WO2024052337A1

WO2024052337A1 - Barrier paper

Info

Publication number: WO2024052337A1
Application number: PCT/EP2023/074315
Authority: WO
Original assignee: Koehler Innovation & Technology Gmbh
Priority date: 2022-09-05
Filing date: 2023-09-05
Publication date: 2024-03-14
Also published as: DE102022122470A1

Abstract

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

Description

barrier paper

Description

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 a packaging comprising the barrier paper.

Packaging generally refers to the shell or (partial or complete) wrapping of an object, particularly for its protection or better handling. Accordingly, a packaging material includes the material constituting such a packaging.

Packaging materials can, for example, be based on paper, plastics and/or metals. The present invention deals with paper-based packaging materials.

The main requirements for packaging materials of any origin are to protect the packaged goods from external influences, as well as to prevent the packaged goods from escaping and to function as an advertising and information carrier. For this purpose, the packaging material should meet different criteria, depending on the packaged goods and the packaging process. In addition to so-called barrier properties against, for example, water, fat, oxygen or mineral oil, suitable packaging materials should also have mechanical and process-specific properties Requirements met. Depending on the packaging system, a packaging material, in particular a flexible packaging material, should have sufficient tear strength, a suitable coefficient of friction (coefficient of friction) and flexibility, it should be heat-sealable and printable from the outside and should not lose its protective effect throughout the entire conversion and packaging process.

Known paper-based, coated packaging materials often contain compounds such as polyvinylidene chloride (halogen-containing) or are composites of paper and metal or plastic foils, have poor tear resistance, which can lead to running problems on packaging systems, and/or are due to too high a coating proportion of adhesive components or is often not recyclable due to the formation of so-called stickies via the paper fiber stream.

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

To solve this problem, mixtures of all types of polymer dispersions and wax emulsions are offered. However, when testing papers produced in laboratory and pilot tests, it was observed that such known mixtures of polymer dispersions and wax emulsions have the disadvantage that grease can penetrate the coating, which in turn leads to an increase in water vapor permeability. There is a risk that direct contact with fatty foods will increase the water vapor permeability. When transferring laboratory recipes to a pilot coating system, heat sealability was also observed to deteriorate. Furthermore, when producing such coatings on a pilot scale, decreasing heat sealability with continued storage time was often observed. This refers to the ability of the material to to create a stable sealing seam through heat sealing, and not the stability of an already existing sealing seam.

The object of the present invention is to eliminate the disadvantages of the known materials and to provide a material that is suitable as a packaging material, particularly for moisture-sensitive foods, and that maintains its water vapor permeability at a low level even when it comes into contact with fat or allows it to increase as little as possible. It must also be usable for heat sealing applications. In particular, a seal seam strength of greater than 4 N/15mm and a water vapor permeability (WVTR) with target values of <20 g/m ² /d (38°C, 90% RH) or <8 g/m ² /d (23 °C, 50% RH).

Furthermore, the material according to the invention should be as easy to produce as possible, have application weights that are as small as possible and, if possible, enable recyclability via the paper fiber stream.

This object is achieved by a barrier paper according to claim 1, ie by a barrier paper comprising a base paper and at least one coating layer Sl applied directly or indirectly to the base paper, the coating layer Sl comprising at least one polymeric binder and at least one wax, and wherein the coating layer Sl has at least one of the following features: a) change in surface tension of not more than +10 mN/m, preferably of not more than +6 mN/m, b) change in the polar component of the surface tension of not more than -0.65 mN/m, preferably not more than -0.60 mN/m, c) change in the polar component of the surface tension of not more than -3.0% points, preferably not more than -1.5% points. whereby the respective change is determined by measuring and comparing the measured values of the surface tension of the polar component of the surface tension before and after a temperature treatment of the barrier paper at 105 ° C for 3 min. Preferred embodiments are defined in the dependent claims.

A paper coated in this way is characterized in particular by the fact that it is particularly suitable as a packaging material for moisture-sensitive and greasy objects, especially food, and can be used for heat sealing applications.

Furthermore, the guide values defined above regarding heat sealability and water vapor permeability can be achieved with such a barrier paper.

The barrier paper according to the invention can ultimately be produced relatively easily and with low application weights and reused via the waste paper cycle.

Numerous specific details are also discussed below to provide a comprehensive understanding of the subject matter at hand. However, it is obvious to those skilled in the art that the subject matter can be practiced and reworked without these specific details.

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

The terminology used in the description of the present disclosure is intended only to describe certain embodiments and should not be construed as limiting the subject matter. As used in this specification and claims, the singular forms "a", "an" and "the" are to be understood to include the plural forms as well, unless the context clearly indicates otherwise. This also applies the other way round, i.e. the plural forms also include the singular forms. It is also understood that the term "and/or" as used herein refers to and includes all possible combinations of one or more of the associated listed items. It is further understood that the terms "includes", "including", "comprises" and/or "comprising" when used in the present description and claims mean the presence of the specified features, steps, operations, Specify elements and/or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components and/or groups thereof.

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

In the present description and the claims, the term “including” can also mean “exclusively”.

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

As mentioned above, the barrier paper according to the invention comprises a base paper and at least one coating layer Sl applied directly or indirectly to the base paper, the coating layer S1 comprising at least one polymeric binder and at least one wax, and the coating layer Sl having at least one of the following features: a ) Change in the surface tension of not more than +10 mN/m, preferably not more than +6 mN/m, b) Change in the polar component of the surface tension of not more than -0.65 mN/m, preferably not more than -0.60 mN/m, c) change in the polar and disperse portion of the surface tension of not more than -3.0% points, preferably not more than -1.5% points, the respective change being measured and comparing the measured values of the surface tension of the polar component of the surface tension before and after a temperature treatment of the barrier paper at 105 ° C for 3 min. If the coating layer S1 is applied directly to the base paper, this means that there are no further coatings or substances between the base paper and the coating layer S1.

If the coating layer S1 is applied indirectly to the base paper, this means that there are further coatings or substances between the base paper and the coating layer S1.

Laboratory tests have shown that it is possible to apply the coating layer S1 directly onto base papers, in particular on calendered base papers with surface thickness and low Cobb value. For a better hold-out of the coating color and to minimize the required coat application, the previous application of a base coat is preferred. Ultimately, economic and production-related considerations also decide which approach is preferred in each individual case.

The determination of the surface tension (alternatively also called surface energy) of solids can be determined using contact angle measurements with at least two different liquids. The manufacturer of measuring devices based on this principle, such as: B. the company DataPhysics Instruments GmbH (D-70794 Filderstadt) describes the connections on their website as follows:

“The cohesion of atoms and molecules, which determines the surface tension of a substance, is due to different types of interactions. In particular, a distinction can be made between disperse and polar interactions. The interactions due to temporal fluctuations in the charge distribution of the atoms/molecules are called disperse interactions (van der Waals interactions). Polar interactions include Coulomb interactions between permanent dipoles or between permanent and induced dipoles (e.g. hydrogen bonds). Accordingly, the surface tension is also made up of a disperse and a polar component. If the ratio of the disperse to the polar portion of the surface tension is compared for two phases, predictions about the adhesion of the two phases to one another can be derived. The more closely the disperse and polar parts match, the more interaction possibilities there are between the phases and the stronger the adhesion can be expected."

