Barrier paper

Abstract

The present invention relates to a barrier paper comprising a base paper and at least one coating color layer S1 applied directly or indirectly to said base paper, said coating color layer S1 comprising at least one polymer binder and at least one wax, a method for producing such a barrier paper, the use of such a barrier paper as a packaging material, and a packaging material comprising such a barrier paper.

Description

[Technical Field]

[0001] The present invention relates to a barrier paper, a method for producing such a barrier paper, the use of the barrier paper as a packaging material, and packages containing the barrier paper. [Background technology]

[0002] Packaging generally refers to the covering or wrapping (partial or complete) of an item, more particularly for its protection or better handling. Packaging material therefore includes the materials that form such packaging.

[0003] The packaging material may consist of, for example, paper, plastic, and / or metal. The present invention deals with paper-based packaging materials.

[0004] The main requirements for packaging materials of all origins are to protect the packaged goods from external influences, to prevent leakage of the packaged goods, and to function as advertising and information carriers. To this end, packaging materials must satisfy various criteria depending on the packaged goods and the packaging process. That is, in addition to so-called barrier properties against, for example, water, fat, oxygen, or mineral oil, suitable packaging materials must also meet mechanical and process-specific requirements. Packaging materials, especially flexible packaging materials, must have sufficient tear resistance, a suitable coefficient of friction, and flexibility depending on the packaging equipment; they must be heat-sealable and printable from the outside, and must not lose their protective effect throughout the entire conversion and packaging process.

[0005] Known paper-based coated packaging materials often contain compounds such as polyvinylidene chloride (which contains halogens) or are composites of paper and metal or plastic films, have tear resistance that could be improved, which can cause operational problems in packaging equipment, and / or are often not recyclable due to an excessively high proportion of sticky moieties in the coating or the formation of so-called stickies through the paper fiber stream.

[0006] It is widely known that polyvinyl alcohol, especially cross-linked polyvinyl alcohol, is linear. Water-soluble, biodegradable barrier coatings are also suitable for paper. Such coatings exhibit good barrier properties against oils, fats, oxygen, solvents, and other non-polar gases, liquids, or solids. However, due to its hydrophilic nature, polyvinyl alcohol is highly permeable to polar compounds such as water. This can also affect its barrier properties against non-polar migrants. This is because polyvinyl alcohol absorbs moisture very well and swells, thus creating pathways through the barrier coating at the molecular level.

[0007] To solve this problem, mixtures of all types of polymer dispersions and wax emulsions have been proposed. 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 drawback that fats can penetrate the coating, which in turn causes an increase in water vapor permeability. As a result, there is a risk that water vapor permeability will increase upon direct contact with fatty foods. When the laboratory method was transferred to a pilot coater, it was also observed that the heat sealability decreased. Furthermore, as the storage time increased, a decrease in heat sealability was often observed when such coatings were produced on a pilot scale. This relates to the ability of the material to produce a stable seal seam by heat sealing, and not to the stability of the existing seal seam. Summary of the Invention [Problem to be solved by the invention]

[0008] The object of the present invention is to provide a material that eliminates the disadvantages of known materials and is suitable as a packaging material, especially for moisture-sensitive foodstuffs, and that remains permeable to low levels of water vapor or only allows as little increase as possible when in contact with fat. It must also be suitable for heat-sealing applications. In particular, it must have a seal seam strength of more than 4 N / 15 mm and a water vapor permeability of 20 g / m2 / d (38℃, 90%RH) and less than 8g / m 2 A target water vapor transmission rate (WVTR) of less than 1 / d (23°C, 50% RH) is aimed for.

[0009] Furthermore, the material according to the invention should be as easy to produce as possible, require as low an application weight as possible and, if possible, allow recyclability via the paper fibre stream. [Means for solving the problem]

[0010] This problem is solved by a barrier paper according to claim 1, namely a barrier paper comprising a base paper and at least one coating color layer S1 applied directly or indirectly to the base paper, the coating color layer S1 comprising at least one polymer binder and at least one wax, the coating color layer S1 having the following characteristics: a) a change in surface tension of +10 mN / m or less, preferably +6 mN / m or less, b) a change in the polar component of the surface tension of less than or equal to -0.65 mN / m, preferably less than or equal to -0.60 mN / m; c) a change in the polar component of the surface tension of less than -3.0% pts, preferably less than -1.5% pts; and Each change is resolved by the barrier paper, determined by measuring and comparing the surface tension measurements of the polar component of the surface tension before and after a 3 minute temperature treatment of the barrier paper at 105°C.

[0011] Preferred embodiments are defined in the dependent claims.

[0012] Papers coated in this way are particularly suitable as packaging materials for moisture-sensitive and greasy goods, especially foodstuffs, and are distinguished by the fact that they can be used in heat-sealing applications.

[0013] Such barrier papers can also be used to achieve the above-specified criteria for heat sealability and water vapor permeability.

[0014] Finally, the barrier paper according to the present invention can be produced relatively easily and at low application weights and can be recycled through the waste paper cycle. DETAILED DESCRIPTION OF THE INVENTION

[0015] Numerous specific details are also discussed below to provide a comprehensive understanding of the present subject matter. However, it will be apparent to one skilled in the art that the present subject matter may be practiced without these specific details. It can also be implemented and reproduced.

[0016] All features of one embodiment may be combined with features of another embodiment unless the features of different embodiments are incompatible.

[0017] The terminology used in the description of this disclosure is intended only to describe certain embodiments and should not be construed as limiting the subject matter. As used in the specification and claims, the singular forms "a" and "an" should be understood to include the plural unless the context clearly dictates otherwise. This is also true vice versa, i.e., the plural also includes the singular. The term "and / or," as used herein, should also be understood to mean and include all possible combinations of one or more of the associated listed elements. Furthermore, the terms "include," "including," "comprise," and / or "comprising," as used in the specification and claims, should be understood to specify the presence of stated features, steps, operations, elements, and / or components, but not to exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0018] In this specification and claims, the terms "include," "comprise," and / or "comprising" may also mean "consisting of," i.e., excluding the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0019] Thus, in this specification and claims, the term "including" can also mean "exclusively."

[0020] Unless otherwise indicated, the designation "%" with respect to formulations and / or compositions means in particular "% (w / w)" relative to the respective total weight of the respective formulation and / or composition.

[0021] As mentioned above, the barrier paper according to the present invention comprises a base paper and at least one coating color layer S1 applied directly or indirectly to the base paper, the coating color layer S1 comprising at least one polymer binder and at least one wax, and the coating color layer S1 has the following characteristics: a) a change in surface tension of +10 mN / m or less, preferably +6 mN / m or less, b) a change in the polar component of the surface tension of less than or equal to -0.65 mN / m, preferably less than or equal to -0.60 mN / m; c) A change in the polar and dispersive components of the surface tension of less than -3.0% pts, preferably less than -1.5% pts and Each change is determined by measuring and comparing the surface tension measurements of the polar component of the surface tension before and after a 3 minute temperature treatment of the barrier paper at 105°C.

[0022] If the coating color layer S1 is applied directly to the base paper, this means that there are no other coatings or substances between the base paper and the coating color layer S1.

[0023] If the coating color layer S1 is applied indirectly to the base paper, this means that there are other coatings or substances between the base paper and the coating color layer S1.

[0024] Laboratory tests have shown that it is possible to apply a coating color layer S1 directly to raw paper, especially to calendered raw paper of a certain surface thickness and low Cobb value. For better holdout of the coating color and to minimize the required coating application, it is preferable to apply a base coat first. Ultimately, economic and production-related considerations also determine which approach is preferred in each individual case.

[0025] The surface tension (alternatively called surface energy) of a solid can be determined by measuring the contact angle with at least two different liquids. Manufacturers of measuring devices based on this principle, such as DataPhysics Instruments GmbH (D-70794 Filderstadt), describe the relationship on their website as follows:

[0026] The atomic and molecular cohesion that determines the surface tension of a substance is due to various types of interactions. In particular, dispersive and polar interactions can be distinguished. Interactions resulting from temporary fluctuations in the charge distribution of atoms / molecules are called dispersion interactions (Van der Waals interactions). Polar interactions include Coulomb interactions between permanent dipoles or between permanent and induced dipoles (e.g. hydrogen bonds). Therefore, surface tension also consists additively of a dispersion component and a polar component.

