical (NSSC) pulp, based on dry weight, wherein the second ply comprises at least 50% by weight of NSSC pulp and less than 50% by weight of unbleached kraft pulp based on dry weight, and wherein the NSSC pulp in the second ply is a washed NSSC pulp having an ash content of less than 1.8% by weight as determined according to Standard ISO 1762: 2019. The invention relates to a method for manufacturing the multilayer sheet liner.

Description

Technical Field

[0001] The present invention relates to a multi-ply liner paper (liner, pad, lining paper) containing NSSC pulp. The multi-ply liner paper can be used directly as a packaging material or as a component of a corrugated board. Background Art

[0002] Liner paper or linerboard is a type of thin paperboard that can be used directly as a packaging material (e.g., as a paper or board substrate for packaging board), but is more commonly used as a component of corrugated board.

[0003] Corrugated board (sometimes called corrugated cardboard or corrugated fiberboard) is a packaging material that can be transformed into different types of packaging solutions. Corrugated cardboard is a fiber-based material made from cellulose fibers. The fibers can be virgin cellulose fibers or recycled cellulose fibers, such as fibers from used corrugated cardboard or other materials.

[0004] Corrugated board comprises at least one fluting medium (fluting) and at least one non-corrugated medium (liner paper or liner board) glued to the surface of the fluting medium. For example, the corrugated board can consist of a layer of fluting medium glued between two layers of liner paper to form a sandwich structure. The sandwich structure can be formed in different ways (such as single-wall, double-wall and triple-wall), as described in, for example, Kirwan M., J., Paper and Paperboard.Packaging Technology, Blackwell Publishing 2005.

[0005] There are different kinds of corrugated board qualities, and these can include different types of liner and corrugated base paper. Examples of liner are kraft liner and testliner. Kraft liner is usually produced from kraft pulp, which may be bleached or unbleached, and may include one or more layers / plies, wherein the top layer / plies are usually optimized to provide a good printing surface and good moisture resistance. Testliner is mainly produced from recycled corrugated board, and is usually manufactured in two layers / plies. Due to the presence of recycled cellulose fibers, testliner may usually have a lower mechanical strength than kraft liner, particularly a lower burst strength. Kraft liner is often used for packaging boxes that require higher strength properties.

[0006] 2-ply linerboards with a top sheet made of unbleached kraft pulp and a bottom sheet containing recycled cellulose fiber pulp (e.g. recycled linerboard) are generally of limited use in food packaging applications due to poor mechanical properties and a potentially high level of contamination of the recycled cellulose fiber content. From 01 April 2021, paper or paperboard for food packaging applications should preferably comply with the BfR XXXVI recommendation for paper and paperboard intended for food contact.

[0007] Replacing the recycled cellulose fiber content with unbleached kraft pulp is not feasible due to the increased cost. The strength and mechanical properties of the liner paper can be improved by adding small amounts of chemical pulp and unbleached kraft pulp to the mechanical pulp. Typically, 5-15% chemical pulp is added. This of course increases the cost and results in a reduced dewatering rate and can also affect runnability and mechanical properties. Another solution is to wash the recycled cellulose fibers, but this will also increase the cost and may affect, for example, the bursting properties of the liner paper.

[0008] New machine concepts and increased machine speeds combined with an increased need for source reduction further increase the demand for pulps with improved properties.

[0009] There remains a need for new and improved linerboard materials that are usable as paper or board substrates for liquid packaging board (LPB) or food service board (FSB) or as linerboard for corrugated board that combine strength, low grammage, water / moisture resistance, low chemical consumption, low cost, and / or high recyclability. DETAILED DESCRIPTION

[0010] It is an object of the present disclosure to provide an improved multi-ply liner paper, such as for use in corrugated board, which solves or ameliorates at least some of the above-mentioned problems.

[0011] Another object of the present disclosure is to provide a method for manufacturing multi-ply liner paper which can reduce the consumption of unbleached kraft pulp (UBKP) in the liner paper without losing the mechanical properties of the UBKP liner paper when used in corrugated board.

[0012] The above-mentioned objects and other objects as appreciated by skilled artisans from this disclosure are achieved through various aspects of the present disclosure.

[0013] NSSC pulp is commonly used in the fluting medium of corrugated board, but its use in linerboard varies to varying degrees due to its optical and mechanical properties. One challenge with NSSC pulp is that the process is primarily designed for high yield and efficient processes. The main goal is to provide a fiber or fiber suspension that meets the requirements of corrugated board / containerboard, such as use in fluting medium or corrugating base. In addition, NSSC pulp typically contains contaminants and organic and inorganic residues, which makes the pulp less suitable for food packaging applications. In addition, the use of such NSSC pulp with a large amount of contaminants and or impurities requires higher dosages of, for example, slimicides, preservatives, dewatering promoters and / or retention aids, which can affect the wet-end chemistry. It is known that the addition of NSSC pulp in linerboard production can have a significant negative impact on the wet-end chemistry and can cause problems with web breaks.

[0014] NSSC pulp, usually made from broadleaf species, is known for its excellent stiffness and high hardness. Neutral sulfite semichemical (NSSC) pulping is an old process well known in the field of paper pulping. One of the reasons for using NSSC pulping is the high yield, usually above 60%. In NSSC pulping, the cooking liquor contains sulfites such as Na 2 SO 3 or (NH 4 ) 2 SO 3 and bases such as NaOH or Na 2 CO 3 . "Neutral" means that the pH of the NSSC cooking liquor is typically between 6 and 10. The pulp can be cooked in a batch or continuous digester. Typically, the cooking time is from 5 minutes to 3 hours and the cooking temperature is 160-200°C. NSSC pulp contains relatively high amounts of residual lignin, such as 15-20%, which makes the NSSC pulp hard. The Kappa value of NSSC pulp is typically above 70. NSSC pulping is "semi-chemical" in the sense that it also involves mechanical refining of the pulp. Refining can be carried out, for example, using a disc refiner at digester pressure or atmospheric pressure.

[0015] Multi-ply liner papers typically comprise a first ply intended as the top or printing layer and comprising primarily unbleached kraft pulp (UBKP) and a second ply intended as the bottom ply facing the fluting medium in the corrugated board and comprising recycled cellulose fiber pulp and having a low content of UBKP.

