WRAPPING PAPER AND METHOD FOR ITS MANUFACTURE

Description

[0001] The present invention relates to a packaging paper with increased barrier properties against oily and greasy materials and a process for its production.

[0002] Packaging papers with enhanced barrier properties against oily and greasy materials are known in the art. Since papers are inherently porous and permeable to water, grease, and oil, they require special measures to ensure these barrier properties.

[0003] In the current state of the art, the required increased barrier properties are achieved either through extremely high fiber refining, with freeness levels of 90° SR (Schopper-Riegler) and higher being selected. However, this measure proves to be expensive due to the high refining energy required and does not achieve a sufficiently high level of grease resistance. Alternatively, the barrier properties are achieved by applying a barrier coating using fluorocarbons. However, fluorocarbons are considered environmentally harmful because they have a long shelf life and are hardly biodegradable.

[0004] The following documents are known in the prior art: EP 2 370 533 A1, EP 1 246 966 B1, EP 2 777 934 A1, WO 2010 / 141581 A1 and DE 601 30 839 T2.

[0005] Based on this prior art, it is the object of the present invention to at least partially overcome or improve the disadvantages of the prior art.

[0006] The object is achieved with a device according to claim 1 and a method according to the invention according to claim 15. Preferred embodiments and modifications are the subject of the subclaims.

[0007] A packaging paper according to the invention is produced from a base paper with a basis weight between 15 g / m² and 500 g / m² and a porosity greater than 150 Gurley-s according to ISO 5636 / 5:2013. This paper comprises a pulp mix of long fibers and short fibers, an ash content of less than 15% according to DIN 54370:2007, and an auxiliary agent.

[0008] The paper has a barrier layer on at least one surface, which is formed from at least one modified starch and a platelet-shaped pigment with an aspect ratio of greater than 1:20, preferably greater than 1:40, in particular 1:60 or 1:80, and a surface hydrophobicizing agent. The proportion of the platelet-shaped pigment in the coating formulation is between 5% and 50%.

[0009] Aspect ratio is understood as a ratio between the diameter and the thickness of the platelet-shaped pigment, according to the equation aspect ratio = D 1 + D 2 / 2 / d

[0010] Where D 1 is the thickness in x-direction, D 2 is the thickness in x-direction and d is the thickness in z-direction of the platelet-shaped pigment.

[0011] For the production of a packaging paper according to the invention, a wide range of base papers can be selected. For example, base paper with a basis weight between 15 g / m² and 500 g / m² can be used. The intended applications for the packaging paper produced according to the invention naturally play a significant role in the selection of the base paper.

[0012] According to the invention, a sufficiently strong, dense, and minimally porous base paper is required. Its porosity should be greater than 150 Gurleys according to ISO 5636 / 5:2013. For this purpose, a pulp mix is ​​used that, on the one hand, has a certain proportion of short fibers to close the pores for impermeability; pulp fibers from eucalyptus, beech, or birch, or combinations thereof, are particularly suitable for this purpose. A certain proportion of long fibers is used to develop the appropriate strength properties; pulp fibers from pine and spruce are particularly suitable for this purpose. A higher proportion of long fibers is used preferably for low basis weights.

[0013] Furthermore, the base paper has an ash content of less than 15% according to DIN 54370:2007 in order to achieve a certain degree of whiteness and to contribute to a balance of strength and density appropriate for the application.

[0014] A packaging paper according to the invention has a barrier layer ("coating") on at least one surface. The coating weight per surface is between 0.1 and 5 g / m², preferably between 0.5 and 5 g / m². This layer is formed from a dispersion of modified starch and a platelet-shaped pigment. Depending on the desired modification, a surface hydrophobicizing agent is also added to the coating liquor (coating agent).

[0015] The pigment is added to the coating liquor to close the pores on the paper surface due to its geometric, platelet-like shape and prevent penetration, particularly excessive binder migration, of the remaining liquor components into the paper. The modified starch of the coating liquor is in the form of nano-starch particles, which are applied to the paper web during coating and bond with the pigments during drying. This forms a stable, pore-closing, and very dense film on at least one paper surface. In combination with the special base paper, this film forms an extremely effective barrier against various liquids, particularly oils, greases, solvents, and possibly water.

