Barrier paper

Abstract

The invention relates to a barrier paper comprising a base paper and at least one painted colour layer S1 applied indirectly or directly to the base paper, the painted colour layer S1 comprising at least one polymeric binder and at least one wax; methods of making such barrier papers; the use of such barrier paper as packaging material; and packaging materials comprising such barrier paper.

Description

[0001] The present invention relates to a barrier paper, a process for producing such a barrier paper, the use of the barrier paper as packaging material and a package comprising the barrier paper.

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

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

[0004] The main demands on packaging materials, regardless of their origin, are to protect the packaged goods from external influences and to prevent the packaged goods from leaking out and to function as advertising and information carriers. For this purpose, the packaging materials should meet different criteria depending on the packaged goods and the unpacking process. Thus, in addition to the above-mentioned barrier properties against, for example, water, fat, oxygen or mineral oil, suitable packaging materials should also meet mechanical and process-specific requirements. Depending on the packaging equipment, the packaging materials, in particular flexible packaging materials, should have sufficient tear resistance, matching friction values ​​(friction coefficients) and flexibility, should be heat-sealable and should be printable from the outside without losing their protective effect during the entire transfer and unpacking process.

[0005] Known coated paper-based packaging materials usually contain compounds such as polyvinylidene chloride (containing halogen) or are composite materials of paper and metal or plastic foils, have tear resistance that requires improvement, can lead to operating problems on packaging equipment, and / or are usually not recyclable due to excessively high coating proportions of adhesive components or due to the formation of so-called stickies by the paper fiber flow.

[0006] Polyvinyl alcohol, in particular crosslinked polyvinyl alcohol, is also known for use as linear, water-soluble, biodegradable barrier coatings (also for paper). Such coatings have good barrier properties against oils, fats, oxygen, solvents and other non-polar gases, liquids or solids. However, polyvinyl alcohol has a very high permeability to polar compounds (e.g. water) due to its hydrophilicity. This can also affect the barrier effect against non-polar migrants, since polyvinyl alcohol absorbs moisture very well, swells and thus creates channels through the barrier coating at the molecular level.

[0007] In order to solve this problem, a mixture formed by any type of polymer dispersion and wax emulsion is provided. However, when testing the prepared paper in laboratory experiments and pilot experiments, it has been observed that such known mixtures formed by polymer dispersion and wax emulsion have the following disadvantages, namely fat can penetrate into the coating, which in turn leads to an increase in water vapor transmission rate. There is thus the following risk, namely the water vapor transmission rate increases when directly contacting fatty foods. It is also observed that the heat sealability deteriorates when the laboratory formulation is transferred to the pilot coating equipment. In addition, when preparing such coatings on a pilot scale, it is generally observed that the heat sealability decreases with the continuous storage time. This ability of the material hereinafter is understood to be the stability of the sealing seam that is produced by heat sealing, rather than the sealing seam that has been produced.

[0008] The object of the present invention is to overcome the disadvantages of the known materials and to provide a material which is suitable for use as a packaging material, in particular for moisture-sensitive food products and which, when in contact with fat, keeps its water vapor transmission rate low or increases it as little as possible. In addition, the material must be usable for heat sealing applications. In particular, it is intended to achieve a sealing seam strength of more than 4 N / 15 mm and a target value of <20 g / m 2 / d (38°C, 90% relative humidity) or <8g / m 2 / d (23°C, 50% relative humidity) water vapor transmission rate (WVTR).

[0009] Furthermore, the material according to the invention should be as simple to produce as possible, be achievable with the lowest possible applied weight and be as recyclable as possible through the paper fiber stream.