[0027] By comparing the ratio of the dispersive to polar components of the surface tension for each of the two phases, predictions can be made regarding the adhesion of the two phases to each other: the better the match between the dispersive and polar components, the more potential interactions there are between the phases, and the stronger adhesion can be expected.

[0028] If a comparison of the measurements can determine that a) there is no significant change in surface tension, i.e., no more than +10 mN / m, and / or b) or c) there is no significant change in the polar component of the surface tension, i.e., no more than -0.65 mN / m or -3.0% pts, the barrier paper has advantageous properties.

[0029] The inventors hypothesize that in coating color layers comprising or consisting of at least one polymer binder and at least one wax, drying of the coating color layer may cause at least partial color separation and / or partial film formation of the coating color layer, resulting in uneven distribution of the wax within the coating color layer. Depending on how the drying parameters are selected for one and the same composition of the coating color layer, different properties of the coating color layer and therefore of the barrier paper may result.

[0030] The inventors have transferred these findings to the coating color layer S1, where the following characteristics of the dried coating color layer S1: a) a change in surface tension of +10 mN / m or less, preferably +6 mN / m or less, b) a change in the polar component of the surface tension of less than or equal to -0.65 mN / m, preferably less than or equal to -0.60 mN / m; c) A change in the polar component of the surface tension of -3.0% pts or less, preferably -1.5% pts or less At least one of the above can be considered as an indicator of the quality of the coating color layer S1 with respect to the characteristics mentioned in the problem, in particular with respect to whether there is partial color separation and / or partial film formation of the coating color layer S1 or whether there is an uneven distribution of wax within the coating color layer S1.

[0031] In other words, the properties of the barrier paper mentioned in the problem definition depend not only on the composition of the coating color layer S1, but also on how this coating color layer S1 has been dried. Therefore, in addition to the composition, the dried coating color layer S1 has the following structural characteristics: a) a change in surface tension of +10 mN / m or less, preferably +6 mN / m or less, b) a change in the polar component of the surface tension of less than or equal to -0.65 mN / m, preferably less than or equal to -0.60 mN / m; c) A change in the polar and dispersive components of the surface tension of less than -3.0% pts, preferably less than -1.5% pts It must have at least one of the following: Here, each change is determined by measuring and comparing the surface tension measurements of the polar component of the surface tension before and after a 3 minute temperature treatment of the barrier paper at 105°C.

[0032] The drying parameters (temperature, time) should preferably be selected for a particular coating color composition S1 so that after drying the coating color layer S1 has at least one, preferably at least two, and particularly preferably all three of the characteristics a) to c). The drying parameters can be determined by a person skilled in the art using simple drying tests.

[0033] For successful drying, it is preferred that the temperature of the coating web during the drying process be above the melting range of the wax for a sufficiently long period of time.

[0034] As has been found in numerous laboratory tests with various polymer-wax mixtures, the surface tension of the coating color layer S1 is preferably between 15 and 40 mN / m, in particular between 20 and 35 mN / m.

[0035] The polar component of the surface tension of the coating color layer S1 is preferably 0 to 12%, in particular 0 to 6%, preferably 0 to 3%, particularly preferably 0 to 1%, where in a preferred embodiment the value 0% is excluded as a lower limit.

[0036] The dispersion component of the surface tension of the coating color layer S1 is preferably 88 to 100%, particularly 94 to 100%, preferably 97 to 100%, particularly preferably 99 to 100%.

[0037] The determination of the surface tension and the polar and dispersive components of the surface tension is determined in accordance with DIN EN ISO 19403-2(2020-04):

[0038] Contact angle measuring device OCA 20 (DataPhysics) equipped with software SCA 20, measurement principle: OWRK method (Owens, Wendt, Rabel, Kaelble).

[0039] Measurement liquids used and origin of entered material constants:

[0040] Water and diiodomethane (Buscher) and 1,5-pentanediol (Gebhardt). 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, 1,5-pentanediol still allows a measurable contact angle on the paper surface before the liquid is absorbed into the paper.

[0041] The temperature treatment of the barrier paper at 105°C for 3 minutes is preferably carried out in a hot air oven (drying oven) to ensure that the paper is actually exposed to 105°C for 3 minutes. For this purpose, the oven is preferably preheated and has a sufficient internal volume (e.g., 100 dm2) so that there is no significant drop in temperature when the front door is briefly opened (for 2-3 seconds) to insert the paper. 3The barrier paper must have dimensions greater than 60 cm (e.g., width x height x depth) x 48 cm x 37 cm. The barrier paper is preferably placed on a metal mesh located at the center height of the drying oven, with cardboard as a support. The metal mesh and cardboard should already have reached oven temperature and must be placed in an oven already preheated to 105°C at least 15 minutes before starting the temperature treatment. It should be noted that the duration of the temperature treatment was preferably set to 3 minutes to ensure that the barrier paper had enough time to actually reach 105°C and that the treatment of the paper did not last too long and therefore did not cause decomposition processes. After removal from the oven, the barrier paper was stored at 23°C and 50% RH (conditioned) for at least 12 hours before further measurements were performed.

[0042] The wax in the coating color layer S1 is preferably a wax according to the following definition of the German Society for Fat Science (DGF):

[0043] "Waxes are substances defined today by their mechanical and physical properties. However, their chemical composition and origin vary greatly. A substance may be described as a wax if it is kneadable at 20°C, solid to brittle hard, has a coarse to fine crystalline structure, is translucent to transparent in color but not glassy, ​​melts above 40°C without decomposition, is slightly liquid (low viscosity) just above its melting point, has a consistency and solubility that are strongly temperature-dependent, and can be polished with little pressure." If more than one of the properties listed above is not fulfilled, the substance is not a wax within the meaning of DGF (DGF Unit Method MI 1(75)).

[0044] Our own laboratory studies have shown that the chemical composition of the wax used does not play a decisive role, but it should be selected so that it melts under the drying conditions technically possible in the coating system. It has been shown that a melting temperature below the boiling point of water (100°C), or even better below 90°C, is advantageous for the formation of a water vapor barrier.

[0045] The polymer binder in the coating color layer S1 is not limited in principle, but includes all polymer binders known to those skilled in the art for binding waxes in paper coatings.

[0046] In principle, hydrophobic polymers can be used, but it is also possible that polar water-soluble binders of synthetic or natural origin or their derivatives may be suitable, provided that the hydrophilic functional groups are shielded by waxes also present in the coating and that the water vapor barrier does not affect the coating.

[0047] The following correlation has been determined in laboratory tests: the lower the wax content, the better the heat sealability, especially the hot tack. However, a low wax content results in a higher water vapor permeability and a relatively high sensitivity of the water vapor barrier to fat contact. If it is intended to use less wax, the water-based coating must dry so that the wax migrates to the surface to obtain a good, less fat-sensitive water vapor barrier.

[0048] In one embodiment, the wax content of the coating color layer S1 is such that the barrier paper has the following characteristics: a) a seal seam strength (cold tack) of the coating color layer S1 to the coating color layer S1 of ≥ 4 N / 15 mm, obtained with heat sealing parameters T = 130-150 ° C, sealing time = 0.3 seconds, sealing pressure = 3.3 bar or ultrasonic sealing parameters resulting in a T of 130-150 ° C and a sealing time of 0.3 seconds and a sealing pressure of 3.3 bar; b) Water vapor transmission rate (WVTR) ≦ 20 g / m2 / d (38℃, 90%rh), c) Water vapor transmission rate (WVTR) ≦ 8 g / m 2 / d (23℃, 50%rh), d) DIN 53116 2003-02 (10 min exposure time and 2000 N / m 2 Increase in water vapor permeability (38°C, 90% rh) after palm kernel fat test according to the pressure load test conditions of 70 g / m 2 / d or less, preferably 60 g / m 2 / d or less, e) DIN 53116 2003-02 (60 min exposure time and 2000 N / m 2 Increase in water vapor permeability after palm kernel fat testing according to the test conditions of (not more than 6 times), f) a static friction coefficient (coating color layer S1 relative to coating color layer S1) of less than 0.9; g) a coefficient of dynamic friction (coating color layer S1 relative to coating color layer S1) of less than 0.6; and The values ​​of a) to g) are 12 g / m 2 The following is determined for the basis weight of the coating color layer S1.

