Substrate having a barrier coating

Abstract

The invention relates to a method for producing a substrate having a barrier coating, comprising the following steps: application of a first layer of a first composition, comprising an aqueous polymer dispersion and less than 0.2 wt.% wax, to a substrate, intermediate drying of the first layer to a defined amount of free surface energy of a surface of the first layer, application of a second layer of a second composition, comprising an aqueous polymer dispersion and 1-8 wt.% wax, to the surface of the intermediately dried first layer, and subsequent drying. The invention also relates to a substrate having a barrier coating, the substrate being obtainable by means of the method.

Description

[0001] Bavariaring 11 D-80336 Munich

[0002] M Ü LLERSCHUPFNER Telephone: + 49 -89 -2199120 Fax: + 49 - 89 - 21991220 & PARTNER E-mail: maximark@propat.de MSP Reference: 45824 PT-WO CB / CN Substrate with barrier coating The invention relates to a method for producing a substrate with a barrier coating, a substrate with a barrier coating and the use of the substrate with a barrier coating as packaging material. Composite materials are often used as packaging materials for food, for example, in which polyethylene is combined with paper or cardboard by means of coextrusion or lamination. However, these cannot usually be recycled and are sent for thermal recycling. The EU Packaging Regulation PPWR stipulates recycling targets that cannot be achieved with the composite materials described.Paper or cardboard packaging made from mineral oil-contaminated, recycled paper with a plastic barrier layer is also known as packaging materials, for example from EP 2714990 A1. The barrier layer is intended to protect packaged materials, such as food, from contamination with mineral oil residues, for example, and to prevent the penetration of water, water vapor, and grease into the paper and cardboard. However, these packaging materials with a barrier layer have the disadvantage that the barrier layer either adheres insufficiently to the coated paper or cardboard substrate, or that large application quantities and thus a large amount of coating material must be used to achieve a sufficient barrier effect.Furthermore, papers untreated with these barrier coatings, for example, papers based on tree-free cellulose, are often inadequately sealable due to their open-pored, absorbent material properties. Furthermore, the known materials with barrier coatings do not simultaneously achieve high barrier effects against water, water vapor, and grease, nor are they sealable and recyclable. Sealability means that the coated side does not need to be glued, but can be bonded by heating or ultrasound (heat sealing or ultrasonic sealing). Most known barrier coatings are not suitable for sealing.The object of the invention is therefore to overcome the above-mentioned disadvantages and to provide a method for coating a substrate, in particular paper or cardboard, and a substrate obtainable thereby with a barrier coating that simultaneously has high barrier effects against water, water vapor, and grease, is sealable and recyclable, in particular with a small application of the coating material, and is also applicable to open-pore substrates. 15 This object is achieved by a method according to claim 1, a substrate with a barrier coating obtainable by this method according to claim 12, a substrate with a barrier coating according to claim 13, and a use according to claim 15. Further features, embodiments, and advantages emerge from the dependent claims and the description.20 One aspect of the invention relates to a method for producing a substrate with a barrier coating, comprising the steps of: a) applying a first layer of a first composition comprising an aqueous polymer dispersion and less than 0.2 wt.-% wax, based on the total weight of the first composition, onto a substrate, b) intermediate drying of the first layer to a free surface energy 30 of a surface of the first layer of 30 - 50 mN / m and a polar portion of the free surface energy of 3 - 10 mN / m, the free surface energy and the polar portion of the free surface energy being measured at room temperature, immediately after intermediate drying, 45824 PT-EP CB / CN using the method according to Owens, Wendt, Rabel and Kaelble with a Krüss MSA measuring device, c) applying a second layer, immediately after intermediate drying, 5 of a second composition comprising an aqueous polymer dispersion and 1 - 8 wt.% wax, based on the total weight of the second composition, onto the surface of the intermediately dried first layer, 10 d) drying the coated substrate from step c).A further aspect of the invention relates to a substrate with a barrier coating, obtainable by the process according to the invention. 