Packaging material with improved barrier effect

Abstract

Disclosed is a packaging material comprising a base paper and a first and a second coating, wherein the base paper has a mass per unit area of at least 30 g / m² and at most 90 g / m², the first coating being located between the base paper and the second coating, forming a barrier against oxygen penetration, and comprising a polymer having hydroxy groups, wherein the hydroxy groups of the polymer are at least partially cross-linked, and wherein the second coating is applied directly to the first coating, forms a barrier against the penetration of water vapour, and comprises a polymer and a wax, wherein the packaging material, on the side on which the first and second coating are applied, has a Bekk smoothness of at least 800 s and at most 20,000 s, and wherein the mean water vapour permeability M of the packaging material is at least 2.0 g / (m² × 24 h) and at most 100.0 g / (m² × 24 h), and the following formula applies to the standard deviation s of the water vapour permeability: s ≤ M ∙ (0.15 + 0.1 ∙ e -0.003∙m²), wherein the mean water vapour permeability M and the standard deviation s of the water vapour permeability in g / (m² × 24 h) are to be inserted into the formula.

Description

[0001] PACKAGING MATERIAL WITH IMPROVED BARRIER EFFECT

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a packaging material that can extend the minimum shelf life of products packaged therein, especially food products, by ensuring that the variance of barrier properties across the surface of the packaging material is particularly low. The invention also relates to a method for producing such a packaging material.

[0004] BACKGROUND AND STATE OF THE ART

[0005] For environmental reasons, there has been a significant demand in recent years to replace packaging materials based on plastic films with other materials. Paper has emerged as a significant alternative. While paper is superior to plastic films in terms of environmental aspects and, for example, printability, there are important technical properties where comparable performance can only be achieved through additional measures.

[0006] One example of such properties is barrier properties. Many packaging material applications require barrier properties, for example, against water vapor, oxygen, water, oils, and fats. In paper, such properties are typically achieved through additional coatings, although there is still room for improvement.

[0007] Strict quality standards must be met, especially for food packaging materials. Packaged food products are subjected to a shelf-life test in which they are examined for changes in taste or color, aging processes (e.g., due to oxidation), and other properties under different storage and climatic conditions. These tests determine the manufacturer's guaranteed shelf life. Extending the shelf life is desirable simply because it can reduce food waste.

[0008] Among other things, the shelf life of food is determined by the permeability of the packaging material to oxygen or water vapor, so efforts are made to create the highest possible barrier on the paper. This typically requires a large amount of material or even coating materials, which make recycling such packaging materials difficult.

[0009] There is therefore a need in the industry to further improve the barrier properties of packaging materials so that the products packaged in them have a longer shelf life.

[0010] SUMMARY OF THE INVENTION

[0011] The object of the invention is to provide a packaging material that can extend the shelf life of the product packaged therein without having to accept significant disadvantages in the ecological aspects of the packaging material.

[0012] This object is achieved by a packaging material according to claim 1, a package according to claim 1, and a method for producing a packaging material according to claim 33. Advantageous further developments are specified in the dependent claims.

[0013] The object is achieved by a packaging material comprising a base paper and a first and a second coating, wherein the base paper has a basis weight of at least 30 g / m 2 and a maximum of 90 g / m 2and wherein the first coating is located between the base paper and the second coating, forms a barrier against the penetration of oxygen, and comprises a polymer having hydroxyl groups, wherein the hydroxyl groups of the polymer are at least partially cross-linked, and wherein the second coating is applied directly to the first coating, forms a barrier against the penetration of water vapor, and comprises a polymer and a wax, wherein the packaging material, on the side to which the first and second coatings are applied, has a Bekk smoothness of at least 800 s and at most 20,000 s, and wherein the average water vapor permeability M of the packaging material is at least 2.0 g / (m 2 x 24 h) and not more than 100.0 g / (m 2 x 24 h) and the standard deviation s of the water vapor permeability is given by the following formula: s < M - (0.15 + 0.1 - e" 0 ' 003 " 2), where the mean water vapor permeability M and the standard deviation s of the water vapor permeability in g / (m 2 x 24 h) are to be inserted into the formula and are determined by measurement according to ISO 2528:2017 at a relative humidity of 85% and a temperature of 23°C at 10 randomly selected, non-overlapping positions on the packaging material in the same direction through the packaging material.

[0014] One way to improve the shelf life of packaged products is to reduce the average water vapor permeability of the packaging material to the lowest possible value. However, this requires more coating material, resulting in more effort and higher costs.

[0015] A key finding of the inventors is that the minimum shelf life of a packaged product does not depend solely on the average water vapor permeability. In fact, when determining the minimum shelf life, the maximum expected water vapor permeability of the packaging material must be taken into account, as the manufacturer of the packaged product must guarantee the minimum shelf life. According to the inventors' findings, the minimum shelf life can be extended by reducing the variance in water vapor permeability. This reduces the maximum expected water vapor permeability, even with the same average water vapor permeability, and the minimum shelf life of the packaged product can be extended.

[0016] An essential aspect of the present invention thus lies in reducing the standard deviation of the water vapor permeability of the packaging material. For this reason, upper limits for this standard deviation are given above and in the further disclosure as a function of the average water vapor permeability. A lower limit for the standard deviation of the water vapor permeability is not defined in the patent claims; rather, it is fundamentally desirable within the meaning of the present invention that this be as small as possible. However, there are technical limits to the lower limit, which, to the knowledge of the inventors, are at a value of approximately 0.1 g / (m 2x 24 h). However, exploiting the technically achievable lower limit of the standard deviation of the water vapor permeability is not the subject of the present invention. Therefore, for the definition of the present invention, only the upper limit of the standard deviation of the water vapor permeability is decisive.

[0017] The average water vapor permeability M of the packaging material of the invention can - depending on the intended use - be between 2.0 g / (m 2 x 24 h) and 100.0 g / (m 2 x 24 h), with preferred ranges defined in more detail below. Within this range, at least for the higher water vapor permeabilities, the coefficient of variation, i.e., the quotient of the standard deviation and the mean value of the water vapor permeability, should not exceed 15%.

[0018] For lower values ​​of the average water vapor permeability M, however, higher variation coefficients of up to 25% are acceptable within the scope of the invention. The purely empirically determined formula for the upper limit of the standard deviation ensures a smooth transition between these ranges. It should be noted that the variance of the water vapor permeability is considerably higher for conventional packaging materials based on coated base papers. For example, the standard deviation of the water vapor permeability for a commercially available packaging paper with a water vapor and grease barrier (barricote BAG WG BA 4762 from Mitsubishi HiTec Paper Europe), which is used as a comparison example for the exemplary embodiments described in more detail below, is 10 g / (m 2 x 24 h) with an average water vapor permeability M of 35 g / (m 2x 24 h), while for the packaging material according to the invention according to the formula given above, the standard deviation at this average water vapor permeability is below a value of 5.3 g / (m 2 x 24 h).