[0016] The present invention is based on the inventive recognition that washed NSSC pulp having a low ash content of less than 1.8 wt. % as determined according to standard ISO 1762:2019 can be advantageously used in large quantities in the bottom ply of a multi-ply liner paper. It has been found that washing of the NSSC pulp reduces the negative impact on wet end chemistry and web breakage problems associated with unwashed NSSC pulp. The washed NSSC pulp in the second ply can increase the strength of the liner paper, especially in liner paper in which washed NSSC pulp is used instead of recycled cellulose fibers (e.g., recycled liner paper). The washed NSSC pulp in the second ply also reduces the consumption of the more expensive UBKP, thereby reducing the cost of the liner paper. The use of washed NSSC pulp in the second ply allows the use of large amounts of NSSC, such as 50% or more of the total fiber content of the second ply.

[0017] According to a first aspect shown herein, there is provided a multi-layer liner for food or beverage packaging material, the multi-layer liner comprising:

[0018] The first layer, and

[0019] The second layer,

[0020] wherein the first ply comprises at least 70 wt. % unbleached kraft pulp and less than 30 wt. % neutral sulfite semi-chemical (NSSC) pulp on a dry weight basis,

[0021] wherein the second ply comprises, on a dry weight basis, at least 50 wt. % NSSC pulp and less than 50 wt. % unbleached kraft pulp, and

[0022] Wherein said NSSC pulp in the second ply is a washed NSSC pulp having an ash content of less than 1.8 % by weight as determined according to standard ISO 1762:2019.

[0023] "NSSC pulp" is obtained from "NSSC pulping", which in turn is defined in the background section. NSSC pulp can be hardwood pulp or softwood pulp, or a mixture thereof. NSSC pulp is preferably hardwood pulp or a hardwood / softwood pulp mixture having less than 15 wt% softwood, preferably less than 10 wt% softwood, and more preferably less than 5 wt% softwood. The hardwood may be, for example, aspen, alder, poplar, eucalyptus, birch, acacia, or beech. NSSC pulp is preferably made using a sulfite (preferably Na 2 SO 3 or (NH 4 ) 2 SO 3 ) and a base (preferably NaOH or Na 2 CO3 ) is prepared by cooking with cooking liquor of 1% tungsten carboxylic acid (2% tungsten carboxylic acid) and 1% tungsten carboxylic acid (2% tungsten carboxylic acid). In some embodiments, the yield of NSSC pulping is above 60%, preferably above 65%, preferably above 70%, and more preferably above 75%. The term "neutral" means that the pH of the NSSC cooking liquor is in the range of 6-10. The cooking time is preferably in the range of 5 minutes to 3 hours. The cooking temperature is preferably in the range of 160-200°C. NSSC pulp may contain a relatively high amount of residual lignin, such as 15-20%. According to ISO 3260, the Kappa number of NSSC pulp is generally above 70, preferably above 80, preferably above 95, and more preferably above 100. NSSC pulping is "semi-chemical" in the sense that it also includes mechanical refining of the pulp. Refining can be carried out, for example, using a disc refiner at digester pressure or atmospheric pressure. Refining can be carried out in one or more steps at the same or different pulp consistencies. The first refining step may preferably be carried out at a higher consistency, such as 5-35%, and the second refining step may preferably be carried out at a lower consistency of <5%.

[0024] The low ash content of washed NSSC pulp can be achieved by washing the pulp. The ash content can also be reduced by more effectively removing the bark before the pulping process.

[0025] In some embodiments, the NSSC pulp has been subjected to washing to reduce the ash content. The purpose of washing is to separate the pulp from the black liquor, to wash away residual materials such as alkali lignin produced during the cooking process, and to purify the pulp. In some embodiments, washing of the NSSC pulp includes using >10 m 3 , preferably >12 m 3 , and more preferably >15 m 3 The NSSC slurry is diluted with 100% clean water / ton of dry NSSC slurry and then subjected to dewatering to a solid content of >40% by weight. In some embodiments, washing of the NSSC slurry comprises using 10-50 m 3 , preferably 12-50 m 3 , and more preferably 15-50 m 3The NSSC pulp is diluted with clean water / ton of dry NSSC pulp and then the pulp is dehydrated to a solid content of>40% by weight. Washing can be performed in one or more washing steps, each washing step comprising diluting the NSSC pulp and then subjecting the pulp to dehydration. Washing can be performed using one or more conventional pulp washing methods and washing equipment, including but not limited to rotary vacuum pulp washers, rotary high-pressure pulp washers, high-pressure and atmospheric diffusion pulp washers, horizontal belt pulp washers and / or dilution / extraction equipment. Washing generally involves diluting the NSSC pulp with water and then removing the water together with the diluted colloidal substances, salts, impurities and fines through a wire screen. A preferred washing procedure uses at least one double screen, drum displacement pulp washer, double roll press, rotary vacuum drum pulp washer, rotary high-pressure drum, horizontal belt press, atmospheric or pressurized diffuser, or extraction press, followed by at least one screw press.

[0026] In some embodiments, at least one washing step, preferably the last washing step, is performed with hot water. The temperature of the hot water is preferably above 50°C, more preferably above 60°C or above 70°C. In some embodiments, the temperature of the hot water is in the range of 50-100°C, 60-100°C or 70-100°C. In some embodiments, the pulp temperature of the washing step performed with hot water is in the range of 40-90°C or in the range of 45-80°C.

[0027] The washing of NSSC pulp can be characterized according to the Nordén efficiency factor (E), preferably normalized to the Nordén efficiency factor at 10% discharge consistency (E 10 ). 10 It can be calculated by the following formula:

[0028]

[0029] in:

[0030] L 0 = slurry inlet liquid, lb / lb slurry

[0031] L 1 = slurry outlet liquid, lb / lb slurry

[0032] x 0 = Slurry inlet solid concentration, weight %

[0033] x 1 = Slurry outlet solid concentration, weight %

[0034] y 1 = solid concentration at the outlet of washing liquid, weight %

[0035] y 2 = washing liquid inlet solid concentration, weight %

[0036] DF = dilution factor = V 2 –L 1

[0037] V 2 = flushing water flow, lb / lb slurry

[0038] In some embodiments, the Norden efficiency factor (E 10 )>2, preferably>2.2, and more preferably>2.5.

[0039] In some embodiments, the Norden efficiency factor (E 10 ) is in the range of 2-6, preferably 2.2-5, and more preferably 2.5-4.