15 The invention also relates to a substrate with a barrier coating, comprising a substrate with a barrier coating, comprising a substrate, a first layer applied directly to the surface of the substrate, comprising a polymer and less than 0.5 wt. % wax, based on the total weight of the first layer, and a layer thickness of the first layer of 2-7 µm, and a second layer applied directly to the first layer, comprising a polymer and 2-20 wt. % wax, based on the total weight of the second layer, and a layer thickness of the second layer of 2-25 µm.Surprisingly, the process according to the invention results in a substrate (carrier) coated with a barrier coating that is very easily recyclable and has an excellent barrier effect against water, water vapor, and grease (multi-barrier coating), even with a low material application or a low thickness of the barrier coating. This is achieved in particular by a combination of a first layer with little or no wax for good adhesion to the substrate and a second layer with wax for a good barrier effect. A central feature of the process according to the invention is the intermediate drying, which leads to optimal wetting between the first and second layers. In addition, the obtainable substrate with barrier coating is sealable, in particular heat-sealable and ultrasonically sealable.Sealing can be achieved either by applying a barrier coating to a barrier coating (varnish against varnish) or by applying a barrier coating to a substrate (varnish against substrate). 10 The substrate with a barrier coating obtainable by the process according to the invention can be used in a very broad temperature range from -40°C (e.g., frozen products) to 140°C (e.g., coffee cups, fast food). It is applicable to virtually all papers and cardboard, in particular to uncoated (sustainable) natural and recycled materials, but also to plastic materials. The substrate with a barrier coating obtainable by the process according to the invention is a recyclable and sustainable alternative to PE-coated composite materials and plastic packaging.The barrier-coated substrate obtainable by the process according to the invention covers a very wide range of applications, for example, for flow packs or bags for moist or fatty foods, drinking cups, fast-food packaging of all kinds, folding boxes for frozen foods, etc. Using the process according to the invention, one side of the substrate, for example, a paper or cardboard, can be coated, or both sides can be coated. One side is preferably coated.Within the scope of the invention, it was found that if the first layer is dried too intensively or completely, the surface tension or the free surface energy drops too much and the polar portion of the free surface energy also drops too much, whereby an even application of the second layer on the first layer is no longer possible due to insufficient wetting or the adhesion between the first and second layers 45824 PT-EP CB / CN becomes insufficient. It was found that the intermediate drying step is advantageously carried out until the free surface energy of the surface of the first layer is 30 - 50 mN / m and the polar portion of the free surface energy is 3 - 10 mN / m. In this way, the residual moisture on the surface of the first layer serves as a type of polar bridge for the second layer. The result is very good wetting of the second layer on the first layer.This results in a maximally filmed, closed surface of the substrate with an excellent barrier effect, while simultaneously requiring minimal application thickness for the first and second layers. 10 The barrier effect within the meaning of the invention relates in particular to water, water vapor, grease, and oxygen. When using the substrate according to the invention with a barrier coating, for example as packaging material, this has the advantage that residues in the substrate material, for example mineral oil residues in recycled paper or cardboard, do not migrate into the packaged material such as food, and no oxygen penetrates from the outside, which, for example, impairs the aroma of food. Furthermore, no water or water vapor, nor any grease, migrates into the packaging material and thereby impairs its properties.The 20 process can be used for paper and cardboard as well as film materials or plastic materials as substrates. The available substrates with a barrier coating can be used in both the food and non-food sectors. 25 The substrate with a barrier coating obtainable using the process according to the invention is extremely recyclable and meets the requirements of the EU Packaging Directive 94 / 62 / EC, which stipulates that raw materials should be reused and that the recycling rate of all packaging waste should be increased to 70% by 2030. 