PACKAGING PAPER

Description

[0001] The present invention relates to unbleached packaging paper for sharp-edged articles and / or articles having unevenly arranged, projecting, substantially non-deformable elevations on at least one of its surfaces, which consists of kraft sulfate pulp as the main component as well as fillers, starch, sizing agents and other processing aids and optionally coating agents.

[0002] Packaging materials made of paper and / or cardboard are used extensively around the world for a wide variety of objects or materials, on the one hand to provide recyclable packaging materials and, on the other hand, to reduce or avoid the amount of non-decomposable waste as much as possible. For this reason, in recent years, paper has been increasingly used in areas where, just a few years ago, only plastics and plastic composite materials were used as packaging material. In these areas of application, specially manufactured papers must often be given greater consideration and attention must be paid to the respective requirements, such as the weight of the packaged objects, possible fat and / or moisture content, the external shape of the packaged objects, as well as the stability of the packaged objects under pressure, temperature stress, etc., making it necessary to provide specially manufactured or treated papers.Paper is known for its use in packaging building materials such as sand, cement, or even stone, as well as for packaging consumer goods, especially food products such as flour, rice, pasta, nuts, and more. Another area of ​​application for paper is the packaging of consumer goods such as toys, clothing, electronic components, household goods, screws, nails, and much more, as well as open packaging such as sacks or carrier bags.

[0003] EP 3 633 104 A1 discloses a process for producing kraft papers that exhibit both high flexural rigidity and good printability. The papers produced using the described process are porous sack papers with a density of over 630 kg / m³, which were wet-calendered during their production.

[0004] Packaging papers must meet the respective requirements of the goods to be packaged in them; in particular, they must have sufficient tear resistance, elasticity, air permeability, etc. On the other hand, for example, packaging paper used for packaging moisture-sensitive materials must have sufficient moisture resistance and, in particular, have a barrier property against moisture or only have very limited moisture permeability. The specific properties that a packaging paper must have for a particular intended use can be estimated and determined by a specialist, taking into account the composition, the manufacturing process, possible orThe necessary treatment steps and materials can be at least roughly estimated by a specialist. However, the production of a paper that meets all of these requirements requires taking a variety of factors into account, which often interact with one another. This means that the final composition of the packaging paper and its production usually requires a lot of trial and error. Problems when using paper as a packaging material often arise when sharp-edged objects have to be packaged or objects have to be packaged that have surface areas with more or less large protrusions, jagged edges, edges, corners, etc. Paper can only be used to a limited extent here because, on the one hand, it can be abraded in uneven areas and, if the structure of the paper is destroyed or torn, it can lose a large part of its original positive properties, such as strength, etc.Another potential risk is that the packaging paper could tear due to contact with the sharp edges or points of the items it contains, resulting in the items being lost, damaged, or degraded due to the loss of intact packaging. To prevent such tearing of packaging paper, it has often been the case in the past that it was coated on at least one side with plastic films, polymers, or other tear-resistant yet elastic materials, or an insert made of such materials was inserted into multi-layer papers to enable paper to be used as packaging material for sharp-edged items or items with uneven surfaces.

[0005] Due to the fact that non-degradable polymers or plastic materials should be avoided as far as possible, there is a requirement for packaging materials made of paper which, on the one hand, are sufficiently elastic, stretchable and flexible so as not to tear under corresponding stresses and, on the other hand, if sharp-edged objects are packed in them, can at least prevent destruction or damage to the packaging, such as punctures, abrasion or tearing by objects packed in them.

[0006] The present invention therefore aims to provide such an unbleached packaging paper with which it is possible to package a wide variety of objects or materials having sharp edges or irregular surfaces without the packaged object penetrating the packaging paper or tearing it.