[0049] Here, the basis weight of the coating color layer S1 is 12 g / m 2 Although not limited to the following values, the above parameters must be satisfied only for such basis weights. The higher the basis weight, the more the parameters must be adjusted accordingly.

[0050] Parameter a) seal seam strength (cold tack) of coating color layer S1 to coating color layer S1 is preferably understood to mean that one sheet of barrier paper is folded in such a way that the coating color layer S1 coincides with itself in the seal seam area, or two sheets of barrier paper are placed on top of each other in such a way that the coating color layers S1 of the two sheets coincide with each other in the seal seam area.

[0051] In one embodiment, the barrier paper according to the invention is preferably characterized in that it has a change in water vapor permeability (38°C, 90% rh) of at most -40%, preferably less than -30%, which change is determined by measuring the water vapor permeability of the barrier paper before and after a temperature treatment at 105°C for 3 minutes and comparing the measured values ​​(as described above).

[0052] In one embodiment, the wax is a wax according to the DGF defined above (DGF Standard Method MI 1(75)).

[0053] In one embodiment, the barrier paper according to the invention preferably comprises at least one wax based on fossil or natural short to medium chain hydrocarbons, their acids, esters, amides and diamides, mixtures or pure substances of hydrogenated vegetable oils; waxes produced by hydrogenation or partial hydrogenation of vegetable and animal oils or fats and / or metallic soaps, preferably heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, triacontane, hentriacontane, dotriacontane , tritriacontane, tetratriacontane, pentatriacontane, hexatriacontane, heptatriacontane, octatriacontane, nonatriacontane, montan wax, carnauba wax, beeswax, candelilla wax, rice wax, sugarcane wax, wax obtained from sunflower seed press cake, particularly preferably beeswax and / or wax obtained by hydrogenation of soybean oil, and / or paraffin wax having an average molecular weight of at least 500 daltons and a viscosity of at least 11 cSt at 100°C.

[0054] Beeswax and / or paraffin wax are particularly preferred, as they are approved for direct contact with food according to the German Federal Institute for Risk Assessment of the Federal Ministry of Food and Agriculture, Germany, Chapter C, Section IV, Point 2 in conjunction with BfR. XXV of June 1, 2019, BfR XXVI of April 1, 2021.

[0055] When paraffin waxes are used, those belonging to FCM substance number 94 of 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.

[0056] In one embodiment, the barrier paper according to the invention is preferably characterized in that the at least one wax is present in an amount of 0.01 to 10% (w / w), preferably 0.01% (w / w) to less than 8.0% (w / w), preferably 0.01% (w / w) to less than 6.0% (w / w), particularly preferably 0.01% (w / w) to less than 5.0% (w / w), most particularly preferably 0.01% (w / w) to 2.0% (w / w) or less, with a lower limit of preferably at least 0.1% (w / w), particularly preferably at least 0.2%, relative to the total weight of the coating color layer S1.

[0057] In one embodiment, the barrier paper according to the invention is preferably such that the at least one polymer binder of the coating color layer S1 is selected from the group comprising copolymers of polyacrylates and unsaturated hydrocarbons; polyolefins; copolymers of unsaturated hydrocarbons and acrylic acid or salts thereof; (partially carboxylated) styrene-butadiene copolymers; styrene-butadiene copolymers; styrene-butadiene; polyvinyl acetate; partially saponified polyvinyl acetate; polyesters, such as polylactides; and polyhydroxyalkanoates (formed from glucose), polyamides; polyurethanes; polyethers; polyethyleneimines; and / or polyvinylamides; preferably polymethyl acrylate, poly methyl methacrylate, polyethyl acrylate, polyethyl methacrylate, poly(n-, iso-, tert-)butyl acrylate, poly(n-, iso-, tert-)butyl methacrylate, polycyclohexyl methacrylate, polyethylhexyl acrylate and copolymers thereof; graft polymers and copolymers thereof with styrene, acrylonitrile, methylstyrene and / or vinyltoluene; particularly preferably styrene-acrylic acid-methyl acrylate-butyl acrylate-ethylhexyl acrylate copolymers, and / or natural polymers such as (modified) polysaccharides, proteins, lignin (derivatives) and other natural macromolecules, such as shellac.

[0058] In one embodiment, the barrier paper according to the invention is preferably characterized in that the at least one polymer binder is present in an amount of from 99.9% (w / w) to more than 92% (w / w), particularly preferably more than 95% (w / w), most preferably more than 98% (w / w), relative to the total weight of the coating color layer S1.

[0059] In one embodiment, the coating color layer S1 comprises only wax and polymer binder.

[0060] In another embodiment, the coating color layer S1 comprises further components or additives in addition to the wax and polymer binder.

[0061] Other possible components of the coating color layer S1 include, for example, pigments, in particular inorganic pigments, such as Ca-carbonates (GCC or PCC), talc, kaolin, natural and / or synthetic silicates.

[0062] Such pigments are preferably contained in the coating color layer S1 in an amount of 0 to 70% (w / w) relative to its total weight. To ensure that the heat-sealability of the coating color layer S1 is not too severely impaired, an amount of 0 to 50% (w / w), preferably 0 to 30% (w / w), particularly preferably 0 to 10% (w / w) should be selected. Preferably, only the value of 0% (w / w) is excluded as a lower limit.

[0063] Platelet-shaped pigments should preferably be selected because they can contribute to improved barrier properties when aligned in a layered direction parallel to the coating. The particle size should preferably be selected so that the particles are fully contained within the layer in a layered orientation. The aspect ratio (ratio of average diameter to thickness, also known as shape factor) should be greater than 10, preferably greater than 100, and particularly preferably greater than 1000.

[0064] Other possible additives include, for example, thickeners, surfactants, crosslinkers and / or rheology modifiers.

[0065] These additives are preferably present in the coating color layer S1 in an amount of 0 to 2% (w / w), preferably 0 to 1% (w / w), relative to the total weight of the dry coating color layer, preferably excluding the value 0% (w / w) as a lower limit.

[0066] The smoothness (according to Bekk (ISO 5627, 1995-03)) of the coating color layer S1 is preferably between 400s and 2500s, preferably between 500s and 2000s.

[0067] The roughness (according to Parker-Print-Surf (PPS) DIN ISO 8791-4, 2008-05) of the coating color layer S1 is preferably 0.8 to 2.0 μm, preferably 1.0 to 1.8 μm.

[0068] The coating weight of the coating color layer S1 (ISO 536, 2020-05) is preferably 4 to 20 g / m 2 , preferably 6 to 15 g / m 2 , particularly preferably 8 to 12 g / m 2 This amount refers to the dried coating color layer S1 of the final product.

[0069] In one embodiment, the barrier paper according to the invention is preferably characterized in that at least one wax is enriched in the coating color layer S1 on the side facing away from the base paper.

[0070] Enriched here is understood to mean, in particular, that the local concentration of wax in the coating color layer S1 on the side facing the base paper is higher than the local concentration of wax in the coating color layer S1 on the side facing the base paper, which is indirectly evidenced by the fact that the polar component of the surface energy does not decrease significantly further during post-drying.

[0071] Further evidence of wax accumulation can be provided by electron spectroscopy (ESCA, also abbreviated as XPS). Wax accumulation in the coating color layer S1 on the side away from the base paper was also detected by the following test.

[0072] Coating tests on the pilot coating system did not achieve the low water vapor permeability that can be achieved with laboratory coating of individual sheets. To check whether poor coating quality (defects, bubbles, wetting problems) or simply insufficient drying and film formation was the cause, the individual sheets were again gently but sufficiently long-term dried in a drying oven (3 minutes, 105°C). The water vapor permeability of the re-dried papers (Comparative Examples 1 and 2) improved, and the polar component of the surface tension was reduced. Since no chemical reaction is expected in the coating, it can be concluded that the non-polar wax migrated to the interface as a result of the second drying.

[0073] In principle, there are no restrictions on the base paper used for the barrier paper according to the invention.

[0074] Base paper: 20-120g / m 2 , preferably 40 to 100 g / m 2 Preferably, the sheet has a basis weight of 1000 gram.

