Coated paper

Abstract

Described is a coated paper comprising a base paper and at least three coatings applied thereto, the at least three coatings comprising, in that order, proceeding from the base paper, a first barrier layer comprising at least one hydrophobic polymer, a second barrier layer comprising at least one hydrophilic polymer, and a third barrier layer comprising at least one hydrophobic polymer, a method for producing such a coated paper, and the use of the coated paper as a packaging material.

Description

[Technical field]

[0001] The present invention relates to a coated paper, to a method for producing this type of coated paper, and to the use of the coated paper as packaging material. [Background technology]

[0002] Packaging generally refers to the covering or (partial or complete) encasement of an object, especially for its protection or better handling. Packaging material therefore includes materials forming such packaging.

[0003] The packaging material may be constructed, for example, based on paper, plastic and / or metal.The present invention relates to a packaging material based on paper.

[0004] Packaging materials based on paper are known. However, up to now, no fiber-based / paper-based flexible packaging materials are known that are suitable for packaging oxidation-sensitive, moisture-rich, and fat-containing objects, especially food products, and at the same time do not contain a barrier layer made of halogen-containing compounds or aluminum, Al2O3, and / or SiO2, which must be applied outside the paper coating machine by lamination or vapor deposition.

[0005] The use of aluminum and / or Al2O3 is particularly disadvantageous because the recovery of aluminum is resource and energy intensive, even for Al2O3 coatings. The production of aluminum releases roughly 3-5 times more carbon dioxide per tonne compared to the production of plastics, e.g. polyethylene. Al 3+ Aluminum is increasingly being criticized as a packaging material, especially for moist and acid-containing foods, since salts can dissolve in it. In addition, recovery of aluminum from barrier papers involves additional efforts: such papers must, for example, be boiled for some time in water under pressure at 120 °C to separate the paper fibers from the metal.

[0006] In particular, the use of SiO2 is disadvantageous, since, depending on the required purity, SiO2 can only be obtained from quartz quarries and not from "sand". Moreover, application processes (chemical vapor deposition) must be used here, which presuppose slow machine operation and imply additional cost expenditure.

[0007] Both SiO2 and Al2O3 coatings may have disadvantages with respect to resistance to bending.

[0008] The use of halogenated compounds, such as halogenated hydrocarbons, is particularly disadvantageous because they are very stable with respect to biodegradation due to their hydrophobic nature. Sunlight or other weathering influences have little effect on these compounds. The combustion process produces corrosive hydrogen halides and dioxins in addition to the usual by-products of the thermal utilization of plastics.

[0009] Known packaging materials often contain compounds such as polyvinylidene chloride (PVDC; halogen-containing), have tear strengths that leave room for improvement, which can lead to operational problems in packaging plants, and are not recyclable through the paper fiber stream due to excessively high coating content. Furthermore, known packaging materials have excessively high permeability to water, water vapor, oxygen and grease, thus leading to a short shelf life of the packaged products. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] DE10196052T1 Summary of the Invention [Problem to be solved by the invention]

[0011] The object of the present invention is to overcome the disadvantages of known materials and to provide a material suitable as a packaging material, especially for oxidation-sensitive, moist and fatty foods, and which can be used for the production of pouches by heat sealing application. Furthermore, the material should not contain any barrier layers based on halogen-containing compounds, aluminum, Al2O3 and / or SiO2. In addition, as far as possible, there should be no adhesion promoters used between the individual layers of the material. Furthermore, the material according to the present invention should be as easy to produce as possible and require the lowest possible application weight so that it can be recycled via the paper fiber stream. [Means for solving the problem]

[0012] This object is achieved by a coated paper according to claim 1, i.e. a coated paper comprising a base paper and at least three coatings applied thereto, the at least three coatings comprising, in that order proceeding from the base paper, a first barrier layer comprising at least one hydrophobic polymer, a second barrier layer comprising at least one hydrophilic polymer and a third barrier layer comprising at least one hydrophobic polymer.

[0013] The papers coated in this way are distinguished in that they are particularly well suited as packaging materials for oxidation-sensitive, moist and fatty objects, in particular foodstuffs, and can be used for the production of pouches in which heat sealing is applied. Furthermore, it is possible to dispense with adhesion promoters between the individual layers, and barrier layers based on halogen-containing compounds, aluminum, Al2O3 and / or SiO2 must not be present.

[0014] This type of coated paper can also be produced relatively easily and at low application weights. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the term "comprise" shall also mean "consist of".

[0016] The term "hydrophobic" refers to a material that cannot be mixed with water or can only be wetted by water with the use of a surfactant. The term "hydrophilic" refers to a material that can be mixed with water or can be wetted by water without the use of a surfactant. Hydrophobic polymers are also called non-polar polymers and hydrophilic polymers are also called polar polymers.

[0017] Hydrophobicity or hydrophilicity can be defined, for example, by the logP value. ow (also commonly and correctly written as n-octanol / water partition coefficient) is a dimensionless partition coefficient known to those skilled in the art that indicates the ratio of the concentrations of a chemical substance in a two-phase system formed by n-octanol and water and is therefore a measure of the hydrophobicity or hydrophilicity of a substance. The logP value is the n-octanol-water partition coefficient K ow The following applies here:

[0018]

number

[0019] K ow is greater than 1 if a substance is more soluble in a fat-like solvent, such as n-octanol, and less than 1 if the substance is more soluble in water. Thus, logP is positive for hydrophilic / lipophilic substances and negative for hydrophilic / lipophobic substances.