[0007] To achieve this object, an unbleached packaging paper according to the invention is essentially characterized in that it contains at least 95% primary pulp containing at least 80%, preferably at least 90%, in particular at least 95% pulp with an average length-weighted fiber length according to ISO 16065-2:2014 of at least 2.0 mm and less than 4.5%, preferably less than 4.0%, in particular less than 3.7% fillers as well as cationic starch and other processing aids, that it has an elongation at break in the machine direction (MD) according to ISO 1924-3:2005 of at least 6.0%, preferably at least 6.5%, that it has a kappa number according to ISO 302:2015 between 35 and 58, preferably 39 and 48 and that it has a puncture energy index according to DIN EN 14477:2004 with a test speed of 10.0 mm / min measured on any side of the Packaging paper in the range of 30 to 75 mJ.m 2< / kg, preferably 35 to 70 mJ.m 2< / kg. The fact that the packaging paper contains at least 95% primary pulp ensures that the packaging paper is of the highest quality and has the best properties. It is known to those skilled in the art that the possible addition of recycled pulp can adversely affect the paper quality and, in particular, impair the strength and elasticity properties of the paper. Surprisingly, it has been shown that a possible addition of secondary pulp in the order of up to a maximum of 5% does not adversely affect the strength and elasticity of the paper.Depending on the food safety requirements for the packaging material in the packaging task and the nature of the food to be packaged, such as dry, moist, and / or fatty, the proportion of primary pulp may need to be adjusted and, for example, increased. Alternatively, appropriate analyses can be carried out on the packaging material to meet and sustainably ensure compliance with food safety requirements. However, this involves considerable additional resources, such as chemical detection reagents and the necessary analytical equipment. The fact that the packaging paper has a kappa number according to ISO 302:2015 between 35 and 58, preferably 39 and 48, ensures that the use of bleaching chemicals can be avoided, thus making the use of the packaging paper advantageous in the food sector.Furthermore, unbleached pulp can bind more starch than bleached pulp fiber. The use of cationic starch also increases the dry strength of the paper to which it is added, which is why, particularly when using unbleached pulp for the production of packaging paper, the aim is to use starch contents of over 12 kg / t of paper atro (atro means absolutely dry). Bleaching paper removes impurities and is used in particular when the surface of the paper has to be printed, for example, since bleached papers are usually easier to print on due to the improved brilliance of the printing inks. However, in the context of the present invention, it should be noted that the packaging paper is used as unbleached packaging paper, for the production of which pulps with kappa numbers according to ISO 302:2015 in the range of 35 or higher were used.

[0008] According to a further development of the invention, the unbleached packaging paper is designed to contain 100% primary pulp. While an admixture of secondary pulp of up to a maximum of 5% does not adversely affect the strength and elasticity of the paper, the use of 100% primary pulp ensures that the packaging paper is suitable for packaging foods with a non-uniform, uneven surface, such as pasta, cereal bars, nuts, or the like.

[0009] With such packaging papers, it is possible, depending on the basis weight of the respective paper, to provide single- or multi-layer packaging papers, which can, for example, serve as a replacement for plastic packaging or packaging cardboard.

[0010] In this case, when the term "fillers" is used, this term is considered to include the ash content present in the paper itself. This is because the amount of ash present in paper does not normally exceed 0.5%.

[0011] When percentages are given in the context of the present invention, percentages by weight are meant in relation to the dry mass, unless otherwise stated.

[0012] By further comprising at least 80% of the primary pulp used being softwood pulp, more preferably at least 90% being softwood pulp, in particular at least 95% having an average length-weighted fiber length according to ISO 16065-2:2014 of at least 2.1 mm, and the remainder being hardwood pulp having an average length-weighted fiber length according to ISO 16065-2:2014 of at least 1.0 mm, it is particularly possible to influence the strength and elasticity properties of the packaging paper produced therewith in the direction of greater elasticity of the packaging paper and thereby prevent premature tearing of the packaging paper produced according to the invention when it comes into contact with sharp-edged objects.

[0013] By limiting the amount, type of application, processing, etc. of paper additives such as filler content, cationic starch, or sizing agents, particularly sizing agents processed at a neutral pH, to values ​​of less than 4.5%, it is essentially possible to provide packaging paper made exclusively from primary pulp. This packaging paper not only has excellent mechanical properties but, particularly due to the small amounts of additional additives or fillers used, is suitable for special purposes such as food packaging, etc., and may also be used as such. Such packaging paper, which is made essentially exclusively from primary pulp, which consists primarily of softwood fibers that may contain small amounts of hardwood fibers,admixed, are selected, as well as small amounts of fillers and starch, achieved by a special treatment, in particular, for example, refining of the cellulose fibers and optionally further process steps, such as treating the paper web on a Clupak system, calendering and the like, an elongation at break in the machine direction according to ISO 1924-3:2005 of at least 6.0%. Examples of suitable primary pulps include long-fiber pulp comprising one or more types of softwood, short-fiber pulp comprising one or more types of hardwood, and mixtures comprising the aforementioned pulps. The pulps are preferably produced according to the kraft sulfate process. Such a packaging paper furthermore has a puncture energy index according to DIN EN 14477:2004 with a test speed of 10.0 mm / min measured on any side of the packaging paper in the range of 30 to 75 mJ.m 2< / kg, which means that if such a paper is used to package sharp-edged objects and / or objects which have unevenly arranged, protruding and essentially non-deformable elevations on at least one of their surfaces, penetration or puncture of the sharp-edged objects through the paper can be prevented. What is surprising here is that a packaging paper which has an elongation at break of over 6.0% also simultaneously has the highest values ​​for the puncture energy index and thus disadvantageous effects which are associated with very high elongation values, such as very strong roughening of the paper surface, can be reduced. With such a packaging paper, it is therefore possible to prevent restrictions in printability.Since excessive elongation also compromises tensile strength, the packaging paper provides an optimally balanced paper in terms of both elongation and strength. Thus, a packaging paper according to the invention can now be used safely and without the risk of loss of the items packaged therein due to abrasion from protruding areas of the items packaged therein, for packaging sharp-edged items such as gravel, pellets, metal parts such as screws, clothing with buttons, shoes with sharp heels, children's toy blocks, but also foodstuffs such as muesli bars, chocolate-nut bars, nuts, pasta, and the like.