Does the comparison of the measured values show that a) there is no significant change in the 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 no more than -3.0% points, the barrier paper has the advantageous properties.

The inventors assume that in a coating layer which comprises or consists of at least one polymeric binder and at least one wax, the drying of the coating layer also causes at least partial segregation and/or partial filming of the coating layer and possibly also an uneven distribution of Wax may be present within the coating layer. For one and the same composition of the coating layer, different properties of the coating layer and thus also of the barrier paper result, depending on how the drying parameters are selected.

The inventors have transferred these findings to the coating layer S1, with at least one of the following features of the dried coating layer S1 a) change in surface tension of not more than +10 mN/m, preferably of not more than +6 mN/m, b) change the polar component of the surface tension of not more than -0.65 mN/m, preferably not more than -0.60 mN/m, c) change in the polar component of the surface tension of not more than -3.0% points, preferably not more than -1.5% points. can be viewed as an indicator of the quality of the coating color layer S1 with regard to the properties mentioned in the task, in particular with regard to whether there is partial segregation and/or partial filming of the Coating color layer S1 is present or whether there is an uneven distribution of wax within the coating color layer S1.

In other words, the properties of a barrier paper mentioned in the task depend not only on the composition of a coating layer S1, but also on how this coating layer S1 was dried. In addition to the composition, the dried coating layer S1 must therefore have at least one of the following structural features: a) change in surface tension of not more than +10 mN/m, preferably not more than +6 mN/m, b) change in the polar component of the Surface tension of not more than -0.65 mN/m, preferably of not more than -0.60 mN/m, c) change in the polar and disperse components of the surface tension of not more than -3.0% points, preferably of not more than -1.5% points, whereby the respective change is determined by measuring and comparing the measured values of the surface tension of the polar component of the surface tension before and after a temperature treatment of the barrier paper at 105 ° C for 3 min.

The drying parameters (temperature, time) for a specific coating color composition S1 should preferably be chosen so that after drying the coating color layer S1 has at least one of the features a) to c), preferably at least two features and particularly preferably all three features. A specialist can determine the drying parameters using simple drying tests.

For successful drying, it is preferred that the web temperature of the coating in the drying process exceeds the melting range of the wax for a sufficiently long period of time.

As was 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. The polar proportion of the surface tension of the coating layer S1 is preferably 0 to 12%, in particular 0 to 6%, preferably 0 to 3% and particularly preferably 0 to 1%, with the values 0% being excluded as a lower limit in a preferred embodiment.

The disperse portion of the surface tension of the coating layer S1 is preferably 88 to 100%, in particular 94 to 100%, preferably 97 to 100% and particularly preferably 99 to 100%

The surface tension and the determination of the polar and disperse components of the surface tension are determined according to DIN EN ISO 19403-2 (2020-04):

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

Measuring liquids used and origin of the material constants entered:

Water and diiodomethane (according to Buscher) and 1,5-pentanediol (according to 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, it still allows measurable contact angles on paper surfaces before the liquid is absorbed by the paper.

The temperature treatment of the barrier paper at 105 ° C for 3 minutes is preferably carried out in a hot air oven (drying oven), although it should preferably be ensured that the paper is actually exposed to 105 ° C for a period of 3 minutes. For this purpose, the oven should preferably be preheated and have a sufficient internal volume (e.g. > 100 dm ³ , e.g. width x height x depth 60 cm x 48 cm x 37 cm) so that when the front door is opened briefly (2-3 s). To put the paper in there is no significant drop in temperature. The barrier paper is preferably placed on a metal grid located in the middle height of the drying oven, on which a cardboard box is preferably placed as a base. The metal grid and cardboard should have already reached the oven temperature and should have been placed in the oven, which has already been preheated to 105°C, for at least 15 minutes before the start of the temperature treatment. It should be noted that the duration of the temperature treatment was preferably placed for 3 minutes to ensure, on the one hand, that the barrier paper has enough time to actually reach 105 ° C and, on the other hand, that the treatment of the paper does not last too long so that no decomposition processes occur. After the barrie papers were removed from the oven, they were stored (air-conditioned) for at least 12 hours at 23°C and 50% RH before further measurements were taken.

The wax in the coating color layer S1 is preferably a wax according to the following definition of the German Society for Fat Research (DGF).

“Waxes are substances that are now defined by their mechanical-physical properties. However, their chemical composition and origin are very different. A substance is called wax if it can be kneaded at 20 °C, is solid to brittlely hard, has a coarse to finely crystalline structure, is translucent to opaque in color but not glassy, melts above 40 °C without decomposition, and is slightly above the melting point is slightly liquid (low viscosity), has a strongly temperature-dependent consistency and solubility and can be polished under light pressure." If more than one of the properties listed above is not met, the substance is according to the DGF (DGF standard method M-I 1 (75)) no wax.

As our own laboratory studies have shown, the chemical composition of the waxes used does not play a decisive role. They should only be selected so that they melt under the technically possible drying conditions in the coating system. It has been shown that it is advantageous for the formation of the water vapor barrier if the melting temperature is below the boiling point of water (100°C), better yet below 90°C.

The polymeric binder in the coating layer S1 is in principle not limited, but includes all polymeric binders that are known to those skilled in the art for binding waxes in paper coatings.

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

The following relationships were 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 comparatively high sensitivity of the water vapor barrier to grease contact. If a small amount of wax is to be used, the aqueous coating should be dried so that wax migrates to the surface in order to obtain a good, less grease-sensitive water vapor barrier.

In one embodiment, the wax content of the coating layer S1 is selected such that the barrier paper has at least one of the following features: a) a seal seam strength (cold tack) coating layer S1 against coating layer S1 of > 4 N/15mm, produced with the heat sealing parameters T = 130 - 150°C, sealing time = 0.3 see, sealing pressure = 3.3 bar or with ultrasonic sealing parameters that cause a T of 130 - 150°C in the sealing medium and a sealing time of 0.3 s and a sealing pressure of 3.3 bar b) a water vapor permeability (WVTR) <20 g/m ² /d (38°C, 90% RH), c) a water vapor permeability (WVTR) <8 g/m ² /d (23°C, 50% RH), d) an increase in the water vapor permeability (38°C, 90% RH) after carrying out the palm kernel fat test according to DIN 53116 2003-02 (under the test conditions of 10 min exposure time and pressure load of 2000 N/m ² ) by no more than 70 g/m ² /d, preferably not more than 60 g/m ² /d, e) an increase in water vapor permeability after carrying out the palm kernel fat test according to DIN 53116 2003-02 (under the test conditions 60 min exposure time and 2000 N/m ² ) of not more than a factor of 6, f) a static coefficient of friction (coating layer S1 against coating layer Sl) of <0.9 g) a kinetic coefficient of friction (coating layer Sl against coating layer Sl) of <0.6 where the values for a) to g) for a basis weight of the coating layer Sl of <12 g/m ² can be determined.

Here, the basis weight of the coating color layer Sl is not limited to values of <12 g/m ² , but the above-mentioned parameters only have to be fulfilled for such basis weights. For higher surface weights, the parameters must be adjusted accordingly.

The parameter a) a sealing seam strength (cold tack) coating layer Sl against coating layer Sl, is preferably understood to mean that a sheet of barrier paper is folded in such a way that the coating layer Sl coincides with itself in the sealing seam area or that two sheets of barrier paper are placed on top of each other ensure that the coating color layers Sl of the two sheets coincide in the sealing seam area.