[0019] In order to achieve a low variance in water vapor permeability, the inventors recognized that a combination of measures in the composition of the packaging material and its manufacturing process is necessary, especially if ecological aspects of the packaging material are to be taken into account.

[0020] The packaging material according to the invention comprises a base paper. The basis weight of the base paper should be low to limit material usage. However, base papers with a low basis weight are less homogeneous than base papers with a high basis weight, which is why the variance in barrier properties is higher for packaging materials comprising such base papers.

[0021] To achieve the desired effect, the base paper has a first and a second coating. The first coating is located between the base paper and the second coating. It creates a barrier against oxygen penetration and comprises a polymer containing hydroxyl groups. A first essential aspect for achieving a low variance in water vapor permeability is that the hydroxyl groups of the polymer are cross-linked. This creates a surface that is particularly favorable for the application of the second coating, which forms the barrier against water vapor penetration.

[0022] In order to achieve a low variance in water vapor permeability, the base paper already provided with the first coating can be calendered according to the process described below. This smoothes the surface and prepares it even better for the application of the second coating, which represents a further essential aspect of the invention. The inventors have surprisingly found that calendering after the application of the first coating and before the application of the second coating makes a significant contribution to reducing the variance in water vapor permeability. On the packaging material, calendering between the application of the first and second coatings results in a high level of smoothness, which is still detectable even after the application of the second coating or, if present, the application of further coatings.In the finished product, this manifests itself in a Bekk smoothness of at least 800 s on the side to which the first and second coatings are applied, which is significantly higher than in comparative prior art examples, where the Bekk smoothness of the coated side is only 400 s or less. The second coating is applied on top of the first coating, and according to the inventors' findings, it is important that the second coating be applied directly to the first coating in order to utilize the surface optimized by the first coating and calendering. The second coating forms a barrier against the penetration of water vapor and comprises a polymer and a wax.Through these measures and the composition of the second coating, which represents another essential aspect of the invention, the coating is particularly homogeneous, and the variance in water vapor permeability can be significantly reduced. The lower variance in water vapor permeability results in a lower expected maximum water vapor permeability, allowing the manufacturer of the packaged product to assume a more favorable value when determining the shelf life and guarantee a longer shelf life.

[0023] The packaging material according to the invention comprises a base paper, wherein the base paper has a basis weight of at least 30 g / m 2 and a maximum of 90 g / m 2 preferably at least 35 g / m 2 and a maximum of 80 g / m 2 and particularly preferably at least 40 g / m 2 and a maximum of 70 g / m 2The basis weight can be measured according to ISO 536:2019. A base paper with a higher basis weight is more favorable in terms of homogeneity, barrier effect, and mechanical properties, but the material consumption is also higher, so the basis weight should be kept as low as possible. The method according to the invention makes it possible to achieve a low variance in water vapor permeability even with a particularly low basis weight, which results in a significant advantage of the packaging material according to the invention. The inventive and preferred intervals allow the best possible combination of material consumption and low variance in water vapor permeability.

[0024] The base paper preferably comprises cellulose fibers, with the cellulose fibers particularly preferably being formed from pulp fibers or regenerated cellulose fibers or a mixture thereof. The pulp fibers are most preferably obtained from softwood, in particular spruce, pine, or fir; from hardwood, in particular beech, birch, or eucalyptus; from hemp, flax, jute, ramie, kenaf, kapok, coconut, abaca, sisal, bamboo, cotton, or esparto grass; or from recycled paper pulp, or are a mixture of pulp fibers from several of these sources.

[0025] The fibers of regenerated cellulose are particularly preferably fibrillatable fibers of regenerated cellulose. Such fibers are sold, for example, under the name Lyocell.

[0026] Preferably, the proportion of cellulose fibers is at least 55% and at most 100% based on the mass of the base paper, particularly preferably at least 60% and at most 95%.

[0027] The base paper preferably comprises filler. The filler is particularly preferably selected from the group consisting of kaolin, talc, calcium carbonate, magnesium carbonate, magnesium oxide, magnesium hydroxide, aluminum oxide, aluminum hydroxide, titanium dioxide, or a mixture thereof. Most preferably, the base paper comprises kaolin because kaolin can contribute to the barrier effect of the base paper.

[0028] Preferably, the proportion of filler is at least 5% and at most 45%, most preferably at least 10% and at most 40%, based on the mass of the base paper.

[0029] Preferably, the base paper is calendered. This makes it easy to increase smoothness and improve the uniformity of the first and second coatings. Calendering of the base paper is different from calendering after application of the first coating.

[0030] Preferably, the base paper, on the side to which the first and second coatings are applied, but before the first and second coatings are applied, has a Bekk smoothness, measured according to ISO 5627:1995, of at least 600 s and at most 10,000 s, more preferably at least 800 s and at most 6,000 s. In addition to the crosslinking of the polymer in the first coating and the calendering between the application of the first and second coatings, the smoothness of the base paper can contribute to reducing the variance in water vapor permeability, which is why this is an additional feature of the base paper with which the inventive effect can be further improved.

[0031] Preferably, the base paper on the side to which the first and second coatings are applied, but before the first and second coatings are applied, has a contact angle with water, measured with a 4 pl drop after 0.1 s, of at least 30° and at most 70°, more preferably at least 40° and at most 65°. This contact angle range is particularly favorable for applying the first coating.

[0032] Preferably, the base paper on the side to which the first and second coatings are applied, but before the first and second coatings are applied, has a specific water absorption capacity of at least 0.1 and at most 0.7, particularly preferably of at least 0.2 and at most 0.5. The specific water absorption capacity is the quotient of the water absorption capacity determined as the Cobböo value according to ISO 535:2014 in g / m 2and the basis weight measured according to ISO 536:2019 in g / m 2 It expresses the water absorption capacity independent of the basis weight.

[0033] The first coating creates a barrier against oxygen penetration and, for this purpose, comprises a polymer containing hydroxyl groups, some of whose hydroxyl groups are crosslinked. The polymer is preferably selected from the group consisting of starch, starch derivatives, polyvinyl alcohol, modified polyvinyl alcohol, carbohydrates, modified carbohydrates, or mixtures thereof. The crosslinking of the hydroxyl groups of the polymer can be achieved using various crosslinking agents, for example, glyoxal or ammonium zirconium carbonate, so the first coating preferably comprises glyoxal or ammonium zirconium carbonate.

[0034] Preferably, the first coating is applied over the entire surface, or at least to 90% or more of the surface of one side of the base paper

[0035] Preferably, the amount of polymer of the first coating, based on the area to which the polymer is actually applied, is at least 0.2 g / m 2 and a maximum of 5.0 g / m 2 , particularly preferably at least 0.5 g / m 2 and a maximum of 4.0 g / m 2 .