[0014] Puncture energy, defined in DIN EN 14477:2004, is the force, taking into account elongation, that must be applied to penetrate a piece of paper or cardboard with a defined test specimen. For packaging paper intended for packaging sharp-edged objects, it is therefore essential that its puncture energy is high enough to prevent it from being penetrated by the objects or parts of the objects packed inside. Furthermore, it is important that packaging is not damaged by penetration by objects packed inside, especially during transport and during handling.The puncture energy index, which is the puncture energy of a paper divided by its grammage, was measured in connection with the present invention using the DIN EN 14477:2004 standard, which is commonly used to determine the puncture energy of flexible packaging materials such as plastic films. In addition to the puncture resistance in Newtons, the elongation upon puncture in mm is also crucial for ensuring that the packaging is not damaged. The integral under a force-elongation curve represents the energy that a material, and according to the present invention a packaging paper, can absorb without causing damage. To determine the puncture energy index in mJ.m 2< / kg, the determined puncture energy in mJ is divided by the grammage according to ISO 536:2019 of the respective paper, converted into kg / m 2<.The puncture energy index is calculated analogously to the calculation of the tensile fracture energy index according to ISO 1924-3:2005.

[0015] In this context, a mean length-weighted fibre length according to ISO 16065-2:2014 of the pulp fibre is understood to be a length-weighted mean value of the fibre lengths.

[0016] As is known to a person skilled in the art, cationic starch refers to a starch which has been subjected to a cationization treatment with bases such as NaOH, KOH, calcium carbonate and a cationizing agent such as 2,3-epoxypropyltrimethylammonium chloride and the like and which has a degree of cationization, ie a proportion of cationic charges, in the range from 0.02 to about 0.06.

[0017] Softwood pulp is understood to be pulp made from softwood, i.e. wood with a dry density of less than 0.55 g / cm 3. Examples of such softwoods are essentially almost all softwoods, such as spruce, larch, fir, pine and Douglas fir, but also hardwoods such as willow, poplar or linden. Hardwood pulp is understood to be pulp made from hardwood, i.e. wood with a dry density of more than 0.55 g / m 3. Examples of hardwoods include beech, oak, ash, birch, poplar, aspen, maple and acacia. A further distinguishing feature between hardwood and softwood is the fiber length of the fibers they contain. This fiber length is influenced not only by the type of wood but also by the age of the tree and the position of the fiber in the cross-section of the trunk.According to the invention, softwoods with a length-weighted average fiber length of at least 2.1 mm and, optionally, hardwoods with a length-weighted average fiber length of at least 1.0 mm are used. This length-weighted fiber length of a pulp fiber is defined in ISO 16065-2:2014 and is determined according to this standard.

[0018] To obtain a packaging paper with particularly good properties, and in particular to prevent the incorporation of undefined components such as residues of printing ink, surface treatment agents, or the like into the paper, the packaging paper according to the invention is further developed to contain 100% primary pulp. If it is ensured that, in addition to primary pulp, the paper contains no recycled pulp, a packaging paper with precisely reproducible properties can be obtained. Furthermore, packaging papers consisting exclusively of primary pulp can be used as packaging paper for food.

[0019] According to a further development of the invention, the unbleached packaging paper is essentially characterized in that the primary pulp is formed from a mixture consisting of at least 80% softwood pulp, more preferably at least 90% softwood pulp, in particular at least 95% softwood pulp with an average length-weighted fiber length according to ISO 16065-2:2014 of at least 2.1 mm, and the remainder hardwood pulp with an average length-weighted fiber length according to ISO 16065-2:2014 of at least 1.0 mm. By selecting the appropriate primary pulp or a corresponding mixture of primary pulps, it is possible to influence not only the properties of the packaging paper, such as its elongation at break and its puncture energy index, but also other properties essential for packaging paper, such as paper strength, tensile strength, air permeability, and the like.