[0040] When washing is performed in series in two or more washing steps, E 10 The values ​​are additive. That is, 10 The first wash step has a value of 2 and E 10 The wash sequence consisting of a second wash step with a value of 1 results in a total E 10 The value is 3.

[0041] In some embodiments, the NSSC pulp is prepared from wood comprising less than 3 wt%, less than 2.5 wt%, less than 2 wt%, or preferably less than 1 wt% or less than 0.8 wt% bark.

[0042] The washed NSSC pulp of the multi-layer liner paper of the present invention has an ash content of less than 1.8% by weight. The ash content can be measured according to standard ISO 1762:2019. In some embodiments, the NSSC pulp has an ash content of less than 1.6% by weight, preferably less than 1.4% by weight, and more preferably less than 1.2% by weight or less than 1.0% by weight or less than 0.9% by weight as determined according to standard ISO1762:2019.

[0043] Ash content, which indicates washing efficiency and purity of the NSSC pulp, can also be measured by measuring the hot water extract conductivity of the NSSC pulp according to ISO 6587. In some embodiments, the washed NSSC pulp has a hot water extract conductivity as determined according to ISO 6587 of less than 30 mS / cm, preferably less than 20 mS / cm, and more preferably less than 15 mS / cm.

[0044] In some embodiments, the conductivity of the washed NSSC pulp when decomposed at 3.5 wt % in distilled water is less than 1200, less than 1000, less than 800, or less than 600, and more preferably less than 500, less than 450, less than 400, less than 350, or less than 300 mS / m.

[0045] In some embodiments, the washed NSSC slurry contains less than 2%, preferably less than 1.8%, more preferably less than 1.6% Pulmac shives (mesh size 0.1 mm).

[0046] In addition to reducing the ash content, washing can also result in a reduction in the content of cellulose fines in the washed NSSC pulp. As used herein, the term "cellulose fines" generally refers to cellulose particles that are significantly smaller in size than cellulose fibers. In some embodiments, as used herein, the term "fines" refers to fine cellulose particles that can pass through a 200 mesh screen (equivalent pore size 76 µm) of a conventional laboratory grading device (SCAN-CM 66:05). The reduction in fines in the washed NSSC pulp can be, for example, in the range of 0.1-10 wt%, or in the range of 0.5-7 wt%.

[0047] During the preparation of semi-chemical pulps such as NSSC, dissolved organic matter is formed. These dissolved organic matter are usually expressed in terms of chemical oxygen demand (COD) according to standard NF T90-101 (referred to herein as COD / t 90 ) measurement. Usually, after preparing semi-chemical pulp, at least 120 kg COD / t 90 In some cases, the values ​​are even higher than 150 or 180 kg COD / t 90 In addition, during further defibrillation (fiber separation) and refining of the pulp, significant amounts of dissolved organic matter may be formed. Depending on the refining conditions, an additional 10-100 kg COD / t 90 or more. It is necessary to optimize the washing of semi-chemical pulp such as NSSC to reduce COD / t 90 Preferably, the washed NSSC slurry contains less than 30 kg COD / t 90 , more preferably less than 20 kg COD / t 90 And most preferably less than 10 kg COD / t 90 .

[0048] The first ply of the multi-ply liner paper comprises at least 70% by weight of unbleached kraft pulp (UBKP). In some embodiments, the first ply comprises at least 75% by weight, preferably at least 80% by weight, of unbleached kraft pulp on a dry weight basis. The first ply may comprise 100% by weight UBKP, but more typically, the ply may further comprise other components such that the first ply comprises 95% by weight or less, 90% by weight or less, or 85% by weight or less UBKP on a dry weight basis. It is preferred that the multi-ply liner paper comprises 70-95% by weight, preferably 80-90% by weight, of unbleached kraft pulp on a dry weight basis.

[0049] Unbleached kraft pulp or UBKP generally refers to unbleached sulfate pulp based on pine and / or spruce. The main raw material of UBKP is preferably pine, but it may also contain up to 45% by weight of spruce. In some embodiments, UBKP has a kappa number above 55, preferably above 60, and more preferably above 70 as measured according to SCAN ISO C-1.

[0050] The first ply may also contain NSSC pulp, but at a lower level than the second ply. The first ply contains less than 30% by weight NSSC pulp on a dry weight basis. Preferably, the first ply contains less than 20% by weight or less than 10% by weight NSSC pulp on a dry weight basis. It is preferred that the first ply contains 5-30% by weight, preferably 5-20% by weight or even more preferably 5-10% by weight NSSC pulp on a dry weight basis. In some embodiments, the first ply does not contain NSSC pulp.

[0051] The portion of the first ply that is not UBKP or NSSC pulp may contain any kind of fiber, such as hardwood and / or softwood fibers, and may include, for example, chemical pulp, mechanical pulp, thermomechanical pulp, or chemical-thermomechanical pulp (CTMP). In some embodiments, the liner paper is kraft liner paper, and the portion of the first ply that is not UBKP is made entirely of virgin fibers. The portion of the first ply that is not UBKP may also contain, for example, recycled cellulose fibers. For example, the first ply of the present disclosure may consist essentially of UBKP or a mixture of UBKP and recycled cellulose fibers. "Recycled cellulose fibers" refers to fibrous materials that have previously been incorporated into certain paper or paperboard products. Recycled fibers are preferably pre-consumer recycled fibers or broken paper obtained from a paperboard manufacturing process. Alternatively or in addition, the portion of the pulp that is not UBKP may contain, for example, reject pulp. For example, the pulp of the present disclosure may consist essentially of UBKP and reject pulp. "Reject pulp" refers to pulp prepared by refining screening rejects from another process.

[0052] In some embodiments, the first layer of the multi-layered liner is optimized to provide a good printing surface and good moisture resistance. In some embodiments, the optimization of providing a good printing surface and good moisture resistance includes surface sizing. In some embodiments, the multi-layered liner is surface sized. In some embodiments, the multi-layered liner is surface sized with starch. In some embodiments, the multi-layered liner is surface sized with a combination of starch and at least one other functional component, and the other functional component is preferably selected from a cross-linking agent, a reinforcing agent, and a hydrophobic sizing agent. The cross-linking agent may be, for example, selected from metal salts such as zirconium carbonate, glyoxal or modified glyoxal, amino plastic resin, formaldehyde, melamine, and modified melamine. In some embodiments, the cross-linking agent is citric acid. The reinforcing agent may be, for example, microfibrillated cellulose (MFC). The hydrophobic sizing agent may be, for example, alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), SMA (styrene maleic anhydride), rosin glue, or a mixture thereof.