[0036] In a preferred embodiment, at least one further coating comprising a barrier material and filler can be applied between the base paper and the first coating, wherein the barrier material of this further coating is selected from the group consisting of starch, acrylic acid polymers, modified acrylic acid polymers, styrene-acrylate copolymers, and mixtures thereof. The filler of this further coating is particularly preferably an inorganic pigment, and most preferably alumina (AlO) or talc. This further coating prevents the first coating from penetrating deeply into the structure of the base paper. This allows a good barrier against oxygen penetration to be created with less material in the first coating.Particularly preferably, the further coating is applied over the entire surface or at least over 90% or more of the surface of one side of the base paper, and most preferably it is applied directly to the base paper.

[0037] Particularly preferably, the mass of the further coating, based on the area to which it is actually applied, is at least 0.2 g / m 2 and a maximum of 4.0 g / m 2 , particularly preferably at least 0.5 g / m 2 and a maximum of 2.5 g / m 2 .

[0038] The second coating creates a barrier against the penetration of water vapor and comprises a polymer and a wax. Preferably, the polymer of the second coating is selected from the group consisting of styrene-butadiene copolymers, carboxylated styrene-butadiene copolymers, styrene-acrylate copolymers, acrylic copolymers, acrylic polymers, ethylene-acrylic acid copolymers, vinyl acetate-acrylic acid copolymers, acrylic acid-maleic acid copolymers, methacrylic acid polymers, methyl methacrylate polymers, and polyurethane, and mixtures thereof. Preferably, the wax of the second coating is selected from the group consisting of vegetable waxes, animal waxes, mineral oil-based waxes, polymeric waxes, semi-synthetic waxes, and synthetic waxes, and mixtures thereof. The wax is particularly preferably a paraffin wax.

[0039] The second coating is applied directly to the first coating and is preferably applied over the entire surface or at least over 90% or more of the area of ​​one side of the base paper.

[0040] Preferably, the combined mass of polymer and wax in the second coating, based on the area to which polymer and wax are actually applied, is at least 1.0 g / m 2 and a maximum of 10.0 g / m 2 , particularly preferably at least 2.0 g / m 2 and a maximum of 8.0 g / m 2 .

[0041] The packaging material may have additional coatings applied to the second coating. Such coatings may preferably serve to protect the first and second coatings, improve printability, make the packaging material heat-sealable, or create additional barriers, for example, against the penetration of water, oils, or greases.

[0042] Between the application of the first and second coatings, the base paper coated with the first coating is calendered according to the process explained below to increase its smoothness and prepare the surface as well as possible for the application of the second coating. This high level of smoothness is maintained even after the application of the second coating, or any additional coatings.

[0043] The packaging material according to the invention therefore has, on the side to which the first, second, and optionally further coatings are applied, a Bekk smoothness of at least 800 s and at most 20,000 s, preferably of at least 1,000 s and at most 10,000 s, and particularly preferably of at least 1,500 s and at most 8,000 s. Bekk smoothness can be measured according to ISO 5627:1995.

[0044] The barrier properties of the packaging material can also be characterized by the Gurley air permeability. The Gurley air permeability, measured according to ISO 5636-5:2013, is preferably at least 20,000 s in at least one direction through the packaging material, and particularly preferably at least 35,000 s. With correspondingly good barrier properties, the air permeability can be so low, i.e., the Gurley air permeability value can be so high, that it cannot be measured or cannot be measured within a reasonable amount of time. In this case, the packaging material can be considered impermeable to air according to the present nomenclature, which represents a particularly preferred embodiment of the packaging material according to the invention.

[0045] To characterize the variance of the barrier properties of the packaging material according to the invention, the mean water vapor permeability and the standard deviation of the water vapor permeability are used. The mean water vapor permeability M and the standard deviation s of the water vapor permeability of the packaging material are determined by measuring according to ISO 2528:2017 at a relative humidity of 85% and a temperature of 23°C at 10 randomly selected, non-overlapping positions on the packaging material in the same direction through the packaging material.

[0046] The packaging material according to the invention has an average water vapor permeability M of at least 2.0 g / (m 2 x 24 h) and not more than 100.0 g / (m 2 x 24 h), preferably at least 5.0 g / (m 2 x 24 h) and not more than 50.0 g / (m 2 x 24 h) and particularly preferably at least 5.0 g / (m 2x 24 h) and not more than 40.0 g / (m 2 x 24 h).

[0047] In a preferred embodiment, the formula s < M ■ (0.12 + 0.1 ■ e -o.oo3 M 2 ^ where the mean water vapor permeability M and the standard deviation s of the water vapor permeability in g / (m 2 x 24 h) are to be inserted into the formula and are determined by measurement according to ISO 2528:2017 at a relative humidity of 85% and a temperature of 23°C at 10 randomly selected, non-overlapping positions of the packaging material in the same direction through the packaging material. In this preferred embodiment, the coefficient of variation of the water vapor permeability is at most 12% for higher water vapor permeabilities and at most 22% for low water vapor permeabilities.

[0048] In a particularly preferred embodiment, the formula s < M ■ (0.10 + 0.1 ■ e -o.oo3 M 2 ^ where the mean water vapor permeability M and the standard deviation s of the water vapor permeability in g / (m 2 x 24 h) are to be inserted into the formula and are determined by measurement according to ISO 2528:2017 at a relative humidity of 85% and a temperature of 23°C at 10 randomly selected, non-overlapping positions of the packaging material in the same direction through the packaging material. In this particularly preferred embodiment, the coefficient of variation of the water vapor permeability is at most 10%, at least at higher water vapor permeabilities, and at most 20%, at low water vapor permeabilities.

[0049] The packaging material according to the invention preferably has an oxygen permeability in at least one direction through the packaging material, measured according to DIN 53380-3:1998-07 at a relative humidity of 0% and a temperature of 23°C, of ​​at least 1 ml / (m 2 xdxioo kPa) and not more than 500 ml / (m 2 xdxioo kPa), particularly preferably at least 5 ml / (m 2 xdxioo kPa) and not more than 400 ml / (m 2 xdxioo kPa).

[0050] The packaging material according to the invention can already have favorable barrier properties without further coatings, but these can be further improved by additional coatings.

[0051] Preferably, the water absorption capacity, expressed as Cobb 3OO -value and measured according to ISO 535:2014 from the side to which the first and second coatings are applied, at least og / m 2 and a maximum of 10 g / m 2and particularly preferably at least og / m 2 and a maximum of 5 g / m 2 .

[0052] Preferably, the barrier against the penetration of oils or fats, expressed as a Kit value and measured according to TAPPI T559-CIT112 from the side to which the first and second coatings are applied, is at least 8 and at most 12, particularly preferably at least 9 and at most 12. The packaging material according to the invention is particularly well suited as packaging for foodstuffs, which place high demands on the barrier properties of the packaging material. This applies not only to foodstuffs, but also to other products that need to be protected from oxygen or water vapor, for example, electronic components or electronic parts, or products that are particularly hygroscopic, such as kitchen towels or hygiene products.