[0020] Favorable values ​​were achieved when, as is the case with a further development of the invention, the unbleached packaging paper is designed such that the primary pulp consists of 100% softwood pulp with an average length-weighted fiber length according to ISO 16065-2:2014 of at least 2.1 mm. It should be noted in this context that packaging paper made from 100% softwood pulp with an average length-weighted fiber length according to ISO 16065-2:2014 of at least 2.1 mm is thinner, has good strength, and is also printable than papers containing hardwood components or made exclusively from hardwood pulp. However, higher hardwood components, for example, make the paper even more uniform in its sheet structure, and the achievable print quality can also be improved.

[0021] The unbleached packaging paper according to the present invention advantageously has a basis weight according to ISO 536:2019 of 45 g / m 2< to 165 g / m 2< , preferably 50 g / m 2< to 160 g / m 2<. Tests have shown that this wide range of basis weights can be ensured in particular by adjusting the fillers added to the cellulose pulp and the refining energy used. For example, it has been shown that the content of cationic starch must be kept low if papers with basis weights in the range of 50 g / m 2< to 70 g / m 2< and a puncture energy index according to DIN EN 14477:2004 in the range of 30 mJ.m 2< / kg to 75 mJ.m 2< / kg are to be produced.

[0022] According to a further development of the invention, the unbleached packaging paper is designed to have a tensile strength index in the machine direction according to ISO 1924-3:2005 between 60 Nm / g and 140 Nm / g. Such tensile strength indices can be achieved with the packaging papers according to the invention due to the low filler content in the paper. When using fillers, particular care must be taken to ensure that they are approved for use in the food industry if the paper is intended for use in the food industry. In this context, particular attention should be paid to grain sizes in the micrometer and nanometer range.

[0023] When using unbleached packaging paper in any application other than food packaging, the choice of filler is less critical. However, to achieve the desired tensile strength index in the machine direction between 60 Nm / g and 140 Nm / g, the filler content should generally be kept low. Another additive used to adjust strength properties could be derivatized starch, preferably cationic starch. In general, all additives used in the papermaking process must be considered to ensure their suitability as a feedstock for the production of food packaging paper.

[0024] According to a development of the invention, the unbleached packaging paper is designed such that the primary pulp is contained as ground pulp, in particular high-consistency ground pulp with a Schopper-Riegler freeness level according to ISO 5267-1:1999 between 13°SR and 20°SR. Refining pulp influences the fiber strength and thus increases the quality of the product manufactured with it from a number of perspectives. In particular, when using non-bleached, i.e. unbleached (i.e. natural brown) pulp, the paper quality can be influenced in such a way that residual wood splinters contained in the pulp and fiber agglomerates not broken down by pulp cooking are finely ground during high-consistency refining, thus better evening out the texture of the paper and, in particular, smoothing it.By providing, according to the invention, a refined, particularly high-consistency refined, pulp with a Schopper-Riegler freeness level according to ISO 5267-1:1999 between 13°SR and 20°SR as the primary pulp after high-consistency refining, the penetration energy can be increased even further. It goes without saying that the pulp can also be additionally refined to a low consistency. Low-consistency refining is carried out at a pulp suspension consistency between 2% and 6%, whereby this step can achieve a further increase in strength and thus also an increase in penetration energy.

[0025] Packaging papers must, on the one hand, be dense enough to prevent loss of powdered materials or reduce water absorption of hygroscopic items packaged therein depending on the application. On the other hand, they must have sufficient air permeability so that, for example, air introduced during filling can also escape through the packaging paper itself. To meet these requirements, according to a further development of the invention, the unbleached packaging paper has a Gurley value according to ISO 5636-5:2013 between 5 s and 45 s, in particular between 10 s and 40 s.

[0026] Depending on the intended use of the unbleached packaging paper, a further development can be designed such that at least one side of the packaging paper has a surface finish, in particular a smoothing and / or coating. Such a surface finish can, for example, influence the moisture barrier properties, but also, in particular, further improve the puncture energy, so that the paper can withstand even greater stresses, especially from uneven or sharp objects wrapped in the paper.