[0053] The second ply comprises at least 50 wt % washed NSSC pulp on a dry weight basis. The second ply comprises a significantly higher content of NSSC pulp than the first ply. In some embodiments, the second ply comprises at least 60 wt %, preferably at least 70 wt %, and more preferably at least 80 wt % washed NSSC pulp on a dry weight basis. The second ply may consist entirely of washed NSSC pulp, but more typically, the second ply may also comprise other components such that the second ply comprises 95 wt % or less, 90 wt % or less, 85 wt % or less, 80 wt % or less, or 75 wt % or less washed NSSC pulp on a dry weight basis.

[0054] The second ply may also contain UBKP, but the second ply contains a significantly lower content of UBKP than the first ply. The second ply contains less than 50 wt% UBKP on a dry weight basis. Preferably, the second ply contains less than 40 wt%, less than 30 wt%, or less than 20 wt% UBKP on a dry weight basis. It is preferred that the second ply contains 5-50 wt%, even more preferably 5-40 wt% or 5-30 wt% UBKP on a dry weight basis.

[0055] The portion of the second ply that is not washed NSSC pulp or UBKP may contain any kind of fiber, such as hardwood and / or softwood fibers, and may include, for example, chemical pulp, mechanical pulp, thermomechanical pulp, or chemi-thermomechanical pulp (CTMP). In some embodiments, the liner is kraft liner, and the portion of the second ply that is not washed NSSC pulp is made entirely of virgin fibers. Thus, in some embodiments, the second ply contains no recycled fibers.

[0056] In some embodiments, the portion of the second ply that is not washed NSSC pulp may comprise recycled cellulose fibers. For example, the second ply of the present disclosure may consist essentially of washed NSSC pulp or a mixture of washed NSSC pulp and recycled cellulose fibers. "Recycled cellulose fibers" refers to fibrous material that has previously been incorporated into certain paper or paperboard products. The recycled fibers are preferably pre-consumer recycled fibers or broken paper obtained from a paperboard manufacturing process. Alternatively or in addition, the portion of the pulp that is not washed NSSC pulp may comprise, for example, bagasse pulp. For example, the pulp of the present disclosure may consist essentially of washed NSSC pulp and bagasse pulp. "Bagasse pulp" refers to pulp prepared by refining screening rejects from another process.

[0057] The addition of washed NSSC pulp in the second ply can improve the strength of the liner paper, especially in multi-ply liner papers where washed NSSC pulp is used instead of recycled fibers. In some embodiments, less than 30 weight percent of the second ply is comprised of broke or recycled cellulose fibers.

[0058] The lining paper of the present disclosure is a multi-layer lining paper comprising a first layer (also referred to as a top layer) and a second layer (also referred to as a bottom layer). The outer surfaces of the multi-layer lining paper (i.e., the surfaces of the top layer and the bottom layer facing away from the other layers) are referred to as the top side and the back side, respectively.

[0059] The liner paper can be made in a paper machine or board machine suitable for making multi-layer liner paper. Paper machines or board machines for making multi-layer liner paper are well known in the art. Typically, the machine configuration includes a stock handling section, a wet end, a press section and a dryer section as well as a calendering section and / or a coating section. At the wet end, the plies of the multi-layer liner paper can be formed separately using different headboxes and laminated in a wet state, or formed together using a multi-layer headbox. If formed separately, the plies are usually laminated or couched together before the press section and the dryer section of the paper machine.

[0060] In some embodiments, the first layer and the second layer of the multi-layer liner paper each have a grammage of 20-150 g / m 2 In the range of 30-100 g / m 2 The total gram weight of the multi-layer liner paper is preferably in the range of 40-300 g / m 2 within the range.

[0061] In some embodiments, the multi-layered liner paper further comprises a reinforcing agent or adhesive applied at the interface between the first layer and the second layer. Preferably, the reinforcing agent or adhesive comprises a mixture of cooked starch or gelatinized starch or uncooked starch, or cooked starch or gelatinized starch or uncooked starch and microfibrillated cellulose (MFC). A preferred reinforcing agent or adhesive is a cooked natural starch or a cooked natural starch mixed with microfibrillated cellulose. In some embodiments, the reinforcing agent or adhesive further comprises a crosslinking agent. The crosslinking agent may, for example, be selected from metal salts such as zirconium carbonate, glyoxal or modified glyoxal, amino plastic resin, formaldehyde, melamine and modified melamine. In some embodiments, the crosslinking agent is citric acid. In some embodiments, the reinforcing agent or adhesive further comprises an insolubilizer. The insolubilizer may be, for example, an amino resin, glyoxal, or a zirconium salt insolubilizer. The amount of the reinforcing agent or adhesive applied at the interface between the second layer and the second layer is preferably based on dry weight at 0.1-5 g / m 2 In the range of 0.5-3 g / m 2 within the range.

[0062] Due to the high content of washed NSSC pulp in the second ply, the multi-ply liner paper has a high content of washed NSSC pulp as a whole. In some embodiments, the amount of washed NSSC pulp in the multi-ply liner paper is at least 10% by weight, preferably at least 20% by weight, and more preferably at least 30% by weight based on dry weight. In some embodiments, the amount of washed NSSC pulp in the multi-ply liner paper is at least 40% by weight, preferably at least 50% by weight, and more preferably at least 60% by weight based on dry weight.

[0063] In some embodiments, the washed NSSC pulp used in the multi-layered noodle paper is a fractionated washed NSSC pulp. The fractionated washed NSSC pulp is obtained by fractionating the washed NSSC pulp starting material into a fine fiber fraction and a coarse fiber fraction by size. The fine fiber fraction has a higher amount of shorter and finer fibers than the starting material. In other words, the average particle size of the washed NSSC pulp of the fine fiber fraction is lower than the average particle size of the washed NSSC pulp of the coarse fiber fraction. The fine fiber fraction can be obtained, for example, by separating the washed NSSC pulp starting material in a pressure screen to achieve a fraction with shorter and finer fibers.