[0053] A packaging according to the invention therefore comprises a packaging material according to one of the preceding embodiments, wherein rice, sugar, pasta, chocolate, chocolate bars, nuts, muesli, cheese, pastries, meat products, coffee, tea, electronic components, electronic parts, kitchen towels or hygiene articles are packaged in the packaging material.

[0054] A further aspect of the invention relates to a method by which a packaging material according to one of the above-mentioned embodiments can be produced. The method according to this aspect of the invention comprises steps A to D.

[0055] A - Providing a base document,

[0056] B - applying a first coating composition to at least one side of the base paper to produce a first coating,

[0057] C - Calendering the coated base paper from step B,

[0058] D - applying a second coating composition directly onto the first coating to produce a second coating, wherein the base paper in step A has a basis weight of at least 30 g / m 2 and a maximum of 90 g / m 2and wherein the first coating from step B forms a barrier against the penetration of oxygen and comprises a polymer which has hydroxyl groups, wherein the hydroxyl groups of the polymer are at least partially cross-linked in step B, and wherein the calendering in step C is carried out such that the packaging material after step D has a Bekk smoothness of at least 800 s and at most 20,000 s on the side to which the first coating in step B and the second coating in step D were applied, and wherein the second coating from step D forms a barrier against the penetration of water vapor and comprises a polymer and a wax, and wherein the average water vapor permeability M of the packaging material after step D is at least 2.0 g / (m 2 x 24 h) and not more than 100.0 g / (m 2x 24 h) and the standard deviation s of the water vapor permeability is given by the following formula: s < M - (0.15 + 0.1 - e" 0 ' 003 " 2 ), where the mean water vapor permeability M and the standard deviation s of the water vapor permeability in g / (m 2 x 24 h) to be inserted into the formula shall be determined by measurement in accordance with ISO 2528:2017 at a relative humidity of 85% and a temperature of 23°C at 10 randomly selected, non-overlapping positions on the packaging material in the same direction through the packaging material.

[0059] According to the inventors' findings, the combination of crosslinking the polymer of the first coating in step B and calendering in step C can prepare the surface of the coated base paper for the application of the second coating in step D in such a way that the variance in water vapor permeability is reduced. This is possible even though the base paper in step A has a low basis weight.

[0060] Preferably, the provision of the base paper in step A comprises producing the base paper on a paper machine, particularly preferably a Fourdrinier paper machine.

[0061] Preferably, the base paper in step A has a basis weight of at least 35 g / m 2 and a maximum of 80 g / m 2 and particularly preferably at least 40 g / m 2 and a maximum of 70 g / m 2 .

[0062] The base paper in step A preferably comprises cellulose fibers, wherein the cellulose fibers are particularly preferably formed from cellulose fibers or fibers of regenerated cellulose or a mixture thereof. The cellulose fibers are very particularly preferably obtained from softwood, in particular spruce, pine, or fir; from hardwood, in particular beech, birch, or eucalyptus; from hemp, flax, jute, ramie, kenaf, kapok, coconut, abaca, sisal, bamboo, cotton, or esparto grass; or from wastepaper pulp, or are a mixture of cellulose fibers from several of these sources.

[0063] The fibers of regenerated cellulose are most preferably fibrillatable fibers of regenerated cellulose.

[0064] Preferably, the proportion of cellulose fibers is at least 55% and at most 100% based on the mass of the base paper in step A, particularly preferably at least 60% and at most 95%.

[0065] The base paper in step A preferably comprises filler. The filler is particularly preferably selected from the group consisting of kaolin, talc, calcium carbonate, magnesium carbonate, magnesium oxide, magnesium hydroxide, aluminum oxide, aluminum hydroxide, titanium dioxide, or a mixture thereof. Most preferably, the base paper in step A comprises kaolin.

[0066] Preferably, the proportion of filler is at least 5% and at most 45%, most preferably at least 10% and at most 40%, based on the mass of the base paper in step A.

[0067] The process according to the invention preferably comprises a step of calendering the base paper from step A between step A and step B. Particularly preferably, during calendering, the base paper passes through at least one roll gap in which a line load of at least 20 kN / m and at most 800 kN / m acts on the base paper.

[0068] Preferably, immediately before step B, the base paper on the side intended for application of the first coating in step B has a Bekk smoothness, measured according to ISO 5627:1995, of at least 600 s and at most 1500 s, particularly preferably at least 800 s and at most 1200 s.

[0069] Preferably, the first coating composition in step B comprises the polymer of the first coating, a crosslinking agent and a solvent, wherein particularly preferably the crosslinking agent is glyoxal or ammonium zirconium carbonate and / or wherein the solvent is preferably water.

[0070] Preferably, the polymer of the first coating composition is selected from the group consisting of starch, starch derivatives, polyvinyl alcohol, modified polyvinyl alcohol, carbohydrates, modified carbohydrates or mixtures thereof.

[0071] Preferably, the application of the first coating composition in step B comprises application in a film press or size press in a paper machine or other coating device integrated into the paper machine or on a separate coating device and further drying the first coating composition.

[0072] Preferably, the first coating composition in step B is applied over the entire surface or at least to 90% or more of the surface of one side of the base paper.

[0073] Preferably, a further coating comprising a barrier material and filler can be applied between step A and step B, wherein the barrier material of this further coating is selected from the group consisting of starch, acrylic acid polymers, modified acrylic acid polymers, styrene-acrylate copolymers, and mixtures thereof. Particularly preferably, the filler of this further coating is an inorganic pigment, and most preferably, alumina (Al 12 O 3 ) or talc. Particularly preferably, the further coating is applied over the entire surface or at least over 90% or more of the surface of the base paper, wherein the further coating is preferably applied directly to the base paper.

[0074] Preferably, in step C, the calendering of the coated base paper from step B comprises passing through at least one and at most 14, particularly preferably at least 4 and at most 12 roll gaps, wherein in at least one of the roll gaps the coated base paper from step B is subjected to a line load of at least 20 kN / m and at most 800 kN / m, particularly preferably at least 40 kN / m and at most 600 kN / m.

[0075] Preferably, the calendering in step C is carried out such that the packaging material after step D has a Bekk smoothness of at least 1000 s and at most 10,000 s, and more preferably at least 1500 s and at most 8,000 s, on the side to which the first coating in step B and the second coating in step D were applied. Bekk smoothness can be measured according to ISO 5627:1995.

[0076] Preferably, the second coating composition in step D comprises the polymer and the wax of the second coating and a solvent, wherein the solvent is particularly preferably water.

[0077] Preferably, the polymer of the second coating is selected from the group consisting of styrene-butadiene copolymers, carboxylated styrene-butadiene copolymers, styrene-acrylate copolymers, acrylic copolymers, acrylic polymers, ethylene-acrylic acid copolymers, vinyl acetate-acrylic acid copolymers, acrylic acid-maleic acid copolymers, methacrylic acid polymers, methyl methacrylate polymers, and polyurethane, and mixtures thereof. The wax of the second coating is selected from the group consisting of vegetable waxes, animal waxes, mineral oil-based waxes, polymeric waxes, semi-synthetic waxes, and synthetic waxes, and mixtures thereof. The wax of the second coating is particularly preferably a paraffin wax.

