Coated paper

Abstract

The invention relates to a coated paper comprising a base paper and at least one coating applied indirectly or directly to the base paper, the coating comprising at least one polymeric binder and at least one wax, characterized in that the polymeric binder has a polar proportion of the surface energy that is equal to or less than the polar proportion of the surface energy of the wax. The invention also relates to a method for producing a packaging material of this kind, and to the use of the packaging material as packaging or as a component of packagings.

Description

[0001] Coated paper

[0002] Description

[0003] The present invention relates to a coated paper, a process for producing such a coated paper, a coated paper obtainable by this process, the use of the coated paper as a packaging material and a packaging comprising the coated paper.

[0004] Packaging generally refers to the covering or (partial or complete) wrapping of an object, particularly for its protection or ease of handling. Consequently, packaging material includes the material that forms such a package.

[0005] Packaging materials can be based on paper, plastics, and / or metals, for example. The present invention relates to paper-based packaging materials.

[0006] The main requirements for packaging materials of any origin are to protect the packaged goods from external influences, to prevent leakage, and to function as an advertising and information medium. To achieve this, the packaging material must meet different criteria depending on the packaged goods and the packaging process. Suitable packaging materials should not only possess barrier properties against, for example, water, water vapor, grease, oxygen, or mineral oil, but also meet mechanical and process-specific requirements. Depending on the packaging system, a packaging material, especially a flexible packaging material, should possess sufficient tear resistance, an appropriate coefficient of friction, and flexibility. It should be heat-sealable and externally printable, and it should not lose its protective effect throughout the entire conversion and packaging process.

[0007] Common paper-based coated papers often contain compounds such as polyvinylidene chloride (containing halogens) or are composites of paper and metal or plastic foils, have a tear resistance that needs improvement, which can lead to running problems on packaging machines, and / or are often not recyclable due to an excessive coating content of adhesive components or the formation of so-called stickies via the paper fiber stream.

[0008] Polyvinyl alcohols, especially cross-linked polyvinyl alcohols, are widely known as linear, water-soluble, biodegradable barrier coatings, including for paper. Such coatings exhibit good barriers against oil, grease, oxygen, solvents, and other non-polar gases, liquids, or solids. However, due to their hydrophilicity, polyvinyl alcohols exhibit very high permeability to polar compounds, such as water. This can also influence the barrier effect against non-polar migrants, as polyvinyl alcohols absorb moisture very well, swell, and thus create pathways through the barrier coating at the molecular level.

[0009] To solve this problem, mixtures of polymer dispersions of all kinds and wax emulsions are offered. However, when testing papers produced in laboratory and pilot tests, it was observed that such known mixtures of polymer dispersions and wax emulsions have the disadvantage that the water vapor permeability is still too high for certain applications or that grease can penetrate the coating, which in turn leads to an increase in water vapor permeability. This creates the risk that the water vapor permeability may increase, particularly in direct contact with fatty foods. The object of the present invention is to eliminate the disadvantages of the known materials and to provide a material that is suitable as packaging material, in particular for moisture-sensitive foods, and that maintains its water vapor permeability at a low level even when in contact with grease.It should also be suitable for sealing applications, especially heat or ultrasonic sealing in conventional packaging systems.

[0010] In particular, it is an object of the invention to provide coated papers that meet at least one of the following five criteria:

[0011] 1. Water vapor barrier, in particular water vapor permeability of not more than 50 g / m 2 / d (38°C, 90% RH)

[0012] 2. Heat sealability of the coating

[0013] 3. Grease resistance of the coating

[0014] 4. Recyclable in the waste paper cycle

[0015] 5. Suitable for packaging food, especially for direct food contact

[0016] This object is achieved by a coated paper according to claim 1, ie by a coated paper comprising a base paper and at least one coating applied directly or indirectly to the base paper, wherein the coating comprises at least one polymeric binder and at least one wax, characterized in that the polymeric binder has a polar fraction of the surface energy which is equal to or less than the polar fraction of the surface energy of the wax.

[0017] The polar fraction of the surface energy of the polymer binder and the polar fraction of the surface energy of the wax are defined as the polar fraction of the surface energy in %. The polar fraction in % is calculated from the relationship: (Polar fraction of the surface energy in mN / m / Total surface energy in mN / m) x 100.

[0018] The polar fraction can be determined as follows: a) Determination of pure wax or of pure polymeric binder melted onto any smooth substrate b) Determination on a dried coating consisting of i.) wax dispersion or ii.) polymer dispersion or iii) mixture of polymer dispersion and wax dispersion 10 g / m each 2 O-dry application to exclude substrate influences (sufficiently thick layer) on pigment-coated base paper. The dispersions may contain additional components such as dispersing agents, stabilizers, or rheology modifiers. The polymer dispersions are dried for 3 minutes at 105°C to create a closed surface; the wax dispersions are dried for 3 minutes at 90°C to prevent excessive penetration of the wax melt into the base paper.

[0019] The determination according to b) was used in the examples and comparative examples because the respective polymeric binder or wax was only available in dispersion form. In this case, the polar fractions were assigned to the polymeric binder or wax to determine whether the polymeric binder had a polar fraction of the surface energy equal to or less than the polar fraction of the surface energy of the wax.

[0020] Preferred embodiments are defined in the dependent claims.

[0021] In the context of the present invention, it was found that the combination of a polymeric binder and a wax having the same or a higher polar fraction of the surface energy than the polymeric binder leads to a surprisingly good water vapor barrier of the coated paper, which, moreover, also has a surprisingly good grease resistance of the water vapor barrier.

[0022] Without being bound to this theory, these surprising results could be explained as follows:

[0023] Regarding the water vapor barrier:

[0024] 1. By adding wax, the water vapor barrier properties of a polymeric binder or coating layer can be improved, or conversely, the water vapor permeability can be reduced (water vapor permeability minimum depending on the mixing ratio of polymeric binder to wax).

[0025] 2. If the polar fraction of the surface energy of the polymeric binder is equal to or less than the polar fraction of the surface energy of the wax, the separation during drying of the coating (coating color layer) is sufficient for an improved water vapor barrier to form. The wax migrates to the coating layer interface during drying (temperature-time profile see, for example, DE 10 2022 122 470.8).

[0026] About the palm kernel fat test (PKFT) and migration test:

[0027] 1. As demonstrated in the present invention, demixing of wax and polymeric binder presumably occurs when the polar fraction of the binder is equal to or less than that of the wax. This causes the wax to migrate to the interface, which, on the one hand, leads to an improvement in the water vapor barrier properties and, on the other hand, may make it easier to dissolve the wax from the interface.

[0028] 2. After the wax has dissolved / migrated from the coating, the water vapor barrier properties deteriorate compared to a coating made of polymeric binders

[0029] 3. A migration test showed that polar wax can be better dissolved by a polar contact medium (e.g. modified polyphenylene oxides, available under the trade name Tenax).

[0030] To prevent wax from dissolving or migrating from the interface, the coating can be provided with an additional coating Bw.