[0027] According to a further development of the invention, the unbleached packaging paper is designed such that the puncture energy index according to DIN EN 14477:2004 differs between a surface-treated side of the packaging paper and an untreated side of the packaging paper by a factor of greater than 1.0 to 1.7. The puncture energy index is generally influenced by surface treatment steps such as the introduction of functional barrier coatings. This ensures that such packaging paper meets all the requirements for packaging sharp-edged orSince paper must meet the properties required for products with irregular surfaces, it is important, on the one hand, to ensure properties such as printability on one surface and, on the other hand, to ensure that the second surface, which comes into contact with foodstuffs with irregular surfaces, continues to have a sufficient puncture energy index. Therefore, a corresponding factor that differs only slightly from 1.0 should be developed during paper production and, in particular, during surface treatment. However, the puncture energy index should preferably be viewed as an inherent paper property and not, or only to a limited extent, dependent on the surface treatment.

[0028] Such a surface treatment is particularly advantageous and useful when one side of the paper comes into contact with sharp-edged objects and the other side is to be printed or written on, for example, in which case the two surfaces of the packaging paper must be subjected to different finishing treatments.

[0029] The invention is explained in more detail below using exemplary embodiments. Example 1: Production of a packaging paper with a grammage of 50 g / m 2< Process description:

[0030] An unbleached pulp consisting of 95% primary softwood pulp with a kappa number of 42 and 5% primary hardwood pulp with a kappa number of 40 was used. This pulp was first subjected to high-consistency refining with a refining capacity of 190 to 210 kWh / ton. The pulp's freeness after high-consistency refining was 17°SR. This pulp was then subjected to low-consistency refining with a refining capacity of 75 kWh / ton until a freeness of at least 18°SR was achieved. The additives are added in the approach flow system of the paper machine. The pH was adjusted to a pH of 6.5 to 7.5 with aluminum sulfate. Cationic starch with a cationization degree of 0.05 was added at a rate of 2.5 kg / t of dry paper. Alkenylsuccinic anhydride was used as a sizing agent at a rate of 0.5 kg / t of dry paper. The pulp contained no fillers.The pulp consistency at the headbox was 0.2%. Dewatering took place on a Foudrinier wire section and a press section with three nips, with line pressures at the three nips of 55 kN / m, 80 kN / m, and 80 kN / m, respectively. Before the still-moist paper was fed to the Clupak system, it was pre-dried in a slalom dryer section and treated in a Clupak system with a differential speed of -4.8%, before undergoing final drying.

[0031] The paper can be used as such, and the paper properties described in the table below were measured using this paper. It goes without saying that the paper can also be calendered, for example in a soft-nip or long-nip calender, or can be subjected to a coating treatment, such as a dispersion coating treatment, which can further alter its properties. Calendering is carried out on the packaging paper when it has a dry content of at least 88%, preferably at least 90%, particularly preferably at least 91%, i.e. the residual moisture content is less than 12%. Furthermore, packaging paper of this type can be used, for example, as a replacement for thin plastic packaging, for example for food products such as muesli bars.

[0032] The paper produced in this way had the following properties: Paper properties standard Unit Direction Result Grammage ISO 536:2019 g / m 2 49 Tensile strength ISO 1924-3:2005 kN / m MD 5,8 Tensile strength index ISO 1924-3:2005 Nm / g MD 118,4 Tensile strength ISO 1924-3:2005 kN / m CD 2,4 Tensile strength index ISO 1924-3:2005 Nm / g CD 49,0 Elongation at break ISO 1924-3:2005 % MD 7,1 Elongation at break ISO 1924-3:2005 % CD 8,8 Tensile fracture work ISO 1924-3:2005 J / m 2 MD 261 Tensile fracture work ISO 1924-3:2005 J / m 2 CD 162 Air permeability Gurley ISO 5636-5:2013 s 22,7 Bendtsen roughness ISO 8791-2:2013 ml / min Top 1170 Bendtsen roughness ISO 8791-2:2013 ml / min bottom 740 Puncture resistance DIN EN 14477:2004 with 10 mm / min N From top 5,7 Puncture energy DIN EN 14477:2004 with 10 mm / min mJ From top 2,6 Puncture energy index DIN EN 14477:2004 with 10 mm / min mJ.m 2 < / kg From top 53,1 Puncture resistance DIN EN 14477:2004 with 10 mm / min N From bottom 4,4 Puncture energy DIN EN 14477:2004 with 10 mm / min mJ From bottom 1,8 Puncture energy index DIN EN 14477:2004 with 10 mm / min mJ.m 2 < / kg From bottom 36,8 Penetration energy factor DIN EN 14477:2004 with 10 mm / min From top to bottom 1,44 Example 2: Production of a packaging paper with a grammage of 100 g / m 2< Process description:

[0033] An unbleached pulp consisting of 100% primary softwood pulp with a kappa number of 42 was first subjected to high-consistency refining at a refining capacity of 220 to 240 kWh / ton, with the pulp's freeness level after high-consistency refining being 17°SR. Subsequently, this pulp was subjected to low-consistency refining at a refining capacity of 80 to 90 kWh / ton until a freeness level of at least 18°SR was achieved. The additives were added in the approach flow system of the paper machine. The pH was adjusted to a pH of 6.8 to 7.3 with aluminum sulfate. Cationic starch, with a cationization degree (DS) of 0.03, was added at a rate of 14 kg / tonne of dry paper. Alkenylsuccinic anhydride was used as a sizing agent at a rate of 0.8 kg / tonne of dry paper. Fillers were also added at a rate of 0.3 kg / tonne of dry paper.The pulp consistency at the headbox was 0.25%. Dewatering took place on a Foudrinier wire section and a press section with three nips, one of which could be a shoe press. The line pressure at the three nips was 60 kN / m, 90 kN / m, or 500 kN / m (in the shoe press). Before the still-moist paper was fed to the Clupak system, it was subjected to contact drying, conventional drying, and hot air application at 169 °C. It was then pre-dried in a slalom dryer section, treated in a Clupak system with a differential speed of -7.9%, and finally dried.

[0034] The paper can be used as is, and the paper properties described in the table below were measured using this paper. It goes without saying that the paper can be additionally calendered, for example, in a soft-nip or long-nip calender, or subjected to a coating treatment, such as a dispersion coating, which can further modify its properties. Such packaging paper can be used, for example, with or without an additional coating, for the production of paper bags, for example, for packaging gravel or game pieces.

[0035] The paper produced in this way had the following properties: Paper properties standard Unit Direction Result Grammage ISO 536:2019 g / m 2 101 Tensile strength ISO 1924-3:2005 kN / m MD 8,4 Tensile strength index ISO 1924-3:2005 Nm / g MD 83,5 Tensile strength ISO 1924-3:2005 kN / m CD 6,4 Tensile strength index ISO 1924-3:2005 Nm / g CD 63,2 Elongation at break ISO 1924-3:2005 % MD 9,4 Elongation at break ISO 1924-3:2005 % CD 9,5 Tensile fracture work ISO 1924-3:2005 J / m 2 MD 412 Tensile fracture work ISO 1924-3:2005 J / m 2 CD 382 Air permeability Gurley ISO 5636-5:2013 s 16,9 Bendtsen roughness ISO 8791-2:2013 ml / min Top 1310 Bendtsen roughness ISO 8791-2:2013 ml / min bottom 1650 Puncture resistance DIN EN 14477:2004 with 10 mm / min N From top 12,9 Puncture energy DIN EN 14477:2004 with 10 mm / min mJ From top 6,4 Puncture energy index DIN EN 14477:2004 with 10 mm / min mJ.m 2 < / kg From top 63,9 Puncture resistance DIN EN 14477:2004 with 10 mm / min N From bottom 11,5 Puncture energy DIN EN 14477:2004 with 10 mm / min mJ From bottom 5,7 Puncture energy index DIN EN 14477:2004 with 10 mm / min mJ.m 2 < / kg From bottom 56,4 Puncture energy factor DIN EN 14477:2004 with 10 mm / min From top to bottom 1,13 Example 3: Production of a packaging paper with a grammage of 130 g / m 2< Process description:

[0036] An unbleached pulp consisting of 100% primary softwood pulp with a kappa number of 41 was first subjected to high-consistency refining at a refining capacity of 220 to 240 kWh / ton, with the pulp's freeness level after high-consistency refining being 18°SR. Subsequently, this pulp was subjected to low-consistency refining at a refining capacity of 80 to 90 kWh / ton until a freeness level of at least 19°SR was achieved. The additives were added in the approach flow system of the paper machine. The pH was adjusted to a pH of 6.7 to 7.3 with aluminum sulfate. Cationic starch, with a cationization degree (DS) of 0.03, was added at a rate of 14 kg / tonne of dry paper, and alkenylsuccinic anhydride was used as a sizing agent at a rate of 0.8 kg / tonne of dry paper. No fillers were added. The pulp consistency at the headbox was 0.25%.Dewatering took place on a Foudrinier wire section and a press section with three nips, one of which could be a shoe press. The line pressure at the three nips was 60 kN / m, 90 kN / m, and 500 kN / m (in the shoe press). Before the still-moist paper was fed to the Clupak system, it was subjected to contact drying, conventional drying, and hot air application at 172 °C. Then, it was pre-dried in a slalom dryer section, treated in a Clupak system with a differential speed of -8.6%, and finally dried.