[0078] Preferably, applying the second coating composition in step D comprises applying it in a counter-rotating gravure coater, a bar coater or a curtain coater and drying the second coating composition.

[0079] Preferably, the second coating composition is applied in step D over the entire surface or at least over 90% or more of the surface of one side of the base paper. The mean water vapor permeability M and the standard deviation s of the water vapor permeability of the packaging material after step D are determined by measurement according to ISO 2528:2017 at a relative humidity of 85% and a temperature of 23°C at 10 randomly selected, non-overlapping positions on the packaging material in the same direction through the packaging material.

[0080] The packaging material according to step D preferably has an average water vapor permeability M of at least 5.0 g / (m 2 x 24 h) and not more than 50.0 g / (m 2 x 24 h) and particularly preferably at least 5.0 g / (m 2 x 24 h) and not more than 40.0 g / (m 2 x 24 h).

[0081] In a preferred embodiment, the formula s < M ■ (0.12 + 0.1 ■ e -o.oo3 M 2 ^ where the mean water vapor permeability M and the standard deviation s of the water vapor permeability in g / (m 2 x 24 h) are to be inserted into the formula.

[0082] In a particularly preferred embodiment, the formula s < M ■ (0.10 + 0.1 ■ e -o.oo3 M 2 ^ where the mean water vapor permeability M and the standard deviation s of the water vapor permeability in g / (m 2 x 24 h) are to be inserted into the formula.

[0083] DESCRIPTION OF A PREFERRED EMBODIMENT AND COMPARISON WITH AN EMBODIMENT NOT IN ACCORDANCE WITH THE INVENTION

[0084] In the following, a preferred embodiment of the packaging material according to the invention and the method according to the invention is described, as well as a packaging material not according to the invention as a comparative example.

[0085] According to step A of the process according to the invention, a base paper with a basis weight of 55 g / m 2, according to ISO 536:2109, produced on a Fourdrinier paper machine, consisting of a mixture of pulp fibers from hardwoods and softwoods and kaolin as a filler. The amount of filler was 5% of the mass of the base paper, the remainder being made up of pulp fibers. The base paper was calendered in a roll gap with a line load of 40 kN / m and had a Bekk smoothness according to ISO 5627:1995 of 1070 s on the side intended for subsequent coating in steps B and D. The contact angle of this side was measured with a drop of 4 pl of water after 0.1 s and was 55 0 .

[0086] The Cobböo value on the side to be coated was measured according to ISO 535:2014 and was 21.6 g / m 2 , resulting in a specific water absorption capacity of 21.6 / 55.0 = 0.393.

[0087] A first coating composition consisting of 74% water and 26% solids was applied to this base paper according to step B. The solids were formed by 36% by weight of modified polyvinyl alcohol, 63% by weight of alumina, and 1% by weight of glyoxal as a crosslinking agent. The coated base paper was then dried. The amount of coating applied was 2.5 g / m 2 .

[0088] In the subsequent step C of the process according to the invention, the coated base paper from step B was calendered in a calender with 4 roll gaps at a line load of 40 kN / m and a temperature of 105°C in order to prepare the surface for the application of the second coating composition.

[0089] In step D of the process according to the invention, a second coating composition comprising a styrene-butadiene copolymer, a paraffin wax, and water was applied directly to the first coating over the entire surface and dried. The combined amount of styrene-butadiene copolymer and wax applied was approximately 6.0 g / m 2 .

[0090] The Bekk smoothness of the resulting packaging material was determined according to ISO 5627:1995 on the side to which the first and second coatings were applied and a value of 1200 s was obtained.

[0091] The Gurley air permeability of the packaging material was determined according to ISO 5636-5:2013. However, the air permeability was too low to be meaningfully measured, so the packaging material can be considered practically airtight.

[0092] The Cobb 3Oo-value of the packaging material was determined according to ISO 535:2014 from the side to which the first and second coatings were applied and a value of <0.1 g / m 2 was obtained. The kit value of the packaging material was determined according to TAPPI T559-cmi2 from the side to which the first and second coatings were applied, and a value of 12 was obtained.

[0093] The oxygen permeability of the packaging material was measured according to DIN 53380-3:1998-07 at a relative humidity of 0% and a temperature of 23°C and a value of 200 ml / (m 2 xdxioo kPa) was obtained.

[0094] The water vapor permeability of the packaging material was measured twice in accordance with ISO 2528:2017 at a relative humidity of 85% and a temperature of 23°C, each time at 10 randomly selected and non-overlapping positions in the same direction through the packaging material. The individual values ​​are given in g / (m 2 x 24 h), shown in Table 1, where column Ai contains the values ​​of the first series of 10 measurements and column A2 contains the values ​​of the second series of 10 measurements. In the rows MW, SD and CoV the mean value (MW) in g / (m 2 x 24 h), the standard deviation (SD) in g / (m 2 x 24 h), and the coefficient of variation (CoV) is given in %.

[0095] The packaging material obtained in this way has - despite comparatively small application quantities of the coatings - an excellent water vapor permeability of only about 15 g / (m 2x 24 h) and a very low standard deviation of the water vapor permeability of only 2.5 g / (m 2 x 24 h), thus falling below the upper limit of the standard deviation of 3.0 g / (m 2 x 24 h).

[0096] In comparison, the paper sold under the name barricote BAG WG BA 4762 by Mitsubishi HiTec Paper Europe as packaging paper with a water vapor and grease barrier has a basis weight of 49 g / m 2 an average water vapor permeability at a temperature of 23°C and a relative humidity of 85% of 35 g / (m 2 x 24 h) and a standard deviation of 10 g / (m 2 x 24 h). The standard deviation of the water vapor permeability is therefore significantly higher than the upper limit of 5.3 g / (m 2 x 24 h).

[0097] According to the inventors' findings, the additional and unusual step of calendering between the application of the first and second coatings is important for the exceptionally advantageous behavior of the packaging material according to the invention. This step, in addition to providing the low variance in water vapor permeability, also manifests itself in the claimed smoothness of the finished packaging material. To demonstrate this, another packaging material with an identical composition was produced in the same way, with the only difference being that calendering was omitted in step C. The water vapor permeability of this (non-inventive) packaging material was also measured twice according to ISO 2528:2017 at a relative humidity of 85% and a temperature of 23°C, each time at 10 randomly selected and non-overlapping positions in the same direction through the packaging material.The individual values ​​are in g / (m. 2 x 24 h) are given in Table 1, where column Bi contains the values ​​of the first series of 10 measurements and column B2 contains the values ​​of the second series of 10 measurements. In the rows MW, SD and CoV the mean value (MW) in g / (m 2 x 24 h), the standard deviation (SD) in g / (m 2 x 24 h), and the coefficient of variation (CoV) is given in %.