[0020] The base paper used in the coated paper according to the invention is in principle not limited.

[0021] Preferred embodiments of the present invention are described below.

[0022] 1. A coated paper, the first barrier layer of which comprises or consists of a material selected from the group consisting of lipophilic substances, paraffins, in particular hard paraffins, waxes, in particular microcrystalline waxes, waxes based on vegetable oils or fats, waxes based on animal oils or fats, vegetable waxes, animal waxes, low molecular weight polyolefins, polyterpenes, and mixtures thereof.

[0023] A coated paper in which migration of materials, particularly hydrophobic materials, is reduced or prevented by a second barrier layer.

[0024] A coated paper in which migration of substances, particularly hydrophobic substances, from or through a first barrier layer into or across a third barrier layer is reduced or prevented.

[0025] A coated paper in which migration of substances, particularly hydrophobic substances, from or through the third barrier layer into the first barrier layer is prevented.

[0026] A coated paper in which the migration of substances selected from the group consisting of lipophilic substances, paraffins, particularly hard paraffins, waxes, particularly microcrystalline waxes, waxes based on vegetable oils or fats, waxes based on animal oils or fats, vegetable waxes, animal waxes, low molecular weight polyolefins, polyterpenes, and mixtures thereof, is reduced or prevented.

[0027] Migration of these substances can be reduced or prevented, inter alia, by a suitable type and amount of at least one hydrophilic polymer in the second barrier.

[0028] The coated paper, wherein the third barrier layer does not contain any substance that is not permitted to come into direct contact with food, except for unavoidable or tolerated impurities, in particular substances selected from the group consisting of lipophilic substances, paraffin, in particular hard paraffin, wax, in particular microcrystalline wax, wax based on vegetable oils or fats, wax based on animal oils or fats, vegetable waxes, animal waxes, low molecular weight polyolefins, polyterpenes, and mixtures thereof.

[0029] Hard paraffins, in particular hard paraffins of natural or synthetic origin, microcrystalline waxes, low molecular weight polypropylenes, natural waxes, low molecular weight polyolefins, polyterpenes and mixtures thereof are in particular those defined in BfR XXV of 01 June 2019 (German Federal Institute for Risk Assessment (under the portfolio of the Federal Ministry of Food and Agriculture)) or in its various versions.

[0030] Thus, the following is prevented: a) migration of these materials into the third barrier layer and / or outward migration from the third barrier layer, in particular into a contact material, in particular a contact material that has come into contact with a fat-containing food, and b) as a result of the reduction or prevention of the migration of these substances, the barrier properties of the layers, in particular of the first, second and / or third barrier layer, are maintained or are otherwise altered or completely lost as a result of the migration, and c) substances migrating from the contact material into the first barrier layer and / or thus modifying the first barrier layer.

[0031] Base paper: 20~120g / m 2 , preferably 40 to 100 g / m 2 It is preferred that the surface area density of the first and second electrodes is 0.1 to 0.5 μm.

[0032] The paper has a long fiber content of 10-80%, preferably 20-50%, and weight %, preferably 50 to 80 weight % short fiber content.

[0033] Long fibres are understood to mean fibres having a fibre length of 2.6 to 4.4 mm, short fibres are understood to mean fibres having a fibre length of 0.7 to 2.2 mm.

[0034] In addition, 0 to 20%, preferably 0 to 5%, of fillers such as GCC (ground (ground) calcium carbonate), known, for example, under the trade name Hydrocarb 60 or Hydrolex 60, PCC (precipitated calcium carbonate), known, for example, under the trade name Precarb 105, natural kaolin and / or talc, as well as retention and / or sizing agents, may additionally be included.

[0035] As used herein, the term "base paper" shall be understood to exclude cardboard and paperboard materials.

[0036] The advantages of such a base paper are, on the one hand, its high flexibility and, on the other hand, its good processing in existing packaging plants, maintaining high machine availability and achieving the required puncture resistance.

[0037] Common packaging machines are, e.g., vertical and horizontal form-fill-seal machines for the production of stand-up pouches, flow packs, pillow packs, and others, machines that bring together two webs of the same or different material and join them by heat sealing, also called tray sealers, chamber belt machines (also using vacuum), pouch fill and seal machines, thermoforming packaging machines, linear filling machines that apply the lid by heat sealing to seal the package, wrapping machines with a final heat sealing step, blister packing machines, and X-fold packaging machines.

[0038] The first barrier layer comprises at least one hydrophobic polymer. This barrier layer preferably acts as a water vapor barrier layer, thus protecting the packaged product from drying out. In the case of dry package contents, they are protected from moisture. In addition, it serves to protect the hydrophilic barrier from moisture from the outside, because this can only have its maximum effect in a dry state.

[0039] The at least one hydrophobic polymer preferably comprises a polyacrylate and / or a polyolefin, a styrene-butadiene copolymer, a polyvinyl acetate (also partially saponified), a polyester, a polyamide, a polyurethane, a polyether, a polyethyleneimine, and / or a polymer based on polyvinylamide. Examples of suitable polymers are, in particular, poly(methyl acrylate), poly(methyl methacrylate), poly(ethyl acrylate), poly(ethyl methacrylate), poly(n-, iso-, tert.-)butyl acrylate, poly(n-, iso-, tert.-)butyl methacrylate, poly(cyclohexyl methacrylate), polyethylhexyl acrylate and their copolymers, graft polymers, and copolymers with styrene, acrylonitrile, methylstyrene or vinyltoluene.