[0037] The paper can be used as is, and the paper properties described in the table below were measured using this paper. It goes without saying that the paper can also be calendered, for example, in a soft-nip or long-nip calender, or subjected to a coating treatment, such as a dispersion coating, which can further modify its properties. Such packaging paper can be designed as a multi-layer packaging paper, with or without an additional coating, and can be used as a replacement for cardboard packaging, for example, for food products such as rice.

[0038] The paper produced in this way had the following properties: Paper properties standard Unit Direction Result Grammage ISO 536:2019 g / m 2 131 Tensile strength ISO 1924-3:2005 kN / m MD 10,3 Tensile strength index ISO 1924-3:2005 Nm / g MD 78,6 Tensile strength ISO 1924-3:2005 kN / m CD 8,2 Tensile strength index ISO 1924-3:2005 Nm / g CD 62,6 Elongation at break ISO 1924-3:2005 % MD 10,3 Elongation at break ISO 1924-3:2005 % CD 9,7 Tensile fracture work ISO 1924-3:2005 J / m 2 MD 566 Tensile fracture work ISO 1924-3:2005 J / m 2 CD 497 Air permeability Gurley ISO 5636-5:2013 s 28,6 Bendtsen roughness ISO 8791-2:2013 ml / min Top 1420 Bendtsen roughness ISO 8791-2:2013 ml / min bottom 1890 Puncture resistance DIN EN 14477:2004 with 10 mm / min N From top 14,5 Puncture energy DIN EN 14477:2004 with 10 mm / min mJ From top 7,0 Puncture energy index DIN EN 14477:2004 with 10 mm / min mJ.m 2 < / kg From top 53,5 Puncture resistance DIN EN 14477:2004 with 10 mm / min N From bottom 13,6 Puncture energy DIN EN 14477:2004 with 10 mm / min mJ From bottom 6,4 Puncture energy index DIN EN 14477:2004 with 10 mm / min mJ.m 2 < / kg From bottom 48,9 Puncture energy factor DIN EN 14477:2004 with 10 mm / min From top to bottom 1,09 Example 4: Production of a packaging paper with a grammage of 160 g / m 2< Process description:

[0039] An unbleached pulp consisting of 100% primary softwood pulp with a kappa number of 41 was first subjected to high-consistency refining at a refining capacity of 240 to 250 kWh / ton, with the pulp's freeness level after high-consistency refining being 17°SR. Subsequently, this pulp was subjected to low-consistency refining at a refining capacity of 45 to 55 kWh / ton until a freeness level of at least 18°SR was achieved. The additives were added in the approach flow of the paper machine. The pH was adjusted to a pH of 6.6 to 7.2 with aluminum sulfate. Cationic starch with a cationization degree (DS) of 0.05 was added at a rate of 7.3 kg / t of dry paper, and alkenylsuccinic anhydride was used as a sizing agent at a rate of 0.3 kg / t of dry paper. Furthermore, no fillers were added at a rate of 0.5 kg / t of dry paper.The pulp consistency at the headbox was 0.20%. Dewatering took place on a Foudrinier wire section, similar to a press section with three nips, with line pressures at the three nips of 60 kN / m, 90 kN / m, and 80 kN / m. Before being fed to the Clupak system, the still-moist paper was subjected to contact drying, convection drying, and hot air application at 165 °C. It was treated in a Clupak system with a differential speed of -10.9% and finally dried.

[0040] The paper can be used as is, and the paper properties described in the table below were measured using this paper. It goes without saying that the paper can also be calendered, for example, in a soft-nip or long-nip calender, or subjected to a coating treatment, such as a dispersion coating, which can further modify its properties. Finally, the paper can also be used, for example, as multi-layer packaging paper, for example, as a replacement for cardboard packaging.

[0041] The paper produced in this way had the following properties: Paper properties standard Unit Direction Result Grammage ISO 536:2019 g / m 2 160 Tensile strength ISO 1924-3:2005 kN / m MD 18,7 Tensile strength index ISO 1924-3:2005 Nm / g MD 116,9 Tensile strength ISO 1924-3:2005 kN / m CD 7,9 Tensile strength index ISO 1924-3:2005 Nm / g CD 49,4 Elongation at break ISO 1924-3:2005 % MD 13,1 Elongation at break ISO 1924-3:2005 % CD 9,3 Tensile fracture work ISO 1924-3:2005 J / m 2 MD 1140 Tensile fracture work ISO 1924-3:2005 J / m 2 CD 520 Air permeability Gurley ISO 5636-5:2013 s 31,2 Bendtsen roughness ISO 8791-2:2013 ml / min Top 4980 Bendtsen roughness ISO 8791-2:2013 ml / min bottom 4420 Puncture resistance DIN EN 14477:2004 with 10 mm / min N From top 17,2 Puncture energy DIN EN 14477:2004 with 10 mm / min mJ From top 10,1 Puncture energy index DIN EN 14477:2004 with 10 mm / min mJ.m 2 < / kg From top 63,2 Puncture resistance DIN EN 14477:2004 with 10 mm / min N From bottom 15,7 Puncture energy DIN EN 14477:2004 with 10 mm / min mJ From bottom 8,7 Puncture energy index DIN EN 14477:2004 with 10 mm / min mJ.m 2 < / kg From bottom 54,4 Puncture energy factor DIN EN 14477:2004 with 10 mm / min From top to bottom 1,161