[0098] Table i - Water vapor permeability of the packaging material according to the invention (Ai,

[0099] A2) and the packaging material not according to the invention (Bi, B2)

[0100] Table 1 shows that the non-inventive comparative example (Bi, B2) already represents a significant improvement over the commercially available product barricote BAG WG BA 4762, both in terms of water vapor permeability itself and in terms of the standard deviation and the coefficient of variation. However, it can also be seen that the additional calendering step C significantly increases the mean water vapor permeability from approximately 27 g / (m 2 x 24 h) to about 15 g / (m 2 x 24 h). No additional coating material is required for this, which is already an advantage of the invention. Furthermore, Table 1 shows that the standard deviation of the water vapor permeability for the packaging material according to the invention (Ai, Ä2) is approximately 2.5 g / (m 2 x 24 h) is significantly lower than that of the non-inventive packaging material (Bi, B2) with over 4.5 g / (m2 x 24 h).

[0101] The standard deviation for the packaging material according to the invention (Ai, A2) is, on average, lower than for the improved, but not yet inventive, packaging material (Bi, B2). The upper limit for the standard deviation specified by the formula is slightly exceeded by the packaging material of the comparative example (Bi, B2), which is why it is not in accordance with the invention, even though it has further features of the invention in a combination that, to the knowledge of the inventors, is not previously known from the prior art and in itself represents an improvement over the prior art.

[0102] It is remarkable and surprising how significant the difference is with regard to water vapor permeability and its variance between the packaging materials (Ai, A2) and (Bi, B2), considering that the comparative example (Bi, B2) uses all other features of the packaging material according to the invention (Ai, A2), including the step of calendering the base paper, which was also present in the comparative example (Bi, B2), but in itself in this configuration is obviously not sufficient to achieve an inventive combination of water vapor permeability and its standard deviation.

[0103] This treatment manifests itself in the finished packaging material—in addition to the reduced variance in water vapor permeability—also in the increased Bekk smoothness, which was determined to be 1200 s on the coated side for the inventive packaging material (Ai, A2) according to ISO 5627:1995. The comparative example (Bi, B2), in contrast, exhibited a Bekk smoothness of only 720 s on the coated side. This demonstrates that this smoothness is indeed a suitable structural parameter for characterizing the inventive packaging material.

[0104] If a value for water vapor permeability is used to determine the best-before date, which is exceeded in less than 1% of cases, then this value, assuming a normal distribution for the packaging material according to the invention (Ai, A2), is approximately 22 g / (m 2x 24 h) and for the also previously unknown, very similar but not inventive packaging material (Bi, B2) about 42 g / (m 2 x 24 h) and is therefore almost twice as high. This shows that products packaged in the packaging material according to the invention can be expected to have a longer shelf life without increasing material consumption or compromising the recyclability of the packaging material.

Claims

CLAIMS 1. Packaging material comprising a base paper and a first and a second coating, wherein the base paper has a basis weight of at least 30 g / m 2 and a maximum of 90 g / m 2 wherein the first coating - between the base paper and the second coating, - forms a barrier against the penetration of oxygen, and - comprises a polymer having hydroxyl groups, wherein the hydroxyl groups of the polymer are at least partially cross-linked, and wherein the second coating - is applied directly to the first coating, - forms a barrier against the penetration of water vapor, and - a polymer and a wax, wherein the packaging material, on the side to which the first and second coatings are applied, has a Bekk smoothness of at least 800 s and at most 20,000 s, and wherein the average water vapor permeability M of the packaging material is at least 2.0 g / (m 2 x 24 h) and not more than 100.0 g / (m 2 x 24 h), and for the standard deviation s of the water vapor permeability the following formula applies s < M ■ (0.15 + 0.1 ■ e -o.oo3 M 2 ^ where the mean water vapor permeability M and the standard deviation s of the water vapor permeability in g / (m 2 x 24 h) are to be inserted into the formula and are to be determined by measurement in accordance with ISO 2528:2017 at a relative humidity of 85% and a temperature of 23°C at 10 randomly selected, non-overlapping positions on the packaging material in the same direction through the packaging material.

2. Packaging material according to claim 1, wherein the base paper has a basis weight of at least 35 g / m 2 and a maximum of 80 g / m 2 and preferably at least 40 g / m 2 and a maximum of 70 g / m 2 has.

3. Packaging material according to claim 1 or 2, wherein the base paper comprises cellulose fibers, wherein the cellulose fibers are preferably formed by pulp fibers or regenerated cellulose fibers or a mixture thereof. 4- Packaging material according to claim 3, wherein said cellulose fibers are obtained from coniferous wood, in particular spruce, pine, or fir; from hardwood, in particular beech, birch, or eucalyptus; from hemp, flax, jute, ramie, kenaf, kapok, coconut, abaca, sisal, bamboo, cotton, or esparto grass, or from waste paper pulp, or are a mixture of cellulose fibers from several of these sources.

5. Packaging material according to claim 3, wherein the regenerated cellulose fibers are fibrillatable regenerated cellulose fibers.

6. Packaging material according to one of claims 3 to 5, in which the proportion of cellulose fibers is at least 55% and at most 100%, preferably at least 60% and at most 95%, in each case based on the mass of the base paper.

7. Packaging material according to one of the preceding claims, in which the base paper comprises filler, wherein said filler is preferably selected from the group consisting of kaolin, talc, calcium carbonate, magnesium carbonate, magnesium oxide, magnesium hydroxide, aluminum oxide, aluminum hydroxide, titanium dioxide or a mixture thereof, wherein the proportion of filler is preferably at least 5% and at most 45%, particularly preferably at least 10% and at most 40%, in each case based on the mass of the base paper.

8. Packaging material according to one of the preceding claims, wherein the base paper is calendered.

9. Packaging material according to one of the preceding claims, in which the base paper on the side to which the first and second coatings are applied has, before application of the first and second coatings, a Bekk smoothness, measured according to ISO 5627:1995, of at least 600 s and at most 10,000 s, preferably at least 800 s and at most 6,000 s.

10. Packaging material according to one of the preceding claims, in which the base paper on the side to which the first and second coatings are applied has, before application of the first and second coatings, a contact angle with water of at least 30° and at most 70°, preferably at least 40° and at most 65°, wherein the contact angle is to be measured with a drop of 4 pl after 0.1 s.

11. Packaging material according to one of the preceding claims, in which the base paper on the side to which the first and second coatings are applied has, before application of the first and second coatings, a specific water absorption capacity of at least 0.1 and at most 0.7, preferably of at least 0.2 and at most 0.5, wherein the specific water absorption capacity corresponds to the quotient of the water absorption capacity determined as a Cobböo value according to ISO 535:2014 in g / m 2 and the basis weight of the base paper measured according to ISO 536:2019 in g / m 2 corresponds.