[0075] It is more preferred that the base paper has a long fiber content of 10 to 80% (w / w), preferably 20 to 50% (w / w), and a short fiber content of 20 to 90% (w / w), preferably 50 to 80% (w / w), based on the total weight of the base paper, the long fibers having a fiber length of 2.6 to 4.4 mm and the short fibers having a fiber length of 0.7 to 2.2 mm.

[0076] The long fiber content ensures strength, especially in relatively thin papers, while the short fiber content makes the paper denser and more compact, and gives it a uniform appearance. If the long fiber content is further increased, the paper becomes too stiff. The lower price of short fiber pulp compared to long fiber pulp also plays a role.

[0077] In addition, 0% (w / w) to 20% (w / w), preferably 0% to 5%, of fillers such as GCC (ground calcium carbonate), for example known under the trade name Hydrocarb 60 or Hydrolex 60, PCC (precipitated calcium carbonate), for example known under the trade name Precarb 105, natural kaolin and / or talc may be present, where the value 0% (w / w) is preferably excluded.

[0078] Furthermore, conventional additives such as retention and / or sizing agents may be present.

[0079] The advantages of such base paper are, on the one hand, its high flexibility and, on the other hand, its good processability in existing packaging systems relative to flexible materials such as plastic films; maintaining high machine availability; and achieving the required puncture resistance.

[0080] In particular for food contact, the base paper contains at least 60% (w / w), preferably at least 75% (w / w), of fibre, at most 25% (w / w), preferably at most 10% (w / w), of fillers and at most 15% (w / w) of auxiliaries. In addition, unavoidable or necessary traces of processing auxiliaries (e.g. reagents, dispersants, mould inhibitors, etc.) may be present in the base paper.

[0081] In one embodiment, the barrier paper is characterized in that it comprises at least one further coating color layer S2 applied directly or indirectly between the base paper and the coating color layer S1 to form a mineral oil and / or fat barrier layer and / or also an oxygen barrier layer, in particular comprising at least one hydrophilic polymer.

[0082] If the coating color layer S2 is applied directly between the base paper and the coating color layer S1, this means that the coating color layer S2 is in contact with the base paper on one side and with the coating color layer S1 on the other side.

[0083] If the coating color layer S2 is applied indirectly between the base paper and the coating color layer S1, this means that the coating color layer must be between the base paper and the coating color layer S1, but does not necessarily have to be in direct contact with them; other intermediate layers are therefore not excluded.

[0084] Preferably, the coating color layer S2 is used to form a barrier layer against mineral oils and / or fats and comprises at least one hydrophilic polymer.

[0085] The preferred target value for mineral oil barrier is 30 g / m 2 The preferred target value for fat resistance for foods that are not consumed immediately is passing the palm kernel fat test according to DIN 53116 Cat. 1 (no pass after more than 24 hours of testing).

[0086] Hydrophilic polymers are often cross-linked and therefore not very flexible. For flexible packaging, it is preferable to select a coating that can withstand folds of up to 180° on the inside (between the coatings) and ideally on the outside as well without allowing fat to pass through.

[0087] The coating color layer S2 should preferably be able to be painted over the (aqueous) coating mass of the coating color layer S1 when in the dry state.

[0088] For this reason, it should preferably not absorb water or swell during the coating process, so that, on the one hand, its own barrier effect (mineral oil, fat and in particular oxygen) is not impaired, and, on the other hand, optimal, defect-free coating of the coating color layer S1 is possible.

[0089] Polymer-based oxygen barriers (which are always also barriers to mineral oils and fats) are usually hydrophilic and can only be painted over if at least some of the free hydrophilic groups are covalently crosslinked when the coating dries. For this purpose, reactive additives such as di- or polyfunctional aldehydes, carboxylic acids, epoxides, or inorganic crosslinkers such as zirconates or borates are preferably used. Another possible group of crosslinkers are PAE resins (polyamidoamine-epichlorohydrin), which are also commonly used as wet strength agents for base paper.

[0090] The use of these additives is prohibited or restricted in cases of food contact.

[0091] Therefore, when looking for a raw material for a barrier against mineral oils and fats, water-soluble polymers are not usually the first choice, but preferably polymer dispersions that are modified by the manufacturer through functionalization to be not very water-soluble but have adequate barrier effect, or by adding insufficient amounts of water-soluble polymers that provide or enhance the overall oil repellency effect.

[0092] Examples of suitable polymers are copolymers of polyvinyl alcohol and polyvinyl acetate, acrylate (co)polymers, acrylonitrile copolymers.

[0093] The use of crosslinked or partially hydrophobized polyvinyl alcohol, ethylene vinyl alcohol or other copolymers of vinyl alcohol (such as those described in EP-A-4041548), carbohydrates and / or proteins is also suitable.

[0094] Preferred polymers are partially saponified polyvinyl alcohols (according to EP 4041548) and / or partially saponified polyvinyl alcohol copolymers, each having an onset temperature determined by DSC of less than 210°C and an average molecular weight (M) preferably less than 100,000 g / mol. w) and the DSC onset temperature is defined as the intersection of the extrapolated baseline and the inflection tangent at the onset of the melting or crystallization peak according to DIN EN ISO 11357-1:2010-03.

[0095] Due to its high surface tension (surface energy), polyvinyl alcohol is particularly suitable for applying thin metal layers which have a much lower primarily dispersive surface tension.

[0096] Preferably, the barrier paper according to the invention may comprise at least one further layer made of or containing metal, in particular aluminum. This can further improve the barrier effect in particular. This additional layer can be designed as an intermediate layer or as a top layer. If designed as an intermediate layer, this layer is preferably arranged directly below or directly above the heat-sealable layer, e.g., the coating color layer S1.

[0097] For this purpose, polyacrylates containing protective colloids, preferably based on starch, are particularly preferred. A suitable polyacrylate is known under the trade name Epotal SP 101 D.

[0098] Also suitable are polyacrylates or polyacrylonitriles, such as those known, for example, under the trade name Rhobarr 214.

[0099] Such polymers have the advantage that they swell less when in contact with water, so that a coating applied to them does not achieve its optimum water vapor barrier when swelled.

[0100] In one embodiment, the hydrophilic polymer is present in the coating color layer S2 in an amount of 30 to 100% (w / w), or 50 to 100% (w / w) based on the total weight of the coating color layer S2.

[0101] Other possible components of the coating color layer S2 include, for example, pigments, in particular inorganic pigments, such as Ca-carbonates (GCC or PCC), talc, kaolin, natural and / or synthetic silicates.

[0102] Such pigments are preferably present in the coating color layer S2 in an amount of 0 to 70% (w / w) relative to its total weight, particularly preferably 0 to 50% (w / w), preferably excluding only the value 0% (w / w) as a lower limit.

[0103] Preferably, platelet-shaped pigments should be selected because they can contribute to improved barrier properties when aligned in a layered direction parallel to the coating. The particle size should preferably be selected so that the particles are fully contained within the layer in a layered orientation. The aspect ratio (ratio of average diameter to thickness, also known as shape factor) should be greater than 10, preferably greater than 100, and particularly preferably greater than 1000.

[0104] In one embodiment, the coating color layer S2 further comprises additional additives. Possible additives include, for example, thickeners, surfactants, crosslinkers and / or rheology modifiers.

[0105] Such additives are preferably present in the coating color layer S2 in an amount of 0 to 2% (w / w) relative to its total weight, particularly preferably 0% (w / w), preferably excluding only the value 0% (w / w) as a lower limit.

[0106] Preferably, the coating color layer S2 does not contain glyoxal.

[0107] The surface tension of the coating color layer S2 is preferably 45 to 70 mN / m, in particular 50 to 65 mN / m, most particularly 57 to 61 mN / m.

[0108] The polar component of the surface tension of the coating color layer S2 is preferably 60 to 95%, particularly preferably 70 to 90%, and particularly preferably 78 to 84%.

[0109] The dispersion component of the surface tension of the coating color layer S2 is preferably 5 to 40%, particularly preferably 10 to 30%, and particularly preferably 16 to 22%.

[0110] The surface tension and each component are determined as defined above.

[0111] Preferably, the surface tension of the coating color layer S2 is at least 5 mN / m higher than that of the coating color layer S1, typically 20-30 mN / m higher, and preferably has a significantly higher polar component, which, as measurements have shown, can be at most 12%, in particular due to the wax content of the coating color layer S1.