[0064] The fine fiber fraction obtained by size fractionation of the washed NSSC pulp is particularly advantageous for use in the first ply of a multi-ply liner paper intended as a top or printing layer, since it has less impact on the optical properties of the liner paper than an unfractionated or coarse fiber fraction of the washed NSSC pulp. The coarse fiber fraction can be advantageously used in the second ply, where it does not affect the optical properties of the liner paper. In a preferred embodiment, the washed NSSC pulp used in the first ply is a fine fiber fraction of a fractionated NSSC. The first ply preferably does not contain NSSC pulp lumps. In a preferred embodiment, the washed NSSC pulp used in the second ply is a coarse fraction of a fractionated washed NSSC pulp. In some embodiments, the average particle size of the washed NSSC pulp used in the first ply is lower than the average particle size of the washed NSSC pulp used in the second ply. In some embodiments, the average particle size is the length-weighted average fiber measured using an FS5 fiber optic analyzer (Valmet) according to standard ISO 16065-2.

[0065] In some embodiments, the multi-layer liner paper further comprises an internal sizing agent. The internal sizing agent is preferably a hydrophobic sizing agent. In some embodiments, the internal sizing agent is selected from alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), rosin size, and mixtures thereof. In some embodiments, the amount of the internal sizing agent in the multi-layer liner paper is in the range of 0.5-6 kg / ton, preferably in the range of 0.8-4 kg / ton, and more preferably in the range of 1-3 kg / ton based on dry weight.

[0066] In some embodiments, at least one side, preferably the top side, of the multi-ply liner paper has a Cobb 30 s value below 40, preferably below 25, and more preferably below 22 as measured according to standard ISO535.

[0067] In some embodiments, the multi-ply liner paper has an equilibrium moisture content (EMC) as determined according to standard ISO 287 at 50% RH of less than 10% by weight, preferably less than 8% by weight.

[0068] The multi-ply liner paper may also contain additives such as natural starch or starch derivatives, cellulose derivatives such as sodium carboxymethylcellulose, fillers, retention and / or drainage chemicals, flocculating additives, deflocculants, dry strength enhancers, softeners, cross-linking aids, sizing chemicals, dyes and colorants, wet strength resins, fixatives, defoaming aids, microbial and slime control aids, or mixtures thereof.

[0069] In some embodiments, all of the pulp used in the multi-ply liner paper is formed from FSC certified wood.

[0070] In some embodiments, the multi-ply liner paper complies with the BfR XXXVI recommendations for paper and paperboard intended for food contact as of April 1, 2021.

[0071] The multi-ply liner paper may further comprise a third ply, wherein the third ply comprises at least 70 wt% unbleached kraft pulp and 5-30 wt%, preferably 5-20 wt% or even more preferably 5-10 wt% neutral sulfite semi-chemical (NSSC) pulp on a dry weight basis. It is preferred that the third ply has the same composition as the first ply. It may be preferred that the first and third plies of the multi-ply liner paper form the outer plies and the second ply forms the middle ply of the multi-ply liner paper. It is also preferred that the NSSC pulp of the third ply is washed.

[0072] In some embodiments, it is preferred that the multi-ply liner is a 2-ply liner. A 2-ply liner comprises only two cellulose base plies, ie only the first and second plies.

[0073] According to a second aspect shown herein, there is provided a method for manufacturing a multi-layer liner paper for food or beverage packaging materials, the method comprising the following steps:

[0074] a) forming a first web layer from a first pulp suspension and dewatering the first web layer to obtain a first ply;

[0075] b) forming a second web layer from the second pulp suspension and dewatering the second web layer to obtain a second ply on the first ply;

[0076] wherein the first pulp suspension comprises at least 70 wt. % unbleached kraft pulp and less than 30 wt. % neutral sulfite semi-chemical (NSSC) pulp on a dry weight basis, and

[0077] wherein the second pulp suspension comprises at least 50 wt% NSSC pulp and less than 50 wt% unbleached kraft pulp on a dry weight basis, and

[0078] Wherein the NSSC pulp in the second pulp suspension is a washed NSSC pulp having an ash content of less than 1.8 wt.-% as determined according to standard ISO 1762:2019.

[0079] In some embodiments, step b) further comprises the following steps:

[0080] b1) providing a raw NSSC pulp having an ash content of at least 2% by weight as determined according to standard ISO 1762:2019;

[0081] b2) washing the raw NSSC pulp so as to obtain a washed NSSC pulp having an ash content of less than 1.8% by weight as determined according to standard ISO 1762:2019; and

[0082] b3) optionally mixing the washed NSSC pulp with at least one internal sizing agent;

[0083] To obtain a washed neutral sulfite semi-chemical (NSSC) pulp of the second pulp suspension.

[0084] The purpose of washing is to separate the pulp from the black liquor, to wash away the residual substances produced in the cooking process such as alkali lignin, and to purify the pulp.

[0085] In some embodiments, step b2) comprises diluting the raw NSSC slurry with water and then removing the water along with the diluted colloidal matter, salts, impurities and fines through a screen.

[0086] In some embodiments, washing of the NSSC slurry comprises using >10 m 3 , preferably >12 m 3 , and more preferably >15 m 3 The NSSC slurry is diluted with 100% clean water / ton of dry NSSC slurry and then subjected to dewatering to a solid content of >40% by weight. In some embodiments, washing of the NSSC slurry comprises using 10-50 m 3 , preferably 12-50 m 3 , and more preferably 15-50m 3 The NSSC pulp is diluted with clean water / ton of dry NSSC pulp and then the pulp is dehydrated to a solid content of>40% by weight. Washing can be performed in one or more washing steps, each washing step comprising diluting the NSSC pulp and then subjecting the pulp to dehydration. Washing can be performed using one or more conventional pulp washing methods and washing equipment, including but not limited to rotary vacuum pulp washers, rotary high-pressure pulp washers, high-pressure and atmospheric diffusion pulp washers, horizontal belt pulp washers and / or dilution / extraction equipment. Washing generally involves diluting the NSSC pulp with water and then removing the water together with the diluted colloidal substances, salts, impurities and fines through a wire screen. A preferred washing procedure uses at least one double screen, drum displacement pulp washer, double roll press, rotary vacuum drum pulp washer, rotary high-pressure drum, horizontal belt press, atmospheric or pressurized diffuser, or extraction press, followed by at least one screw press.