[0031] Preferably, the further coating Bw comprises the same polymeric binder (for example, the same polyolefin copolymer in the coating and in the further coating Bw) or a different polymeric binder (for example, a polyolefin copolymer in the coating and a polyvinyl alcohol in the further coating Bw). Preferably, the further coating Bw has a lower basis weight than the coating, in particular a basis weight of > 1 g / m 2 and < 10 g / m 2 , preferably > 2 g / m 2 and < 9 g / m 2 . Preferably, the weight per unit area of ​​the further coating Bw is chosen to be as low as is practically possible in order to completely cover the coating, and in such a way that the dissolution of the wax from the interface by external influences can nevertheless be prevented or at least significantly reduced.

[0032] Such a coated paper is in particular heat-, cold- or ultrasonically sealable or knurlable (e.g. closure of a package comprising a coated paper according to the invention by means of knurling in a packaging machine) and ensures a sufficiently low water vapor permeability to be used, for example, as packaging for moisture-sensitive and fatty foods.

[0033] Finally, the coated paper according to the invention can be produced relatively easily using various processes and with low application weights.

[0034] Numerous specific details are also discussed below to provide a thorough understanding of the subject matter. However, it will be apparent to one skilled in the art that the subject matter can be practiced and recreated without these specific details.

[0035] All features of one embodiment may be combined with features of another embodiment if the features of the different embodiments are not incompatible.

[0036] The terminology used in the description of the present disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the subject matter. As used in this description and the claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly dictates otherwise. The reverse is also true, meaning that the plural forms also include the singular forms. It is also understood that the term "and / or," as used herein, refers to and includes all possible combinations of one or more of the related listed elements.It is further understood that the terms "includes," "including," "comprises," and / or "comprising," when used in the present description and claims, specify the presence of the stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0037] In the present description and claims, the terms "includes", "comprises" and / or "comprising" may also mean "consisting of", that is, the presence or addition of one or more other features, steps, operations, elements, components and / or groups is excluded.

[0038] In this description and the claims, the term "including" may therefore also mean "exclusively".

[0039] Unless otherwise stated, information in "%" in the context of formulations and / or compositions refers to "% by weight", in particular based on the respective total weight of the respective formulations and / or compositions.

[0040] As mentioned above, the coated paper according to the invention comprises a base paper and at least one coating applied directly or indirectly to the base paper, wherein the coating comprises at least one polymeric binder and at least one wax, characterized in that the polymeric binder has a polar fraction of the surface energy which is equal to or less than the polar fraction of the surface energy of the wax.

[0041] If the coating is applied directly to the base paper, this means that there are no other coatings or substances between the base paper and the coating. If the coating is applied indirectly to the base paper, this means that there are other coatings and / or substances between the base paper and the coating.

[0042] In one embodiment, the coated paper according to the invention is characterized in that it consists of a base paper and at least one coating applied directly to the base paper, wherein the coating comprises at least one polymeric binder and at least one wax, wherein the polymeric binder has a polar fraction of the surface energy which is equal to or less than the polar fraction of the surface energy of the wax.

[0043] According to this embodiment, no further coatings are present besides the applied coating as defined above.

[0044] Laboratory tests have shown that it is possible to apply the coating directly onto the base paper, especially when using calendered base paper with a surface thickness and a low Cobb value. For better hold-out of the coating and to minimize the required coating application, the prior application of a primer, such as a starch, polymer, or pigment primer, is preferred. Ultimately, economic and production-technical considerations also determine which approach is preferred in each individual case.

[0045] The surface tension (alternatively called surface energy) of the dry, solid layers plays an important role in the effectiveness of barrier layers and their adhesion to the substrate. It can be determined by contact angle measurements with at least two different liquids. Manufacturers of measuring instruments based on this principle, such as DataPhysics Instruments GmbH (D-70794 Filderstadt), describe the relationship on their website as follows:

[0046] "The cohesion of atoms and molecules, which determines the surface tension / surface energy of a substance, is due to different types of interactions. In particular, a distinction can be made between disperse and polar interactions. Interactions due to temporal fluctuations in the charge distribution of the atoms / molecules are called disperse interactions (van der Waals interactions). Polar interactions include Coulomb interactions between permanent dipoles or between permanent and induced dipoles (e.g., hydrogen bonds). Accordingly, the surface tension / surface energy is also composed additively of a disperse and a polar component.

[0047] If the ratio of dispersed to polar surface energies for two phases is compared, predictions about the adhesion of the two phases to each other can be derived. The more closely the dispersed and polar portions correspond, the more interaction possibilities there are between the phases and the stronger the adhesion can be expected.

[0048] The polar and disperse fractions of the surface energy of the wax and the polymeric binder are determined according to DIN EN ISO 19403-2 (2020-04):

[0049] Contact angle measuring device OCA 25 (DataPhysics) with dpiMAX software, measuring principle: OWRK method (Owens, Wendt, Rabel, Kaelble).

[0050] Measuring fluids used and origin of the entered material constants:

[0051] Water and diiodomethane (according to Buscher) and 1,5-pentanediol (according to Gebhardt).

[0052] In contrast to DIN EN ISO 19403-2 (2020-04), 1,5-pentanediol is used as the third measuring liquid because, unlike other non-polar measuring liquids, it still allows measurable contact angles on paper surfaces before the liquid is absorbed by the paper.

[0053] As determined in numerous laboratory tests with various dried films comprising the wax or polymeric binder used in the coating of the coated paper according to the invention, the surface energy of the dried coating containing the wax is preferably between 15 and 40 mN / m, in particular between 20 and 30 mN / m. The surface energy of a dried layer containing the polymeric binder is preferably between 15 and 45 mN / m, in particular between 20 and 35 mN / m.

[0054] However, it has been shown that it is not so much the ratio of the surface energies of the wax to the polymeric binder that is crucial, but rather that the polar part of the surface energy of the wax is greater than the polar part of the surface energy of the polymeric binder.

[0055] Therefore, in one embodiment, the coated paper according to the invention is characterized in that the wax has a polar fraction of the surface energy of 3% to 30%, in particular 8% to 26%, preferably 11% to 23% and particularly preferably 14% to 20%.

[0056] The disperse fraction of the surface energy of the wax is preferably 70 to 97%, in particular 74 to 92%, preferably 77 to 89% and particularly preferably 80% to 86%.

[0057] The polar fraction of the surface energy of the polymeric binder is preferably 0 to 9%, in particular 0 to 5%, preferably 0 to 3% and particularly preferably 0 to 2%, wherein in a preferred embodiment the values ​​0% are just excluded as a lower limit.

[0058] The disperse portion of the surface energy of the polymeric binder is preferably 91 to 100%, in particular 95 to 100%, preferably 97 to 100% and particularly preferably 98 to 100%.

[0059] In one embodiment, the coated paper according to the invention is preferably characterized in that the coating is coated or printed, in particular the coating is a water-based coating or printing ink layer.

[0060] In one embodiment, the coated paper according to the invention is characterized in that the coated paper has a water vapor transmission rate (WVTR) of not more than 50 g / m 2 / d, measured at a temperature of 38 °C and a humidity of 90% RH, or not more than 17 g / m 2 / d, measured at a temperature of 23 °C and a humidity of 85% RH.

[0061] The water vapor transmission rate was determined according to ISO / FDIS 2528:2017(E): It should be noted that the coated side of the coated paper faces the desiccant.