[0010] This object is achieved by a barrier paper according to claim 1, that is to say by a barrier paper comprising a base paper and at least one paint layer S1 applied indirectly or directly to the base paper, wherein the paint layer S1 comprises at least one polymeric binder and at least one wax, and wherein the paint layer S1 has at least one of the following features:

[0011] a) a surface tension change of not more than +10 mN / m, preferably not more than +6 mN / m,

[0012] b) a partial change in the polarity of the surface tension of not more than -0.65 mN / m, preferably not more than -0.60 mN / m,

[0013] c) a change in the polar fraction of the surface tension of not more than -3.0%, preferably not more than -1.5%,

[0014] The corresponding changes are determined by measuring and comparing the measured values ​​of the surface tension and the polar part of the surface tension before and after the temperature treatment of the barrier paper at 105° C. for 3 minutes.

[0015] Preferred embodiments are defined in the dependent claims.

[0016] Such coated paper is particularly unique in that it is particularly well suited as a packaging material for moisture-sensitive fatty objects, in particular food products, and can be used for heat-sealing applications.

[0017] Furthermore, the reference values ​​defined above with respect to heat sealability and water vapor transmission rate can be achieved with such barrier papers.

[0018] Finally, the barrier paper of the present invention can be produced relatively simply and with a small applied weight and can be recycled via old paper.

[0019] Numerous specific details are also explained below to provide a broad understanding of the current subject matter. However, it is obvious to those skilled in the art that the subject matter can also be practiced and modified without these specific details.

[0020] If the features of different embodiments are identical, all features of one embodiment may be combined with the features of other embodiments.

[0021] The terms used in the specification of the present disclosure are only used to illustrate certain embodiments and should not be construed as limiting the subject matter. As used in this specification and in the claims, the singular forms "one", "a kind of" and "the" should be understood to also include plural forms, as long as the context does not clearly indicate otherwise. The opposite content is also used, that is to say, the plural form also includes the singular form. It can also be understood that, as used herein, the term "and / or" relates to all possible combinations of one or more of the listed related elements and includes these combinations. It can also be understood that when the terms "comprise", "contain", "include" and / or "include" are used in this specification and in the claims, these terms indicate that there are given features, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, steps, operations, elements, parts and / or their groups.

[0022] In this specification and claims, the terms "comprise", "include" and / or "comprising" may also mean "consisting of", that is, excluding the existence or addition of one or more other features, steps, operations, elements, components and / or groups.

[0023] In the present description and the claims, the term “including” may therefore also mean “exclusively”.

[0024] Unless otherwise indicated, the values ​​stated in "%" within the context of the formulations and / or compositions relate to "% by weight", in particular based on the respective total weight of the respective formulation and / or composition.

[0025] As mentioned above, the barrier paper of the present invention comprises a base paper and at least one paint color layer S1 applied indirectly or directly on the base paper, wherein the paint color layer S1 comprises at least one polymeric binder and at least one wax, and wherein the paint color layer S1 has at least one of the following features:

[0026] a) a surface tension change of not more than +10 mN / m, preferably not more than +6 mN / m,

[0027] b) a partial change in the polarity of the surface tension of not more than -0.65 mN / m, preferably not more than -0.60 mN / m,

[0028] c) a change in the polar and dispersive parts of the surface tension of not more than -3.0%, preferably not more than -1.5%,

[0029] The corresponding change is determined by measuring and comparing the measured values ​​of the surface tension of the polar part of the surface tension before and after the barrier paper has been subjected to a temperature treatment at 105° C. for 3 minutes.

[0030] If the priming color layer S1 is applied directly to the base paper, this means that no further coatings or substances are present between the base paper and the priming color layer S1.

[0031] If the painted color layer S1 is applied indirectly to the base paper, this means that a further coating or substance is present between the base paper and the painted color layer S1.

[0032] Laboratory experiments have shown that although it is possible to apply the paint color layer S1 directly to the base paper, especially to the calendered base paper with surface starch and low reproducibility, it is preferred to apply the base paint in advance for better support (Hold-Out) of the paint color and to minimize the required paint application. Finally, economic and production process considerations also determine which working method is preferred.