In one embodiment, the barrier paper according to the invention is preferably characterized in that the water vapor permeability (38 ° C, 90% RH) has a change of a maximum of -40%, preferably <-30%, the change being determined by measuring and comparing the measured values of the water vapor permeability is determined before and after a temperature treatment of the barrier paper at 105 ° C for 3 min (analogous to the above statements).

In one embodiment, the wax is a wax according to DGF (DGF standard method M-I 1 (75)), as defined above.

In one embodiment, the barrier paper according to the invention is preferably characterized in that the at least one wax is a wax based on mixtures or pure substances of fossil or natural short to medium chain hydrocarbons, their acids, esters, amides and diamides, hydrogenated vegetable oils, by hydrogenation or partial hydrogenation from Waxes and/or metal soaps made from vegetable oils and animal oils or fats, preferably heneicosan, docosan, tricosan, tetracosan, pentacosan, hexacosan, heptacosan, octacosan, nonacosan, triacontan, hentriacontan, dotriacontan, tritriacontan, tetratriacontan, pentatriacontan, hexatriacontan, heptatriaontan, octatriacon tan, Nonatriacontan, montan waxes, carnauba wax, beeswax, candelilla wax, rice bran wax, sugar cane wax, wax obtained from sunflower seed press cake, particularly preferably beeswax and/or wax obtained by hydrogenation of soybean oil, and/or paraffin waxes with an average molecular weight of at least 500 Daltons and a viscosity of at least 11 cSt at 100°C

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

When using paraffin waxes, particular preference is given to those specified in the EU Commission Regulation No. 10/2100 of January 14, 2011 "on plastic materials and articles intended to come into contact with food" of the FCM- Material No. 94.

In one embodiment, the barrier paper according to the invention is preferably characterized in that the at least one wax is in an amount of 0.01 to 10% by weight, preferably from 0.01 to <8.0% by weight, preferably from 0.01 <6.0% by weight, particularly preferably from 0.01 to <5.0% by weight, and most preferably from 0.01 <2.0% by weight, preferably the lower limit is at least 0.1 % by weight, particularly preferably at least 0.2% by weight, based on the total weight of the coating color layer Sl, is contained in this.

In one embodiment, the barrier paper according to the invention is preferably characterized in that the at least one polymeric binder in the coating layer S1 is selected from the group comprising polyacrylates and copolymers with unsaturated hydrocarbons, polyolefins, copolymers consisting of unsaturated hydrocarbons and acrylic acid or their salts (partly carboxylated) styrene-butadiene copolymers, styrene-butadiene copolymers, styrene-butadienes, polyvinyl acetates, partially saponified polyvinyl acetates, Polyesters, for example polylactides and polyhydroxyalkanoates (produced from glucose), polyamides, polyurethanes, polyethers, polyethyleneimines, and / or polyvinylamides, preferably selected from the group comprising polymethyl acrylates, polymethyl methacrylates, polyethyl arylates, polyethyl methacrylates, poly (n-, iso-, tert. -) butyl acrylates, poly(n-, iso-, tert-) butyl methacrylates, polycyclohexyl methacrylates, polyethylhexyl acrylates and their copolymers, graft polymers, and copolymers thereof with styrene, acrylonitrile, methylstyrene and/or vinyl toluene, particularly preferably styrene acrylate/methyl acrylate/butyl acrylate /Ethylhexyl acrylate copolymer, and/or natural polymers such as (modified) polysaccharides, proteins, lignin (derivatives) and other natural macromolecules such as shellac.

In one embodiment, the barrier paper according to the invention is preferably characterized in that the at least one polymeric binder is in an amount of 99.9 to > 92% by weight, particularly preferably > 95% by weight and very particularly preferably > 98% by weight. %, based on the total weight of the coating layer Sl, is contained in it.

In one embodiment, the coating layer S1 comprises only the wax and the polymeric binder.

In another embodiment, the coating layer S1 comprises, in addition to the wax and the polymeric binder, further components or additives.

Other possible components of the coating layer Sl include, for example, pigments, in particular inorganic pigments, such as Ca carbonate (GCC or PCC), talc, kaolins, natural and/or synthetic silicates.

Such pigments are preferably contained in an amount of 0 to 70% by weight, based on the total weight of the dry coating layer Sl. So that the heat-sealability of the coating layer Sl is not impaired too much, amounts of 0 to 50% by weight, better 0 to 30% by weight and most preferably 0 to 10% by weight should be selected.

The value 0% by weight is preferably excluded as the lower limit. Platelet-shaped pigments are preferred, as these can contribute to improving the barrier when aligned laminarly parallel to the coating. The particle size should preferably be chosen so that the particles are completely enclosed in the layer when aligned in a laminar manner. The aspect ratio (ratio of average diameter to thickness, also called form factor) should be greater than 10, preferably greater than 100 and particularly preferably greater than 1000.

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

These additives are preferably each contained in an amount of 0 to 2% by weight, preferably 0 to 1% by weight, based on the total weight of the dry coating layer Sl. The value 0% by weight is preferably excluded as the lower limit.

The smoothness of the coating layer Sl (according to Bekk (ISO 5627, 1995-03)) is preferably from 400 s to 2500 s, preferably from 500 to 2000 s.

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

The application amount (ISO 536, 2020-05) of the coating layer Sl is preferably 4 to 20 g/m ² , preferably 6 to 15 g/m ² and particularly preferably 8 to 12 g/m ² . The amount refers to the dried coating layer Sl in the final product.

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

The term enriched here means in particular that the local concentration of wax in the coating layer Sl on the side facing away from the base paper is greater than the local concentration of wax in the coating layer Sl on the side facing the base paper, which is indirectly This proves that the polar component of the surface energy does not decrease significantly further during post-drying.

Further evidence of wax accumulation can be carried out using electron spectroscopy (ESCA, also abbreviated as XPS). The accumulation of wax in the coating color layer S1 on the side facing away from the base paper was also recognized by the following experiments.

During coating tests on a pilot coating system, the low water vapor permeability that could be achieved by laboratory coating of individual sheets was not achieved. In order to check whether poor quality of the coating (defects, air bubbles, wetting problems) or simply insufficient drying and film formation was the cause, individual sheets were gently dried in the drying oven for a sufficiently long time (3 min, 105°C). The water vapor permeability of the after-dried papers (Comparative Examples 1 and 2) improved and the polar component of the surface tension decreased. Since no chemical reaction is to be expected in the coating, the conclusion can be drawn that the non-polar wax migrated to the interface during post-drying.

The base paper used in the barrier paper according to the invention is in principle not limited.

It is preferred that the base paper has a basis weight of 20 to 120 g/m ² , preferably 40 to 100 g/m ² .

Furthermore, it is preferred that the base paper has a long fiber content of 10 to 80% by weight, preferably 20 to 50% by weight, and a short fiber content of 20 to 90% by weight, preferably 50 to 80% by weight. , based on the total weight of the base paper, where a long fiber is a fiber with a fiber length of 2.6 to 4.4 mm and a short fiber is a fiber with a fiber length of 0.7 to 2.2 mm.

The long fiber content ensures the strength of the comparatively thin paper, while the short fiber content makes the paper denser and more closed and gives it a uniform appearance. A further increase in the long fiber content would make the paper too stiff become. Another role is played by the lower price of short fiber pulp compared to long fiber pulp.