[0042] All paper tests and all values ​​were conducted / determined under test conditions according to ISO 187:1990 (23 °C ±1 °C and 50% ±2% relative humidity). It is, of course, known to those skilled in the art that paper is strongly influenced by climatic conditions and, in particular, can change its properties in humid or warm environments, or even in extremely cold and dry environments. The packaging papers produced and tested in connection with the present invention showed only a reduction of approximately 5% in puncture energy at 75% relative humidity compared to the value at 50% relative humidity, so that the packaging papers can be used even under harsh climatic conditions, particularly high humidity, for packaging almost any sharp-edged object or goods with an uneven surface.This is due, among other things, to the relatively high starch content of the packaging papers as well as to the Clupak and / or high-consistency milling treatments.

Claims

1. Unbleached packaging paper for sharp-edged objects and / or objects which have non-uniformly arranged, protruding, substantially non-deformable elevations on at least one of its surfaces, which consists of kraft pulp as the main constituent as well as fillers, starch, sizing agents and further process adjuvants as well as optionally coating agents, characterized in that it contains at least 95% primary pulp containing at least 80%, preferably at least 90%, in particular at least 95% pulp having an average length-weighted fibre length of at least 2.0 mm as well as less than 4.5%, preferably less than 4.0%, in particular less than 3.7% fillers as well as cationic starch and other process adjuvants, that it has a strain at break in the machine direction (MD) according to ISO 1924-3:2005 of at least 6.0%, preferably at least 6.5%, that it has a Kappa number ISO 302:2015 between 35 and 58, preferably 39 and 48 and that it has a puncture energy index according to DIN EN 14477:2004 measured at a test speed of 10.0 mm / min on an arbitrary side of the packaging paper in the range of 30 to 75 mJ.m2 / kg, preferably 35 to 70 mJ.m2 / kg.

2. Unbleached packaging paper according to Claim 1, characterized in that it contains 100% primary pulp.

3. Unbleached packaging paper according to Claim 1 or 2, characterized in that the primary pulp consists of a mixture consisting of at least 80% soft wood pulp, preferably at least 90% soft wood pulp, in particular at least 95% with an average length-weighted fibre length according to ISO 16065-2:2014 of at least 2.1 mm as well as remainder hard wood pulp having an average length-weighted fibre length according to ISO 16065-2:2014 of at least 1.0 mm.

4. Unbleached packaging paper according to Claims 1, 2 or 3, characterized in that the primary pulp consists of 100% soft wood pulp with an average length-weighted fibre length according to ISO 16065-2:2014 of at least 2.1 mm.

5. Unbleached packaging paper according to one of Claims 1 to 4, characterized in that the grammage in accordance with ISO 536:2019 of the packaging paper is 45 g / m2 to 165 g / m2.

6. Unbleached packaging paper according to one of Claims 1 to 5, characterized in that it has a tensile strength index in the machine direction in accordance with ISO 1924-3:2005 between 60 and 140 Nm / g.

7. Unbleached packaging paper according to one of Claims 1 to 6, characterized in that the primary pulp is contained as a ground, in particular high-consistency ground pulp having a Schopper-Riegler degree of grinding in accordance with ISO 5267-1:1999 between 13°SR to 20°SR.

8. Unbleached packaging paper according to one of Claims 1 to 7, characterized in that it has a Gurley value in accordance with ISO 5636-5:2013 between 5 s and 45 s, in particular 10 s and 40 s.

9. Unbleached packaging paper according to one of Claims 1 to 8, characterized in that at least one side of the packaging paper is surface-treated, in particular calendered and / or coated.

10. Unbleached packaging paper according to Claim 9, characterized in that the puncture energy index in accordance with DIN EN 14477:2004 between a surface-treated side of the packaging paper and an untreated side of the packaging paper differs by a factor greater than 1.0 to1.7.