[0112] The coating weight of the coating color layer S2 (ISO 536, 2020-05) is preferably 3 to 12 g / m 2 , particularly preferably 8 to 10 g / m 2 This amount relates to the dried coating color layer S2 of the final product.

[0113] The smoothness (according to Bekk (ISO 5627, 1995-03)) of the coating color layer S2 is preferably between 80s and 500s, preferably between 100 and 200s.

[0114] The roughness (according to Parker-Print-Surf (PPS) DIN ISO 8791-4, 2008-05) of the coating color layer S2 is preferably 2 to 4 μm, preferably 2.5 to 3.5 μm.

[0115] In one embodiment, the barrier paper according to the invention is characterized in that a further coating colour layer S3 is present directly on the base paper, in particular the coating colour layer comprising or consisting of at least one inorganic pigment and a polymeric binder.

[0116] The inorganic pigments are preferably platelet shaped and include, in particular, talc, precipitated calcium carbonate, or silicates, preferably phyllosilicates, most preferably kaolin.

[0117] The aspect ratio (ratio of average diameter to thickness, also known as shape factor) should be approximately 7-40:1, preferably approximately 15-30:1.

[0118] The particle size of the platelet-like pigment is preferably adjusted so that at least about 70%, preferably at least about 85%, of the particles have a particle size (Sedigraph) of less than about 2 μm. The pH value of the platelet-like pigment in aqueous solution is preferably 6-8.

[0119] Suitable polymer 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. Starch-based binders (modified starch solutions, crosslinked starch dispersions, so-called biolattices) and polymer-starch hybrid latexes can also be used.

[0120] The polymeric binder preferably comprises a polyacrylate-based polymeric binder.

[0121] The polymeric binder preferably comprises a styrene-acrylate copolymer, preferably a styrene-butyl acrylate copolymer, especially a styrene-n-butyl acrylate copolymer.

[0122] A suitable styrene-n-butyl acrylate copolymer is known, for example, under the trade name Acronal S 305 FD.

[0123] Overall, the coating color layer S3 may be a hydrophobic precoat.

[0124] In another embodiment, the coating color layer S3 is completely hydrophilic.

[0125] The coating color layer S3 preferably contains 5 to 50% (w / w), preferably 10 to 30% (w / w), of polymer binder, based on the dried coating color layer in the final product.

[0126] The coating color layer S3 also preferably contains 50 to 95% (w / w), preferably 70 to 90% (w / w), of inorganic pigments, this amount being based on the dried coating color layer in the final product.

[0127] Additionally, the coating color layer S3 may contain additives such as thickeners, e.g., acrylate-based thickeners, surfactants, and / or rheology modifiers. The use of crosslinking agents is also contemplated. Preferably, the coating color layer contains a zirconium-based crosslinking agent, which is itself crosslinked with formaldehyde.

[0128] These additives are preferably present each in an amount of 0 to 2% (w / w), preferably greater than 0 to 2% (w / w), the value 0% (w / w) being preferably excluded, this amount relating to the dried coating color layer S3 in the final product.

[0129] The coating weight of the coating color layer S3 (ISO 436, 2020-05) is preferably 1 to 10 g / m 2 , and particularly preferably 2 to 6 g / m 2 This amount refers to the dried coating color layer in the final product.

[0130] If such a coating color layer S3, also called a precoat or primer, is applied, it has the advantage that the paper surface is sealed, and further coating color layers applied thereto are only slightly transferred to the paper. This coating color layer also reduces the average roughness depth of the base paper, providing an advantageous coating color holdout characterized by area coverage and a defined surface energy, so that the coated coating color layer can be optimally formed and an optimal barrier can be formed with as few applications as possible, which has a beneficial effect on the cost structure. Additionally, the precoat is such that the interlayer adhesion between the base paper and the coating color layer is not significantly reduced, which may be important for subsequent sealing applications.

[0131] The surface tension of the coating color layer S3 is preferably 15 to 40 mN / m, particularly 22 to 30 mN / m.

[0132] The polar component of the surface tension of the coating color layer S3 is preferably 10 to 50%, particularly 15 to 30%.

[0133] The dispersion component of the surface tension of the coating color layer S3 is preferably 50 to 90%, particularly 70 to 85%.

[0134] The surface tension and each component are determined as defined above.

[0135] For good wetting and interlayer adhesion, the surface tension of the precoat should be higher, or at least more polar, than the layer above.

[0136] In the case of an embodiment having a layer S2, this cannot be guaranteed because the coating color layer S2 itself already has a high surface tension and a high polar content. The highly polar coating color layer S3 will swell excessively when coated with an aqueous coating formulation, which may cause cracks after drying. Therefore, the data showing the surface tension of the coating color layer S3 has proven to be a universal basis for directly coating the coating color layer S1 or the coating color layer S2 in particular.

[0137] The smoothness (according to Bekk (ISO 5627, 1995-03)) of the coating color layer S3 is preferably between 80s and 200s, preferably between 90s and 120s.

[0138] The roughness (according to Parker-Print-Surf (PPS) DIN ISO 8791-4, 2008-05) of the coating color layer S3 is preferably 2.8 to 4.0 μm, preferably 3.2 to 3.6 μm.

[0139] In one embodiment, the barrier paper according to the present invention may comprise further layers in addition to the coating color layers S1, S2 and S3 described above.

[0140] For example, the uncoated side of the paper may be provided with one or more coatings that are easier to print on than the surface of the base paper that only has a starch film.

[0141] To improve the overall barrier of the paper, the smooth surface can be vaporized (eg, by phase deposition in a vacuum) with a metal or metal oxide.

[0142] A prerequisite for this is preferably a smooth surface, such as in this case the coating color layer S2 or also the coating color layer S1, or even a smooth printed coating on the uncoated side of the barrier.

[0143] Barrier lacquers are also known, which can be applied to the entire surface or only to certain areas, for example by a converter.

[0144] One example would be the product HYDRO-LAC GA oxygen barrier coating from the manufacturer Hubergroup Print Solutions. This lacquer can be applied to the uncoated side of the coating color layer S1 or barrier paper, or even better to a smooth printed coating.

[0145] The barrier paper can be used as a heat-sealable barrier paper, but it can also be coated with a cold seal adhesive on one of its two sides, especially if the paper is to be used in a packaging machine designed for cold seal adhesives.

[0146] Preferably, one of the two sides, preferably the printed side as well, can use an additional heat seal adhesive for sealing between the front and back sides (A / B seal).

[0147] In one embodiment, the barrier paper includes the coating color layers S1 and S3 defined above.

[0148] In one embodiment, the barrier paper comprises the coating color layers S1, S2 and S3 defined above.

[0149] Again, the coating color layer S3 can be applied in two or more coats as described above.

[0150] The barrier paper according to the invention can be produced economically using all known papermaking and coating processes (film press with or without pre-dosing, roll application, doctor blade, blade, curtain coater, spray coater).

[0151] However, it is preferred to obtain the barrier paper according to the invention by a process in which an aqueous suspension or solution comprising the starting materials for the respective coating colour layer S1 or coating colour layers S2+S1 is applied to a base paper preferably coated with coating colour layer S3, the aqueous coating suspension or solution having a solids content of 15 to 55% (w / w), preferably 20 to 45% (w / w), and applied by a curtain coating process; in the case of coating colour layers S2+S1, both coats can be applied successively with intermediate drying intervals, or preferably by a double curtain coating process, with a working speed of the coating system of at least 100 m / min, preferably 200 m / min or more.

[0152] The barrier paper is then preferably dried, where drying should be done gently so that the web temperature never exceeds 90°C, as otherwise boiling bubbles may form which can impair or, in extreme cases, destroy the quality of the barrier. Non-contact drying systems consisting of a group of infrared dryers whose drying capacity can be individually adjusted, followed by several hot air hoods which can also be individually adjusted, have proven their worth. Optionally, a second section with IR dryers can then be installed to achieve better film formation.

[0153] This process is particularly advantageous from an economic point of view and also for uniform application to the paper web.

[0154] If the solids content falls below a value of approximately 15 wt%, a large amount of water has to be removed by gentle drying in a short time, which has a detrimental effect on the coating speed and therefore reduces the economic efficiency. On the other hand, if the value exceeds 55% (w / w), the only effect is increased technical efforts to ensure the stability of the coating color curtain during the coating process and drying of the applied film, since in this case the machine again has to run very fast.