[0016] The barrier is so well-developed and effective that very high barrier values ​​are achieved in all food packaging and barrier tests known and used in the paper industry. A significant advantage of the paper according to the invention is that very high barrier values ​​are achieved consistently, i.e., in all test procedures performed. Numerous tests were conducted to measure and optimize the barrier effect. These tests include, for example, the following test procedures, which were developed based on market and / or customer requirements: The so-called "KIT test" according to TAPPI T 559 cm - 12 (TAPPI: Technical Association of the Pulp and Paper Industry); the DIN grease permeability test according to DIN 53116 - 2003; the so-called "TAPPI turpentine test" according to TAPPI T 454 om - 15; the chicken oil test, the so-called "hot oil test", according to an in-house test method of Drewsen, as of 2016; and the so-called "Nutella test", according to an in-house test method of Drewsen, as of 2016.

[0017] The so-called "hot oil test" has the following steps: Heat frying oil in a beaker fitted with a stirrer to approximately 50°C. Commercially available cooking oil, such as sunflower oil, can be used as the frying oil. It has a fresh viscosity of 18 to 22 mPa s, particularly 20 mPa s at 20°C. Measure 50 ml of oil (using a graduated cylinder). Place a paper towel in the plastic / test tray. Place the greaseproof paper to be tested ("test specimen") on the paper towel. Place a sponge on the test specimen and slowly pour the measured amount of oil (50 ml) over the sponge. Place another test specimen on the sponge and weigh it down with a metal plate and a 1 kg weight. Allow the oil-soaked sponge to soak for 20 minutes, then remove the weight and metal plate. Place the upper and lower test specimens with the oil-wetted side facing up and wipe off any excess oil. Visually assess both test specimens, both viewed from above and through: If the oil / grease tightness is good or high, no or only a few small (< 2 mm 2< ) oil penetrations are detectable.If the oil / grease tightness is low, the test time should be gradually reduced and the time at which no oil penetration is detectable should be determined. Preferably, the following time intervals are chosen, based on the oil / grease tightness test according to DIN: 20 min, 10 min, 5 min, 1 min.

[0018] The so-called "Nutella test" has the following steps: Place a white DIN A4 sheet on the tabletop as a base. Place a DIN A4 sample of the paper to be tested on top. Spread a hazelnut spread, e.g., Nutella, over an area of ​​approximately 5 x 5 cm; the spread must completely cover the test area. Lift the test specimen at regular intervals and check the base for any Nutella and / or grease penetrations. Visually assess the penetrations, both top and bottom: If the oil / grease resistance is good / high, no or only a few small (< 2 mm 2< ) oil / grease penetrations are visible. If the oil / grease resistance is low, large-area penetrations are visible. In this case, the test time at which no penetrations are visible must be stated. The following time intervals are preferred: 10 min, 30 min, 60 min, 4 h, 24 h.

[0019] In the tests mentioned, the top and screen sides of the paper must be checked.

[0020] The above-mentioned tests were conducted with very good results. Furthermore, the rule of thumb is: the higher the coating weight, the greater the barrier effect.

[0021] This means that the papers according to the invention are suitable for a very wide range of applications wherever a barrier effect against natural or synthetic fats, oils, and solvents, or possibly water or mixtures of these substances, is required. Examples include vegetable fats, chocolate fats, animal fats such as chicken fats, but also lubricating greases, etc. Depending on the desired application, low to very high densities can be selected.

[0022] A further advantage is that this excellent barrier effect against the substances mentioned is achieved using natural, biodegradable and recyclable additives, in particular without the use of fluorocarbons and / or synthetic binders.

[0023] Furthermore, according to a particularly preferred embodiment, the base paper comprises wet strength agents to ensure a certain degree of wet strength during production. Wet strength agents must develop a stronger (preferably a covalent) bond to the fibers that cannot be displaced by water molecules. Typically, polymers or multifunctional compounds with reactive groups are used as wet strength agents. These only react with the OH groups of the pulp fibers under drying conditions, thereby bridging several fibers together.

[0024] In one embodiment, the modified starch is a modified corn starch, in particular it is a film former based on nanoscale starch, which as a commercial product in particular has a moisture content between 2 and 6%, a density between 0.5 and 0.7 kg / l, a particle size between 50 and 150 nm, a Brookfield viscosity (preferably according to DIN EN ISO 2555-2000-01) at 25% solids and room temperature between 175 and 350 mPas and does not need to be cooked for technical use.

[0025] This has the advantage that - due to the appropriate ionization, among other things - a very good bond with the pigments is achieved during drying, which leads to a high density of the paper.

[0026] In one embodiment, the modified starch is also suspendable in cold water, ie in water in a temperature range between 10°C and 55°C, in particular below the gelatinization temperature.