In addition, 0% by weight to 20% by weight, preferably 0% by weight to 5% by weight, of fillers, preferably excluding the value 0% by weight, such as GCC (ground calcium carbonate), that for example known under the trade name Hydrocarb 60 or Hydroplex 60, PCC (precipitated calcium carbonate), which is known for example under the trade name Precarb 105, natural kaolin and / or talc.

Common auxiliary substances, such as retention agents and/or sizing agents, can also be included.

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

In particular for contact with food, the base paper comprises at least 60% by weight, preferably at least 75% by weight of fibers, at most 25% by weight, preferably at most 10% by weight of fillers and at most 15% by weight of auxiliary materials. In addition, unavoidable or necessary traces of processing aids (e.g. reagents, dispersants, anti-mould agents, etc.) may be present in the base paper.

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

If the coating layer S2 is applied directly between the base paper and the coating layer S1, this means that the coating layer S2 is in contact with the base paper on one side and with the coating layer S1 on the other side. If the coating layer S2 is applied indirectly between the base paper and the coating layer S1, this means that the coating layer must be present between the base paper and the coating layer S1, but does not necessarily have to be in direct contact with them; Further intermediate layers are therefore not excluded.

Preferably, the coating layer S2 serves to form a mineral oil and/or fat barrier layer and comprises at least one hydrophilic polymer.

Preferred target values for the mineral oil barrier are n-hexane permeabilities of <30 g/m ² /d. The preferred target value for fat tightness for foods that are not consumed immediately is passing the palm kernel fat test in accordance with DIN 53116 Cat. 1 (no leaks even after a test period of more than 24 hours).

Hydrophilic polymers are often cross-linked and therefore not very flexible. For the coating of flexible packaging, it is preferable to choose such that it can withstand bends of up to 180° inwards (coating to coating) and ideally also outwards, without grease coming through.

The coating layer S2 should preferably be able to be coated with the (aqueous) coating composition of the coating layer S1 in the dry state.

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

Since a polymer-based oxygen barrier (always also a mineral oil and grease barrier) is generally hydrophilic, it can only be painted over if at least some of the free hydrophilic groups are covalently cross-linked when the coating dries. For this purpose, reactive additives such as bi- or multifunctional aldehydes, carboxylic acids, epoxides or inorganic crosslinkers, such as. B. zirconates or borates are used. Another possible group of crosslinkers are PAE resins (polyamidoamine-epichlorohydrin), which are also used as wet strength agents for base papers. The use of these additives is either prohibited or limited for food contact.

Therefore, when looking for raw materials for mineral oil and fat barriers, the choice usually does not fall on water-soluble polymers, but rather on polymer dispersions, which are adjusted by the manufacturers through functionalization so that they have the appropriate barrier effect without being significantly water-soluble. or by adding a deficit of water-soluble polymers, which ensure or enhance the overall oleophobic effect.

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

Also suitable is the use of crosslinked or partially hydrophobized polyvinyl alcohols, ethylene vinyl alcohols, or other copolymers of vinyl alcohol (for example those described in EP 4041548 A1), carbohydrates and/or proteins.

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

Due to their high surface tension (surface energy), polyvinyl alcohols are particularly suitable for applying additional thin metal layers that have a significantly lower and predominantly disperse surface tension

The barrier paper according to the invention can preferably comprise at least one further layer which consists of or comprises metals, in particular aluminum. In this way, the barrier effect in particular can be further improved. This further layer can be used as an intermediate layer or as Top layer formed his. Designed as an intermediate layer, this layer is preferably located directly below or above a heat-sealable layer, for example the coating layer Sl.

Polyacrylates, which preferably contain a starch-based protective colloid, are particularly preferred. A suitable polyacrylate is known under the trade name Epotal SP 101 D.

Also suitable are polyacrylates or polyacrylonitriles, which are known, for example, under the trade name Rhobarr 214.

Such polymers have the advantage that they swell little when they come into contact with water, because when they swell, a layer painted on them does not achieve its optimal water vapor barrier.

In one embodiment, the hydrophilic polymer is contained in an amount of 30 to 100% by weight, or 50 to 100% by weight, based on the total weight of the coating color layer S2.

Other possible components of the coating layer S2 include, for example, pigments, in particular inorganic pigments, such as Ca carbonate (GCC or PCC), talc, kaolins, natural and/or synthetic silicates.

Such pigments are preferably contained in an amount of 0 to 70% by weight, particularly preferably 0 to 50% by weight, based on the total weight of the coating color layer S2. Preferably, the value 0% by weight is just excluded as a lower limit.

Platelet-shaped pigments are preferred, as these can contribute to improving the barrier when aligned laminarly parallel to the coating. The particle size should preferably be chosen so that the particles are completely enclosed in the layer when aligned in a laminar manner. The aspect ratio (ratio of average diameter to thickness, also called form factor) should be greater than 10, preferably greater than 100 and particularly preferably greater than 1000. In one embodiment, the coating layer S2 further comprises further additives. Possible additives include, for example, thickeners, surfactants, crosslinkers and/or rheology modifiers.

Such additives are preferably contained in an amount of 0 to 2% by weight, particularly preferably 0 to 2% by weight, based on the total weight of the coating color layer S2. Preferably, the value 0% by weight is just excluded as a lower limit.

Preferably, the coating layer S2 does not contain any glyoxal.

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

The polar proportion of the surface tension of the coating layer S2 is preferably 60 to 95%, in particular 70 to 90% and particularly preferably 78 to 84%.

The disperse portion of the surface tension of the coating color layer S2 is preferably from 5 to 40%, in particular 10 to 30% and particularly preferably from 16 to 22%.

The surface tension and the respective proportions are determined as defined above.

Preferably, the surface tension of the coating layer S2 is at least 5 mN/m, generally 20 to 30 mN/m, greater than that of the coating layer Sl, and preferably has a significantly higher polar proportion, since this is due to the wax content in the coating layer Sl in particular measurements have shown that it can be a maximum of 12%.

The application amount (ISO 536, 2020-05) of the coating color layer S2 is preferably 3 to 12 g/m ² and particularly preferably 8 to 10 g/m ² . The amount refers to the dried coating layer S2 in the final product.

The smoothness of the coating layer S2 (according to Bekk (ISO 5627, 1995-03)) is preferably 80 to 500 s, preferably from 100 to 200 s. The roughness of the coating color layer S2 (according to Parker-Print-Surf (PPS) DIN ISO 8791-4, 2008-05) is preferably 2 to 4 pm, preferably 2.5. to 3.5 p.m.

In one embodiment, the barrier paper according to the invention is characterized in that a further coating layer S3 is present directly on the base paper, in particular a coating layer which comprises or consists of at least one inorganic pigment and a polymeric binder.

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

The aspect ratio (ratio of average diameter to thickness, also called form factor) should be about 7 to 40 to 1, preferably about 15 to 30 to 1.

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

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

The polymeric binder preferably comprises a polymeric binder based on a polyacrylate.

The polymeric binder preferably comprises a styrene-acrylate copolymer, preferably a styrene-butyl acrylate copolymer, especially a styrene-n-butyl acrylate copolymer. A suitable styrene-n-butyl acrylate copolymer is known, for example, under the trade name Acronal S 305 FD.