30 The process according to the invention is preferably applicable to recycled paper and cardboard, substrates in the form of untreated paper, particularly preferably based on tree-free cellulose, for example from agricultural waste 45824 PT-EP CB / CN such as hemp or bagasse (sugar cane) or bamboo paper.Open-pored, absorbent materials cannot usually be provided with barrier layers using conventional coating or painting techniques, or can only be provided inadequately. 5 The steps of the process are carried out successively in the specified order a), b), c), d). In a preferred embodiment, the substrate is made of paper, cardboard, plastic or a combination thereof. A combination is preferably a composite material made of paper, cardboard and / or plastic. 10 More preferably, it is paper or cardboard, most preferably paper or cardboard made from recycled material and / or tree-free cellulose, for example hemp, sugar cane, bamboo. 15 In the first step a) of the process according to the invention, a first layer made of a first composition is applied to a substrate, the first composition comprising an aqueous polymer dispersion and less than 0.2 wt.-% wax, based on the total weight of the first composition. In step c), a second layer of a second composition is applied, the second composition comprising an aqueous polymer dispersion and 1-8 wt.% wax, based on the total weight of the second composition. The first composition preferably comprises an aqueous polymer dispersion and less than 0.1 wt.% wax, particularly preferably less than 0.05 wt.% wax, based on the total weight of the first composition. The second composition preferably comprises an aqueous polymer dispersion and 1-7 wt.% wax, more preferably 1.5-5 wt.% wax, particularly preferably 2-4 wt.% wax, based on the total weight of the second composition. A wax in the sense of the invention is, as usual, a mixture of various hydrocarbons that melt above about 40°C.Waxes are almost insoluble in water and soluble in organic, non-polar solvents. Waxes are generally divided into natural and synthetic waxes, and among natural waxes, a distinction is made between animal, vegetable, and mineral waxes. According to the invention, the wax is preferably a vegetable wax or a mixture of vegetable waxes. Particular preference is given to sugar cane wax, carnauba wax, candelilla wax, cork wax, guaruma wax, palm wax, cotton wax, rice bran wax, flax wax, peat wax, rose wax, jasmine wax, myrtle wax, polyamide wax, PP wax (polypropylene wax), PE wax (polyethylene wax), ouricuri wax, Fischer-Tropsch wax, wax fig wax, and mixtures thereof. Particularly good barrier effects can be achieved with these waxes. The polymer of the aqueous polymer dispersion of the first and second compositions can be the same or different. It is preferably the same.The polymer of the aqueous polymer dispersion is preferably a thermoplastic polymer, more preferably a (meth)acrylate polymer, (meth)acrylate copolymer, or polyvinyl alcohol, even more preferably a (meth)acrylate-olefin copolymer or polyvinyl alcohol, particularly preferably a copolymer of (meth)acrylate and styrene or a styrene derivative. (Meth)acrylate is understood, as usual, to mean acrylate, methacrylate, or acrylate-methacrylate. The first and / or second composition preferably has a pH of 7-9.5, more preferably 8-9. The solids content of the first composition and / or the second composition is preferably 25-50% by weight, more preferably 35-45% by weight, and most preferably 38-42% by weight. The TG (glass transition temperature) of the polymer of the first and / or second composition is preferably 0-60 °C, more preferably 0-40 °C and most preferably 3-10 °C.These polymers allow particularly good adhesion to the substrates and between the two layers, as well as particularly good barrier effects in combination with the above-mentioned waxes. The intermediate drying of the first layer in step b) of the process according to the invention is carried out to a free surface energy of the surface of the first 45824 PT-EP CB / CN layer of 30-50 mN / m and a polar component of the free surface energy of 3-10 mN / m. The unit mN / m (millinewtons per meter) corresponds to the energy per surface in mJ / m. 2(millijoules per square meter) and is regularly given in mN / m. 5 In a preferred embodiment of the invention, the intermediate drying of the first layer takes place until the free surface energy of the first layer is 35 - 45 mN / m and the polar component of the free surface energy is 3.5 - 9 mN / m. 10 The intermediate drying of the first layer is particularly preferably carried out until the free surface energy of the first layer is 38 - 42 mN / m and the polar component of the free surface energy is 3.8 - 8 mN / m. The polar component of the free