[0155] In the curtain coating process, a free-falling curtain of coating dispersion is formed. The coating dispersion in the form of a thin film (curtain) is "poured" onto a substrate by free fall to apply the coating dispersion to the substrate. German Patent No. 10196052 discloses the use of the curtain coating process in the production of information recording materials, whereby a curtain of several coating dispersion films is applied to a substrate to achieve multiple recording layers.

[0156] In a preferred embodiment of the process according to the invention, the aqueous deaerated coating suspension has a viscosity (Brookfield, 100 rpm, 20°C) of about 100 to about 400 mPas. Values ​​below about 80 mPas or above about 500 mPas result in insufficient runnability of the coating mass in the coating equipment. Particularly preferably, the viscosity of the aqueous deaerated coating suspension is about 150 to about 300 mPas.

[0157] In a preferred embodiment, the dynamic surface tension of the aqueous coating suspension can be adjusted to about 35 to about 55 mN / m, preferably about 38 to about 52 mN / m (measured 50 ms after bubble formation) according to the standard for bubble pressure tensiometry (ASTM D 3825-90) as described below to optimize the process. Better control of the coating process can be achieved by determining the dynamic surface tension of the coating color and adjusting it by selecting an appropriate surfactant and determining the required amount of surfactant.

[0158] The individual coatings can be produced online on a paper machine equipped with a coating device, or offline on a coating machine in a separate coating process. For development purposes and for producing prototypes, paper can also be produced on a laboratory scale by squeegeeing and subsequent drying in a drying cabinet. Drying can be carried out in a similar manner to the temperature treatment described above, for example, for 3 minutes at 90°C in a drying cabinet. Temperatures higher than 100°C, preferably 105°C, can also be set, as this slower drying process has less risk of forming boiling bubbles.

[0159] In another embodiment, the individual coating color layers can also be applied to the base paper using the following process:

[0160] The coating color layer can be applied to the base paper using printing processes (eg, flexographic and gravure printing) and / or to an already existing coating color layer.

[0161] The coating color layer can be applied dry as a melt by extrusion to the base paper and / or to an already existing coating color layer.

[0162] This technique has the advantage that significantly more material can be applied, but this is only of interest if the entire product does not need to be recyclable as paper. The disadvantages are a lower application speed, higher energy consumption and a higher minimum application weight.

[0163] The coating color layer can be applied, for example, by stacking or backing the paper in the form of a plastic film onto the base paper and / or existing coating color.

[0164] The coating color layers can also be applied one after the other in several application steps.

[0165] The present invention further relates to a barrier paper obtainable by the above process.

[0166] Finally, the present invention also relates to the use of the above-mentioned barrier paper as a packaging material or as a component of a packaging material, in particular a heat-sealable packaging material, for sealing flexible packaging materials, preferably by applying a cold seal lacquer or other medium for packaging foodstuffs, in particular fatty and moisture-sensitive foods, luxury foods, such as tobacco, coffee, tea, medicinal herbs, as well as household products, cosmetics and other moisture-sensitive consumer goods, such as washing powders, coffee pads, sanitary napkins, diapers and handkerchiefs, to protect them from mineral oil vapours from the environment.

[0167] The barrier paper according to the invention can be used in all standard packaging machines, such as vertical and horizontal form-fill-seal machines for the production of stand-up pouches, flow packs or pillow packaging, bubble bags or cushions as a replacement for plastic air pillow bags or cushions, machines that join two webs of the same or different material together and join them by heat sealing, such as tray sealers, chamber belt machines (also with vacuum), pouch filling and sealing machines, thermoforming packaging machines, linear filling machines that apply lids by heat sealing for sealing, wrapping machines with a finishing heat sealing step, blister packaging machines, and X-fold packaging machines.

[0168] In a further preferred embodiment of the invention, the paper coated according to the invention is attached to cardboard or cardboard, in particular by lining, laminating or bonding.

[0169] The present invention further relates to packaging materials, especially heat-sealable packaging materials, consisting of or comprising the barrier paper described above.

[0170] The invention will now be described in more detail with reference to the following non-limiting examples. [Example]

[0171] Base paper from the production line was used in Comparative Examples 1-3 and Examples 1-5.

[0172] Pure base paper was produced on an associated paper machine (38% (w / w) long fiber, 57% (w / w) short fiber, 5% (w / w) calcium carbonate filler, alkyl ketene dimer, fully sized, and had a water Cobb value of 25 g / m 2 ), smoothed using a smoothing device, and coated on both sides with enzymatically partially degraded and cationically modified potato starch (approximately 1 g / m 2 ) was applied using a film press.

[0173] The paper machine is equipped with Yankee cylinders and is therefore capable of producing paper that is smooth on one side.

[0174] In a second step, the paper was coated with a coating color layer S3 in a production coater, using a blade coater on the non-smooth side, which was the side facing away from the smoothing cylinder during the smoothing process (Comparative Examples 1-3 and Examples 1-3).

[0175] In Examples 4 and 5, the coating color S3 was applied in two steps. 2 is already applied online to the non-smooth side of the paper machine, and an additional 4 g / m 2 was directly applied using a blade coater in the same manner as in the previous Examples and Comparative Examples.

[0176] In Comparative Examples 1, 2 and 3, the coating color layer S2 and then the coating color layer S1 directly onto the coating color layer S2 were applied separately in a pilot coating system using a curtain coater in a separate coating test.

[0177] In Comparative Example 1a and Examples 4 and 5, the coating color layer S1 was applied directly to the coating color layer S3 in the same manner.

[0178] The drying equipment consists of a series of electric infrared dryers followed by a block of air hoods (hot air drying).

[0179] Information regarding the length of the drying section, the web temperature at the paper surface and the residence time in each drying zone can be found in Tables 1 and 2a, the production parameters being only for the application of the coating color layer S1.

[0180] Examples 1, 2, and 3 were also made on a production coating machine using a curtain coater. Again, the drying equipment consisted of a block of infrared dryers, this time powered by natural gas, followed by a block of air hoods. Example 2 did not contain coating color layer S2. Coating color layer S1 was applied directly to coating color layer S3. However, Examples 1 and 3 again contained coating color layer S2.

[0181] Information about the length of the drying section, the web temperature at the paper surface, and the residence time in each drying zone can be seen in Table 2, where the only production parameters are those related to the installation of coating color layer S1. Since less drying of coating color layer S2 is required, there is no difference between the mineral oil and fat barriers produced on a pilot or production coating line.

[0182] Preparation of Coating Color S1 (Comparative Examples 1-3 and Examples 1-3) (Formulations from a Pilot Plant Scaled Up to the Same as a Production Plant) Aqueous coating suspensions with 20-60% solids: 38.1 kg of water was prepared and mixed with 452.8 kg of 97.8% (w / w) styrene acrylate / methyl acrylate / butyl acrylate / ethylhexyl acrylate and 2.0% (w / w) beeswax, or 91.82% (w / w) styrene acrylate / methyl acrylate / butyl acrylate / ethylhexyl acrylate and 8.0% (w / w) beeswax in the case of Comparative Example 3. Then, 0.523 kg of the extensional rheology aid Sterocoll DF 4 (BASF SE, polyacrylamide, W / O emulsion) and 0.188 kg of the defoamer Genapol PF 10 (Clariant Produkte (Germany) GmbH, polymerization product of propylene oxide and ethylene oxide) were added as additives. This resulted in a pH of approximately 8.5 and a Brookfield viscosity of approximately 160 mPas.

[0183] Preparation of Coating Color S1 (Examples 4 and 5): Aqueous coating suspensions with 20-60% solids: 16 kg of water was prepared and mixed with 267 kg of an aqueous suspension consisting of 90 parts of a carboxylated styrene-butadiene polymer and 10 parts of paraffin wax with a chain length of C21-C38. Then, 6.5 kg of a solution of polyvinyl alcohol type 8-88 and 15.6 kg of polyvinyl alcohol type 28-99 were added as thickeners. Then, 0.2 kg of the extension rheological aid Sterocoll DF 4 (BASF SE, polyacrylamide, W / O emulsion) and 0.7 kg of the defoamer Genapol PF 10 (Clariant Produkte (Germany) GmbH, polymerization product of propylene oxide and ethylene oxide) were added as additives. The surfactant added was 1.7 kg of Dynawet 2050 (CTP GmbH), a nonionic surfactant formulation with CAS-#160875-66-1, as the main active ingredient. This resulted in a viscosity of 230 mPas and a pH of 6.5.