12. Packaging material according to one of the preceding claims, wherein said polymer of the first coating, which has hydroxy groups and whose hydroxy groups are partially cross-linked, is selected from the group consisting of starch, starch derivatives, polyvinyl alcohol, modified polyvinyl alcohol, carbohydrates, modified carbohydrates or mixtures thereof.

13. Packaging material according to one of the preceding claims, wherein the first coating comprises glyoxal or ammonium zirconium carbonate.

14. Packaging material according to one of the preceding claims, wherein the first coating is applied over the entire surface, or at least over 90% or more of the surface of one side of the base paper.

15. Packaging material according to one of the preceding claims, in which the amount of polymer of the first coating, based on the area to which the polymer is actually applied, is at least 0.2 g / m 2and a maximum of 5.0 g / m 2 , preferably at least 0.5 g / m 2 and a maximum of 4.0 g / m 2 amounts.

16. Packaging material according to one of the preceding claims, wherein at least one further coating comprising a barrier material and filler is applied between the base paper and the first coating, wherein the barrier material of the further coating is selected from the group consisting of starch, acrylic acid polymers, modified acrylic acid polymers, styrene-acrylate copolymers and mixtures thereof.

17. Packaging material according to claim 16, wherein the filler of said further coating is an inorganic pigment, preferably alumina (Ä12O3) or talc.

18. Packaging material according to one of claims 16 or 17, wherein the further coating is applied over the entire surface or at least over 90% or more of the surface of one side of the base paper, wherein the further coating is preferably applied directly to the base paper.

19. Packaging material according to one of claims 16 to 18, in which the mass of the further coating, based on the area to which it is actually applied, is at least 0.2 g / m 2 and a maximum of 4.0 g / m 2 , preferably at least 0.5 g / m 2 and a maximum of 2.5 g / m 2 amounts.

20. Packaging material according to one of the preceding claims, wherein the polymer of the second coating is selected from the group consisting of styrene-butadiene copolymers, carboxylated styrene-butadiene copolymers, styrene-acrylate copolymers, acrylic copolymers, acrylic polymers, ethylene-acrylic acid copolymers, vinyl acetate-acrylic acid copolymers, acrylic acid-maleic acid copolymers, methacrylic acid polymers, methyl methacrylate polymers and polyurethane and mixtures thereof.

21. Packaging material according to one of the preceding claims, wherein the wax of the second coating is selected from the group consisting of vegetable waxes, animal waxes, mineral oil-based waxes, polymeric waxes, semi-synthetic waxes and synthetic waxes and mixtures thereof, wherein the wax is preferably a paraffin wax.

22. Packaging material according to one of the preceding claims, in which the second coating is applied over the entire surface or at least over 90% or more of the surface of one side of the base paper.

23. Packaging material according to one of the preceding claims, in which the combined mass of polymer and wax in the second coating, based on the area to which polymer and wax are actually applied, is at least 1.0 g / m 2 and a maximum of 10.0 g / m 2 , particularly preferably at least 2.0 g / m 2 and a maximum of 8.0 g / m 2 amounts.

24. Packaging material according to one of the preceding claims, which has a Bekk smoothness of at least 1000 s and at most 10,000 s, and preferably at least 1500 s and at most 8000 s, on the side to which the first coating, the second coating and optionally further coatings are applied. 25- Packaging material according to one of the preceding claims, wherein the Gurley air permeability, measured according to ISO 5636-5:2013, in at least one direction through the packaging material is at least 20,000 s and preferably at least 35,000 s.

26. Packaging material according to one of the preceding claims, which has an average water vapor permeability M of at least 5.0 g / (m 2 x 24 h) and not more than 50.0 g / (m 2 x 24 h) and preferably at least 5.0 g / (m 2 x 24 h) and not more than 40.0 g / (m 2 x 24 h).

27. Packaging material according to one of the preceding claims, in which the formula s < M - (0.12 + 0.1 - e" applies to the average water vapor permeability M and the standard deviation s of the water vapor permeability. 0 ' 003 " 2 ), where the mean water vapor permeability M and the standard deviation s of the water vapor permeability in g / (m 2x 24 h) are to be inserted into the formula.

28. Packaging material according to one of the preceding claims, in which the formula s < M - (0.10 + 0.1 - e" applies to the average water vapor permeability M and the standard deviation s of the water vapor permeability. 0 ' 003 " 2 ), where the mean water vapor permeability M and the standard deviation s of the water vapor permeability in g / (m 2 x 24 h) are to be inserted into the formula.

29. Packaging material according to one of the preceding claims, which has an oxygen permeability in at least one direction through the packaging material, measured according to DIN 53380-3:1998-07 at a relative humidity of 0% and a temperature of 23°C, of ​​at least 1 ml / (m 2 xdxioo kPa) and not more than 500 ml / (m 2 xdxioo kPa), particularly preferably at least 5 ml / (m 2 xdxioo kPa) and not more than 400 ml / (m 2 xdxioo kPa).

30. Packaging material according to one of the preceding claims, whose water absorption capacity, expressed as Cobb 3OO -value and measured according to ISO 535:2014 from the side to which the first and second coatings are applied, at least og / m 2 and a maximum of 10 g / m 2 and preferably at least og / m 2 and a maximum of 5 g / m 2 amounts.

31. Packaging material according to one of the preceding claims, in which a barrier against the penetration of oils or fats, expressed as a Kit value and measured according to TAPPI T559-cmi2 from the side to which the first and second coatings are applied, is at least 8 and at most 12, preferably at least 9 and at most 12.

32. Packaging material according to one of the preceding claims, wherein rice, sugar, pasta, chocolate, chocolate bars, nuts, cereals, cheese, pastries, meat products, coffee, tea, electronic components, kitchen towels or hygiene articles are packaged in the packaging material.

33. A process for producing a packaging material according to any one of claims 1 to 31, comprising the following steps Ab to D: A - Providing a base document, B - applying a first coating composition to at least one side of the base paper to produce a first coating, C - Calendering the coated base paper from step B, D - applying a second coating composition directly onto the first coating to produce a second coating, wherein the base paper in step A has a basis weight of at least 30 g / m 2 and a maximum of 90 g / m 2and wherein the first coating from step B forms a barrier against the penetration of oxygen and comprises a polymer which has hydroxyl groups, wherein the hydroxyl groups of the polymer are at least partially cross-linked in step B, and wherein the calendering in step C is carried out such that the packaging material after step D has a Bekk smoothness of at least 800 s and at most 20,000 s on the side to which the first coating in step B and the second coating in step D were applied, and wherein the second coating from step D forms a barrier against the penetration of water vapor and comprises a polymer and a wax, and wherein the average water vapor permeability M of the packaging material after step D is at least 2.0 g / (m 2 x 24 h) and not more than 100.0 g / (m 2x 24 h), and for the standard deviation s of the water vapor permeability the following formula applies s < M ■ (0.15 + 0.1 ■ e -o.oo3 M 2 ^ where the mean water vapor permeability M and the standard deviation s of the water vapor permeability in g / (m 2 x 24 h) are to be inserted into the formula and are determined by measurement according to ISO 2528:2017 at a relative humidity of 85% and a temperature of 23°C at 10 randomly selected, non-overlapping positions on the packaging material in the same direction through the packaging material.