Overall, the coating layer S3 can be a hydrophobic primer.

In another embodiment, the coating layer S3 is hydrophilic overall.

The coating layer S3 preferably contains 5 to 50% by weight, preferably 10 to 30% by weight, of polymeric binder. The amount refers to the dried coating layer in the final product.

The coating color layer S3 further contains preferably 50 to 95% by weight, preferably 70 to 90% by weight, of inorganic pigment. The amount refers to the dried coating layer in the final product.

In addition, the coating layer S3 can contain additives such as thickeners, e.g. acrylate-based thickeners, surfactants and/or rheology modifiers. The use of networkers is also conceivable. The coating layer preferably contains a zirconium-based crosslinker and is itself crosslinked with formaldehyde.

These additives are preferably each contained in an amount of 0 to 2% by weight, preferably greater than 0 to 2% by weight, with the value 0% by weight preferably being excluded. The amount refers to the dried coating layer S3 in the final product.

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

If such a coating layer S3, also called a precoat or primer, is applied, this has the advantage that the paper surface is sealed and the further coating layer applied on it only migrates slightly into the paper. Furthermore, this coating layer reduces the average roughness depth of the base paper and offers an advantageous coating color holdout, which is characterized by an area-wide application and a defined surface energy, so that a coated coating is achieved Coating color layer can optimally form and can form an optimal barrier with as little application as possible, which has an advantageous effect on the cost structure. In addition, the primer is designed in such a way that the layer adhesion between the base paper and the coating color layer is not significantly reduced, which can be important for later sealing applications .

The surface tension of the coating layer S3 is preferably 15 to 40 mN/m, in particular 22 to 30 mN/m.

The polar portion of the surface tension of the coating color layer S3 is preferably 10 to 50%, in particular 15 to 30%.

The disperse portion of the surface tension of the coating color layer S3 is preferably 50 to 90%, in particular 70 to 85%.

For good wetting and layer adhesion, the surface tension of the primer should be higher or at least more polar than that of the layer on top.

If an embodiment with a layer S2 is present, this may not be guaranteed since the coating layer S2 itself already has a high surface tension and a high polar content. A highly polar coating layer S3 would swell too much when coated with an aqueous coating formulation, which could lead to cracks after drying. Therefore, the data given on the surface tension of the coating layer S3 in particular have proven to be a universal basis for the direct coating of the coating layer S1 or the coating layer S2.

The smoothness of the coating layer S3 (according to Bekk (ISO 5627, 1995-03)) is preferably 80 to 200 s, preferably 90 to 120 s

The roughness of the coating color layer S3 (according to Parker Print Surf (PPS) DIN ISO 8791-4, 2008-05) is preferably 2.8 to 4.0 pm, preferably 3.2 to 3.6 pm. In one embodiment, the barrier paper according to the invention can comprise further layers in addition to the coating color layers SI, S2 and S3 described above.

50, for example, the uncoated side of the paper can be provided with one or more coatings that are more printable than the surface of the base paper that is only provided with a starch film.

In order to improve the overall barriers of a paper, smooth surfaces can be vapor-deposited with metals or metal oxides (e.g. via vacuum vapor deposition).

The prerequisite for this is preferably smooth surfaces, such as in this case the coating layer S2 or the coating layer Sl, or even a smooth printing line on the uncoated side of the barrier paper.

Barrier varnishes are also known, e.g. B. a processor can also apply it over a large area or only to certain areas.

An example would be the product HYDRO-LAC GA oxygen barrier varnish from the manufacturer Hubergroup Print Solutions. This varnish can be applied to the coating layer Sl or to the uncoated side of the barrier paper, or better yet to a smooth printing line.

The barrier paper can be used as heat-sealable barrier paper, but there is still the option of applying cold-seal adhesive to one of the two sides, especially if the paper is to be used on a packaging system designed for cold-seal adhesive.

Preferably, one of the two sides, preferably the print side, can also be equipped with another heat-sealing adhesive with the aim of sealing between the front and back (A/B sealing).

In one embodiment, the barrier paper comprises the coating color layers

51 and S3, as defined above. In one embodiment, the barrier paper comprises the coating layers SI, S2 and S3, as defined above.

Here too, the coating layer S3 can be applied in two or more coatings as described above.

The barrier paper according to the invention can be obtained economically using all known methods of paper production and coating (film press with or without pre-metering, roller application, doctor blade, blade, curtain coater, spray coater).

However, it is preferred to obtain the barrier paper according to the invention using a process in which an aqueous suspension or solution comprising the starting materials of the respective coating layer S1, or coating layers S2+S1, is applied to the base paper, preferably coated with a coating layer S3, wherein the aqueous application suspension or solution has a solids content of 15 to 55% by weight, preferably 20 to 45% by weight, and with a curtain coating process (curtain coating), in the case of the coating color layers S2 + Sl, the two coatings can be applied one after the other with intermediate drying or preferably with a double curtain coating process (double curtain coating) at an operating speed of the coating system of at least 100 m / min, preferably > 200 m / min.

The barrier paper is then preferably dried, whereby the drying should be carried out gently so that the web temperature never exceeds 90°C, otherwise boiling bubbles can form which worsen the quality of the barriers or, in extreme cases, destroy them. Contactless drying systems consisting of a group of infrared dryers whose drying performance can be individually adjusted, followed by several hot air hoods that can also be individually adjusted, have proven successful. Optionally, a second section with IR dryers can be installed afterwards to achieve better film formation.

This process is particularly advantageous from an economic point of view and due to the uniform application over the paper web. If the solids content falls below approximately 15% by weight, the economic efficiency deteriorates because a large amount of water has to be removed in a short time through gentle drying, which has a disadvantageous effect on the coating speed. On the other hand, if the value of 55% by weight is exceeded, then this only leads to increased technical effort in order to ensure the stability of the coating color curtain during the coating process and the drying of the applied film, since in this case the machine is again very must run quickly.

In the curtain coating process, a freely falling curtain of a coating dispersion is formed. The coating dispersion, which is in the form of a thin film (curtain), is “poured” onto a substrate by free fall in order to apply the coating dispersion to the substrate. DE 10 196 052 TI discloses the use of the curtain coating coating process in the production of information recording materials , wherein multilayer recording layers are realized by applying the curtain consisting of several coating dispersion films to substrates.

In a preferred embodiment of the method according to the invention, the aqueous deaerated application suspension has a viscosity of about 100 to about 400 mPas (Brookfield, 100 rpm, 20 ° C). If the value of around 80 mPas is not reached or the value of around 500 mPas is exceeded, this leads to poor running ability of the coating material on the coating unit. The viscosity of the aqueous deaerated application suspension is particularly preferably about 150 to about 300 mPas.

In a preferred embodiment, to optimize the process, the dynamic surface tension of the aqueous application suspension can be set to about 35 to about 55 mN/m, preferably to about 38 to about 52 mN/m (measured 50 ms after bubble formation) based on the standard for bubble pressure tensiometry ( ASTM D 3825-90), as described below). Better control over the coating process can be achieved by determining the dynamic surface tension of the coating color and adjusting it specifically by selecting the appropriate surfactant and determining the required amount of surfactant. The individual coatings can be formed on-line on a paper machine with a coating mechanism or in a separate coating process off-line on a coating machine. For development purposes and the production of prototypes, the paper can also be produced on a laboratory scale using a hand squeegee and subsequent drying in a drying oven. The drying can e.g. B. analogous to the temperature treatment described above for 3 minutes at 90 ° C in a drying cabinet. Since the risk of boiling bubbles forming is lower with this slow drying process, a temperature of greater than 100°C can also be set, preferably 105°C.