[0062] In one embodiment, the coated paper according to the invention is characterized in that the coated paper comprises at least one further coating.

[0063] In a preferred embodiment, a layer comprising starch (starch layer) and / or modifications thereof (modified starches) may be present directly on at least one side of the base paper, preferably directly on both sides of the base paper of the coated paper according to the invention.

[0064] The starch coating is preferably used in an amount of 0.1 to 3, particularly preferably 0.2 to 1.5 g / m 2 , applied.

[0065] A starch coating on the side of the base paper where the coating is present has the advantage of sealing the surface of the base paper, thus improving the adhesion of the coating and reducing or preventing penetration of the coating into the base paper.

[0066] The starch coating preferably has a Bekk smoothness of greater than 20 s, more preferably greater than 50 s and most preferably from 50 to 200 s.

[0067] Furthermore, for example, the uncoated side of the base paper can be provided with one or more other coatings that are more printable than the surface of the base paper that is only coated with a starch coating. In one embodiment, a primer is applied to at least one side of the base paper, preferably directly to both sides of the base paper.

[0068] Preferably, a starch coat, as defined above, and a precoat, in particular as defined below, are present in this order between the base paper and the coating.

[0069] In one embodiment, the coated paper according to the invention is characterized in that it consists of a base paper, a one- or two-side coated precoat as defined above and below, and at least one coating applied directly to the base paper, wherein the coating comprises at least one polymeric binder and at least one wax, wherein the polymeric binder has a polar fraction of the surface energy which is equal to or less than the polar fraction of the surface energy of the wax.

[0070] According to this embodiment, no further coatings are present besides the one- or two-sided primer and the applied coating as defined above and below.

[0071] Preferably, such a pre-coat, also referred to as a primer, comprises or consists of at least one inorganic pigment and a polymeric binder, wherein the polymeric binder of the pre-coat is not the same as the polymeric binder of the coating.

[0072] The inorganic pigment is preferably platelet-shaped and comprises in particular a talc, precipitated calcium carbonate or silicate, preferably a layered silicate and most preferably a kaolin.

[0073] The aspect ratio of the platelet-shaped pigment (ratio of average diameter to thickness, also called form factor) should be about 7 to 40 to 1, preferably about 15 to 30 to 1.

[0074] The particle size of the platelet-shaped pigment is preferably adjusted so that at least about 70%, preferably at least about 85%, of the particles have a particle size of about <2 pm (Sedigraph). The pH of the platelet-shaped pigment in aqueous solution is preferably 6 to 8.

[0075] Suitable polymeric binders include, in particular, acrylate-based or styrene / butadiene-based binders. In principle, all polymers that can be used as binders for pigment coatings in the paper industry are suitable. The use of starch-based binders (solutions of modified starches, dispersions of cross-linked starches, so-called biolatices) and polymer-starch hybrid latices is also possible.

[0076] The polymeric binder preferably comprises a polymeric binder based on a polyacrylate.

[0077] The polymeric binder preferably comprises a styrene-acrylate copolymer, preferably a styrene-butyl acrylate copolymer, in particular a styrene-n-butyl acrylate copolymer.

[0078] A suitable styrene-n-butyl acrylate copolymer is known, for example, under the trade name Acronal S 305 FD.

[0079] The primer can be hydrophobic overall.

[0080] In another embodiment, the primer is entirely hydrophilic.

[0081] The primer preferably contains 5 to 50 wt.%, more preferably 10 to 30 wt.%, of polymeric binder. This amount refers to the dried primer in the final product.

[0082] The primer preferably further contains 50 to 95% by weight, more preferably 65 to 85% by weight, of inorganic pigment. This amount refers to the dried primer in the final product.

[0083] The primer can also contain additives such as thickeners, e.g., acrylate-based thickeners, surfactants, and / or rheology modifiers. The use of crosslinking agents is also conceivable. The primer preferably contains an ammonium zirconium carbonate crosslinking agent and is itself crosslinked with formaldehyde.

[0084] These additives are preferably present in an amount of 0 to 2 wt.%, preferably greater than 0 to 2 wt.%, with the value 0 wt.% preferably being excluded. This amount refers to the dried primer in the final product.

[0085] The application quantity (ISO 436, 2020-05) of the primer is preferably 1 to 20 g / m 2 and particularly preferably 3 to 10 g / m 2 . The quantity refers to the dried primer in the final product.

[0086] Applying such a primer has the advantage that the base paper surface is sealed and any subsequent coating applied thereon only migrates slightly into the paper. Furthermore, the primer reduces the average roughness of the base paper and offers a favorable coating holdout, characterized by a comprehensive application and a defined surface energy. This means that the coated polymer binder and wax can be optimally applied as a coating and an optimal barrier can be formed with the least possible application, which has a beneficial effect on the cost structure. In addition, the primer is designed in such a way that the layer adhesion between the base paper and the coating is not significantly reduced, which can be important for subsequent sealing applications. This also applies if there is a layer of starch between the primer and the base paper.

[0087] The primer can also be applied in the form of two or more separate coats of the same or different formulation.

[0088] The surface energy of the primer is preferably 15 to 40 mN / m, in particular 22 to 30 mN / m.

[0089] The surface energy is determined as defined above.

[0090] For good wetting and interlayer adhesion, the surface tension of the primer should be higher or at least more polar than that of the layer above it. If necessary, care should be taken to ensure that the surface energy of the coating and the primer are matched. A highly polar primer would swell excessively when coated with an aqueous coating formulation, which could lead to cracking after drying. Therefore, the specified data on the surface energy of the primer have proven particularly useful.

[0091] The smoothness of the primer (according to Bekk (ISO 5627, 1995-03)) is preferably 80 to 200 s, preferably 90 to 120 s.

[0092] The roughness of the precoat (according to Parker-Print-Surf (PPS) DIN ISO 8791-4, 2008-05) is preferably 2.8 to 4.0 pm, preferably 3.2 to 3.6 pm.

[0093] In one embodiment, the packaging material according to the invention can comprise, in addition to the above-described primer and coating, further layers, such as sealing coatings such as cold-seal adhesives or additional hot-seal adhesives, metallizations, and / or additional barrier layers (oxygen barriers, mineral oil barriers, oil and grease barriers, aroma barriers, additional wax-free water vapor barriers, etc.). These layers can be applied directly or indirectly to at least one of the two sides of the coated paper, but also between the individual layers of the coated paper.

[0094] The coated paper according to the invention can preferably comprise at least one further layer consisting of or comprising metals, in particular aluminum. This allows the barrier effect to be further improved. This further layer can be formed as an intermediate layer or as a cover layer. Formed as an intermediate layer, this layer is preferably located directly below or above a heat-sealable layer, for example, the coating.

[0095] Alternatively, to improve the overall barrier properties of a coated paper, smooth surfaces can be vapor-deposited with metals or metal oxides (e.g., via vacuum vapor deposition). This requires, preferably, smooth surfaces or a smooth printing line on the uncoated side of the base paper.

[0096] Barrier coatings are also known, which a processor can apply over the entire surface or only to specific areas.

[0097] One example would be the HYDRO-LAC GA oxygen barrier varnish from Hubergroup Print Solutions. This varnish can be applied to the coating or to the uncoated side of the base paper, or even better, to a smooth printing coat.