[0040] In addition to the hydrophobic polymer, waxes may be provided. Suitable waxes include compounds such as fossil or natural short- to medium-chain hydrocarbons, their acids, esters, amides and diamides, mixtures or pure substances, colloquially referred to as "waxes". Suitable waxes are, for example, heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, triacontane, hentriacontane, dotriacontane, tritriacontane, tetratriacontane, pentatriacontane, hexatriacontane, heptatriacontane, octatriacontane, nonatriacontane; montan wax, natural waxes (carnauba wax, beeswax, candelilla wax), waxes produced by hydrogenation or partial hydrogenation of vegetable and animal oils or fats, and metal soaps, such as Ca stearate.

[0041] Suitable polymers and polymer / wax mixtures are known, in particular, under the trade names CHT Coat 230, Vapor Coat 2200, Vapor Coat 1300, BimBA 8510, BimBA 8888, Cartaseal VWF, Cartaseal SWF, Sealcoat SL251, Rhobarr 320, B-Coat SP1, B-Coat WB 100, B-Coat 50 / 3, Chemipearl S300, Ultraseal W-951, Ultraseal W-952, Ukaphob HR 530, Induprint SE 2555, Wukoseal (u with an umlaut) 630, Extomine BG-EM 52%, EurikaCoat 3624, Aquacer 1061 and Epotal SP 106.

[0042] The at least one hydrophobic polymer is preferably 1 to 100% by weight based on the total weight of the first barrier layer. weight %, particularly preferably 50 to 99.5 weight %, or 50-100 weight % in the first barrier layer.

[0043] The first barrier layer as a whole is preferably hydrophobic.

[0044] The first barrier layer may include additives such as thickeners, e.g., acrylate-based thickeners, surfactants, e.g., sulfosuccinates, extensional rheology aids, e.g., polyacrylamides, carboxymethylcellulose, polyvinyl alcohols, and / or aldehydes and polyaldehydes, crosslinkers, zirconates, polyepoxides, epichlorohydrin resins, and / or hydroacids.

[0045] These additives are preferably present in an amount of from 0.1 to 1% by weight relative to the total weight of the first barrier layer in each case. weight Contains in an amount of %.

[0046] The application amount of the first barrier layer is preferably 1 to 20 g / m 2, and particularly preferably 5 to 10 g / m 2 The amounts refer to the dry first barrier layer in the final product.

[0047] The second barrier layer comprises at least one hydrophilic polymer, which preferably acts as an oxygen barrier layer, thus protecting the packaged product from oxidation.

[0048] The hydrophilic polymer preferably comprises a polymer based on polyvinyl alcohol. Examples of suitable polymers are, in particular, polymers based on vinyl alcohol or copolymers of ethylene and vinyl alcohol.

[0049] Suitable polymers are known especially under the trade names Exceval AQ 4104, Exceval HR 3010, Sealcoat HS 25 and MichemFlexB 1001.

[0050] The at least one hydrophilic polymer is preferably 1 to 100% by weight based on the total weight of the second barrier layer. weight %, particularly preferably 50 to 99.5 weight %, or 50-100 weight % in the second barrier layer.

[0051] The second barrier layer as a whole is preferably hydrophilic.

[0052] The second barrier layer may include additives such as thickeners, e.g., acrylate-based thickeners, surfactants, e.g., sulfosuccinates, extensional rheology aids, and / or aldehydes and polyaldehydes, crosslinkers, zirconates, polyepoxides, epichlorohydrin resins, and / or hydroacids.

[0053] These additives are preferably present in an amount of from 0.1 to 1% by weight relative to the total weight of the second barrier layer in each case. weight Contains in an amount of %.

[0054] The application amount of the second barrier layer is preferably 1 to 20 g / m 2 , particularly preferably 1 to 10 g / m 2 The amounts refer to the dry second barrier layer in the final product.

[0055] The third barrier layer comprises at least one hydrophobic polymer. This barrier layer preferably acts as a water vapor barrier layer, thus protecting the packaged product from drying out. In the case of dry package contents, they are protected from moisture. In addition, it helps to protect the hydrophilic barrier from moisture from the inside, because this can only have its maximum effect in a dry state.

[0056] The at least one hydrophobic polymer contained within the third barrier layer is preferably a thermoplastic polymer, and therefore the layer is heat-sealable.

[0057] The coated paper according to the invention is therefore characterised in a further preferred embodiment in that the third barrier layer is heat-sealable.To this end, the third barrier layer preferably comprises at least one thermoplastic polymer.

[0058] The coated paper according to the present invention preferably has a seal seam strength of 1.5N / 15mm to 10N / 15mm, where the seal seam strength of the coated paper was determined as follows.

[0059] The coated papers were sealed transversely to the direction of the paper web at 3.3 bar for 0.3 s in the temperature range of 100°C to 200°C, and the seal seam strength was determined according to DIN 55529 (2012).

[0060] The term "heat sealing" is understood to mean the joining of two layers of coated paper, preferably by localized heating.

[0061] The at least one hydrophobic polymer preferably comprises a polyacrylate and / or a polyolefin, a styrene-butadiene copolymer, a polyvinyl acetate (also partially saponified), a polyester, a polyamide, a polyurethane, a polyether, a polyethyleneimine, and / or a polymer based on polyvinylamide. Examples of suitable polymers are, in particular, poly(methyl acrylate), poly(methyl methacrylate), poly(ethyl acrylate), poly(ethyl methacrylate), poly(n-, iso-, tert.-)butyl acrylate, poly(n-, iso-, tert.-)butyl methacrylate, poly(cyclohexyl methacrylate), polyethylhexyl acrylate and their copolymers, graft polymers, and copolymers with styrene, acrylonitrile, methylstyrene or vinyltoluene.