[0027] This leads to lower energy requirements in the production of the packaging paper. In some embodiments, a device for heating the starch and / or the water required for this can even be dispensed with. This leads to further reductions in expenditure, for example, a reduction in the costs of purchasing and operating the paper machine.

[0028] In one embodiment, the hydrophobizing agent is an anionic surface sizing agent.

[0029] For example, anionic polymers are used for this purpose, such as modified copolymers of styrene and maleic anhydride, copolymers of methacrylate and acrylate monomers, copolymers of styrene with acrylate / methacrylate monomers, polyurethane dispersions or copolymers and graft polymers of acrylonitrile.

[0030] In one embodiment, the pulp mix has a proportion of between 0 to 70% long fibers and 30 to 100% short fibers, preferably a proportion of between 10 to 60% long fibers and 40 to 90% short fibers and in particular a proportion of 50% long fibers and 50% short fibers.

[0031] Depending on the application, this has the advantage that a balanced and requirement-specific ratio between strength and density is achieved for a paper according to the invention. For example, with a grammage of 40 g / m², a paper according to the invention achieves wet breaking strength values ​​of more than 4.0 and 2.5 N / 15 mm longitudinally and transversely, respectively, and porosity values ​​of more than 180 Gurleys.

[0032] In one embodiment, the long-fiber pulp is a spruce and / or pine sulfate or sulfite pulp, and the short-fiber pulp is a eucalyptus, beech, and / or birch sulfate or sulfite pulp. Experiments have shown that the combination of these substances leads to very good results in a paper according to the invention.

[0033] In one embodiment, the total ash content is less than 15%, preferably less than 10%, in particular less than 7% and greater than 0%.

[0034] In one embodiment, the basis weight of the base paper is preferably between 18 g / m 2 and 400 g / m 2 , in particular between 20 g / m 2 and 300 g / m 2 , preferably between 22 g / m 2 and 250 g / m 2 , particularly preferably between 25 g / m 2 and 160 g / m 2 , and in particular it is approximately 40 g / m 2 . The basis weight of the selected base paper depends primarily on the required use.

[0035] In one embodiment, the at least one auxiliary agent is selected from a group comprising conditioning agents for pulp, cationic resin dispersion, kaolin slurries, polyamide wet strength resins, polyaluminum chloride, biopolymer and carboxymethylcellulose (CMC) with anionic charges.

[0036] The substances mentioned contribute to the charge adjustment and to a further increase in the strength properties.

[0037] In one embodiment, the porosity of the paper according to the invention is preferably greater than 180 Gurley-s and less than 25,000 Gurley-s, more preferably greater than 200 Gurley-s and less than 10,000 Gurley-s, and in particular it is approximately 5,000 Gurley-s.

[0038] This means that the barrier layer according to the invention also significantly increases the impermeability to gases, such as air. Although the thickness of the barrier layer is small compared to the thickness of the underlying paper, the barrier layer generally contributes significantly more to the impermeability of the paper according to the invention than the underlying paper. This applies both to the impermeability to oils, grease, etc., and to the impermeability to gases.

[0039] In one embodiment, the weight ratio between the modified starch and the platelet-shaped pigments with an aspect ratio > 20 is more than 50% starch and less than 50% pigments, particularly preferably more than 65% starch and less than 35% pigments, and in particular 85% starch and 15% platelet-shaped pigments.

[0040] In one embodiment, the weight fraction of the modified starch is between 30% and 95%, preferably between 55% and 80%, particularly preferably between 60% and 70% and in particular 60% or 65%, and the weight fraction of the platelet-shaped pigment with an aspect ratio > 20 is between 70% and 5%, preferably between 45% and 20%, particularly preferably between 40% and 30% and in particular 40% or 35%.

[0041] The weight ratio of the mixture of modified starch and platelet-shaped pigments - and thus also the resulting density of the paper - depends primarily on the required use.

[0042] In one embodiment, the barrier layer has an oil and grease resistance, according to DIN standard 53116 - 2003, of at least level 5, particularly preferably of at least level 4 and in particular of level 3.

[0043] In one embodiment, the barrier layer has an oil and grease impermeability according to DIN EN ISO 16532-2:2007 of at least 3 KIT, particularly preferably of at least 6 KIT and in particular of 12 KIT.

[0044] In one embodiment, the barrier layer has an oil and grease resistance according to the TAPPI standard of 60 s to 1800 s.

[0045] In one embodiment, the barrier layer has an oil and grease resistance according to the so-called "hot oil test" - explained above - from 1 min to 20 min.