In further embodiments, the individual coating color layers can also be applied to the base paper using the following methods:

A coating layer can be applied to the base paper and/or to existing coating layers using printing processes (e.g. flexographic printing and gravure printing).

The coating layer can be applied water-free as a melt by extrusion onto the base paper and/or onto existing coating layers.

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, however, are lower application speeds, higher energy consumption and a higher minimum application weight.

The coating layer can be applied by lamination or laminating paper, for example in the form of plastic films, to the base paper and/or to existing coating layers.

The coating color layers can also be applied one after the other over several application steps. The present invention further relates to a barrier paper which is obtainable using the processes described above.

Finally, the present invention also relates to the use of a barrier paper as described above as a packaging material or as a component of packaging material, in particular heat-sealable packaging material but also by applying cold sealing lacquer or other media for closing flexible packaging, preferably for food, in particular for packaging greasy and moisture-sensitive packaging Food, luxury goods such as tobacco, coffee, tea, medicinal herbs, as well as household items, cosmetic products, other moisture-sensitive consumer goods such as washing powder, coffee pads, sanitary napkins, baby diapers and handkerchiefs and to protect them from mineral oil vapors from the environment.

The barrier paper according to the invention can be used on all common packaging systems. For example, vertical and horizontal tubular bag machines (form-fill-seal) for the production of, among other things, stand-up bags, flow packs or pillow packs, air cushion bags or pillows as a replacement for plastic air cushion bags or pillows. Machines that bring two webs of the same or different materials together and through Connect heat seal, e.g. B. also tray sealers, chamber belt machines (also with vacuum), bag filling and sealing machines, thermoforming packaging machines, linear filling machines that attach lids by heat sealing for sealing, wrapping machines with a final heat sealing step, blister packaging machines and X-fold packaging machines.

In a further, preferred embodiment of the invention, the coated paper according to the invention is applied to cardboard or cardboard, in particular by laminating, laminating or gluing.

The present invention also relates to a packaging material, in particular a heat-sealable packaging material, consisting of or comprising a barrier paper as described above The invention is explained in detail below using non-limiting examples.

Examples

For comparative examples 1 to 3 and examples 1 to 5, base papers from a production line were used.

The pure base paper was produced on the associated paper machine (38% by weight long fiber, 57% by weight short fiber, 5% by weight calcium carbonate as filler, fully sized with alkyl ketene dimer on water cobb 25 g/m ² ), smoothed using a calender and enzymatically partially degraded cationically modified potato starch (approx. 1 g/m ² ) was applied to both sides using a film press.

The paper machine is equipped with a smoothing cylinder (Yankee cylinder) and is therefore able to produce paper that is smooth on one side.

As a second step, this paper was provided with a coating layer S3 on a production coating machine, which was applied using a blade coater to the less smooth side, which was on the side facing away from the smoothing cylinder during the smoothing process (Comparative Examples 1 to 3 and Examples 1 to 3).

For Examples 4 and 5, the coating color S3 was applied in two steps. 4 g/m ² were already applied online on the paper machine to the less smooth side, while a further 4 g/m ² were applied immediately afterwards using a blade coater, as in the previous examples and comparative examples

For comparative examples 1, 2 and 3, the coating layer S2 and then the coating layer S1 were applied directly to the coating layer S2 individually in separate coating tests on a pilot coating system, both using curtain coaters.

In comparative example la and examples 4 and 5, the coating layer S1 was applied directly to the coating layer S3 in the same way.

The drying unit consists of a series of electric infrared dryers followed by a block of air hoods (hot air drying). The information on the length of the drying sections, the web temperature of the paper surface and the residence time in the respective drying area can be found in Tables 1 and 2a, whereby the manufacturing parameters are only given for the application of the coating layer S1

Examples 1, 2 and 3 were also produced on a production coating machine using a curtain coater. There, too, the drying unit consists of a block of infrared dryers, but here operated with natural gas, followed again by a block consisting of air hoods. Example 2 does not contain any coating layer S2. The coating layer S1 is applied directly to the coating layer S3. While Examples 1 and 3 still contain a coating layer S2.

The information on the length of the drying sections, the web temperature of the paper surface and the residence time in the respective drying area can be found in Table 2, whereby the manufacturing parameters are only given for the application of the coating color layer S1. The drying of the coating layer S2 is less demanding, so that there are no differences in the mineral oil and grease barrier between production on the pilot or production coating system.

Production of the coating color S1 (comparative examples 1 to 3 and examples 1 to 3) (recipe from pilot plant, scaled up identically for production plant) Aqueous application suspension with a solids content of 20 to 60%:

38.1 kg of water are introduced and 452.8 kg of styrene acrylate/methyl acrylate/butyl acrylate/ethylhexyl acrylate 97.8% by weight and beeswax 2.0% by weight, in the case of comparative example 3 styrene acrylate/methyl acrylate /butyl acrylate/ethylhexyl acrylate 91.82% by weight and beeswax 8.0% by weight mixed. The following additives are 0.523 kg of the expansion rheology aid Sterocoll DF 4 (BASF SE, polyacrylamide, W/O emulsion) and 0.188 kg of the defoamer Genapol PF 10 (Clariant Products (Deutschland) GmbH, polymerization product of propylene oxide and ethylene oxide). The result is a pH value of approx. 8.5 and a viscosity (Brookfield) of approx. 160 mPas.

Production of the coating color S 1 (Examples 4 and 5):

Aqueous application suspension with a solids content of 20 to 60%: 16 kg of water are introduced and mixed with 267 kg of an aqueous suspension consisting of 90 parts of a carboxylated styrene-butadiene polymer and 10 parts of a paraffin wax with chain lengths C 21 - C 38. Solutions of 6.5 kg of polyvinyl alcohol of type 8-88 and 15.6 kg of polyvinyl alcohol of type 28-99 follow as thickeners. The following additives are 0.2 kg of the expansion rheology aid Sterocoll DF 4 (BASF SE, polyacrylamide, W/O emulsion) and 0.7 kg of the defoamer Genapol PF 10 (Clariant Products (Deutschland) GmbH, polymerization product of propylene oxide and ethylene oxide). 1.7 kg of Dynawet 2050 (CTP GmbH), a non-ionic surfactant preparation with CAS # 160875-66-1 as the main active ingredient, is added as a surfactant. The result is a viscosity of 230 mPas and a pH value of 6.5.

Production of the coating color S2: (Recipe from pilot plant, scaled up identically for production plant).

77 kg of water are introduced and mixed with 228.6 kg of Epotal SP 101 D (BASF SE, polyacrylate with starch-based protective colloid). The following additives are 0.957 kg of the thickener Texturecel 100 GA (DDP Specialty Products Germany GmbH, carboxymethylcellulose), 0.081 kg of the extensional rheology aid Sterocoll DF 4 and 0.210 kg of the defoamer Genapol PF 10. A pH value of 8.8 is set by adding caustic soda , and the result is a viscosity (Brookfield) of approx. 200 mPas.