[0062] In addition to the hydrophobic polymer, waxes may be provided. Suitable waxes include compounds such as fossil or natural short- to medium-chain hydrocarbons, their acids, esters, amides and diamides, mixtures or pure substances, colloquially referred to as "waxes". Suitable waxes are, for example, heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, triacontane, hentriacontane, dotriacontane, tritriacontane, tetratriacontane, pentatriacontane, hexatriacontane, heptatriacontane, octatriacontane, nonatriacontane; montan wax, natural waxes (carnauba wax, beeswax, candelilla wax), waxes produced by hydrogenation or partial hydrogenation of vegetable and animal oils or fats, and metal soaps, such as Ca stearate.

[0063] Suitable polymers and polymer / wax mixtures are known, in particular, under the trade names Vapor Coat 1300, BimBA 8888, Cartaseal SWF, Sealcoat SL251, Rhobarr 320, B-Coat SP1, B-Coat WB 100, B-Coat 50 / 3, Chemipearl S300, Ultraseal W-951, Ultraseal W-952, Wukoseal 630, EurikaCoat 3624 and Epotal SP 106.

[0064] The at least one hydrophobic polymer is preferably 1 to 100% by weight based on the total weight of the third barrier layer. weight %, particularly preferably 50 to 100 weight %, or 50 to 99.5 weight % in the third barrier layer.

[0065] The third barrier layer as a whole is preferably hydrophobic.

[0066] The third barrier layer may comprise thickeners, such as acrylate-based thickeners, surfactants, such as sulfosuccinates, extensional rheological aids, such as acrylate-based extensional rheological aids, waxes, such as fatty acid or fatty acid amide based waxes, additives for reducing susceptibility to abrasion and increasing slip, such as phyllosilicates, in particular magnesium silicate hydrate or aluminosilicates, and / or additives, such as aldehydes and polyaldehydes, crosslinkers, zirconates, polyepoxides, epichlorohydrin resins and / or hydroacids.

[0067] These additives preferably comprise in each case 0 to 50 wt. % based on the total weight of the third barrier layer. weight %, preferably 0 to 30 weight Contains in an amount of %.

[0068] The application amount of the third barrier layer is preferably 1 to 20 g / m 2 , and particularly preferably 5 to 10 g / m 2The amounts refer to the dry third barrier layer in the final product.

[0069] In certain embodiments, when the packaged contents contain fat in addition to water, the third barrier layer should not contain any low molecular weight fat-soluble components, except for the minimum amount that is acceptable for contact with high-fat foods. Therefore, waxes to improve the water vapor barrier are largely eliminated, and polymer systems must be used that form an acceptable water vapor barrier without wax and are heat-sealable in the ideal scenario. Suitable for this purpose are, for example, copolymers of non-polar monomers, such as acrylic acid and other ethylenically unsaturated carboxylic acids with ethylene, which have a certain grease barrier in addition to the water vapor barrier. Known products are, for example, Cartaseal SWF, Wukoseal 630 and Sealcoat SL 251.

[0070] However, the first barrier layer may also comprise a wax since the second barrier layer with its function as an oxygen, grease and mineral oil barrier also forms an excellent barrier against waxes which generally have strong non-polar characteristics.

[0071] In a further preferred embodiment of the coated paper according to the invention, a precoat comprising at least one inorganic pigment and a polymeric binder is provided between the base paper and the first barrier layer.

[0072] Inorganic pigments include in particular silicates, preferably phyllosilicates, very particularly preferably kaolin.

[0073] The polymeric binder preferably comprises a polyacrylate-based polymeric binder.

[0074] Examples of suitable polymer binders are, in particular, acrylate-based or styrene-based / 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 are also possible.

[0075] Suitable polymer binders are known inter alia under the trade names Acronal 305S, Ligos K 4079, Acronal S 728, XZ94346.01, XZ94346.00.

[0076] The precoat is preferably 1 to 70 weight %, preferably 5 to 50 weight % polymer binder. Amounts refer to dried precoat in final product.

[0077] Precoat is more preferably 50 to 95 weight %, preferably 80 to 90 weight % inorganic pigment. The amounts refer to the dried precoat in the final product.

[0078] Additionally, the precoat may include additives such as thickeners, e.g., acrylate-based thickeners, surfactants, and / or rheology modifiers. The use of crosslinking agents is also contemplated. Preferably, the precoat includes a zirconium-based crosslinking agent and is itself crosslinked with formaldehyde.

[0079] These additives are preferably in each case 0 to 2 weight %. The amounts refer to the dried precoat in the final product.

[0080] The amount of precoat applied is preferably 1 to 10 g / m 2 , and particularly preferably 2 to 6 g / m 2 The amounts refer to the dried precoat in the final product.

[0081] When such a precoat (also called primer) is applied, this has the advantage, for example, that the paper surface is sealed and that a further barrier layer coated thereon does not migrate into the paper. Moreover, this precoat reduces the average roughness depth of the base paper so that the applied barrier layer can form optimally and gives an advantageous "hold-out", which is distinguished by application covering the entire surface and a defined surface energy. In addition, the precoat mediates the ply adhesion between the base paper and the barrier layer, which can be important for subsequent sealing applications.

[0082] The coated paper according to the invention is, in a further preferred embodiment, characterised in that a sealing layer comprising at least one thermoplastic polymer is provided on the third barrier layer.