[0046] In one embodiment, the barrier layer has an oil and grease resistance according to the so-called "Nutella test" of 1 hour to 24 hours.

[0047] A particular advantage of the paper according to the invention is that it achieves excellent results in a wide range of these tests, even when—as the breadth of the tests conducted demonstrates—the impermeability to a range of quite heterogeneous fats, oils, solvents, and / or possibly water is tested. This means that papers according to the invention are suitable for a very wide range of applications wherever a barrier effect against natural or synthetic fats, oils, and solvents, or possibly water or mixtures of these substances, is required.

[0048] A packaging paper according to the invention is produced in a process comprising the steps: Providing a base paper with a predetermined dry content of between 2% and 9%, whose basis weight is between 15 g / m 2< and 500 g / m 2< and whose porosity is greater than 150 Gurley-s with a pulp mix of long fibers and short fibers, an ash content of less than 15% and an auxiliary agent; providing a coating agent with at least one modified starch, a platelet-shaped pigment with an aspect ratio of greater than 1:20, preferably greater than 1:40, in particular 1:60 or 1:80, a surface hydrophobicizing agent and water; applying the coating to the base paper by means of a coating unit, a printing unit or a coating machine; drying the coating on the base paper.

[0049] For the production of a packaging paper according to the invention, a wide range of base papers can be selected. For example, base paper with a basis weight between 15 g / m² and 500 g / m² can be used. The intended applications for the packaging paper produced according to the invention naturally play a significant role in the selection of the base paper. According to the invention, a sufficiently strong, as dense as possible, and minimally porous base paper is required. The refining of the base paper plays a role here; that is, a base paper with the highest possible specific refining energy is used.

[0050] A packaging paper according to the invention has a barrier layer ("coating") on at least one surface. For this purpose, a coating agent is provided, which is formed from a dispersion comprising: modified starch, platelet-shaped pigment, a surface hydrophobicizing agent, and water.

[0051] The coating is applied to the base paper by means of a coating unit, a printing unit, a coating machine, or by spraying. The process according to the invention can therefore be carried out on a wide variety of paper machine types.

[0052] The line is then dried on the base paper.

[0053] The platelet-shaped pigment seals the pores on the paper surface due to its geometric, platelet-like shape. The modified starch in the coating liquor is in the form of tiny nano-starch particles that bond with the platelet-shaped pigment during drying. This forms a stable, pore-sealing, and very dense film on at least one paper surface. This film, especially in combination with the dense base paper, forms an effective barrier against various liquids, especially oils, greases, solvents, and possibly water.

[0054] In the manufacturing process, in addition to the refining of the base paper, the solids content and the temperature and viscosity of the coating liquor, the drying and the smoothing of the coated paper also play a role.

[0055] Furthermore, according to a particularly preferred embodiment, the base paper used in production comprises wet strength agents to ensure a certain degree of wet strength during production. Wet strength agents must develop a stronger (preferably a covalent) bond to the fibers that cannot be displaced by water molecules. Typically, polymers or multifunctional compounds with reactive groups are used as wet strength agents. These only react with the OH groups of the pulp fibers under the drying conditions, thereby bridging several fibers together.

[0056] In one embodiment, the solids content according to DIN EN 827:2006 of the coating agent is between 10% and 35%, preferably between 20% and 30%, and in particular this is approximately 28%.

[0057] In one embodiment, the solids content according to DIN EN 827:2006 of the coating agent is between 20% and 60%, preferably between 30% and 50%, particularly preferably between 35% and 45%.

[0058] In one embodiment, the temperature of the glue liquor is 30 to 60° C.

[0059] The coated paper should be dried as quickly as possible. This is preferably done by contactless drying followed by contact drying, for example, using an air-turn dryer and / or infrared heater, followed by a drying cylinder.

[0060] Smoothing should be carried out under the highest possible pressure. Pressures with a line force of 30 to 300 kN / m, preferably 80 to 120 kN / m, are used.

[0061] Furthermore, the best possible runnability of the paper on the paper machine should be aimed for, which can be achieved in particular by uniform coating application and sufficient strength of the paper.

[0062] The platelet-shaped pigment is added to the coating liquor to close the pores on the paper surface due to its geometric, platelet-shaped shape and to prevent penetration, particularly excessive penetration, of the other liquor components into the paper. The modified starch of the coating liquor is in the form of tiny nano-starch particles that are applied to the paper web during coating and bond with the pigments during the drying process. This forms a stable, pore-closing, and very dense film on at least one paper surface. This film, in combination with the dense base paper, creates an extremely effective barrier against various liquids, particularly oils, greases, solvents, and possibly water.