[0184] Preparation of Coating Color S2: (Formulation from pilot plant scaled up exactly like production plant).

[0185] 77 kg of water is prepared and mixed with 228.6 kg of Epotal SP 101 D (BASF SE, polyacrylate with starch-based protective colloid). 0.957 kg of thickener Texturecel 100 GA (DDP Specialty Products Germany GmbH, carboxymethylcellulose), 0.081 kg of extension rheological aid Sterocoll DF 4, and 0.210 kg of antifoaming agent Genapol PF 10 are then mixed in as additives. A pH value of 8.8 is set by adding sodium hydroxide solution to obtain a viscosity (Brookfield) of approximately 200 mPas.

[0186] Both coating colors are suitable for curtain coaters and are degassed by vacuum in the working vessel of the coater before coating.

[0187] Creating Coating Color S3: The compositions are shown in Table 1: those skilled in the art are sufficient to prepare a coating mass that can be applied to these specifications.

[0188] The composition of each coating color layer, drying parameters and determined properties of the barrier paper are summarized in Table 1 below.

[0189] Description of measurement methods for which no standard is known or for which we have developed our own method:

[0190] Heat sealability: Although tests for the seal seam strength of existing seal seams are clearly defined by e.g. DIN 55529: 2012-09, there are no standardized methods for testing the suitability of materials for heat sealing. This is apparently due to the fact that packagers prefer to develop their own acceptance tests for heat-sealable films or papers that are adapted to their packaging systems.

[0191] Based on industry sector information, relatively critical sealing conditions were applied (sealing time 0.3 s, sealing pressure 3.33 bar, smooth sealing jaws). The sealing ability is tested by sealing two sealable coatings of paper against each other. To determine the optimum sealing temperature, test specimens are made that are sealed at different temperatures of the sealing jaws (100-200°C).

[0192] Hot tack (high temperature seam strength): carried out according to DIN 55571-2 method C. It should also be noted that the same sealing conditions as for the heat sealability test apply. A cooling time of 80 ms was selected between sealing and force measurement. The force is measured over a pull length of 80 mm.

[0193] Palm kernel fat test according to DIN 53116: Test condition I (pressure 2000 N / m 2 and exposure time >24 hours (actually 25 hours). 2 The printed side of Koehler Paper SE's C1S paper is used as the display paper.

[0194] Palm kernel fat test on wrinkled paper: For folded samples, a 180° fold is made with a roller that applies a load of 330 g / cm to the resulting fold, where the coating can be inside (internal fold) or outside (external fold).

[0195] Hexane Vapor Transmission Rate (HVTR): Here, n-hexane is filled into a beaker (solvent resistant), tightly sealed with a test specimen, and the weight loss is followed over time. The test is performed at 23°C and 50% humidity. The coated side faces inwards towards the hexane vapor atmosphere. Suitable cups with PTFE seals are available from specialist retailers.

[0196] Determination of water vapor permeability according to ISO / FDIS 2528: It should be noted that here too the coated side of the test specimen faces the desiccant.

[0197] Dependence of the water vapor permeability of a coating on fat contact: The test specimens are first subjected to a palm kernel fat test in accordance with DIN 53116 2003-02. The corresponding test conditions are specified. At the end of the exposure time, after wiping off the fat, the water vapor transmission rate (WVTR) of the paper is determined in accordance with ISO / FDIS 2528. After wiping off the fat (which contains red dye as standard), a certain amount remains in or on the water vapor barrier coating. However, since a certain water vapor permeability is established during the measurement, this does not cause any further changes in the WVTR.

[0198] Determining the dynamic surface tension of a dried paper coating is described herein.

[0199] Notes on Tables 1, 2 and 2a: * The columns marked contain measurements of the paper shown on the left after 3 minutes at 105°C in a hot air drying oven. A binder type E 115 drying oven with the following internal dimensions W x H x D was used: 60 x 48 x 40 cm (internal volume 115 dm 3 ), drying oven temperature range: 0-250°C, natural convection, no circulating air fan). Inside the oven, there is a metal grid at mid-height, on top of which is a cardboard approximately 2 mm thick. The oven is preheated to 105°C for at least 30 minutes. The door is opened briefly (less than 2 seconds) and the test specimens are placed on the cardboard. After 3 minutes, the specimens are removed and conditioned for at least 12 hours at 23°C and 50% rh before further measurements are made.

[0200] [Table 1] TIFF2025529254000002.tif248152TIFF2025529254000003.tif248150TIFF20255292540 00004.tif248149TIFF2025529254000005.tif249146TIFF2025529254000006.tif249148

[0201] [Table 2] TIFF2025529254000008.tif249150TIFF2025529254000009.tif248151TIFF2025529254000010.tif24915 0TIFF2025529254000011.tif249152TIFF2025529254000012.tif249150TIFF2025529254000013.tif24958

[0202] [Table 2a] TIFF2025529254000015.tif207164TIFF2025529254000016.tif205160TIFF2025529254000017.tif206121

[0203] Example 2: (Example 2 in Table 1) Another heat-sealable paper according to the present invention with a water vapor barrier for flexible packaging was tested.

[0204] The paper is suitable for a variety of applications as secondary and primary packaging, especially for products in the food and non-food sector that require a water vapor barrier.

[0205] The advantages of this paper are: - No optical brighteners - Water vapor barrier for optimal product protection - Good sealing properties - Outstanding strength properties - Suitable for direct food contact - 100% virgin fiber pulp - Very good runnability in converting and packaging systems - Recyclable in the paper cycle - Particularly suitable for flexographic, gravure and digital printing is.

[0206] The properties of this paper are summarized in Table 3 below.

[0207] [Table 3]

[0208] Example 3: (Example 1 in Table 1) Another heat-sealable paper according to the present invention made from virgin fiber pulp with a barrier to water vapor, fat and mineral oil residues was tested.

[0209] The paper is suitable for a variety of uses in the tobacco industry, particularly for refined tobacco products.

[0210] The advantages of this paper are: - High degree of whiteness - No optical brighteners - Smooth surface - Good sealing properties - Very good odor barrier - High resistance to buckling failure - Outstanding strength properties - Suitable for direct food contact - 100% virgin fiber pulp - Outstanding print and lacquer holdout - Very good running properties in converting and packaging systems - Particularly suitable for flexographic and gravure printing is.

[0211] The properties of this paper are summarized in Table 4 below.

[0212] [Table 4]

[0213] Example 4: (Example 1 in Table 1) Another heat-sealable paper according to the present invention with a water vapor barrier for flexible packaging was tested.

[0214] The paper is suitable for a variety of uses as secondary and primary packaging for tobacco products such as tobacco volume pouches with barrier, tobacco pouches and coated tobacco innerliners.

[0215] The advantages of this paper are: - No optical brighteners - Water vapor barrier for optimal product protection - Good sealing properties - Outstanding strength properties - Suitable for direct food contact - 100% virgin fiber pulp - Very good running properties in converting and packaging systems - Recyclable in the paper cycle - Particularly suitable for flexographic and gravure printing is.

[0216] The properties of this paper are summarized in Table 5 below.

[0217] [Table 5]

[0218] Example 5: (Example 1 in Table 1) Another fat-resistant, heat-sealable paper according to the present invention made from virgin fiber pulp with water vapor and mineral oil barrier properties was tested.

[0219] The paper is suitable for a variety of applications in flexible packaging for dry and powdered products in the food and non-food sectors.

[0220] The advantages of this paper are: - High degree of whiteness - No optical brighteners - Smooth surface - Good sealing properties - High resistance to buckling failure - Outstanding strength properties - Suitable for direct food contact - 100% virgin fiber pulp - Outstanding print and lacquer holdout - Very good running properties in converting and packaging systems - Particularly suitable for flexographic, gravure and digital printing is.

[0221] The properties of this paper are summarized in Table 6 below.