[0083] Such a sealing layer is especially advisable when the at least one hydrophobic polymer in the third barrier layer does not include a thermoplastic polymer, ie, is not heat-sealable.

[0084] The sealing layer preferably comprises a thermoplastic polymer based on polyacrylate, styrene / butadiene copolymer and / or polyolefin.

[0085] Examples of suitable polymers are, in particular, acrylates, poly(methacrylates), poly(methyl acrylate), poly(methyl methacrylate), poly(ethyl acrylate), poly(ethyl methacrylate), poly(n-, iso-, tert.-)butyl acrylate, poly(n-, iso-, tert.-)butyl methacrylate, poly(cyclohexyl methacrylate), polyethylhexyl acrylate and their copolymers, graft polymers, and copolymers with styrene, acrylonitrile, methylstyrene or vinyltoluene.

[0086] Suitable polymers are known, inter alia, under the trade names Vapor Coat 1300, BimBA 8888, Cartaseal SWF, Rhobarr 320, B-Coat WB 100, B-Coat 50 / 3, Chemipearl S300, Ultraseal W-952, Wukoseal 630, EurikaCoat 3624, Epotal SP 106, Hypod 2000, Extomine BS-OF 40%, Aquaseal X2200, Cartaseal SCR, CHT Coat 8080, Sealcoat MB46HE and Extomine BG-EM 48%.

[0087] The at least one thermoplastic polymer is preferably 1 to 100% by weight based on the total weight of the sealing layer. weight %, particularly preferably 70 to 100 weight % or 70~99.5 weight % of the sealing layer.

[0088] The sealing layer may contain thickeners, such as acrylate-based thickeners, surfactants, such as sulfosuccinates, extensional rheological aids, such as acrylate-based extensional rheological aids, waxes, phyllosilicates, in particular magnesium silicate hydrate or aluminosilicates, additives for reducing sensitivity to abrasion and increasing slip, and / or additives such as crosslinkers.

[0089] These additives preferably comprise in each case 0 to 50% by weight relative to the total weight of the sealing layer. weight %, preferably 0 to 30 weight Contains in an amount of %.

[0090] The amount of precoat applied is preferably 1 to 10 g / m 2 , and particularly preferably 1 to 5 g / m 2 The amounts refer to the dry sealing layer in the final product.

[0091] The coated paper according to the present invention preferably has a seal seam strength of 1.5N / 15mm to 10N / 15mm, where the seal seam strength of the coated paper was determined as follows.

[0092] The coated papers were sealed transversely to the direction of the paper web at 3.3 bar for 0.3 s in the temperature range of 100°C to 200°C, and the seal seam strength was determined according to DIN 55529 (2012).

[0093] The coated paper according to the invention is preferably characterized in that no adhesion promoters are used between the individual barrier layers, adhesion promoters being understood here in particular to mean substances which are applied between the individual barrier layers in order to ensure or improve the adhesion of the particular barrier layers to one another.

[0094] The coated paper according to the present invention is additionally preferably characterized in that the coated paper is free of halogen-containing compounds. In particular, the three barrier layers are free of halogen-containing compounds. In addition, the precoat and / or sealing layer are likewise free of halogen-containing compounds.

[0095] The coated paper according to the invention is also characterised in that it does not comprise any aluminium, Al2O3 and / or SiO2 layers, in particular does not comprise aluminium, Al2O3 and / or SiO2 as pure substances.

[0096] The coated paper according to the invention is also characterised in that the first, second and / or third barrier layer does not comprise any aluminium, Al2O3 and / or SiO2 layers and / or does not comprise aluminium, Al2O3 and / or SiO2, in particular not as pure substances.

[0097] Furthermore, the sealing layer is preferably characterized in that it does not contain or consist of any aluminum, Al2O3 and / or SiO2, in particular not as a pure substance.

[0098] The coated paper according to the invention can be obtained using known production methods.

[0099] However, the aqueous suspensions containing the starting materials for the first, second and third barrier layers are successively applied to the base paper, and the aqueous applied suspensions are weight %, preferably 30 to 50 weight % and is applied by a curtain coating process at an operating speed of the coating plant of at least 200 m / min.

[0100] This method is particularly advantageous from an economic point of view and for uniform application over the entire paper web.

[0101] The solid content value is about 10 weight If the water content is less than 60%, a large amount of water must be removed in a short time by gentle drying, which has a detrimental effect on the coating speed, resulting in poor economic efficiency. weight If the value of 10.0% is exceeded, this only leads to more technical efforts to ensure the stability of the coating curtain material during the coating process and the drying of the applied film, since the machines still have to run at very high speeds.

[0102] 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" by free fall onto a substrate to apply the coating dispersion to the substrate. Document DE10196052T1 discloses the use of the curtain coating process in the production of information recording materials, where a multi-layer recording layer is realized by applying a curtain of multiple coating dispersion films to the substrate.

[0103] Also conceivable is an embodiment of the method according to the invention in which a "double curtain" is used. This means that two successive barrier layers are applied immediately one after the other. The application is here carried out immediately one after the other such that the first applied layer is not yet dry before the second barrier layer is applied. The two layers are therefore preferably applied "wet-on-wet".

[0104] All definitions relating to the curtain coating process apply equally to the double curtain coating process.

[0105] The method according to the invention is preferably characterized in that the first and second or second and third barrier layers are applied immediately successively wet-on-wet by a double curtain coating process.

[0106] The advantage of wet-on-wet application by a double curtain coating process is that the two barrier layers have a stronger bond and it is possible to omit an adhesion promoter, particularly one disposed therebetween.