Both coating colors are suitable for curtain coaters and are deaerated by vacuum in the working container of the coating machines before coating.

Production of the coating color S3:

The composition is shown in Table 1: For a person skilled in the art, this information is sufficient to produce a spreadable coating composition.

The composition of the respective coating layers, the drying parameters and the determined properties of the barrier papers are summarized in Table 1 below. Description of the measurement methods for which no standard is known or separate procedures have been developed:

Heat sealability: While the seal seam strength of an existing seal seam is tested by e.g. B. DIN 55529: 2012-09 is clearly defined, there is no standardized method with which to test the suitability of a material for heat sealability. This is obviously because packers prefer to develop their own incoming inspections for heat-sealable films or papers tailored to their packaging systems.

Based on industry information, relatively critical sealing conditions were used (sealing time 0.3 s, sealing pressure 3.33 bar, smooth sealing jaws). Sealability is tested in such a way that the two sealable coatings of a paper are sealed against themselves. To determine the optimal sealing temperature, test specimens are produced that were sealed at different temperatures of the sealing jaws (100-200°C).

Hot tack (hot seam strength): Is carried out in accordance with DIN 55571-2-Procedure C. It should also be noted that the same sealing conditions apply as for testing heat sealability. 80 ms was chosen as the cooling time between sealing and force measurement. The force measurement is carried out over a pull length of 80 mm.

Palm kernel fat test according to DIN 53116: Test condition I (pressure 2000 N/m ² and exposure time > 24 h was chosen, practice 25 h). The print side of a NexCoat-Smart 60 g/m ² CIS paper (Koehler Paper SE) is used as the display paper.

Testing the palm kernel fat test on a folded paper: For folded samples, a fold of 180° is created with a roller that applies a load of 330 g/cm to the resulting fold and in which the coating is on the inside (inside fold) or outside (outside fold). can be located.

Hexane permeability (HVTR, hexane vapor transmission rate): Here, n-hexane is filled into a beaker (solvent-resistant), sealed tightly with the test specimen and the weight loss is monitored over time. The test is carried out at 23°C and 50% humidity. The coated side faces inwards Hexane vapor atmosphere. Corresponding cups with PTFE seals are available from specialist retailers.

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

Dependence of the water vapor permeability of the coating on contact with fat: The test specimen is first subjected to a palm kernel fat test analogous to DIN 53116 2003-02. The corresponding test conditions are specified. At the end of the exposure time, after wiping off the grease, the water vapor permeability (WVTR) of the paper is determined according to ISO/FDIS 2528. After wiping off the grease (which by default contains a red dye), some remains in or on the water vapor barrier coating. However, this does not lead to any further change in the WVTR, as a constant water vapor permeability is established over the course of the measurement.

The determination of the dynamic surface tension of the dry paper coatings is explained in the description.

Regarding tables 1, 2 and 2a:

The columns marked with * contain the measured values of the paper indicated on the left after a 3-minute treatment in the hot air drying oven at 105°C. A binder type E 115 drying oven was used with the following internal dimensions: width x height x depth: 60 x 48 x 40 cm ( Internal volume 115 dm ³ ), drying oven temperature range: 0 - 250°C, natural convection, no circulating air fan). In the oven there is a metal grid at the middle height and a cardboard box about 2 mm thick lying on it. Now the oven is preheated to 105°C for at least 30 minutes. While the door is opened briefly (< 2 s), the test specimen is placed on the box. After 3 minutes, the test specimen is removed and air-conditioned for at least 12 hours at 23°C and 50% RH before further measurements are taken. Table 1: Comparative examples

* Post-drying: 105 °C, 3 min

** no coating layer S2

Table 2: Examples

* Post-drying: 105 °C, 3 min

** no 2nd coat of paint

Table 2a: Examples

* Post-drying: 105 °C, 3 min

Example 2: (Example 2 from Table 1)

Another heat-sealable paper according to the invention with a water vapor barrier for flexible packaging was tested.

The paper is suitable for various applications as secondary packaging and primary packaging, especially for food and non-food products that require a water vapor barrier.

Advantages of the paper are:

- Without optical brighteners

- Water vapor barrier for optimal product protection

- Good sealability

- Excellent strength properties

- Suitable for direct food contact

- 100% virgin fiber pulp

- Very good running properties on converting and packaging systems

- Recyclable in the paper cycle

- Particularly suitable for flexo, gravure and digital printing

The properties of the paper are summarized in Table 3 below.

Table 3:

Example 3: (Example 1 from Table 1)

Another heat-sealable paper according to the invention made from virgin fiber pulp with barriers against water vapor, grease and mineral oil residues was tested.

The paper is suitable for various applications in the tobacco industry for particularly demanding tobacco products.

Advantages of the paper are:

- High degree of whiteness

- Without optical brighteners

- Smooth surface

- Good sealability

- Very good aroma barrier

- High kink-break resistance

- Excellent strength properties

- Suitable for direct food contact

- 100% virgin fiber pulp

- Excellent print and varnish condition

- Very good running properties on converting and packaging systems

- Particularly suitable for flexographic and gravure printing

The properties of the paper are summarized in Table 4 below.

Table 4:

Example 4: (Example 1 from Table 1)

The paper is suitable for various applications as secondary packaging and primary packaging for tobacco products such as tobacco volume pouches, tobacco pouches and coated tobacco inner liners with a barrier.

Advantages of the paper are:

- Without optical brighteners

- Water vapor barrier for optimal product protection

- Good sealability

- Excellent strength properties

- Suitable for direct food contact

- 100% virgin fiber pulp

- Very good running properties on converting and packaging systems

- Recyclable in the paper cycle

- Particularly suitable for flexographic and gravure printing

The properties of the paper are summarized in Table 5 below.

Table 5:

Example 5: (Example 1 from Table 1)

Another fat-resistant heat-sealable paper according to the invention made from virgin fiber pulp with a water vapor barrier and a mineral oil barrier was tested.

The paper is suitable for various applications in flexible packaging for dry and powdery filling goods from the food and non-food sectors.

Advantages of the paper are:

- High degree of whiteness

- Without optical brighteners

- Smooth surface

- Good sealability

- High kink-break resistance

- Excellent strength properties

- Suitable for direct food contact

- 100% virgin fiber pulp

- Excellent print and varnish condition

- Very good running properties on converting and packaging systems

- Particularly suitable for flexo, gravure and digital printing

The properties of the paper are summarized in Table 6 below.

Table 6:

Claims

Expectations

1. Barrier paper, comprising a base paper and at least one coating layer Sl applied directly or indirectly to the base paper, the coating layer Sl comprising at least one polymeric binder and at least one wax, and wherein the coating layer Sl has at least one of the following features: a) change in the Surface tension of not more than +10 mN/m, preferably not more than +6 mN/m, b) change in the polar component of the surface tension not more than - 0.65 mN/m, preferably not more than -0.60 mN/ m, c) change in the polar component of the surface tension not more than -3.0% points, preferably not more than -1.5% points, the respective change being determined by measuring and comparing the measured values of the surface tension and the polar component of the Surface tension is determined before and after temperature treatment of the barrier paper at 105 ° C for 3 min.