[0098] In a preferred embodiment, at least one further coating may comprise polysaccharides, in particular modified polysaccharides such as fatty acid derivatives of polysaccharides and particularly preferably polysaccharides or modified polysaccharides obtained from seaweed or algae or contained in seaweed or algae.

[0099] The coated paper can be heat or ultrasonically sealed, but it is also possible to apply cold seal adhesive to one of the two sides of the coated paper, especially if the coated paper is to be used on a packaging line designed for cold seal gluing.

[0100] Preferably, one of the two sides, preferably the print side, can be provided with an additional heat-sealing adhesive with the aim of sealing between the front and back (A / B sealing).

[0101] In one embodiment, the coated paper comprises a precoat and a coating as defined above.

[0102] In one embodiment, the coated paper comprises a starch coat, a precoat and a coating as defined above.

[0103] Here, too, the primer can be applied in two or more layers, as described above. In a preferred embodiment, the coated paper comprises a starch-coated base paper, a primer, and a coating as defined above.

[0104] In a further preferred embodiment, the coated paper according to the invention comprises or has at least the following structure: a) Between base paper and coating, in particular a precoat and optionally a further barrier coat (e.g. mineral oil or oxygen barrier) b) Directly or indirectly on coating, in particular a protective layer (for example comprising the polymeric binder or another polymeric binder) or a barrier layer (for example grease, water vapor, oxygen barrier) c) Directly or indirectly on base paper opposite the coating, in particular a printable layer (for example a layer comprising starch, starch coat), a protective layer (for example comprising the polymeric binder or another polymeric binder) or a barrier layer (for example grease, water vapor, oxygen barrier) d) A metal layer, preferably comprising aluminum

[0105] The polymeric binder in the coating is not limited in principle, but includes all polymeric binders known to the person skilled in the art for binding waxes in paper coatings and which have a lower polar fraction of the surface energy than the wax contained in the coating.

[0106] In principle, hydrophobic polymers can be used. However, polar, water-soluble binders of synthetic or natural origin, or derivatives thereof, may also be suitable, provided the hydrophilic functional groups are shielded by the waxes also present in the coating and the water vapor barrier does not impair the coating.

[0107] In one embodiment, the coated paper according to the invention is preferably characterized in that the polymeric binder is selected from the group of polyolefins, polyolefin copolymers, ethylene-acrylic acids, ethylene-acrylic acid copolymers, or combinations thereof, wherein these polymers or copolymers may be modified or unmodified, and wherein the polymeric binder preferably comprises acid-modified polyolefin copolymer, in particular carboxylic acid- or sulfonic acid-modified polyolefin copolymer. Preferred water-based polyolefin dispersions / polyolefin copolymer dispersions are available, for example, under the trade names Dow Rhobarr 320, Dow Rhobarr 620, and Dow Hypod 2000 or are described in WO 2021 / 225764 A1. As our own laboratory studies have shown, the chemical composition of the waxes used does not play a decisive role.They should simply be selected so that they melt under the technically feasible drying conditions in the coating system and have a higher polar surface energy than the polymeric binder in the coating. It has been shown that it is advantageous for the development of water vapor barrier properties if the melting point is below the boiling point of water (100°C), or even better, below 90°C.

[0108] The wax in the coating is preferably a wax according to the following definition of the German Society for Fat Research (DGF).

[0109] "Waxes are substances defined today by their mechanical and physical properties. Their chemical composition and origin, however, vary greatly. A substance is referred to as a wax if it is malleable at 20 °C, solid to brittle, has a coarse to finely crystalline structure, is translucent to opaque in color but not glassy, ​​melts above 40 °C without decomposition, is slightly liquid (slightly viscous) slightly above the melting point, has a strongly temperature-dependent consistency and solubility, and is polishable under light pressure." If more than one of the properties listed above is not met, the substance is not a wax according to the DGF (DGF Standard Method MI 1 (75)).

[0110] In one embodiment, the coated paper according to the invention is preferably characterized in that the wax is selected from: a) natural, animal, vegetable, mineral, semi-synthetic, synthetic waxes, b) microwaxes c) waxes based on mixtures or pure substances of fossil, animal or vegetable short to medium-chain hydrocarbons, their acids, esters, amides and / or diamides, d) hydrogenated or partially hydrogenated vegetable oils, vegetable fats or waxes produced from animal oils and / or animal fats, e) metal soaps, preferably based on heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, triacontane, hentriacontane, dotriacontane, tritriacontane, tetratriacontane, pentatriacontane, hexatriacontane, heptatriaontane, octatriacontane, Nonatriacontane, montan wax, f) carnauba wax, beeswax, candelilla wax, rice bran wax, sugar cane wax or paraffin wax,in particular with an average molecular weight of at least 500 Daltons and a viscosity of at least 11 cSt at 100°C, wax obtained from sunflower seed presscake, g) waxes comprising esters with a C15-C17-C(O)-O-C16-C18 structural unit (structural unit I), h) waxes with a structural unit II, i) waxes obtained by partial hydrogenation of vegetable oils, in particular soybean oil, j) combinations of these groups.

[0111] In a preferred embodiment, the wax of the coating comprises wax comprising esters having a Ci5-Ci7-C(O)-O-Ci6-Ci8 structural unit (structural unit I), wax having a structural unit II, wax obtained by at least partial hydrogenation of soybean oil, and / or paraffin wax.

[0112] In a further preferred embodiment, the wax of the coating consists of or comprises wax according to WO2024 / 121241 A1, in particular wax consisting of or comprising one or more esters, in particular selected from the list of linear monoesters of the following formula (1), linear diesters of the following formula (2), or linear diesters of the following formula (3), or mixtures thereof. In the description, such a wax is also referred to as wax with a structural unit II.

[0113] Formula (1): RI-C(O)-O-R2, where Ri is a linear Cs-Czs-alkyl radical, preferably a linear Cn-Ci7-alkyl radical, and R2 is a linear C4-C24-alkyl radical, preferably a linear Ci2-Cis-alkyl radical.

[0114] Formula (2): R3-C(O)-O-R4-OC(O)-R5, where R3 and R5 are independently a linear C3-C23 alkyl radical, preferably a linear Cn-Ci7 alkyl radical, R4 is a linear C4-C24 alkanediyl radical, preferably a linear Ci2-Ci8 alkanediyl radical.

[0115] Formula (3): R6-OC(O)-R7-C(O)-O-R8, where R5 and Rs are independently a linear C4-C24 alkyl radical, preferably a linear C12-C18 alkyl radical, and R7 is a linear C2-C22 alkanediyl radical, preferably a linear C10-C16 alkanediyl radical.

[0116] Particularly preferred are waxes that are approved for direct food contact according to BfR XXVI of 1 April 2021, Chapter C, Section IV, Point 2 with reference to BfR XXV of 1 June 2019, Federal Institute for Risk Assessment of the Federal Ministry of Food and Agriculture, Germany.

[0117] Beeswax and / or paraffin wax are particularly preferred, as they are approved for direct food contact according to BfR XXVI of April 1, 2021, Chapter C, Section IV, Item 2, with reference to BfR XXV of June 1, 2019, Federal Institute for Risk Assessment of the Federal Ministry of Food and Agriculture, Germany. The waxes described in the previous section are also approved for direct food contact, but they are not specifically listed in BfR XXVI.