[0107] In a preferred embodiment of the method according to the invention, the deaerated aqueous application suspension has a viscosity of about 100 to about 800 mPas (Brookfield, 100 rpm, 20 ° C). If the viscosity falls below a value of about 100 mPas or exceeds a value of about 800 mPas, this leads to poor runnability of the coating medium in the coating unit. The viscosity of the deaerated aqueous application suspension is particularly preferably about 200 to about 500 mPas. The viscosity of the successive coating media in the double curtain process should decrease from the bottom to the top. In case of incorrectly set coating, the probability of the formation of a heel at the point where the curtains meet increases and also the occurrence of "wetting failure".

[0108] In a preferred embodiment, the surface tension of the aqueous coating suspension can be set at about 25 to about 70 mN / m, preferably about 35 to about 60 mN / m (measured 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 obtained by determining the dynamic surface tension of the coating material and targeting it by selecting an appropriate surfactant and by determining the required amount of surfactant.

[0109] Dynamic surface tension is measured by a bubble pressure tensiometer. The maximum internal pressure of a gas bubble formed through a capillary in a liquid is measured. The internal pressure p (Laplace pressure) of a spherical gas bubble depends on the radius of curvature r and the surface tension σ according to the Young-Laplace equation:

[0110]

number

[0111] When a gas bubble forms at the tip of a capillary in a liquid, the curvature first increases and then decreases again, resulting in a pressure maximum. The maximum curvature, and therefore the maximum pressure, occurs when the radius of curvature is equal to the capillary radius.

[0112] Pressure curve during bubble pressure measurement, position of pressure maximum: The radius of the capillary is determined by a reference measurement, which is performed with a liquid of known surface tension, usually water. If the radius is then known, the surface tension can be calculated from the pressure maximum value pmax. Since the capillary is immersed in the liquid, the hydrostatic pressure p0 (resulting from the immersion depth and the density of the liquid) must be subtracted from the measured pressure (for modern measuring instruments this is done automatically). This results in the following equation for the bubble pressure law:

[0113]

number

[0114] The measurements correspond to the surface tension at a certain surface lifetime, which is the time from the onset of bubble formation to the appearance of a pressure maximum. By varying the rate at which the bubbles form, the dependence of surface tension on surface lifetime can be recorded, resulting in a curve in which surface tension is plotted over time.

[0115] This dependence plays an important role for the use of surfactants, since sometimes due to low surfactant diffusion and adsorption rates, the equilibrium value of the interfacial tension is never reached in many processes.

[0116] The successive coating media in the double curtain should have a decreasing surface tension from bottom to top, otherwise poor wetting may occur. Intersecting surface tension curves may also work if the difference is very small, but this is not preferred.

[0117] The individual barrier layers may be formed in separate coating processes, either on-line or off-line.

[0118] In a further embodiment, an individual barrier layer may be applied to the base paper using the following method.

[0119] The individual barrier layers can be applied to the base paper by printing methods and / or to other existing barrier layers.

[0120] Individual barrier layers can be applied by multiple extrusions (3-4 different polymer melts) to the base paper and / or to other existing barrier layers.

[0121] This technique therefore has the advantage that much more barrier material can be applied, which is only of interest if the entire product does not need to be recyclable as paper, while the disadvantages are the slower application speed, higher energy consumption, and larger minimum application weight.

[0122] The individual barrier layers may be applied by laminating the paper, for example in the form of a plastic material coating applied to the base paper and / or to other existing barrier layers.

[0123] The individual barrier layers may be applied successively over multiple application steps. For this purpose, it may be necessary to increase the surface energy of the dried coating for the coating on top by various processes. These processes include, for example, corona or plasma treatment as well as flame treatment, UV treatment or chemical activation processes.

[0124] In another embodiment, the method according to the invention is preferably characterized in that no separate barrier layer is applied to the base paper and / or to other existing barrier layers by vapour deposition of metals or metal oxides.

[0125] Any combination of the above methods is also possible.

[0126] The present invention further relates to a coated paper obtainable by the above process.

[0127] The present invention also relates to the use of a coated paper as described above or obtainable by the process described above as packaging material.

[0128] Finally, the present invention also relates to the use of a coated paper as described above or obtainable by the process described above as packaging material for food products, in particular for high-fat and oxidation-sensitive foods such as meat and dairy products.

[0129] In a further preferred embodiment of the present invention, the coated paper according to the invention is applied to cardboard or paperboard, in particular by lamination or gluing.

[0130] Finally, the present invention also relates to the use of a composite in which the coated paper according to the invention is applied, in particular by lamination or gluing, to cardboard or paperboard as packaging material for food, in particular for high-fat and oxidation-sensitive foods such as meat and dairy products.

[0131] In this way, packaging materials can be produced in a simple and economical manner that have the advantages of both material components, such as the increased strength and stiffness of cardboard or paperboard compared to coated paper, as well as the described advantages of coated paper. Application can be carried out, for example, using starch.

[0132] Preferably therefore the coated paper is a component of a packaging material based on cardboard or paperboard.

[0133] With these packaging materials according to the invention, heavier food products such as meat, fish or cheese in particular can be safely packaged and attractively presented to customers in the form of upright packages in retail outlets.

[0134] These packaging materials are preferably 95 weight %. A further advantage of the present invention is now that these packaging materials according to the invention are not composite packaging according to § 3(5) of the German Packaging Act, and therefore this embodiment of the present invention contributes significantly to reducing the impact of packaging waste on the environment.

[0135] The invention is explained in more detail below on the basis of non-limiting examples.