surface energy is even more preferably 3 - 5, further preferably 3.5 - 4.5, particularly preferably 3.8 - 4.2 mN / m. 15 This enables particularly good adhesion between the first and second layers and a particularly uniform formation of the second layer, even with a small amount of material applied.Furthermore, it is preferred that the disperse portion of the surface energy of the first layer at the surface after intermediate drying is ≥ 32 mN / m, more preferably ≥ 35 mN / m. The final result, in terms of barrier effect and maximum film-formed surface, 20 depends on the drying state of the primer (coating unit). The assessment of the finished coating (barrier effect) can be monitored, for example, with olive oil and / or water. If the barrier is insufficient, it can be increased, for example, by reducing the intermediate drying 25. The coating application rate of the barrier coating in coating unit 2 (second layer) is not increased, as is sometimes done with competitive products, but advantageously via the described procedure of optimal wetting 30 → "polar bridge".The free surface energy and the polar component of the free surface energy, as well as the polar component of the free surface energy, are measured according to 45824 PT-EP CB / CN using the Owens, Wendt, Rabel, and Kaelble method using a Krüss MSA measuring device (MSA = Mobile Surface Analyzer from Krüss), for example, an MSA Flexible Liquid measuring device from Krüss. The measurement with the Krüss MSA measuring device is taken immediately after intermediate drying. The measurement is carried out at room temperature (approximately 25 °C). “Immediately after” in the sense of the invention with regard to the measurement means directly thereafter, preferably within about 0 - 10 s (seconds), more preferably within about 2 - 8 s. “Immediately after” in the sense of the invention with regard to the application of the second layer after intermediate drying means directly thereafter, preferably within about 0 - 10 s, more preferably within about 0.05 - 1 s.The Owens-Wendt-Rabel-Kaelble method is a standard method for determining the surface free energy of a solid using the contact angle with several liquids. The surface free energy is split into a polar component and a dispersed component. The background of this measurement method is a relationship between the contact angle θ, the surface tension of the liquid σl, and the interfacial tension σ. sl between liquid and solid and the free surface energy σs of the solid: In order to calculate the free surface energy from the contact angle, the second unknown quantity σsl is determined. The interfacial tension σsl is calculated using the two surface tensions σs and σl and the similar interactions between the phases. These interactions are expressed as the geometric mean of a dispersive 45824 PT-EP CB / CN fraction σ Dand a polar component σ P the surface tension or free surface energy: 5 To measure the free surface energy of the solid, at least two liquids with known dispersive and polar components of the surface tension are required, whereby at least one of the liquids must have a polar component > 0. 10 According to the two-component model, the interfacial tension depends on whether polar and dispersive components can interact with corresponding components of the adjacent phase. For example, the interfacial tension becomes smaller compared to the polar liquid water if the solid 15 is also polar. If, on the other hand, the polar component of the solid is low, the root term (σPl ⋅ σPs) decreases. 1 / 2a small value. The polar interactions then make only a small contribution to reducing the interfacial tension. This corresponds to poor wetting and a high contact angle. 20 As described above, intermediate drying to the stated values ​​of the free surface energy and the polar component of the free surface energy results in sufficient free surface energy remaining on the surface of the first layer to enable good adhesion of the second layer to the surface of the first layer. This ensures that the second layer from the second composition is applied evenly with sufficient wetting. The remaining water in the intermediately dried, i.e. partially dried, first layer serves as a kind of polar bridge for the second layer.30 The intermediate drying in step b) is preferably carried out at a temperature of 20 - 70 °C, preferably 20 - 60 °C, more preferably 30 - 50 °C, particularly preferably 35 - 45 °C. The intermediate drying is preferably carried out for 0.03 - 3.0 s, preferably 45824 PT-EP CB / CN 0.04 - 2.0 s, more preferably 0.05 - 0.9 s, even more preferably 0.06 - 0.6 s, particularly preferably 0.1 - 0.3 s. The intermediate drying is preferably carried out as hot air drying. 