[0118] When using paraffin waxes, those listed in FCM substance No. 94 of the EU Commission Regulation No. 10 / 2100 of 14 January 2011 "on plastic materials and articles intended to come into contact with food" are particularly preferred.

[0119] Further preferred is the use of an aqueous wax dispersion obtained by dispersing (A) a nonionic surfactant, (B) an anionic surfactant and (C) a wax in water and characterized in that the wax (C) contains an ester compound having a structural unit derived from a fatty acid and a structural unit derived from an aliphatic alcohol, wherein the content of the nonionic surfactant (A) is 40 to 99 parts by mass based on a total of 100 parts by mass of the nonionic surfactant (A), the anionic surfactant (B) and the wax (C), while it is 5 to 50 parts by mass based on a total of 100 parts by mass of the nonionic surfactant (A), the anionic surfactant (B), the wax (C) and water.

[0120] In one embodiment, the coated paper according to the invention is preferably characterized in that the coating has a wax-enriched interface on the side of the coating facing the base paper.

[0121] In a further embodiment, the coated paper according to the invention is preferably characterized in that the coating has a wax-enriched interface on the side of the coating facing away from the base paper.

[0122] In a further embodiment, the coated paper according to the invention is preferably characterized in that the coating has a wax-enriched interface on the side of the coating facing the base paper.

[0123] This can be achieved by coating the base paper with the coating comprising the at least one polymeric binder and the at least one wax. The drying of the coating, unlike the usual drying process, occurs in such a way that the coating faces downward during drying. The wax can thus accumulate at the interface on the side facing the base paper (separates upwards). This has the advantage that the wax at the now inner interface is better protected from external influences, such as contact with packaged goods, especially moist and / or greasy packaged goods.

[0124] Enriched here means in particular that the local

[0125] Concentration of wax in the coating at one surface / interface of the coating is higher than the average wax concentration in the entire coating, or the concentration of wax in the coating at one surface / interface of the coating is higher than at the other surface / interface of the coating.

[0126] For example, "enriched" can be understood here to mean that the local concentration of wax in the coating on the side or surface / interface facing away from the base paper is greater than the local concentration of wax in the coating on the side or surface / interface facing the base paper (or vice versa), which is indirectly demonstrated by the fact that the polar component of the surface energy does not decrease significantly further during subsequent drying.

[0127] Further detection of wax enrichment can be carried out using electron spectroscopy (ESCA, also abbreviated XPS).

[0128] Without being bound by this theory, it is assumed that under the drying conditions described in this context, the wax migrates to the surface of the coating due to its lower density and accumulates there. If the coated paper is dried with the base paper at the bottom, an accumulation of wax is observed on the side facing away from the base paper. If the coated paper is dried with the base paper at the top, an accumulation of wax is observed on the side facing the base paper.

[0129] In one embodiment, the coating comprises only the polymeric binder and the wax, wherein certain weight ratios of the polymeric binder to the wax are advantageous.

[0130] In a preferred embodiment, the coating comprises a polymeric binder and wax, comprising esters with a C15-C17-C(O)-O-C16-C18 structural unit (structural unit I), wax with a structural unit II, wax obtained by at least partial hydrogenation of soybean oil, and / or paraffin wax. The following relationships were determined in laboratory tests: The lower the wax content, the better the heat sealability, especially the hot tack. However, a lower wax content results in higher water vapor permeability and a comparatively high sensitivity of the water vapor barrier to grease contact. If little wax is to be used, the aqueous coating should be dried in such a way that wax migrates to the surface in order to obtain a good water vapor barrier that is not very sensitive to grease.

[0131] In one embodiment, the coated paper according to the invention is characterized in that the at least one polymeric binder and the at least one wax are present in the coating in a weight ratio of 70:30 to 99:1, preferably of 80:20 to 95:5, particularly preferably of 85:15 to 95:5, in particular 90:10.

[0132] In one embodiment, the coated paper according to the invention is characterized in that the at least one polymeric binder is present in the coating in an amount of 70 to 98 wt.%, preferably 80 to 95 wt.%.

[0133] In one embodiment, the coated paper according to the invention is characterized in that the at least one wax is present in the coating in an amount of 2 to 30 wt.%, preferably 5 to 20 wt.%.

[0134] The coating is preferably obtained by applying a dispersion comprising the at least one polymeric binder and at least one wax directly or indirectly to the base paper and forming a film by heat application. Although this dispersion is not limited with regard to the solvent or other additives used, some dispersions have proven particularly effective.

[0135] Therefore, it is preferred if the dispersion containing the at least one wax and the at least one polymeric binder is a water-based dispersion. Even more preferred is the aqueous dispersion containing an anionic polymeric binder, particularly preferably an acid-modified anionic polymeric binder. In another embodiment, the dispersion comprising the at least one polymeric binder and the at least one wax comprises further constituents or additives.

[0136] In one embodiment, the coated paper according to the invention is preferably characterized in that the coating comprises further coating components and auxiliaries, in particular for adjusting the rheology of the coating. Carboxymethylcelluloses (CMC) are particularly suitable as rheology auxiliaries for adjusting the extensibility (important in the curtain coating process) and viscosity of the coating dispersion (coating color). Optionally, the coating dispersion can contain pigments, particularly preferably inorganic pigments, phyllosilicates, talc, kaolins, mica, bentonites, or platelet-shaped precipitated calcium carbonate.

[0137] Such pigments are preferably present in an amount of 0 to 70 wt.%, based on the total weight of the coating. To avoid excessively impairing the heat-sealability of the coating, amounts of 0 to 50 wt.%, better 0 to 30 wt.%, and most preferably 0 to 10 wt.%, should be selected. Preferably, the value of 0 wt.% is excluded as a lower limit.

[0138] The coating preferably comprises a polymeric binder based on a polyolefin and talc as a pigment, with the proportion of talc relative to the total weight of the dried coating preferably being in the range of >0 to 50 wt.%, preferably 15 to 40 wt.%. The polyolefin is particularly preferably a polyethylene-based polyolefin (PE-based).

[0139] Platelet-shaped pigments are preferred, as they can contribute to improving the barrier when aligned laminarly parallel to the coating. The particle size should preferably be selected so that the particles are completely enclosed in the layer when aligned laminarly. The aspect ratio (ratio of average diameter to thickness, also called the form factor) should be greater than 10, preferably greater than 100, and particularly preferably greater than 1000. Other possible additives include, for example, thickeners, surfactants, crosslinkers, and / or rheology modifiers.

[0140] These additives are preferably present in an amount of 0 to 2 wt.%, preferably 0 to 1 wt.%, based on the total weight of the coating. Preferably, the value of 0 wt.% is excluded as a lower limit.

[0141] The roughness of the coating (according to Parker-Print-Surf (PPS) DIN ISO 8791-4, 2008-05) is preferably from 0.8 to 2.0 pm, preferably from 1.0 to 1.8 pm.

[0142] The application quantity (ISO 536, 2020-05) of the coating, comprising the at least one polymeric binder and at least one wax, is preferably 4 to 20 g / m 2 , preferably 6 to 15 g / m 2 and particularly preferably 8 to 12 g / m 2 . The amount refers to the dried coating comprising the at least one polymeric binder and at least one wax in the final product.