34. The method according to claim 33, wherein the provision of the base paper in step A comprises producing the base paper on a paper machine, particularly preferably a Fourdrinier paper machine.

35. A method according to claim 33 or 34, wherein the base paper in step A has a basis weight of at least 35 g / m 2 and a maximum of 80 g / m2 and preferably at least 40 g / m 2 and a maximum of 70 g / m 2 has.

36. A process according to any one of claims 33 to 35, wherein the base paper in step A comprises cellulose fibers, wherein said cellulose fibers are particularly preferably formed by pulp fibers or regenerated cellulose fibers or a mixture thereof.

37. A process according to claim 36, wherein the pulp fibers are obtained from coniferous wood, in particular spruce, pine, or fir; from hardwood, in particular beech, birch, or eucalyptus; from hemp, flax, jute, ramie, kenaf, kapok, coconut, abaca, sisal, bamboo, cotton, or esparto grass, or from waste paper pulp, or are a mixture of pulp fibers from several of these sources.

38. The method of claim 36, wherein the regenerated cellulose fibers are fibrillatable regenerated cellulose fibers.

39. A process according to any one of claims 36 to 38, wherein the proportion of cellulose fibers is at least 55% and at most 100% based on the mass of the base paper in step A, and preferably at least 60% and at most 95%.

40. A method according to any one of claims 33 to 39, wherein the base paper in step A comprises filler, wherein said filler is preferably selected from the group consisting of kaolin, talc, calcium carbonate, magnesium carbonate, magnesium oxide, magnesium hydroxide, aluminum oxide, aluminum hydroxide, titanium dioxide or a mixture thereof, wherein the proportion of filler is preferably at least 5% and at most 45%, particularly preferably at least 10% and at most 40% based on the mass of the base paper in step A.

41. A method according to any one of claims 33 to 40, wherein the method comprises a step of calendering the base paper from step A between step A and step B.

42. A method according to claim 41, wherein the base paper during calendering between step A and step B passes through at least one roll gap in which a line load of at least 20 kN / m and at most 800 kN / m acts on the base paper.

43. A method according to any one of claims 33 to 42, wherein the base paper immediately before step B, on the side intended for application of the first coating in step B, has a Bekk smoothness, measured according to ISO 5627:1995, of at least 600 s and at most 1500 s, preferably at least 800 s and at most 1200 s.

44. A method according to any one of claims 33 to 43, wherein the first coating composition in step B comprises the polymer of the first coating, a cross-linking agent and a solvent, wherein the cross-linking agent is preferably glyoxal or ammonium zirconium carbonate and / or wherein the solvent is preferably water.

45. A method according to any one of claims 33 to 44, wherein the polymer of the first coating is selected from the group consisting of starch, starch derivatives, polyvinyl alcohol, modified polyvinyl alcohol, carbohydrates, modified carbohydrates or mixtures thereof.

46. ​​A method according to any one of claims 33 to 45, wherein applying the first coating composition in step B comprises applying it in a film press or size press in a paper machine or other coating device integrated into the paper machine or on a separate coating device and further drying the first coating composition.

47. A method according to any one of claims 33 to 46, wherein the first coating composition in step B is applied over the entire area or at least to 90% or more of the area of ​​one side of the base paper.

48. A method according to any one of claims 33 to 47, wherein between step A and step B a further coating is applied which comprises a barrier material and filler, wherein the barrier material of said further coating is selected from the group consisting of starch, acrylic acid polymers, modified acrylic acid polymers, styrene-acrylate copolymers and mixtures thereof, and wherein said filler of said further coating is an inorganic pigment, in particular alumina (Al 12 O 3 ) or talc.

49. A method according to claim 48, wherein said further coating is applied over the entire area or at least over 90% or more of the area of ​​one side of the base paper, wherein the further coating is preferably applied directly to the base paper.

50. The method according to any one of claims 33 to 49, wherein in step C the calendering of the coated base paper from step B comprises passing through at least one and at most 14, preferably at least 4 and at most 12, roll gaps, wherein in at least one of the roll gaps the coated base paper from step B is subjected to a line load of at least 20 kN / m and at most 800 kN / m, preferably at least 40 kN / m and at most 600 kN / m.

51. A method according to any one of claims 33 to 50, wherein the calendering in step C is carried out such that the packaging material after step D has, on the side to which the first coating in step B and the second coating in step D were applied, a Bekk smoothness of at least 1000 s and at most 10,000 s, and preferably at least 1500 s and at most 8000 s.

52. A method according to any one of claims 33 to 51, wherein the second coating composition in step D comprises the polymer and wax of the second coating and a solvent, wherein the solvent is preferably water.

53. The method of any one of claims 33 to 52, wherein the polymer of the second coating is selected from the group consisting of styrene-butadiene copolymers, carboxylated styrene-butadiene copolymers, styrene-acrylate copolymers, acrylic copolymers, acrylic polymers, ethylene-acrylic acid copolymers, vinyl acetate-acrylic acid copolymers, acrylic acid-maleic acid copolymers, methacrylic acid polymers, methyl methacrylate polymers and polyurethane and mixtures thereof; and the wax of the second coating is selected from the group consisting of vegetable waxes, animal waxes, mineral oil-based waxes, polymeric waxes, semi-synthetic waxes and synthetic waxes and mixtures thereof, wherein said wax of the second coating is preferably a paraffin wax.

54. The method of any one of claims 33 to 53, wherein applying the second coating composition in step D comprises applying it in a counter-rotating gravure coater, a bar coater, or a curtain coater and drying the second coating composition.

55. A method according to any one of claims 33 to 54, wherein the second coating composition in step D is applied over the entire area or at least over 90% or more of the area of ​​one side of the base paper.

56. A method according to any one of claims 33 to 55, wherein the packaging material after step D has an average water vapor permeability M of at least 5.0 g / (m 2 x 24 h) and not more than 50.0 g / (m 2 x 24 h) and preferably at least 5.0 g / (m 2 x 24 h) and not more than 40.0 g / (m 2 x 24 h).

57. A method according to any one of claims 33 to 56, wherein the formula s < M - (0.12 + 0.1 - e" 0 ' 003 " 2 ), where the mean water vapor permeability M and the standard deviation s of the water vapor permeability in g / (m 2 x 24 h) are to be inserted into the formula.

58. A method according to any one of claims 33 to 56, wherein the formula s < M - (0.10 + 0.1 - e" 0 ' 003 " 2 ), where the mean water vapor permeability M and the standard deviation s of the water vapor permeability in g / (m 2 x 24 h) are to be inserted into the formula.

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