5 The process according to the invention therefore also relates to a process for producing a substrate with a barrier coating, comprising the steps of: a) applying a first layer of a first composition comprising an aqueous polymer dispersion and less than 0.2 wt.-% wax, based on the total weight of the first composition, onto a substrate, b) intermediate drying of the first layer at a temperature of 20 - 70 °C, preferably 20 - 60 °C, more preferably 30 - 50 °C, particularly preferably 35 - 45 °C, for 0.03 - 3.0 s, preferably 0.04 - 2.0 s, more preferably 0.05 - 0.9 s, even more preferably 0.06 - 0.6 s, particularly preferably 0.1 - 0.3 s. c) applying a second layer of a second composition comprising an aqueous polymer dispersion and 1 - 8 wt.% wax, based on the total weight of the second composition, preferably 1 - 7 wt.% wax, onto the surface of the intermediately dried first layer, d) drying the coated substrate from step c). 25 The application of the first layer in step a) is preferably carried out using a flexographic printing process. A roller, such as an anilox roller, is used.The surface of the roller is preferably a compressible material (sleeve, paint plate). The roller surface preferably has a Shore hardness of 40–60 Shore A, preferably 45–50 Shore A. The surface roughness of the roller material is preferably R. a = 0.4 – 0.6 and R z= 4 – 6. 45824 PT-EP CB / CN In the case of rough and / or open-pored substrates, it can be advantageous to carry out mechanical compression of the intermediately dried first layer after intermediate drying and before application of the second layer. This is preferably carried out using a roller, more preferably a calendering roller. The mechanical compression of the intermediately dried first layer ensures that the first layer is pressed into any unevenness in the substrate and the entire surface is compacted and prepared for coating with the second layer. 10 The application of the second layer in step c) is preferably carried out using a flexographic printing process, semi-flexographic printing process or screen printing, in particular using a flexographic printing process. A roller such as an anilox roller is used for this purpose.15 When applying the second layer comprising a second composition to the intermediately dried first layer, the intermediately dried first layer preferably has a free surface energy of 30 - 50 mN / m and a polar portion of the free surface energy of 3 - 10 mN / m at the time of application of the second layer. More preferably, the intermediately dried first layer has a free surface energy of 35 - 45 mN / m and a polar portion of the free surface energy of 3.5 - 9.0 mN / m at the time of application of the second layer. Particularly preferably, the intermediately dried first layer has a free surface energy of 38 - 42 mN / m and a polar portion of the free surface energy of 3.8 - 8.0 mN / m at the time of application of the second layer.The polar portion of the free surface energy is even more preferably 3-5, further preferably 3.5-4.5, particularly preferably 3.8-4.2 mN / m. This enables particularly good adhesion between the first and second layers and a particularly uniform formation of the second layer, even with a small amount of material applied. It is further preferred that the disperse portion of the surface energy of the first layer at the surface at the time of application of the second layer is ≥ 32 mN / m, further preferably ≥ 35 mN / m. 45824 PT-EP CB / CN Preferred is therefore a process for producing a substrate with a barrier coating, comprising the steps: 5 a) applying a first layer from a first composition comprising an aqueous polymer dispersion and less than 0.2 wt.-% wax, based on the total weight of the first composition, onto a substrate, 10 b) intermediate drying of the first layer to a free surface energy of a surface of the first layer of 30 - 50 mN / m and a polar portion of the free surface energy of 3 - 10 mN / m, the free surface energy and the polar portion of the free surface energy being measured at room temperature, immediately after intermediate drying,15 using the method according to Owens, Wendt, Rabel and Kaelble with a Krüss MSA measuring device, c) applying a second layer, immediately after intermediate drying, from a second composition comprising an aqueous polymer dispersion 20 and 1 - 8 wt.-% wax, based on the total weight of the second composition, to the surface of the intermediately dried first layer, wherein the intermediately dried first layer at the time of application of the second layer has a free surface energy of 30 - 50 mN / m and a polar portion of the free surface energy of 3 - 10 25 mN / m, d) drying the coated substrate from step c). At the time of application of the second layer, the intermediately dried first layer preferably has a free surface energy of 35 - 45 mN / m and 45824 PT-EP CB / CN a polar portion of the free surface energy of 3 - 9 mN / m, more preferably a free surface energy of 38 - 42 mN / m and a polar portion of the free surface energy of 3 - 8 mN / m. In the process according to the invention, an amount of 3 - 20 g / m is preferably used when applying the first layer and / or when applying the second layer. 