2. Barrier paper according to claim 1, wherein the wax content of the coating layer Sl is selected such that the barrier paper has at least one of the following features: a) a sealing seam strength (cold tack) after sealing the coating layer Sl against the coating layer Sl of > 4 N /15mm, with the heat sealing parameters sealing temperature of 130 to 150 °C, sealing time of 0.3 see, sealing pressure of 3.3 bar or with ultrasonic sealing parameters that cause a sealing temperature of 130 to 150 °C and a sealing time of 0.3 s and a sealing pressure of 3.3 bar, b) a water vapor permeability (WVTR) < 20 g/m ² /d (38°C, 90% RH), c) a water vapor permeability (WVTR) < 8 g/m ² /d (23 °C, 50% RH), d) an increase in water vapor permeability (38°C, 90% RH) after carrying out the palm kernel fat test according to DIN 53116 under the test conditions (10 min exposure time and pressure load of 2000 N/m ² ), by not more than 70 g/m ² /d, preferably not more than 60 g/m ² /d, e) an increase in the water vapor permeability after carrying out the palm kernel fat test according to DIN 53116 under the test conditions (60 min exposure time and 2000 N/m ² ) of not more than a factor of 6, f) a static coefficient of friction (coating layer S1 against coating layer Sl) of < 0.9, g) a kinetic coefficient of friction ( Coating color layer Sl versus coating color layer Sl) of <0.6, the values for a) to g) being determined for a basis weight of the coating color layer Sl of <12 g/m ² .

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

4. Barrier paper according to any one of the preceding claims, wherein the wax is a wax as defined by DGF (DGF standard method M-I 1 (75)).

5. Barrier paper according to any one of the preceding claims, wherein the at least one wax is a wax based on mixtures or pure substances of fossil or natural short to medium chain hydrocarbons, their acids, esters, amides and diamides, hydrogenated vegetable oils, by hydrogenation or partial hydrogenation of vegetable oils and animal oils or fats and/or metal soaps, preferably heneicosan, docosan, tricosan, tetracosan, pentacosan, hexacosan, heptacosan, octacosan, Nonacosan, triacontan, hentriacontan, dotriacontan, tritriacontan, tetratriacontan, pentatriacontan, hexatriacontan, heptatriaontan, octatriacontan, nonatriacontan, montan waxes, carnauba wax, beeswax, candelilla wax, rice bran wax, sugar cane wax, wax obtained from sunflower seed press cake, particularly preferably beeswax and/or wax obtained by Hydri eration of Soybean oil, and/or paraffin waxes with an average molecular weight of at least 500 Daltons and a viscosity of at least 11 cSt at 100°C.

6. Barrier paper according to any one of the preceding claims, wherein the at least one wax in an amount of 0.01 to 10% by weight, preferably from 0.01 to <8.0% by weight, preferably from 0.01 <6 .0% by weight, particularly preferably from 0.01 to <5.0% by weight, and most preferably from 0.01 <2.0% by weight, the lower limit is preferably at least 0.1% by weight. -%, particularly preferably at least 0.2% by weight, based on the total weight of the coating color layer Sl, is contained in this.

7. Barrier paper according to any one of the preceding claims, wherein the at least one polymeric binder in the coating layer Sl is selected from the group comprising polyacrylates and copolymers with unsaturated hydrocarbons, polyolefins, copolymers consisting of unsaturated hydrocarbons and acrylic acid or salts thereof (partially carboxylated) Styrene-butadiene copolymers, styrene-butadiene copolymers, styrene-butadienes, polyvinyl acetates, partially saponified polyvinyl acetates, polyesters, such as polylactides, and polyhydroxyalkanoates made from glucose, polyamides, polyurethanes, polyethers, polyethyleneimines, and / or polyvinylamides, preferably selected from the group , comprising polymethyl acrylates, polymethyl methacrylates, polyethyl arylates, polyethyl methacrylates, poly (n-, iso-, tert-) butyl acrylates, poly (n-, iso-, tert-) butyl methacrylates, polycyclohexyl methacrylates, polyethylhexyl acrylates and their copolymers, graft polymers, as well Copolymers thereof with styrene, acrylonitrile, methylstyrene and/or vinyl toluene, particularly preferably styrene acrylate/methyl acrylate/butyl acrylate/ethylhexyl acrylate copolymer and/or natural polymers, such as polysaccharides or modified polysaccharides, proteins, lignin or lignin derivatives and other natural macromolecules, such as shellac.

8. Barrier paper according to any one of the preceding claims, wherein the at least one polymeric binder is in an amount of 99.9 to >92% by weight, preferably >94% by weight, particularly preferably >95% by weight and very particularly preferred > 98% by weight based on the total weight of the coating layer Sl contained in this.

9. Barrier paper according to any one of the preceding claims, wherein the at least one wax in the coating layer Sl is enriched on the side facing away from the base paper, which is indirectly proven by the fact that the change in the polar component of the surface tension is not more than - 0.65 mN / m, and/or the change in the polar component of the surface tension is not more than -3.0% points, the respective change being determined by measuring and comparing the measured values of the polar component of the surface tension before and after a temperature treatment of the barrier paper at 105 ° C is determined for 3 min.

10. Barrier paper according to any one of the preceding claims, wherein the base paper has a basis weight of 20 to 120 g/m ² , preferably 40 to 100 g/m ² .

11. Barrier paper according to any one of the preceding claims, wherein the base paper has a long fiber content of 10 to 80% by weight, preferably from 20 to 50% by weight, and a short fiber content of 20 to 90% by weight, preferably from 50 to 80 % by weight, wherein a long fiber is a fiber with a fiber length of 2.6 to 4.4 mm and a short fiber is a fiber with a fiber length of 0.7 to 2.2 mm.

12. Barrier paper according to one of the preceding claims, wherein the base paper has a filler content of 0% by weight to 20% by weight, preferably 0% by weight to 5% by weight, of fillers, preferably the value 0% by weight. % is excluded, the fillers including in particular ground calcium carbonate (GCC), precipitated calcium carbonate (PCC), kaolin and / or talc.

13. Barrier paper according to any one of the preceding claims, wherein the barrier paper has at least one further coating color layer S2 applied indirectly or directly between the base paper and the coating color layer S1, in particular to form a mineral oil and / or fat barrier layer and / or also an oxygen barrier layer, comprising at least one hydrophilic polymer.

14. Barrier paper according to any one of the preceding claims, wherein a further coating layer S3 is present directly on the base paper, in particular a coating layer color layer which comprises or consists of at least one inorganic pigment and a polymeric binder.

15. A process for producing a barrier paper according to any one of the preceding claims, characterized in that an aqueous suspension comprising the starting materials of the coating color layer Sl is applied directly or indirectly to the base paper, the aqueous application suspension having a solids content of 15 to 55% by weight. %, preferably from 20 to 45% by weight, and with a curtain coating process at an operating speed of the coating system of at least 100 m / min and then dried, the drying preferably taking place using infrared or heat radiators and a subsequent air hood area and the Web temperature remains <90°C throughout the drying area.

16. Barrier paper, obtainable by the method according to claim 15.

17. Use of a barrier paper according to any one of claims 1 to 14 or claim 16 as a packaging material or as a component of packaging material, in particular heat-sealable packaging material, preferably for food, in particular for packaging greasy and moisture-sensitive food and for protecting it from mineral oil vapors from the environment.

18. Packaging material, in particular heat-sealable packaging material, consisting of a barrier paper or comprising a barrier paper according to any one of claims 1 to 14 or according to claim 16.

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