[0136] The materials mentioned in the description and used in the examples are summarized in the table below, along with their trade names and associated manufacturers.

[0137] [Table 1] EXAMPLES

[0138] The following coatings are applied at 60 g / m2 with 40% long fibre and 60% short fibre content: 2 Applied to base paper.

[0139] Precoat / Primer: The precoat contains 75.9% pigment (Capim NP), 22.8% latex (Ligos K4079) and 1.3% rheology modifiers (0.2% Acroflex VX559, 1.1% Auerzirc PZCS20).

[0140] Barrier layer 1: V1+V2: The first barrier layer contains 99.05% styrene / butadiene copolymer (CHT Coat 230) and 0.95% rheology modifier (0.1% Sterocoll DF3; 0.15% Acroflex VX559; 0.7% Aerosol OT 70 PG).

[0141] V3+V4+V5: The first barrier layer contains 99.3% polymer (BimBA 8510) and 0.7% rheology modifier (0.7% Aerosol OT 70 PG).

[0142] Barrier Layer 2: The second barrier layer contains 99.5% polyvinyl alcohol mixed with glyoxal (V1+2: MFB 1000; V3: MFB 1001). The remaining 0.5% contains rheology modifiers (0.1% Sterocoll DF3; 0.4% Aerosol OT 70 PG).

[0143] Barrier layer 3: V1+V2+V3: The third barrier layer contains 98.74% styrene / butadiene copolymer (Ultraseal W-952) and 1.26% rheology modifier (0.08% Sterocoll DF3; 0.69% Acroflex VX559; 0.49% Aerosol OT 70 PG).

[0144] V4+V5: The third barrier layer contains 97.74% ethylene / acrylic acid copolymer (Wukoseal 630) and 2.26% rheology modifier (0.18% Sterocoll DF3, 0.08% Acroflex VX559, 0.25% Aerosol OT 70 PG, 1.66% Metolat 368, 0.10% Genapol PF10).

[0145] For this purpose, a precoat was applied using a blade. The first and second barrier layers were applied in a double curtain process. The third barrier layer was applied as a single curtain.

[0146] [Table 2] [Table 2A]

[0147] Coated papers according to the invention were compared to commercially available papers (see table below).

[0148] [Table 3]

[0149] [Table 4]

[0150] Examples V4 and V5: V4: V3+ The third barrier layer does not contain any substances which, with the exception of unavoidable or tolerated impurities, are not permitted to come into direct contact with food, in particular substances selected from the group of paraffins, in particular hard paraffins, waxes, in particular microcrystalline waxes, low molecular weight polyolefins, polyterpenes and mixtures thereof, as well as waxes obtained from plants or animals or produced from vegetable oils / fats or animal oils / fats.

[0151] V5: Similar to V4, but with half the applied weight of the 3rd barrier layer.

[0152] Algro Guard OHG: The material has a precoat based on aluminum silicate and a PVDC coating applied to it 8 μm thick. The permeability to oxygen and hexane is similar to the examples V1 to V3 according to the invention; the permeability to water vapor is even slightly better. The obtained sealing power is within the range of the examples according to the invention. However, it is considered a major disadvantage that the material contains PVDC as a barrier medium. This cannot be justified from an ecological point of view.

[0153] Algro Finess / PET: This is a paper coated with 20 μm PE / PET. Acrylate-co-acrylonitrile was used as an adhesion promoter or precoat. The water vapor transmission rate and sealing power are comparable to the examples according to the invention, but the hexane and oxygen transmission rates are very high.

[0154] Algro Finess / PETmet: The material is paper coated with metallized PE or PET. This of course has a very good barrier due to the metallization. The main difference with the example according to the invention is the metallization, which is considered very disadvantageous from an economic and ecological point of view.

[0155] Barricote BAG WG: The material first has a clay-containing precoat and then a functional coating with poly(ethylene-co-acrylic acid). The water vapor transmission rate is between 1.7 and 4 times that of examples V1 to V3; the sealing power is also at the same level as "Shieldplus 1" and is therefore 27 to 50% lower than in the examples according to the invention.

[0156] SealSilk: SealSilk is constructed similarly to Barricote BAG WG. Here, a coat of GCC with styrene / butadiene latex was applied first, followed by a poly(ethylene-co-acrylic acid) dispersion. The sealing force of this material is still about 1 N / 15 mm lower than that of the inventive examples V1-V3. All permeation rates (WVTR, OTR, HVTR) are much lower than those of the inventive examples.

[0157] ShieldPlus 1: The material "ShieldPlus 1" has a simple PE coating. At 3.5N / 15mm it seals 27-50% weaker than the examples according to the invention. Furthermore, the oxygen permeability of the material is very high. The hexane permeability of the material was not checked but is not expected to be particularly high. The water vapour barrier is good, which can clearly be attributed to PE.

[0158] "ShieldPlus 2-4" "ShieldPlus 2-4" consists of a styrene / butadiene coat and a PVOH coat; in addition, one or both coats contain clay. The water vapor and hexane permeabilities of these materials are within the range of the examples according to the invention (WVTR between V3 and V1), but the oxygen permeability is very high, thus making the material unsuitable for sensitive foods. Additionally, the material is not heat sealable.

Claims

1. A coated paper comprising a base paper and at least three coatings applied thereto, the at least three coatings comprising, in that order proceeding from the base paper, a first barrier layer comprising at least one hydrophobic polymer, a second barrier layer comprising at least one hydrophilic polymer, and a third barrier layer comprising at least one hydrophobic polymer; a precoat comprising at least one inorganic pigment and a polymeric binder is disposed between the base paper and the first barrier layer; the first barrier layer comprises 50 to 99.5 wt. % of the at least one hydrophobic polymer; The precoat comprises 1 to 70% by weight of the polymer binder; Coated paper.