2 , more preferably 5 – 16 g / m 2, even more preferably 7 – 14 g / m 2 and most preferably 8 – 12 g / m 2of the composition (the first composition or the second composition). Drying in step d) (final drying) is preferably carried out at a temperature of 20 - 100 °C, more preferably 50 - 90 °C, particularly preferably 70 - 80 °C. Drying in step c) is preferably carried out for 2 to 48 h, particularly preferably 4 to 24 h. Drying in step d) (final drying) is particularly preferably carried out by hot air drying. After drying, the layer thickness of the first layer is 2 - 7 µm, preferably 3 - 6 µm, particularly preferably 3.5 - 5 µm. The layer thickness of the second layer after drying is 2 - 7 µm, preferably 3 - 6 µm, particularly preferably 3.5 - 5 µm. The layer thickness is determined by measuring the height of the layer in a cross-section, for example under a light microscope. For this purpose, the layer thicknesses are determined at at least three locations, preferably three to five locations, and the arithmetic mean is determined.This is then the layer thickness, which can also be referred to as the average layer thickness. The process according to the invention produces a substrate with a barrier coating that is very well sealed, heat-resistant up to 140°C, and suitable for freezing down to -40°C. The substrate with a barrier coating obtainable by the process according to the invention can have a grease barrier of KIT 12 and / or a water vapor barrier (MVTR) of 15 g / m. 2 d up to 20 g / m 2d and / or Cobb values ​​(Cobb 1800) of at least 0.8 g / m² to 2 g / m² or better can be achieved (measured MVTR according to DIN 53122, Cobb value according to DIN EN 20535 and KIT according to ISO 16532-2). These values ​​45824 PT-EP CB / CN are superior to the known barrier coatings or, in the case of known water-based barrier coatings, they are only achieved with significantly thicker coatings. 5 The invention also relates to a substrate with a barrier coating, obtainable by the process according to the invention. The preferred and particularly preferred embodiments described for the process according to the invention are also preferred and particularly preferred for the substrate with a barrier coating obtainable by the process according to the invention.10 The substrate with barrier coating obtainable by the process according to the invention is characterized in particular by the features that the first layer has a low wax content and the second layer a high wax content. This improves the adhesion of the first layer to the substrate, 15 particularly to polar substrates such as paper, cardboard, or polymers that have polar groups. The high wax content of the second layer ensures, in particular, a good barrier effect of the coating. These two layers have different hydrophilicity and hydrophobicity due to the greatly different wax content. This fundamentally complicates the adhesion of the 20 layers to one another. The excellent adhesion is achieved according to the invention by the intermediate drying step because the only partial drying leaves a water content in the first layer as a kind of polar bridge for the second layer.The substrate with a barrier coating obtainable by the process according to the invention is therefore characterized by particularly good adhesion between the first and second layers, which would not be expected due to the ingredients, in particular the different wax content. The invention also relates to a substrate with a barrier coating, comprising a substrate with a barrier coating, comprising a substrate, a first layer applied directly to the surface of the substrate, comprising a polymer and less than 0.5 wt.% wax, based on the total weight of the first layer, and a layer thickness of the first layer of 2 - 7 µm, and a second layer applied directly to the first layer, comprising a polymer and 2 - 20 wt.