[0143] The base paper used in the coated paper according to the invention is not limited in principle.

[0144] In one embodiment, the coated paper according to the invention is preferably characterized in that the base paper has a basis weight of 20 to 120 g / m 2 , preferably from 30 to 100 g / m 2, has.

[0145] Furthermore, it is preferred that the base paper comprises long and short fibers, wherein a long fiber is a fiber with a fiber length of 2.6 to 4.4 mm and a short fiber is a fiber with a fiber length of 0.7 to 2.2 mm, and the long fiber content is preferably from 10 to 80 wt.%, preferably from 20 to 60 wt.%, and the short fiber content is preferably from 20 to 90 wt.%, preferably from 50 to 70 wt.%.

[0146] The long-fiber content, in particular, ensures the strength of the comparatively thin base paper, while the short-fiber content makes the base paper denser and more cohesive, giving it a uniform appearance. A further increase in the long-fiber content would make the base paper too stiff. The lower price of short-fiber pulp compared to long-fiber pulp also plays a role.

[0147] In addition, 0 wt% to 20 wt%, preferably 0 wt% to 5 wt%, of fillers, preferably excluding 0 wt%, such as GCC (ground calcium carbonate), known for example under the trade name Hydrocarb 60 or Hydroplex 60, PCC (precipitated calcium carbonate), known for example under the trade name Precarb 105, natural kaolin and / or talc may be contained in the base paper.

[0148] Furthermore, common auxiliary substances such as retention agents and / or sizing agents may be contained in the base paper.

[0149] Particularly for food contact, the base paper comprises at least 60 wt.%, preferably at least 75 wt.% fiber, at most 25 wt.%, preferably at most 10 wt.% fillers, and at most 15 wt.% additives. In addition, unavoidable or necessary traces of processing aids (e.g., reagents, dispersants, anti-mold agents, etc.) may be present in the base paper.

[0150] The advantage of such a base paper is, on the one hand, its high flexibility and, on the other hand, its good processability on existing packaging lines for flexible materials such as plastic films, maintaining high machine availability and achieving the necessary puncture resistance.

[0151] The coated paper according to the invention can be used as a heat-sealable packaging material, but it is also possible to apply cold seal adhesive to one of the two sides over the entire surface or partially to the intended sealing seam areas, in particular if the base paper is to be used on a packaging system designed for cold seal bonding.

[0152] Preferably, one of the two sides of the base paper, preferably the print side, can also be provided with another heat-sealing adhesive over the entire surface or partially in the intended sealing seam areas, with the aim of sealing between the front and back sides (A / B sealing).

[0153] In one embodiment, the coated paper according to the invention is characterized in that the coated paper, consisting of the uncoated base paper or the one- or two-side starch-coated base paper, the precoat and the coating, has a water vapor transmission rate (WVTR) of not more than 50 g / m 2 / d, preferably not more than 40 g / m 2 / d, particularly preferably not more than 30 g / m 2 / d, measured at a temperature of 38 °C and a humidity of 90% RH, or not more than 17 g / m 2 / d, preferably not more than 13 g / m 2 / d, particularly preferably not more than 10 g / m 2 / d measured at a temperature of 23 °C and a humidity of 85% RH.

[0154] In one embodiment, the coated paper according to the invention is characterized in that the coating comprises a polymeric binder and wax comprising esters having a Ci5-Ci7-C(O)-O-Ci6-Ci8 structural unit, wax obtained by at least partial hydrogenation of soybean oil, and / or paraffin wax, and in that the at least one polymeric binder and the at least one wax are present in the coating in a weight ratio of 70:30 to 99:1, preferably of 80:20 to 95:5, particularly preferably of 85:15 to 95:5, in particular 90:10.

[0155] In one embodiment, the coated paper according to the invention is characterized in that the coating comprises a polymeric binder and wax, comprising esters having a C 15 -C 17 -C(O)-O-C 16 -C 18 structural unit, wax obtained by at least partial hydrogenation of soybean oil, and / or paraffin wax, that the at least one polymeric binder and the at least one wax are present in the coating in a weight ratio of 70:30 to 99:1, preferably of 80:20 to 95:5, particularly preferably of 85:15 to 95:5, in particular 90:10, and that the coating has a wax-enriched interface on the side facing away from the base paper or on the side of the coating facing away from the base paper.In one embodiment, the coated paper according to the invention is characterized in that the coating comprises a polymeric binder and wax comprising esters having a Ci5-Ci7-C(O)-O-Ci6-Ci8 structural unit, wax obtained by at least partial hydrogenation of soybean oil, and / or paraffin wax, that the at least one polymeric binder comprises a polyolefin copolymer, and that the at least one polymeric binder and the at least one wax are present in the coating in a weight ratio of 70:30 to 99:1, preferably of 80:20 to 95:5, particularly preferably of 85:15 to 95:5, in particular 90:10.

[0156] In one embodiment, the coated paper according to the invention is characterized in that the coating comprises a polymeric binder and wax, comprising esters having a C 15 -C 17 -C(O)-O-C 16 -C 18 structural unit, wax obtained by at least partial hydrogenation of soybean oil, and / or paraffin wax, that the at least one polymeric binder comprises a polyolefin copolymer, and that the at least one polymeric binder and the at least one wax are present in the coating in a weight ratio of 70:30 to 99:1, preferably of 80:20 to 95:5, particularly preferably of 85:15 to 95:5, in particular 90:10, and that the coating has a wax-enriched interface on the side facing away from the base paper or on the side of the coating facing away from the base paper.

[0157] The coated paper according to the invention can be obtained economically using all known papermaking and coating processes (film press with or without pre-dosing, roller application, doctor blade, blade, curtain coater, spray coater).

[0158] In one embodiment, the process according to the invention for producing a coated paper, in particular for producing the coated paper according to the invention, comprising a base paper, is characterized in that a coating or printing ink comprising at least one dispersion comprising at least one polymeric binder and at least one wax is applied and dried directly or indirectly on at least one side of the base paper, wherein the polar portion of the surface energy of the polymeric binder is equal to or less than the polar portion of the surface energy of the wax.

[0159] In a preferred embodiment of the process according to the invention, the coating or printing ink is applied directly or indirectly to at least one side of the base paper, wherein the coating or printing ink has a solids content of 20 to 60 wt.%, preferably of 30 to 50 wt.%, and is applied by a curtain coating process at an operating speed of the coating system of at least 300 m / min and is then filmed by heat input in order to contain a filmed coating, wherein the filming is preferably carried out by means of IR drying and / or hot air drying.

[0160] If the solids content falls below approximately 20 wt.%, the cost-effectiveness deteriorates, as a large amount of water must be removed quickly through gentle drying, which adversely affects the coating speed. On the other hand, if the value exceeds 60 wt.%, this simply leads to increased technical effort to ensure the stability of the application suspension curtain during the coating process and the drying of the applied coating, as the machine must again run at very high speeds.

[0161] In a further embodiment of the process according to the invention, the coating or printing ink is dried and filmed at a surface temperature of 75 to 100 °C, preferably for a period of 1 to 20 seconds, preferably 2 to 10 seconds.