[0087] In some embodiments, at least one washing step, preferably the last washing step, is performed with hot water. The temperature of the hot water is preferably above 50°C, more preferably above 60°C or above 70°C. In some embodiments, the temperature of the hot water is in the range of 50-100°C, 60-100°C or 70-100°C. In some embodiments, the pulp temperature of the washing step performed with hot water is in the range of 40-90°C or in the range of 45-80°C.

[0088] In some embodiments, step b2) comprises washing the raw NSSC pulp to obtain a washed NSSC pulp having an ash content of less than 1.6 wt. %, preferably less than 1.4 wt. %, and more preferably less than 1.2 wt. % or less than 1.0 wt. % or less than 0.9 wt. % as determined according to standard ISO 1762:2019.

[0089] The washing of NSSC pulp can be characterized according to the Nordén efficiency factor (E), preferably normalized to the Nordén efficiency factor at 10% discharge consistency (E 10 ). 10 It can be calculated by the following formula:

[0090]

[0091] in:

[0092] L 0 = slurry inlet liquid, lb / lb slurry

[0093] L 1 = slurry outlet liquid, lb / lb slurry

[0094] x 0 = Slurry inlet solid concentration, weight %

[0095] x 1 = Slurry outlet solid concentration, weight %

[0096] y 1 = solid concentration at the outlet of washing liquid, weight %

[0097] y 2 = washing liquid inlet solid concentration, weight %

[0098] DF = dilution factor = V 2 –L 1

[0099] V 2 = flushing water flow, lb / lb slurry

[0100] In some embodiments, the Norden efficiency factor (E10 )>2, preferably>2.2, and more preferably>2.5.

[0101] In some embodiments, the Norden efficiency factor (E 10 ) is in the range of 2-6, preferably 2.2-5, and more preferably 2.5-4.

[0102] When washing is performed in series in two or more washing steps, E 10 The values ​​are additive. That is, 10 The first wash step has a value of 2 and E 10 The wash sequence consisting of a second wash step with a value of 1 results in a total E 10 The value is 3.

[0103] In some embodiments, step b2) comprises washing the raw NSSC pulp to obtain a washed NSSC pulp having a hot water extract conductivity as measured according to ISO6587 of less than 30 mS / cm, preferably less than 20 mS / cm, and more preferably less than 15 mS / cm.

[0104] The terms first and second web layers do not necessarily indicate the order in which the web layers are formed. The web layers may be formed simultaneously or separately in any order.

[0105] In some embodiments, the first and second web layers are formed separately and partially dewatered using different headboxes and one or more wires, and then laminated in a wet state.

[0106] In some embodiments, the first and second web layers are formed and partially dewatered together using a multi-sheet headbox and a single wire.

[0107] For example, the first web layer may be formed separately and partially dewatered and subsequently laminated with the second web layer in a wet state to obtain the second ply on the first ply. Alternatively, the second web layer may be formed and dewatered together with the first web layer.

[0108] In some embodiments, the first pulp suspension comprises at least 75 wt%, preferably at least 80 wt%, unbleached kraft pulp on a dry weight basis.

[0109] In some embodiments, the first pulp suspension comprises less than 20 wt%, preferably less than 10 wt% washed NSSC pulp on a dry weight basis. Preferably, the first pulp suspension comprises 5-20 wt%, or even more preferably 5-10 wt% washed NSSC pulp on a dry weight basis.

[0110] In some embodiments, the second slurry suspension comprises at least 60 wt%, preferably at least 70 wt%, more preferably at least 80 wt% washed NSSC slurry on a dry weight basis.

[0111] In some embodiments, at least 30% of the pulp of the second pulp suspension is comprised of recycled cellulosic fibers.

[0112] In some embodiments, the first layer and the second layer each have a grammage of 20-150 g / m 2 In the range of 30-100 g / m 2 within the range.

[0113] In some embodiments, the amount of washed NSSC pulp in the multi-ply liner paper is at least 10 wt%, preferably at least 20 wt%, more preferably at least 30 wt% on a dry weight basis.

[0114] In some embodiments, the average particle size of the washed NSSC slurry used in the first slurry suspension is lower than the average particle size of the washed NSSC slurry used in the second slurry suspension.

[0115] The method comprises forming a plurality of webs from a pulp suspension and dewatering. Methods for forming and dewatering a web having a plurality of layers are well known in the art. The liner paper can be made in a paper machine or board machine suitable for making multi-layer liner paper. Paper machines or board machines for making multi-layer liner paper are well known in the art. Typically, the machine configuration comprises a stock handling section, a wet end, a press section and a drying section as well as a calendering section and / or a coating section.

[0116] The web is typically formed and dewatered in a wet-end forming section that contains one or more wires as is conventional in the art. The plies can be formed separately using different headboxes and laminated in the wet state, or formed together in a multi-ply headbox. The web is typically formed in a gap former, but it can also be formed in a Fourdrinier type former. If formed separately, the wet plies are typically laminated or laid together before the press and dryer sections of the paper machine.

[0117] Before lamination, a reinforcing agent or adhesive may be applied between the first ply and the second ply. Preferably, the reinforcing agent or adhesive comprises a mixture of cooked starch or gelatinized starch or uncooked starch, or cooked starch or gelatinized starch or uncooked starch and microfibrillated cellulose (MFC). A preferred reinforcing agent or adhesive is a cooked natural starch or a cooked natural starch mixed with microfibrillated cellulose. In some embodiments, the reinforcing agent or adhesive further comprises a crosslinking agent. The crosslinking agent may be, for example, citric acid. In some embodiments, the reinforcing agent or adhesive further comprises an insoluble material. The insoluble material may be, for example, an amino resin, glyoxal, or a zirconium salt insoluble material. The reinforcing agent or adhesive is preferably added in a paste or aqueous dispersion using a non-contact deposition technique (such as spraying or foaming or curtain application). Preferably, the solid content of the aqueous dispersion is in the range of 0.5-50% by weight, and more preferably in the range of 1-30% by weight. The amount of the reinforcing agent or adhesive applied is preferably based on dry weight in the range of 0.1-5 g / m 2 In the range of 0.5-3 g / m 2 within the range.

[0118] The web is usually subjected to further dewatering, which may for example comprise passing the formed multilayer web through the press section of a paper machine, wherein the web is passed between large rolls loaded under high pressure to squeeze out as much water as possible. The press section may consist of a conventional nip press unit and a press fabric felt and / or may have one or more shoe presses or extended dewatering nips. These may be operated under various nips or press loads (including different positions, temperatures and delay times). The press section may be provided with one or more shoe presses to maximize production. If one or more shoe presses are used, these may be operated under a press level of more than 800 kN / m, such as more than 1000 kN / m, such as more than 1200 kN / m or such as more than 1450 kN / m. The removed water is usually received by a fabric or felt.