[0033] The determination of the surface tension (also referred to as surface energy) of a solid can be determined by contact angle measurements with at least two different liquids. Manufacturers of measuring equipment based on this principle, such as DataPhysicsInstruments GmbH (D-70794Filderstadt), describe the following relationship on their website:

[0034] "The atomic and molecular cohesion that causes the surface tension of a substance is due to different types of interactions. In particular, a distinction can be made between dispersive and polar interactions. Interactions due to fluctuations in the atomic / molecular charge distribution over time are referred to as dispersive interactions (van der Waals interactions). Coulomb interactions between permanent dipoles or between permanent and induced dipoles are summarized as polar interactions (e.g. hydrogen bridges). Accordingly, the surface tension is the additive combination of a dispersive and polar component.

[0035] If the ratio of the dispersive part to the polar part of the specific surface tension is calculated for each of the two phases, then a prediction about the adhesion of the two phases to each other can be derived from this. The greater the consistency of the dispersive part and the polar part, the greater the probability of interaction between the phases and the greater the adhesion to be calculated. "

[0036] If the comparison shows the following measured values: it can be determined that a) there is no substantial change in the surface tension, that is, not more than +10 mN / m, and / or b) or c) there is no substantial change in the polar part of the surface tension, that is, not more than -0.65 mN / m or not more than -3.0%, then the barrier paper has favorable properties.

[0037] The inventors assume that in a coating layer comprising at least one polymeric binder and at least one wax or a combination thereof, the drying of the coating layer also causes the coating layer to at least partially separate and / or partially form a film and in some cases there may also be an uneven distribution of the wax within the coating layer. For the same coating layer composition, depending on how the drying parameters are selected, different properties of the coating layer and thus also different properties of the barrier paper are produced.

[0038] The inventors have transferred this knowledge to the painted color layer S1, wherein the dried painted color layer S1 has at least one of the following characteristics:

[0039] a) a surface tension change of not more than +10 mN / m, preferably not more than +6 mN / m,

[0040] b) a partial change in the polarity of the surface tension of not more than -0.65 mN / m, preferably not more than -0.60 mN / m,

[0041] c) a change in the polar fraction of the surface tension of not more than -3.0%, preferably not more than -1.5%,

[0042] It can be considered as an indicator of the quality of the paint layer S1 with respect to the properties mentioned in the target, in particular whether there is partial separation and / or partial filming of the paint layer S1 or whether there is an uneven distribution of wax within the paint layer S1.

[0043] In other words, the properties of the barrier paper mentioned in the invention object depend not only on the composition of the paint color layer S1, but also on how to dry the paint color layer S1. Therefore, in addition to the composition, the dried paint color layer S1 must also have at least one of the following structural features:

[0044] a) a surface tension change of not more than +10 mN / m, preferably not more than +6 mN / m,

[0045] b) a partial change in the polarity of the surface tension of not more than -0.65 mN / m, preferably not more than -0.60 mN / m,

[0046] c) a change in the polar and dispersive parts of the surface tension of not more than -3.0%, preferably not more than -1.5%,

[0047] The corresponding change is determined by measuring and comparing the measured values ​​of the surface tension of the polar part of the surface tension before and after the temperature treatment of the barrier paper at 105° C. for 3 minutes.

[0048] For a specific paint color composition S1, the drying parameters (temperature, time) should preferably be selected as follows so that after drying, the paint color layer S1 has at least one of the characteristics a) to c), preferably at least two characteristics, and particularly preferably all three characteristics. A person skilled in the art can determine the drying parameters by means of simple drying experiments.

[0049] For successful drying it is preferred that the temperature of the coated web during drying be above the melting range of the wax for a sufficiently long period of time.

[0050] As has been found in numerous laboratory experiments with different polymer-wax mixtures, the surface tension of the paint layer S1 is preferably between 15 and 40 mN / m, in particular between 20 and 35 mN / m.