[0162] The surface temperature is the temperature that the coated paper reaches during film formation and can be adjusted depending on the web temperature and the duration of the heat application.

[0163] Contactless processes such as IR drying and / or hot air drying, whose heat input can be individually adjusted, have proven effective for drying the coating suspension. This process is particularly advantageous from an economic perspective and due to the uniform application over the base paper, preferably the paper web.

[0164] In the curtain coating process, a freely falling curtain of a coating suspension is formed. The coating suspension, in the form of a thin film (curtain), is "poured" onto the base paper by free fall to apply the coating suspension to the base paper. DE 10 196 052 TI discloses the use of the curtain coating process in the production of information recording materials, whereby multilayer recording layers are realized by applying the curtain consisting of several coating dispersion films to base papers.

[0165] In a preferred embodiment of the process according to the invention, the aqueous deaerated application suspension has a viscosity of approximately 100 to approximately 400 mPas (Brookfield, 100 rpm, 20 °C). If the value falls below approximately 80 mPas or exceeds approximately 500 mPas, this leads to poor runnability of the coating slip on the coating unit. Particularly preferably, the viscosity of the aqueous deaerated application suspension is approximately 150 to approximately 300 mPas. Suitable substances for adjusting the viscosity and the required elasticity of the coating slip include, for example, acrylate thickeners, carboxymethylcellulose, especially products with a high molecular weight, polyvinyl alcohols, and / or polyacrylamides.

[0166] In a preferred embodiment, in order to optimize the process, the dynamic surface energy of the aqueous dispersion comprising the at least one polymeric binder and the at least one wax can be adjusted to about 35 to about 55 mN / m, preferably to about 38 to about 52 mN / m (measured 50 ms after bubble formation) in accordance with the standard for bubble pressure tensiometry (ASTM D 3825-90), as described below. Better control over the coating process is obtained if the dynamic surface energy of the dispersion comprising the at least one polymeric binder and the at least one wax is determined and specifically adjusted by selecting the appropriate surfactant and by determining the required amount of surfactant. Sodium docusates are preferably used as surfactants.

[0167] When drying the coated paper web in the paper machine or paper coating machine (preferably equipped with infrared dryers and hot air drying units), care must be taken to prevent premature overheating and the associated blistering, and to ensure that a temperature of 80-90°C is reached in the further course of the drying process so that the polymers form a film and the now liquid wax content can accumulate evenly on the surface of the coating without causing the wax to bloom.

[0168] For development purposes and to produce prototypes, the coated paper can also be produced on a laboratory scale using a hand doctor blade or automated doctor blade device at room temperature, followed by drying in a drying cabinet. Drying can be carried out, for example, analogously to the previously described temperature treatment for 3 minutes at 90°C in a drying cabinet. Since the risk of bubble formation is lower during this slow drying process than in a coating system, a temperature of greater than 100°C, preferably 105°C, can also be set.

[0169] In further embodiments, the dispersion comprising the at least one polymeric binder and the at least one wax can also be applied to the base paper by the following methods:

[0170] The dispersion comprising the at least one polymeric binder and the at least one wax can be applied to the base paper by means of printing processes (e.g. flexographic printing and gravure printing).

[0171] The present invention further relates to a coated paper which is obtainable by the processes described above and is recyclable as paper according to "CEPI Recyclability Test Method 2 (October 2022)".

[0172] Finally, the present invention also relates to the use of a coated paper as described above as packaging material or as a component of packaging material, in particular heat-, cold- or ultrasonically sealable packaging, preferably for foodstuffs, cosmetics, hygiene articles, tobacco, in particular for packaging moisture-sensitive and / or fatty foods and for protecting them from air humidity or fats from the environment. The coated paper according to the invention can be used on all common packaging systems. Examples include vertical and horizontal tubular bag machines (form-fill-seal) for producing, among other things, stand-up pouches, flow packs or pillow packs, air cushion bags or pillows as a replacement for plastic air cushion bags or pillows, machines that bring two webs of the same or different materials together and join them by heat sealing, e.g.also tray sealers, chamber belt machines (also with vacuum), bag filling and closing machines, thermoforming packaging machines, linear filling machines that attach lids by heat sealing for closing, wrapping machines with a final heat sealing step, blister packaging machines and X-fold packaging machines.

[0173] The invention is explained in detail below using non-limiting examples.

[0174] Examples

[0175] For Examples 1 to 8 and Comparative Examples 1 to 4, paper from a production line was used as base paper.

[0176] The pure base paper was produced on the associated paper machine (40 wt.% long fiber, 60 wt.% short fiber), smoothed by means of a calender and cationically modified potato starch (approx. 1 g / m 2 ) was applied. The basis weight of the base paper was 60 g / m2 according to ISO 536 (2020).

[0177] The paper machine is equipped with a Yankee cylinder and is therefore able to produce paper that is smooth on one side.

[0178] The base paper was then coated on a coating machine with a precoat (22.8 wt.% styrene-n-butyl acylate (binder), 75.8 wt.% kaolin (inorganic pigment), and small amounts of ammonium zirconium carbonate (crosslinker). The basis weight of the coated paper was 68 g / m 2 according to ISO 536 (2020).

[0179] In the second step, the respective application quantity of a dispersion comprising the at least one polymeric binder and the at least one wax was applied to the individual papers using a laboratory doctor blade. The respective compositions are shown in Table 1, with the weight ratio of dried polymer to dried wax dispersion being 90:10 for all examples and comparative examples (except for Example 2: 95:5), and the coating application being 10 g / m 2 (dry) were chosen.

[0180] The drying of the coating (coating paint) applied at room temperature (approx. 23°C) at 105°C for 3 min (except for Example 4: 120°C for 3 min) is preferably carried out in a hot-air oven, whereby care must be taken that the paper is actually exposed to 105°C (120°C, Example 4) for a period of 3 min. For this purpose, the oven must be preheated and have a sufficient internal volume (> 100 dm 3(e.g. width x height x depth 60 cm x 48 cm x 37 cm) so that when the front door is opened briefly (2-3 s) to insert the paper, there is no significant drop in temperature. The paper is placed on a metal grid located in the middle of the oven, preferably with a cardboard base. The metal grid and cardboard must already have reached the oven temperature and have been placed in the oven, which has already been preheated to 105°C (120°C, example 4), for at least 15 minutes before the start of the temperature treatment.

[0181] The composition of the respective coating and the individual components of the dispersion, comprising the at least one polymeric binder and the at least one wax, the drying parameters, and the determined properties of the coated papers are summarized in the following Table 1. Further characterizations of the polymeric binder dispersions and wax dispersions used in the examples and comparative examples can be found in Table 2.

[0182] Description of measurement methods for which no standard is known or for which own procedures have been developed:

[0183] Heat sealability: While testing the seal strength of an existing seal is clearly defined, for example, by DIN 55529: 2012-09, there is no standardized method for testing a material's suitability for heat sealability. This is evidently due to the fact that packers prefer to develop their own incoming inspections for heat sealable films or papers, tailored to their packaging systems.

[0184] Based on industry information, relatively critical sealing conditions were applied (sealing time 0.3 s, sealing pressure 3.33 bar, smooth sealing jaws). Sealability is tested by sealing the two sealable coatings of a paper against each other. To determine the optimal sealing temperature, test specimens are produced and sealed at various sealing jaw temperatures (100-200°C).