[0119] After the press section, the multilayer web may be subjected to drying in a drying section. Drying may, for example, include drying the multilayer web by passing the multilayer web around a series of heated drying cylinders. Drying may typically remove moisture to a level as low as about 1-15% by weight, preferably about 2-10% by weight.

[0120] According to the third aspect shown in this document, a food or beverage packaging material is provided, which comprises the multi-layer sheet noodle paper according to the first aspect or the multi-layer sheet noodle paper obtained according to the method according to the second aspect, wherein the first layer faces the printing surface of the packaging material and the second layer faces the interior of the packaging material.

[0121] In some embodiments, the food or beverage packaging material is liquid packaging board, food service board, or corrugated board.

[0122] In some embodiments, the food or beverage packaging material is a corrugated board. The corrugated board comprises at least one layer of non-corrugated liner paper, which is glued to at least one layer of corrugated medium paper. For example, the corrugated board can be composed of a layer of corrugated medium paper sandwiched between two layers of liner paper. In a preferred embodiment, the corrugated medium paper is glued to the second layer of the multi-layer liner paper.

[0123] The multi-layer liner paper can also be used as a free-standing substrate, i.e., a board or cardboard that does not form part of a corrugated board. The free-standing substrate can be used, for example, as a paper or board substrate for a liquid packaging board (LPB) or a food service board (FSB). Thus, in some embodiments, the food or beverage packaging material is a liquid packaging board or a food service board. The multi-layer liner paper used as a liquid packaging board (LPB) or a food service board (FSB) can be further coated with additional functional layers (such as a print-receptive layer barrier or barrier layer) or laminated with additional paper or plastic films.

[0124] In some embodiments, as of April 1, 2021, the food or beverage packaging material complies with the recommendations of BfR XXXVI on paper and paperboard for food contact.

[0125] According to the fourth aspect shown in this document, a food or beverage packaging container is provided, which packaging container comprises a multi-layer noodle paper according to the first aspect or a multi-layer noodle paper obtained according to the method according to the second aspect, wherein the first layer faces the printed surface of the packaging container and the second layer faces the interior of the packaging container.

[0126] Although the present invention has been described with reference to various exemplary embodiments, it will be appreciated by those skilled in the art that various changes may be made and elements thereof may be substituted with equivalents without departing from the scope of the present invention. In addition, many modifications may be made to adapt specific situations or materials to the teachings of the present invention without departing from the basic scope of the present invention. Therefore, the present invention is not intended to be limited to the specific embodiments disclosed as the best mode contemplated for carrying out the present invention, but the present invention will include all embodiments falling within the scope of the appended claims.

[0127] Example

[0128] These examples show that large amounts of washed NSSC pulp can be used in 2-ply liner paper without negatively affecting the mechanical or optical properties of the liner paper.Three 135 gsm 2-ply liner paper samples containing UBKP in the top sheet and RCF, NSSC, and washed NSSC in the bottom sheet, respectively, were prepared and analyzed.

[0129] The NSSC slurry was washed by using >10 m 3 Clean water / ton of dry NSSC pulp was carried out on the dilution of the NSSC pulp. The pulp was then subjected to dewatering on a dewatering fabric to a solids content of >40 wt%.

[0130] The volatile organic compounds (VOC) of the samples were qualitatively and quantitatively analyzed using a headspace gas chromatography equipped with a flame ionization detector (HS GC / FID or HS GC / MS).

[0131] The sample (2.0 g) was heated to 90 °C for 40 min in a closed sample bottle and the evaporated (gaseous) compounds in the space above the sample were analyzed.

[0132] The amount of total volatile compounds and hexanal was determined and calculated. The compounds were identified by comparison with a spectral library.

[0133] Preparation method of two-layer noodle paper

[0134] A 2-ply linerboard comprising a top sheet (corresponding to the first ply of the present invention) and a bottom sheet (corresponding to the second ply of the present invention) was prepared on a pilot machine equipped with 2 headboxes and 2 wires, a press section and a drying section. The target final moisture content of the 2-ply structure was 8% by weight and the target grammage was 135 g / m 2 .

[0135] Example 1 (Comparative) - 100% RCF in the backsheet

[0136] A 2-ply sheet of 135 g / m2 was prepared according to the above 2-ply liner paper preparation method using 100% unbleached kraft pulp (UBKP) in the top sheet and 100% recycled cellulose fiber pulp (RCF) in the bottom sheet (as described in Table 1). 2 Linerboard. The linerboard was analyzed and the results are presented in Table 1. Ash content 1.3 wt%, SR 32, conductivity pH 6.6. Quantitative and qualitative determination of VOC gave a total amount of volatiles of 16100 ppb and an amount of hexanal of 4060 ppb.

[0137] Example 2 (Comparative) - 100% NSSC slurry in bottom sheet

[0138] According to the above two-layer noodle paper preparation method, a two-layer sheet of 135 g / m 2 Linerboard. In this example, the backsheet comprises 100% unwashed NSSC pulp (1) (as described in Table 1). The linerboard was analyzed and the results are presented in Table 1.

[0139] Example 3 - 100% washed NSSC pulp in the bottom sheet

[0140] According to the above two-layer noodle paper preparation method, a two-layer sheet of 135 g / m 2 Linerboard. In this example, the backing sheet comprises 100% washed NSSC pulp (2) (as described in Table 1). The linerboard was analyzed and the results are presented in Table 1. The ash content was 0 wt%, the SR of the NSSC was 25, the conductivity was 1.32 mS / cm, and the pH was 6.2. The quantitative and qualitative determination of VOC gave a total amount of volatiles of 9790 ppb and an amount of hexanal of 3110 ppb. This shows that washed NSSC pulp can provide a significant reduction in total VOC and hexanal.

[0141] Table 1.

[0142]

[0143] Unless otherwise indicated, the physical properties discussed in this disclosure are measured according to the following standards:

[0144] Weight ISO 536

[0145] Roughness ISO 8791-2:2013

[0146] Cobb 30 s ISO 535

[0147] Water content 50% rh ISO 287

[0148] Scott Binding Force TAPPI T569

[0149] SCTISO 9895

[0150] Burst index ISO 2759

[0151] Burst strength ISO 2759

[0152] Unless otherwise indicated, standard methods can then be used to determine physical and mechanical properties in both the cross direction (cd) and the machine direction (md).