% wax, based on the total weight of the second layer, and a layer thickness of the second layer of 2 - 7 µm.10 The layer thickness of the first layer is preferably 3-6 µm, particularly preferably 3.5-5 µm. The layer thickness of the second layer is preferably 3-6 µm, particularly preferably 3.5-5 µm. In the substrate with barrier coating according to the invention, the polymer 15 is also preferably a copolymer of (meth)acrylate and styrene or a styrene derivative. The substrate is preferably made of paper, cardboard, plastic, or a combination thereof. Paper or cardboard made of tree-free cellulose is preferred. It is understood that the features mentioned above and those to be explained below can be used not only in the specified combinations, but also in other combinations or on their own, without departing from the scope of the present invention. The mentioned advantages of features or combinations of several features are merely examples and can be used alternatively or cumulatively.The combination of features25 of different embodiments of the invention or of features of different patent claims is possible, deviating from the selected references of the patent claims. The invention is further explained below using examples. 30 EXAMPLES Example 1: 45824 PT-EP CB / CN A 90 g / m² 2 Sugarcane paper in a web width of 1.80 m coated on one side using the process of the invention (Fischer & Krecke central cylinder flexographic printing press). The printing press produces at a speed of 200 m / min. The coated material is part of a round-wound can, which consists of a three-layer composite of 90 g / m 2Sugarcane paper. The inner layer – in contact with the contents – is coated with the barrier coating. The stability of the can is ensured by the heat-sealing properties and the resulting bonding during the wrapping process. First layer: Printing unit 1: Application of the first composition (primer) consisting of an aqueous polymer dispersion and less than 0.2 wt.% wax based on an acrylate / methacrylate-styrene copolymer. The coating is applied using an anilox roller with a theoretical cupping volume of 15 cm 3 / m 2 and varnish transfer using a cliché / sleeve. Printing unit 2: analogous use as in printing unit 1. Alternatively, a printing roller with a theoretical cupping volume of 30 cm 3 / m 2The intermediate drying is set within a control range of 35 to 50°C to ensure the ideal surface tension of the primer (free surface energy of the surface of the first layer of approximately 40 mN / m and a polar component of the free surface energy of approximately 4 mN / m, measured according to the Owens, Wendt, Rabel, and Kaelble method with a Krüss MSA measuring device). Second layer: In a separate printing unit: Application of the second composition (barrier coating) consisting of an aqueous polymer dispersion and 4 wt.% wax based on aqueous acrylate / methacrylate-styrene copolymers. The coating is applied using an anilox roller with a theoretical cupping volume of 30 cm 3 / m 2and varnish transfer via cliché / sleeve. 45824 PT-EP CB / CN The barrier varnish is dried via the final drying system of the system (hot air drying). The temperature is set to 80 to 90°C. 5 EXAMPLE 2: Process analogous to Example 1: Printing machine: Uteco flexographic printing machine Material: 45g / m 2 Kraft paper white 10 Width of the paper roll: 1,000 mm Coating: one-sided Use / Product: Flowpacks for bags for nut kernel mixtures (fatty contents) First layer / coating application 1: Anilox roller with theoretical scoop volume of 15 18 cm 3 / m 2 , Polymer as in Example 1 Intermediate drying (as in Example 1) second layer / coating application 2: Anilox roller with theoretical scoop volume of 18 cm 3 / m 2, Polymer as in Example 1 20 The following tests show that the setting of the intermediate drying has an immediate, direct influence on the barrier effect and overprintability or overpainting ability of the barrier coating. ^ Test setup: 25 o Printing substrate: sugar cane paper 70g / m² o 1st coat of varnish → Primer LW01 (primer, water-based varnish, based on acrylate copolymer) o 2nd coat of varnish → Barrier LW02 (barrier, water-based varnish, based on acrylate copolymer) 30 o Application quantity 12μm wet using a spiral doctor blade ^ Measurement method: 45824 PT-EP CB / CN o Contact angle determination / surface tension measurement KRÜSS MSA ^ Test procedure: 5 o Test No. 1 → (according to the invention) 1. Coating of the paper with Primer LW01 2. Brief drying of the coating o Test No. 2 → (comparative test) 1. Coating of the paper with LW01 10 2. Drying of the coating in a drying cabinet at 100°C for 30sec o Test No. 3 → (comparative test) 1. Coating the paper with LW01 2.Intermediate drying at room temperature for 5sec 15 3. Coating with LW02 4. Drying of the coating at room temperature for 5sec o Test №4 →(Comparison test) 1. Coating of the paper with LW01 2. Intermediate drying at room temperature for 5sec 20 3. Coating with LW02 4. Drying of the coating in a drying cabinet at 100°C for 30sec ^ Result: 25 o Test №1 → Total energy (free surface energy) = 43.83 Polarity (pol. fraction of free surface energy) = 6.77 o Test №2 → Total energy = 33.06 30 Polarity = 1.20 o Test №3 → Total energy = 53.94 45824 PT-EP CB / CN Polarity = 15.52 o Test №4 → Total energy = 38.35 polarity = 1.40.