[0185] Seal seam strength (hot tack): Performed according to DIN 55571-2 Method C. It should also be noted that the same sealing conditions apply as for the heat sealability test. The cooling time between sealing and force measurement was chosen to be 80 ms. The force measurement is carried out over a tensile length of 80 mm. Water vapor permeability is determined according to ISO / FDIS 2528:2017(E). Here, too, the coated side of the test specimen faces the desiccant.

[0186] Dependence of the coating's water vapor transmission rate on grease contact: The test specimen is first subjected to a palm kernel fat test (PKFT) in accordance with DIN 53116 2003-02. The corresponding test conditions are specified. At the end of the exposure time, after the grease has been wiped off, the water vapor transmission rate (WVTR) of the paper is determined according to ISO / FDIS 2528:2017(E). After wiping off the grease (which by default contains a red dye), a certain amount remains in or on the water vapor barrier coating. However, this does not lead to any further change in the WVTR, as a constant water vapor transmission rate is established over the course of the measurement.

[0187] The determination of the surface energies of the dry paper coatings is explained in the description. To determine the surface energies of the polymeric binders and waxes, the coatings were applied to the base paper, each containing only one component. The conditions were the same as for the polymeric binder and wax coatings in the examples and comparative examples.

[0188] The polar and disperse fractions of the surface energy of the wax and the polymeric binder are determined according to DIN EN ISO 19403-2 (2020-04):

[0189] Contact angle measuring device OCA 25 (DataPhysics) with dpiMAX software, measuring principle: OWRK method (Owens, Wendt, Rabel, Kaelble).

[0190] Measuring fluids used and origin of the entered material constants:

[0191] Water and diiodomethane (according to Buscher) and 1,5-pentanediol (according to Gebhardt).

[0192] In contrast to DIN EN ISO 19403-2 (2020-04), 1,5-pentanediol is used as the third measuring liquid because, unlike other non-polar measuring liquids, it still allows measurable contact angles on paper surfaces before the liquid is absorbed by the paper.

[0193] As a supplement to the procedure described in DIN EN ISO 19403-2 (2020-04), it should be noted that in the case of all three measuring liquids, the contact angle is measured immediately after the drop has been placed on the substrate (dosage volume 1.00 pl and dosing rate 1.00 pl / s), as soon as it has stabilized at least briefly, before the droplet deliquesces or penetrates into the substrate.

[0194] Table la: Examples

[0195]

[0196]

[0197] Table lb:Comparative examples.

[0198]

[0199]

[0200] Table 2a: Characterization of the polymeric binder dispersions

[0201]

[0202]

[0203] Table 2b: Characterization of the wax dispersions

[0204]

[0205]

Claims

Claims 1. Coated paper comprising a base paper and at least one coating applied directly or indirectly to the base paper, wherein the coating comprises at least one polymeric binder and at least one wax, characterized in that the polymeric binder has a polar fraction of the surface energy which is equal to or less than the polar fraction of the surface energy of the wax.

2. Coated paper according to claim 1, characterized in that the at least one wax has a polar fraction of the surface energy of 3% to 30%, in particular 8% to 26%, preferably 11% to 23% and particularly preferably 14% to 20%.

3. Coated paper according to claim 1 or claim 2, characterized in that the coating is coated or printed, in particular the coating is a water-based coating or printing ink layer.

4. Coated paper according to any one of the preceding claims, characterized in that the coated paper has a water vapor transmission (WVTR) of not more than 50 g / m 2 / d, measured at a temperature of 38 °C and a humidity of 90% RH, or not more than 17 g / m 2 / d, measured at a temperature of 23 °C and a humidity of 85% RH.

5. Coated paper according to any one of the preceding claims, characterized in that the coated paper comprises at least one further coating.

6. Coated paper according to any one of the preceding claims, characterized in that the at least one polymeric binder is selected from the group of polyolefins, polyolefin copolymers, ethylene-acrylic acids, ethylene-acrylic acid copolymers or combinations thereof, wherein these polymers or copolymers may be modified or unmodified and wherein the polymeric binder preferably comprises acid-modified polyolefin copolymer, in particular carboxylic acid- or sulfonic acid-modified polyolefin copolymer.

7. Coated paper according to any one of the preceding claims, characterized in that the at least one wax is selected from a) natural, animal, vegetable, mineral, semi-synthetic, synthetic waxes, b) microwaxes c) waxes based on mixtures or pure substances of fossil, animal or vegetable short to medium-chain hydrocarbons, their acids, esters, amides and / or diamides, d) hydrogenated or partially hydrogenated vegetable oils, vegetable fats or waxes produced from animal oils and / or animal fats, e) metal soaps, preferably based on heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, triacontane, hentriacontane, dotriacontane, tritriacontane, tetratriacontane, pentatriacontane, hexatriacontane, heptatriaontane, Octatriacontane, Nonatriacontane, Montan wax, f) Carnauba wax, Beeswax, Candelilla wax, Rice bran wax,Sugar cane wax or paraffin wax, in particular with an average molecular weight of at least 500 Daltons and a viscosity of at least 11 cSt at 100°C, wax obtained from sunflower seed presscake, g) waxes comprising esters with a C15-C17-C(O)-O-C16-C18 structural unit (structural unit I) h) wax with a structural unit II, i) waxes obtained by partial hydrogenation of vegetable oils, in particular soybean oil, j) combinations of these groups.

8. Coated paper according to any one of the preceding claims, characterized in that the coating has a wax-enriched interface on the side facing away from the base paper or on the side of the coating facing away from the base paper.

9. Coated paper according to any one of the preceding claims, characterized in that the at least one polymeric binder and the at least one wax are present in the coating in a weight ratio of 70:30 to 99:1, preferably of 80:20 to 95:5, particularly preferably of 85:15 to 95:

5.

10. Coated paper according to any one of the preceding claims, characterized in that the at least one polymeric binder is present in an amount of 70 to 98 wt.%, preferably 80 to 95 wt.%, in the coating.

11. Coated paper according to any one of the preceding claims, characterized in that the at least one wax is present in an amount of 2 to 30 wt.%, preferably 5 to 20 wt.%, in the coating.

12. Coated paper according to any one of the preceding claims, characterized in that the base paper has a basis weight of 20 to 120 g / m2 , preferably from 30 to 100 g / m 2 , has.

13. A process for producing a coated paper, in particular according to any one of the preceding claims, comprising a base paper, characterized in that on at least one side of the base paper, directly or indirectly, a coating or printing ink comprising at least one dispersion comprising the at least one polymeric binder and the at least one wax is applied and dried, wherein the polar fraction of the surface energy of the polymeric binder is equal to or less than the polar fraction of the surface energy of the wax.

14. Coated paper obtainable by the process according to claim 13.

15. Use of a coated paper according to any one of claims 1 to 12 or 14 as packaging or as a component of packaging or air cushion packaging material, in particular heat- or cold-sealable packaging, preferably for tobacco products, detergents and cleaning agents or foodstuffs, in particular for packaging moisture-sensitive and / or fatty foods and for protecting them from atmospheric humidity or fats from the environment.