[0051] The polar portion of the surface tension of the paint layer S1 is preferably 0 to 12%, in particular 0 to 6%, preferably 0 to 3% and particularly preferably 0 to 1%, wherein in a preferred embodiment the value 0% is directly excluded as a lower limit.

[0052] The dispersion fraction of the surface tension of the paint layer S1 is preferably 88 to 100%, in particular 94 to 100%, preferably 97 to 100% and particularly preferably 99 to 100%.

[0053] Determination of the surface tension and the polar and dispersive parts of the surface tension according to DIN EN ISO 19403-2 (2020-04):

[0054] The contact angle measurement device OCA 20 (DataPhysics) and software SCA 20 were used, and the measurement principle was the OWRK method (Owens, Wendt, Rabel, Kaelble).

[0055] The measured liquid used and the source of the material constants entered are:

[0056] Water and diiodomethane (according to Buscher) as well as 1,5-pentanediol (according to Gebhardt). In contrast to DIN EN ISO 19403-2 (2020-04), 1,5-pentanediol is used as the 3rd measuring liquid because, unlike other non-polar measuring liquids, it still allows a measurable contact angle on the paper surface before the liquid is absorbed by the paper.

[0057] The temperature treatment of the barrier paper at 105° C. for 3 minutes is preferably carried out in a hot air oven (drying oven), wherein preferably care is taken 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 occupy a sufficient internal volume (e.g. >100 dm 3 , for example width x height x depth 60cm x 48cm x 37cm), so that no significant temperature drop occurs when the front door is opened for a short time (2-3 seconds) to insert the paper. The barrier paper is preferably placed on a metal grid at the middle height of the drying oven, on which cardboard is preferably placed as a base. The metal grid and the cardboard should have reached the oven temperature in advance and have been placed in the oven preheated to 105°C at least 15 minutes before the start of the temperature treatment. It should be noted that the duration of the temperature treatment is preferably set to 3 minutes, thereby ensuring that the barrier paper has enough time to actually reach 105°C on the one hand, and on the other hand the treatment of the paper is not stopped for too long, thereby not stopping the decomposition process. After removing the barrier paper from the oven, it is stored (temperature conditioned) at 23°C and 50% relative humidity for at least 12 hours before further measurements are carried out.

[0058] The wax in the paint color layer S1 is preferably a wax according to the following definition of the German Society for the Study of Fat (DGF).

[0059] "Waxes are substances that are today defined by their mechano-physical properties. In contrast, their chemical composition and origin vary greatly. A wax is defined as a material that is kneadable at 20° C., has a firm to breakable hardness, has a coarse to fine crystalline structure, is transparent to opaque but glassy in color, melts without decomposing above 40° C., is slightly liquid (low-viscosity) just above the melting point, has a consistency and solubility that are strongly dependent on temperature, and can be polished under slight pressure." If more than one of the above properties is not met, the substance is not a wax according to DGF (DGF unit method MI 1 (75)).

[0060] As our own laboratory studies have shown, the chemical composition of the waxes used does not play a decisive role. These waxes should only be selected so that they melt in the coating system under technically appropriate drying conditions. It has been shown that for the formation of a water vapor barrier, it is advantageous if the melting temperature is below the boiling point of water (100° C.), preferably still below 90° C.

[0061] The polymeric binder for applying the color layer S1 is not theoretically limited but includes all polymeric binders known to those skilled in the art for binding wax to paper coatings.

[0062] In principle, hydrophobic polymers can be used. However, it is also possible that synthetic, naturally derived, water-soluble polar binders or derivatives thereof may be suitable, as long as the hydrophilic functions are shielded by the presence of wax in the coating as well and the water vapor barrier does not affect the coating.

[0063] The following relationship was found in laboratory experiments: The lower the wax proportion, the better the heat sealability, especially also the hot tack. However, low wax contents result in a higher water vapor permeability and a relatively high sensitivity of the water vapor barrier to fat contact. If less wax is to be used, the aqueous coating should be dried so that the wax migrates to the surface in order to obtain a good water vapor barrier that is less sensitive to fat.