[0222] [Table 6]

Claims

1. A barrier paper comprising a base paper and at least one coating color layer S1 directly or indirectly applied to the base paper, wherein the coating color layer S1 comprises at least one polymer binder and at least one wax, and the coating color layer S1 has the following characteristics: a) Surface tension change of +10 mN / m or less, preferably +6 mN / m or less. b) Change in the polarity component of the surface tension of -0.65 mN / m or less, preferably -0.60 mN / m or less, c) Change in the polarity component of the surface tension to -3.0% pts or less, preferably -1.5% pts or less. Having at least one of the following, Each change is determined by measuring the surface tension of the barrier paper before and after a temperature treatment at 105°C for 3 minutes, and comparing the measured surface tension with the polarity component of the surface tension. Barrier paper.

2. The wax content of the coating color layer S1 is such that the barrier paper has the following characteristics: a) Heat seal parameters of a seal temperature of 130-150°C, a seal time of 0.3 seconds, and a seal pressure of 3.3 bar, or ultrasonic seal parameters that produce a seal temperature of 130-150°C, a seal time of 0.3 seconds, and a seal pressure of 3.3 bar, wherein the seal joint strength (cold tack) of the coating color layer S1 after sealing is 4 N / 15 mm or more. b) Water vapor transmission rate (WVTR) ≤ 20 g / m ２ / d (38°C, 90% r.h.), c) Water vapor transmission rate (WVTR) ≤ 8 g / m ２ / d (23°C, 50% r.h.), d) Test conditions (exposure time of 10 minutes and 2000 N / m) ２ After performing a palm kernel fat test according to DIN 53116 under pressure load, 70 g / m² ２ / d or less, preferably 60 g / m ２ Increase in water vapor permeability (38°C, 90% r.h.) of d or less. e) Test conditions (60 minutes of exposure time and 2000 N / m) ２ After performing the palm kernel lipid test according to DIN 53116, the increase in water vapor permeability by a factor of 6 or less was observed. f) Static friction coefficient less than 0.9 (coating color layer S1 relative to coating color layer S1), g) Dynamic friction coefficient less than 0.6 (Coating color layer S1 relative to coating color layer S1) Selected to have at least one of the following values, where the value for a) to g) is 12 g / m ２ The barrier paper according to claim 1, determined with respect to the basis weight of the coating color layer S1 as follows.

3. The barrier paper according to claim 2, characterized in that the water vapor permeability (38°C, 90% RH) has a change of at most -40%, preferably less than -30%, and the change is determined by measuring the water vapor permeability of the barrier paper before and after a temperature treatment of 105°C for 3 minutes and comparing the measured values.

4. The barrier paper according to claim 1, wherein the wax is a wax defined by DGF (DGF standard method M-I 1(75)).

5. The waxes mentioned above include at least one wax based on fossil or natural short-to-medium chain hydrocarbons, their acids, esters, amides and diamides, mixtures of hydrogenated vegetable oils or pure substances; waxes and / or metal soaps produced by hydrogenation or partial hydrogenation of vegetable oils and animal oils or fats, preferably hen-eikosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, triacontane, hen-triacontane, do-triacontane, tri-triacontane, tetra-triacontane. The barrier paper according to claim 1, wherein the wax is contane, pentatriacontane, hexatriacontane, heptatriacontane, octatricontane, nonatriacontane, montane wax, carnauba wax, beeswax, candelilla wax, rice wax, sugarcane wax, wax obtained from sunflower seed press cake, particularly preferably beeswax and / or wax obtained by hydrogenation of soybean oil, and / or paraffin wax having an average molecular weight of at least 500 daltons and a viscosity of at least 11 cSt at 100°C.

6. The barrier paper according to claim 1, wherein the at least one wax is present in an amount of 0.01 to 10% (w / w), preferably 0.01% (w / w) to less than 8.0% (w / w), preferably 0.01% (w / w) to less than 6.0% (w / w), more preferably 0.01% (w / w) to less than 5.0% (w / w), most preferably 0.01% (w / w) to 2.0% (w / w), and preferably the lower limit is at least 0.1% (w / w) of the total weight of the coating color layer S1, and particularly preferably at least 0.2% (w / w).

7. The at least one polymer binder in the coating color layer S1 is a copolymer of polyacrylate and unsaturated hydrocarbon; polyolefin; copolymer of unsaturated hydrocarbon and acrylic acid or a salt thereof; (partially carboxylated) styrene-butadiene copolymer; styrene-butadiene copolymer; styrene-butadiene; polyvinyl acetate; partially saponified polyvinyl acetate; polyester, e.g., polylactide; and polyhydroxyalkanoate (derived from glucose). Barrier paper according to claim 1, selected from the group comprising polyamides; polyurethanes; polyethers; polyethyleneimines; and / or polyvinylamides; preferably polymethyl acrylate, polymethyl methacrylate, polyethyl arylate, polyethyl methacrylate, poly(n-,iso-,tert.-)butyl acrylate, poly(n-,iso-,tert.-)butyl methacrylate, polycyclohexyl methacrylate, polyethylhexyl acrylate and copolymers thereof; graft polymers, and copolymers thereof with styrene, acrylonitrile, methylstyrene, and / or vinyltoluene; particularly preferably styrene-acrylic acid-methyl acrylate-butyl acrylate-ethylhexyl acrylate copolymer, and / or natural polymers, e.g., (modified) polysaccharides, proteins, lignin (derivatives), and other natural macromolecules such as shellac.

8. The barrier paper according to claim 1, wherein the at least one polymer binder is present in the coating color layer S1 in an amount of 99.9% (w / w) to more than 92% (w / w), preferably more than 94% (w / w), more preferably more than 95% (w / w), and most preferably more than 98% (w / w), based on its total weight.

9. The barrier paper according to claim 1, wherein at least one type of wax is enriched in the coating color layer S1 on the side away from the base paper, which is indirectly detected by the fact that the change in the polarity component of the surface tension does not exceed -0.65 mN / m and / or the change in the polarity component of the surface tension does not exceed -3.0% pts, and each change is determined by measuring the polarity component of the surface tension before and after a temperature treatment of the barrier paper at 105°C for 3 minutes and comparing the measured values.

10. The base paper has a grammage of 20 to 120 g / m ２ , preferably 40 to 100 g / m ２ , wherein the barrier paper according to claim 1.

11. The barrier paper according to claim 1, wherein the base paper has a long fiber content of 10-80% (w / w), preferably 20-50% (w / w), and a short fiber content of 20-90% (w / w), preferably 50-80% (w / w), wherein the long fibers are fibers with a fiber length of 2.6-4.4 mm, and the short fibers are fibers with a fiber length of 0.7-2.2 mm.

12. The barrier paper according to claim 1, wherein the base paper contains a filler with a filler content of 0% (w / w) to 20% (w / w), preferably 0% (w / w) to 5% (w / w), preferably excluding the value of 0% (w / w), and the filler particularly contains heavy calcium carbonate (GCC), precipitated calcium carbonate (PCC), kaolin and / or talc.

13. The barrier paper according to claim 1, wherein the barrier paper includes at least one further coating color layer S2 directly or indirectly attached between the base paper and the coating color layer S1 for forming a mineral oil and / or fat barrier layer and / or oxygen barrier layer, particularly containing at least one hydrophilic polymer.

14. The barrier paper according to claim 1, wherein the coating color layer S3 further comprises at least one inorganic pigment and a polymer binder, or a coating color layer consisting of these is directly present on the base paper.

15. A method for producing barrier paper according to claim 1, characterized in that an aqueous suspension containing the starting material of the coating color layer S1 is indirectly or directly applied to the base paper, the aqueous coating suspension having a solid content of 15 to 55% (w / w), preferably 20 to 45% (w / w), is applied by a curtain coating process at a coating machine operating speed of at least 100 m / min, is then dried, the drying is preferably carried out in the area of ​​a subsequent air hood using infrared or thermal radiation, and the web temperature remains below 90°C in the entire drying area.

16. Barrier paper that can be obtained by the method described in claim 15.

17. Use of the barrier paper according to claim 1 or 16, preferably as a packaging material or as a component of a packaging material, particularly as a component of a heat-sealable packaging material, for food products, in particular for packaging fatty and moisture-sensitive food products and protecting them from mineral oil vapors from the environment.

18. A packaging material, particularly a heat-sealable packaging material, comprising or including the barrier paper described in claim 1 or claim 16.