[0063] In one embodiment, the coating application on the top side and / or on the bottom side of the base paper is in each case between 0.1 and 7.0 g / m 2< , preferably between 0.5 and 5.0 g / m 2< , particularly preferably between 1.0 and 4.0 g / m 2< and in particular between 1.5 and 3.0 g / m 2< .

[0064] The thickness of the coating depends significantly on the intended use of the packaging paper according to the invention. For example, to achieve the very high required barrier strength, the coating should be particularly thick. The coating thickness is, for example, between 0.1 and 7 µm. If necessary, the coating is also applied on both sides.

[0065] A packaging paper according to the invention has, in principle, a broad range of applications. These packaging papers can be used as barrier papers against oily and greasy materials, e.g., to wrap or pack hot or cold foods such as meat, sausage, fish, cheese, snacks such as French fries or pizzas, as well as fruit and vegetables, etc., during retail sale or directly after production. Since a wide range of base papers can be selected for the production of packaging papers according to the invention, these papers can be produced in a variety of forms, for example, as simple sheets of paper, foldable cardboard, or even as thermoformable papers. In general, these papers are suitable for a wide range of applications wherever a barrier effect against oils, solvent-oil mixtures, vegetable fats, chicken fats, chocolate fats, etc. is required.In addition, these papers can also be used for machine parts such as screws, seals, etc., which are either to be stored or shipped in oils, solvents, etc., or which - e.g. during shipping - are to be protected against grease, oils, solvents, and possibly water, etc.

[0066] The invention is further explained below using various experiments.

[0067] It should be noted that these examples encompass modifications and additions that would immediately occur to those skilled in the art. Furthermore, this preferred embodiment does not represent a limitation of the invention, in the sense that modifications and additions are within the scope of the present invention.

[0068] Fig. 1shows a table of experiments in which papers according to the invention, i.e., with a fluoropolymer-free coating, were tested against papers according to the prior art. The following test methods were used: The so-called "KIT test," according to TAPPI T 559 cm - 12. DIN grease permeability test, according to DIN 53116 - 2003. The so-called "TAPPI turpentine test," according to TAPPI T 454 om - 15. A test with chicken oil, the so-called "hot oil test," according to an in-house test method of the Drewsen company, as of 2016. The so-called "Nutella test," according to an in-house test method of the Drewsen company, as of 2016.

[0069] For all experiments, basis weights between 31 and 70 g / m² and thicknesses between 41 and 49 µm were used. The porosity of the base papers ranged from 200 to 1,000 Gurley s. The ash content ranged from 0 to 2%, with sizing between 1.5 and 60.

[0070] These tests show a clear difference to state-of-the-art papers:In the so-called "KIT test," KIT levels 4, 5, and 12 are achieved for papers with low, medium, and high grease resistance, respectively, whereas state-of-the-art papers with similar basis weights and coat thicknesses achieve KIT levels 2, 5, and 8. The DIN grease permeability test, according to DIN 53116 (2003), resulted in DIN levels IV, IV, III, and III, compared to DIN levels > V, V, and IV, III, respectively, for state-of-the-art papers. Tests with the so-called "TAPPI turpentine test" resulted in values ​​of 60-120, 300-600, 1200-1800, compared to 30-60, 600-300, and 600-1800 TAPPI seconds for state-of-the-art papers. A test with chicken oil, the so-called "hot oil test," according to the test method specified above, yielded values ​​of 5 / 5 / 15-20 minutes, compared to 1 / 5 / 20 minutes for state-of-the-art papers. The so-called "Nutella test," according to the test method specified above, yielded values ​​of 4 / 4 / 24 hours, compared to 1 / 4 / 24 hours for state-of-the-art papers..

[0071] The measured values ​​show that fluoropolymer-free papers according to the invention achieved at least the same density values ​​as state-of-the-art papers in every test, and in many cases even significantly exceeded these values. Thus, papers according to the invention not only have the advantage of better environmental compatibility, but also regularly exhibit higher density values ​​for a wide range of applications.