Claims

45824 PT-EP CB / CN Patent claims 1. A method for producing a substrate with a barrier coating, comprising the steps of: 5 a) applying a first layer of a first composition, comprising an aqueous polymer dispersion and less than 0.2 wt. % wax, based on the total weight of the first composition, to a substrate, 10 b) intermediate drying of the first layer to a free surface energy of a surface of the first layer of 30 - 50 mN / m and a polar fraction of the free surface energy of 3 - 10 mN / m, wherein the free surface energy and the polar fraction of the free surface energy are measured at room temperature, immediately after intermediate drying, using the method according to Owens, Wendt, Rabel and Kaelble with a Krüss MSA measuring device, 20 c) applying a second layer, immediately after intermediate drying, of a second composition, comprising an aqueous polymer dispersion and 1 - 8 wt.-% wax, based on the total weight of the second composition, on the surface of the intermediately dried first layer, 25 d) drying the coated substrate from step c).

2. Process according to claim 1, characterized in that the free surface energy is 35 - 45 mN / m and the polar portion of the free surface energy is 3.5 - 9.0 mN / m. 30 3. Process according to claim 1 or 2, characterized in that in step a) 3 - 20 g / m², preferably 7 - 14 g / m² of the first composition and / or. 45824 PT-EP CB / CN in step c) 3 - 20 g / m², preferably 7 - 14 g / m² of the second composition are applied.

4. Process according to one of the preceding claims, characterized in that the substrate is selected from paper, cardboard, plastic or a combination thereof, preferably selected from paper or cardboard made from tree-free cellulose.

5. Process according to one of the preceding claims, characterized in that the intermediate drying is carried out at a temperature of 20 - 70 °C, preferably 20 - 60 °C, and / or for 0.03 - 3.0 s, preferably 0.04 - 2.0 s.

6. Process according to one of the preceding claims, characterized in that the wax is a vegetable wax or a mixture of vegetable waxes.

7. Method according to one of the preceding claims, characterized in that the application of the first layer in step a) is carried out using a flexographic printing process with a roller. 8.Method according to claim 7, characterized in that the roller has a Shore hardness of 40 - 60 Shore A on the surface. 25 9. Method according to one of the preceding claims, characterized in that the aqueous polymer dispersion in step a) is an aqueous dispersion of a copolymer of (meth)acrylate and styrene and / or the aqueous polymer dispersion in step c) is an aqueous dispersion of a copolymer of (meth)acrylate and styrene. 30 10. Method according to one of the preceding claims, characterized in that the first composition has a solids content of 25 - 50. 45824 PT-EP CB / CN wt. %, based on the total weight of the first composition and / or the second composition has a solids content of 25 - 50 wt. %, based on the total weight of the second composition. 5 11. Process according to one of the preceding claims, characterized in that after drying according to step d), the layer thickness of the first layer is 3 - 6 µm and / or the layer thickness of the second layer is 3 - 6 µm. 10 12. Substrate with barrier coating, obtainable by the process according to one of claims 1 - 11.

13. Substrate with barrier coating, comprising 15 a substrate, a first layer applied directly to the surface of the substrate, comprising a polymer and less than 0.5 wt.-% wax, based on the total weight of the first layer, and a layer thickness of the first layer of 2 - 7 µm, and 20 a second layer applied directly to the first layer, comprising a polymer and 2 - 20 wt.% wax, based on the total weight of the second layer, and a layer thickness of the second layer of 2 - 7 µm. 25 14. Substrate with barrier coating according to claim 13, characterized in that the polymer is a (meth)acrylate-styrene copolymer.

15. Use of a substrate with barrier coating according to one of claims 12 - 14 as packaging material. 30.