Claims

1. A multi-layered noodle paper for food or beverage packaging material, the multi-layered noodle paper comprising: The first layer, and The second layer, wherein the first ply comprises at least 70 wt. % unbleached kraft pulp and less than 30 wt. % neutral sulfite semi-chemical (NSSC) pulp on a dry weight basis, wherein the second ply comprises, on a dry weight basis, at least 50 wt. % NSSC pulp and less than 50 wt. % unbleached kraft pulp, and Wherein the NSSC pulp in the second ply is a washed NSSC pulp having an ash content of less than 1.8 wt. % measured according to standard ISO 1762:2019.

2. The multi-layer liner paper according to claim 1, wherein the washed NSSC pulp has an ash content of less than 1.6% by weight, preferably less than 1.4% by weight, and more preferably less than 1.2% by weight or less than 1.0% by weight or less than 0.9% by weight, determined according to standard ISO 1762:2019.

3. The multi-ply liner paper according to any one of the preceding claims, wherein the washed NSSC pulp has a hot water extract conductivity measured according to ISO 6587 of less than 30 mS / cm, preferably less than 20 mS / cm, and more preferably less than 15 mS / cm.

4. The multi-ply liner paper according to any one of the preceding claims, wherein the first ply comprises at least 75 wt%, preferably at least 80 wt%, unbleached kraft pulp on a dry weight basis.

5. The multi-ply liner paper according to any one of the preceding claims, wherein the first ply comprises less than 20 wt%, preferably less than 10 wt% NSSC pulp on a dry weight basis.

6. The multi-ply liner paper according to any one of the preceding claims, wherein the second ply comprises at least 60 wt%, preferably at least 70 wt%, more preferably at least 80 wt% NSSC pulp on a dry weight basis.

7. The multi-ply liner paper according to any one of the preceding claims, wherein less than 30% by weight of the second ply consists of broke or recycled cellulosic fibers.

8. The multi-ply liner paper according to any one of the preceding claims, wherein the first ply and the second ply each have a grammage of 20-150 g / m 2 In the range of 30-100 g / m 2 within the range.

9. The multi-ply lining paper according to any one of the preceding claims, wherein the amount of NSSC pulp in the multi-ply lining paper is at least 10 wt%, preferably at least 20 wt%, more preferably at least 30 wt% on a dry weight basis.

10. The multi-ply liner paper according to any one of the preceding claims, wherein the average particle size of the washed NSSC pulp used in the first ply is lower than the average particle size of the washed NSSC pulp used in the second ply.

11. The multi-ply liner paper according to any one of the preceding claims, wherein the multi-ply liner paper further comprises an internal sizing agent.

12. The multi-ply lining paper according to any one of the preceding claims, wherein at least one side of the multi-ply lining paper has a Cobb 30 s value measured according to standard ISO 535 of below 40, preferably below 25 and more preferably below 22.

13. Multi-ply lining paper according to any one of the preceding claims, wherein the multi-ply lining paper has an equilibrium moisture content (EMC) at 50% RH measured according to standard ISO 287 of less than 10% by weight, preferably less than 8% by weight.

14. The multi-ply liner according to any one of the preceding claims, wherein the multi-ply liner is a 2-ply liner.

15. A method for producing a multilayer sheet liner for food or beverage packaging material, comprising the following steps: a) forming a first web layer from a first pulp suspension and dewatering the first web layer to obtain a first ply; b) forming a second web layer from a second pulp suspension and dewatering the second web layer to obtain a second ply on the first ply; wherein the first pulp suspension comprises at least 70 wt. % unbleached kraft pulp and less than 30 wt. % neutral sulfite semi-chemical (NSSC) pulp on a dry weight basis, and wherein the second pulp suspension comprises at least 50 wt% NSSC pulp and less than 50 wt% unbleached kraft pulp on a dry weight basis, and Wherein the NSSC pulp in the second pulp suspension is a washed NSSC pulp having an ash content of less than 1.8 wt. % measured according to standard ISO 1762:2019.

16. The method for manufacturing multi-layer noodle paper according to claim 15, wherein step b) further comprises the following steps: b1) providing a raw NSSC pulp having an ash content of at least 2% by weight as determined according to standard ISO 1762:2019; b2) washing the raw NSSC pulp so as to obtain a washed NSSC pulp having an ash content of less than 1.8% by weight, measured according to standard ISO 1762:2019; as well as b3) optionally mixing the washed NSSC pulp with at least one internal sizing agent; to obtain the washed neutral sulfite semi-chemical (NSSC) pulp of the second pulp suspension.

17. The method for manufacturing multi-layer liner paper according to claim 16, wherein step b2 comprises diluting the NSSC slurry with water, and then removing the water together with the diluted colloidal substances, salts, impurities and fines through a wire screen.

18. The method for manufacturing a multi-layer liner paper according to any one of claims 16-17, wherein step b2 comprises washing the raw NSSC pulp to obtain a washed NSSC pulp having an ash content of less than 1.6% by weight, preferably less than 1.4% by weight, and more preferably less than 1.2% by weight or less than 1.0% by weight or less than 0.9% by weight, as determined according to standard ISO 1762:2019.

19. The method for manufacturing the multi-layer liner paper according to any one of claims 16 to 18, wherein step b2 comprises washing the raw NSSC pulp to obtain a washed NSSC pulp having a hot water extract conductivity of less than 30 mS / cm, preferably less than 20 mS / cm, and more preferably less than 15 mS / cm, as measured according to ISO 6587.

20. Food or beverage packaging material comprising a multi-ply liner paper according to any one of claims 1 to 14 or obtained according to any one of claims 15 to 19, wherein the first ply faces the printed side of the packaging material and the second ply faces the interior of the packaging material.

21. The food or beverage packaging material according to claim 20, wherein the food or beverage packaging material is liquid packaging paperboard, food service paperboard or corrugated paperboard.

22. A food or beverage packaging container comprising a multi-ply liner paper according to any one of claims 1 to 14 or obtained according to any one of claims 15 to 19, wherein the first ply faces the printed surface of the packaging container and the second ply faces the interior of the packaging container.

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