Claims

1. Packaging paper having barrier properties particularly with respect to oily and greasing materials, made from a base paper having a basis weight of between 15 g / m2 and 500 g / m2 and a porosity of greater than 150 Gurley-s according to ISO 5636 / 5:2013, with a pulp mix consisting of a fraction of 0 to 70% long fibres and 30 to 100% short fibres, with an ash fraction according to DIN 54370:2007 of less than 15%, and with an auxiliary, characterized in that the paper on at least one surface has a barrier layer formed at least of a nanoscale cationic potato starch as film former and / or a nanoscale modified corn starch as film former, a platelet-shaped pigment having an aspect ratio of greater than 1:20, preferably of greater than 1:40, more particularly of 1:80, and an anionic surface hydrophobizing agent as surface sizing agent.

2. Packaging paper according to Claim 1, characterized in that the base paper further comprises a wet strength agent.

3. Packaging paper according to either of the preceding claims, characterized in that the pulp mix comprises a fraction of between 10 to 60% long fibres and 40 to 90% short fibres and more particularly a fraction of 50% long fibres and 50% short fibres.

4. Packaging paper according to any of the preceding claims, characterized in that the ash fraction is less than 15%, preferably less than 5% and more particularly is between 0% and 5%.

5. Packaging paper according to any of the preceding claims, characterized in that the ash fraction is less than 15%, preferably less than 10%, and greater than 0%.

6. Packaging paper according to any of the preceding claims, characterized in that the porosity is preferably greater than 180 Gurley-s and less than 25 000 Gurley-s, more preferably greater than 200 Gurley-s and less than 10 000 Gurley-s, and more particularly about 5000 Gurley-s.

7. Packaging paper according to any of the preceding claims, characterized in that the weight ratio between the modified starch and the platelet-shaped pigment having an aspect ratio > 20 is more than 50% starch and less than 50% platelet-shaped pigment, more preferably more than 65% starch and less than 35% platelet-shaped pigment, and more particularly 85% starch and 15% platelet-shaped pigment.

8. Packaging paper according to any of the preceding claims, characterized in that the weight fraction of the modified starch is between 30% and 95%, preferably between 55% and 80%, more preferably between 60% and 70% and more particularly 60% or 65%, and that of the platelet-shaped pigment having an aspect ratio > 20 is between 70% and 5%, preferably between 45% and 20%, more preferably between 40% and 30% and more particularly 40% or 35%.

9. Packaging paper according to any of the preceding claims, characterized in that the barrier layer has an oil and grease imperviosity according to DIN standard 53116 - 2003 of at least level 5, more preferably of level 4 and more particularly of level 3.

10. Packaging paper according to any of the preceding claims, characterized in that the barrier layer has an oil and grease imperviosity according to TAPPI standard T 454 om - 15 of at least 60 s, more preferably of 60 - 600 s and more particularly of 60 - 1800 s.

11. Packaging paper according to any of the preceding claims, characterized in that the barrier layer has an oil and grease imperviosity according to the "Hot Oil Test" of at least 1 minute, more preferably of 1 to 10 minutes and more particularly of 1 to 20 minutes.

12. Packaging paper according to any of the preceding claims, characterized in that the barrier layer has an oil and grease imperviosity according to the "Nutella Test" of at least 1 hour, preferably of at least 24 hours.

13. Method for making a packaging paper according to any of the preceding claims, with the steps of: - providing a base paper with mandated dry matter content of between 5% and 15%, having a basis weight of between 15 g / m2 and 500 g / m2 and a porosity of greater than 150 Gurley-s, with a pulp mix consisting of a fraction of 0 to 70% long fibres and 30 to 100% short fibres, with an ash fraction of less than 15% and with an auxiliary; - providing a coating material with at least one nanoscale cationic potato starch as film former and / or a nanoscale modified corn starch as film former, a platelet-shaped pigment having an aspect ratio of greater than 1:20, preferably of greater than 1:40, more particularly of 1:80, an anionic surface hydrophobizing agent as surface sizing agent and water; - applying the coating to the base paper by means of a coating unit, a printing unit, a coating machine, or in a spraying process; - drying the coating on the base paper.

14. Method according to Claim 13, characterized in that the solids content according to DIN EN 827:2006 of the coating material is between 25% and 30%, preferably between 27.5% and 30% and more particularly is about 28%.

15. Method according to Claim 13 or 14, characterized in that the solids content according to DIN EN 827:2006 of the coating material is between 20% and 60%, preferably between 30% and 50%, more preferably between 35% and 45%.

16. Method according to Claim 13, 14 or 15, characterized in that the coatweight on the top side and / or on the bottom side of the base paper is in each case between 0.1 to 7.0 g / m2, preferably between 0.5 to 5.0 g / m2, more preferably between 1.0 to 4.0 g / m2 and more particularly between 1.5 to 3.0 g / m2.