[0064] In one embodiment, the wax ratio of the color coating layer S1 is selected so that the barrier paper has at least one of the following characteristics:

[0065] a) the seal seam strength (cold adhesion) of the color coating layer S1 to the color coating layer S1 is ≥ 4N / 15mm under heat sealing parameters T = 130-150°C, sealing time = 0.3s, sealing pressure = 3.3 bar or ultrasonic sealing parameters of T of 130-150°C, 0.3s sealing time and 3.3 bar sealing pressure caused in the sealing medium,

[0066] b)≤20g / m 2 / d (38°C, 90% relative humidity) water vapor transmission rate (WVTR),

[0067] c)≤8g / m 2 / d (23℃, 50% relative humidity) water vapor transmission rate (WVTR),

[0068] d) Under test conditions according to DIN 53116 2003-02 (10 minutes action time and 2000 N / m 2 The water vapor transmission rate (38°C, 90% relative humidity) of palm kernel fat after testing under pressure load) is not more than 70 g / m2 / d, preferably not more than 60 g / m2 / d,

[0069] e) Under test conditions according to DIN 53116 2003-02 (60 minutes action time and 2000 N / m 2 ) after the palm kernel fat test, the water vapor transmission rate is not increased by more than 6 times,

[0070] f) Static friction coefficient <0.9 (painted color layer S1 against painted color layer S1)

[0071] g) Dynamic friction coefficient of <0.6 (painted color layer S1 against painted color layer S1)

[0072] For ≤12g / m 2 The values ​​a) to g) are determined from the weight per unit area of ​​the paint color layer S1.

[0073] Here, the weight per unit area of ​​the color layer S1 is not limited to ≤12 g / m 2 , but only the above parameters need to be met at such a weight per unit area. At a larger weight per unit area, these parameters need to be adapted accordingly.

[0074] Parameter a) The sealing seam strength (cold adhesion) of the paint layer S1 for the paint layer S1 is preferably understood as folding a piece of barrier paper so that the paint layer S1 covers itself in the sealing seam area, or stacking two pieces of barrier paper so that the paint layers S1 of the two pieces of paper cover each other in the sealing seam area.

[0075] In one embodiment, the barrier paper of the present invention is preferably characterized in that the water vapor transmission rate (38°C, 90% relative humidity) has a variation of maximum -40%, preferably <-30%, wherein the variation is determined by measuring and comparing the measured values ​​of the water vapor transmission rate before and after temperature treatment of the barrier paper at 105°C for 3 minutes (similar to the previous embodiment).

[0076] In one embodiment, the wax is a wax according to DGF (DGF Unit Method MI 1(75)) as defined above.

[0077] In one embodiment, the barrier paper according to the invention is preferably characterized in that the at least one wax comprises waxes based on mixtures or pure substances of fossil or natural short-chain to medium-chain hydrocarbons, their acids, esters, amides and diamides, hydrogenated vegetable oils, waxes prepared by hydrogenation or partial hydrogenation of vegetable and animal oils or fats and / or metal soaps, preferably heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, triacontan, triacontan, dotriacontan, trictriacontan, tetratriacontan, pentatriacontan, hexatriacontan, heptatriacontan, octatriacontan, nonacosane, montan wax, carnauba wax, beeswax, candelilla wax, rice bran wax, sugar cane wax, waxes obtained from sunflower kernel presscake, particularly preferably beeswax and / or waxes obtained by hydrogenation of soybean oil, and / or paraffin waxes having an average molecular weight of at least 500 Daltons and a viscosity of at least 11 cSt at 100°C.