2. 2. The coated paper of claim 1, characterized in that the first barrier layer comprises or consists of a material selected from the group of oleophilic substances, paraffins, waxes, low molecular weight polyolefins, polyterpenes, and mixtures thereof.

3. Coated paper as described in claim 2, characterized in that the paraffin is selected from hard paraffin and / or the wax is selected from microcrystalline waxes, waxes based on vegetable oils or fats, waxes based on animal oils or fats, vegetable waxes, animal waxes.

4. 2. The coated paper of claim 1, wherein material migration is reduced or prevented by the second barrier layer.

5. Coated paper as described in claim 4, characterized in that the substance is a hydrophobic substance.

6. 6. Coated paper according to any one of claims 1 to 5, characterized in that migration of substances from or through the first barrier layer into or across the third barrier layer is reduced or prevented.

7. The coated paper of claim 6, wherein the substance is a hydrophobic substance.

8. 8. Coated paper according to claim 1, characterized in that migration of substances from or through the third barrier layer into the first barrier layer is prevented.

9. The coated paper of claim 8, wherein the substance is a hydrophobic substance.

10. 10. Coated paper according to any one of claims 1 to 9, characterized in that the migration of substances selected from the group of oleophilic substances, paraffins, waxes, low molecular weight polyolefins, polyterpenes and mixtures thereof is reduced or prevented.

11. Coated paper as described in claim 10, characterized in that the paraffin is selected from hard paraffin and / or the wax is selected from microcrystalline waxes, waxes based on vegetable oils or fats, waxes based on animal oils or fats, vegetable waxes, animal waxes.

12. 12. Coated paper according to any one of claims 1 to 11, characterized in that the third barrier layer does not contain any substances that are not acceptable for direct contact with food, except for unavoidable or tolerated impurities.

13. The coated paper described in claim 12, characterized in that the substance that is not acceptable for direct contact with food is a substance selected from the group of lipophilic substances, paraffins, waxes, low molecular weight polyolefins, polyterpenes, and mixtures thereof.

14. Coated paper as described in claim 13, characterized in that the paraffin is selected from hard paraffin and / or the wax is selected from microcrystalline waxes, waxes based on vegetable oils or fats, waxes based on animal oils or fats, vegetable waxes, animal waxes.

15. 15. Coated paper according to any one of the preceding claims, characterized in that a sealing layer comprising at least one thermoplastic polymer is provided on the third barrier layer.

16. The base paper is 20 to 120 g / m ２ 16. Coated paper according to claim 1, characterized in that it has an areal density of 17. The coated paper of claim 16, wherein the base paper has an area density of 40 to 100 g / m 2 .

18. 18. Coated paper according to any one of the preceding claims, characterized in that the first barrier layer comprises at least one hydrophobic polymer based on polyacrylate and / or polyolefin.

19. 19. Coated paper according to any one of the preceding claims, characterized in that the second barrier layer comprises at least one hydrophilic polymer based on polyvinyl alcohol.

20. 20. Coated paper according to any one of the preceding claims, characterized in that the third barrier layer comprises at least one hydrophobic polymer based on polyacrylate, styrene / butadiene copolymer and / or polyolefin.

21. 2. The coated paper of claim 1, characterized in that the inorganic pigment comprises a silicate and / or the polymeric binder comprises a polymeric binder based on polyacrylate.

22. The coated paper of claim 21, wherein the silicate is a phyllosilicate.

23. The coated paper of claim 21, wherein the silicate is kaolin.

24. 16. Coated paper according to claim 15, characterized in that the sealing layer comprises a thermoplastic polymer based on polyacrylate, styrene / butadiene copolymer and / or polyolefin.

25. 25. Coated paper according to any one of the preceding claims, characterized in that no adhesion promoter is used between the individual barrier layers.

26. 26. Coated paper according to any one of the preceding claims, characterized in that it is free of halogen-containing compounds.

27. Aluminum, Al ２ O ３ and / or SiO ２ 27. Coated paper according to any one of the preceding claims, characterized in that it does not comprise a layer.

28. 28. The coated paper according to any one of claims 1 to 27, characterized in that the base paper has a long fibre content of 10-80% and a short fibre content of 20-90% by weight, the long fibres being fibres with a fibre length of 2.6-4.4 mm and the short fibres being fibres with a fibre length of 0.7-2.2 mm.

29. 29. A method for producing the coated paper according to any one of claims 1 to 28, characterized in that an aqueous application suspension comprising starting materials for the first, second and third barrier layers is applied successively to the base paper, said aqueous application suspension having a solids content of 10-60% by weight and being applied by a curtain coating process at an operating speed of the coating plant of at least 200 m / min.

30. The method according to claim 29, characterized in that the aqueous application suspension has a solids content of 30 to 50% by weight.

31. 31. The method according to claim 29 or 30, characterized in that the first and second or the second and third barrier layers are applied in immediate succession wet-on-wet by a double curtain coating process.

32. 29. Use of the coated paper according to any one of claims 1 to 28 as a packaging material or as a component of a packaging material.

33. The use according to claim 32, wherein the packaging material, or a component of the packaging material, is a packaging material based on cardboard or paperboard, and / or is a packaging material used for food products, and / or is a packaging material used for edible fats or oils and / or fat-containing food products.

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