[0078] Beeswax and / or paraffin are particularly preferred since their use for direct food contact is permitted according to BfR XXVI of 01 April 2021, Chapter C, Part IV, Point 2 (cf. BfR XXV of 01 June 2019) of the Federal Institute for Risk Assessment of the German Federal Ministry of Food and Agriculture.

[0079] When paraffin waxes are used, those which are classified as FCM substance number 94 in Commission Regulation (EC) No. 10 / 2100 of 14 January 2011 “on plastic materials and articles intended to come into contact with foodstuffs” are particularly preferred.

[0080] In one embodiment, the barrier paper of the present invention is preferably characterized in that, relative to the total weight of the paint color layer S1, the at least one wax is contained in the paint color layer in an amount of 0.01 to 10 weight %, preferably 0.01 to <8.0 weight %, preferably 0.01 <6.0 weight %, particularly preferably 0.01 to <5.0 weight % and very particularly preferably 0.01 ≤ 2.0 weight %, preferably with a lower limit of at least 0.1 weight %, particularly preferably at least 0.2 weight %.

[0081] In one embodiment, the barrier paper of the present invention is preferably characterized in that the at least one polymeric binder in the painted color layer S1 is selected from the group consisting of polyacrylates and copolymers with unsaturated hydrocarbons, polyolefins, copolymers consisting of no hydrocarbons and acrylic acid or its salts, (partially carboxylated) styrene-butadiene copolymers, styrene-butadiene copolymers, styrene-butadiene, polyvinyl acetate, partially saponified polyvinyl acetate, polyesters such as polylactic acid, and polyhydroxyalkanoates prepared from glucose, polyamides, polyurethanes, polyethers, polyethyleneimines, and / or polyvinylamides, preferably is selected from the group comprising the following items: polymethyl acrylate, polymethyl methacrylate, polyethyl acrylate, polyethyl methacrylate, poly(n-, iso-, tert-)butyl acrylate, poly(n-, iso-, tert-)butyl methacrylate, polycyclohexyl methacrylate, polyethylhexyl acrylate and copolymers thereof, grafted polymers, and copolymers thereof with styrene, acrylonitrile, methyl styrene and / or vinyl toluene, particularly preferably styrene acrylate / methyl acrylate / butyl acrylate / ethylhexyl acrylate copolymers and / or natural polymers, such as (modified) polysaccharides, proteins, lignin (derivatives) and other natural macromolecules such as shellac.

[0082] In one embodiment, the barrier paper of the present invention is preferably characterized in that the at least one polymeric binder is contained in the paint layer in an amount of 99.9 to >92 wt. %, particularly preferably >95 wt. % and very particularly preferably >98 wt. %, relative to the total weight of the paint layer S1.

[0083] In one embodiment, the paint color layer S1 only includes the wax and the polymer binder.

[0084] In another embodiment, in addition to the wax and the polymer binder, the color coating layer S1 further comprises other components or additives.

[0085] Other possible components of the paint layer S1 include, for example, pigments, in particular inorganic pigments such as calcium carbonate (GCC or PCC), talc, kaolin, natural and / or synthetic silicates.

[0086] Such pigments are preferably contained in an amount of 0 to 70 wt % relative to the total weight of the dry color layer S1. Since the heat sealability of the color layer S1 is not affected too much, 0 to 50 wt %, more preferably 0 to 30 wt % and very particularly preferably 0 to 10 wt % can be selected.

[0087] Preference is given here to directly excluding the value of 0% by weight as a lower limit.

[0088] Preferably, flake pigments can be selected, since flake pigments can contribute to an improved barrier effect in the case of lamellar orientation parallel to the coating. The particle size can preferably be selected such that in the case of lamellar orientation the particles are completely contained in the layer. The aspect ratio (ratio of average diameter to thickness, also referred to as shape factor) should be greater than 10, preferably greater than 100 and particularly preferably greater than 1000.

[0089] Other possible additives include, for example, thickeners, surfactants, crosslinkers and / or rheology modifiers.

[0090] These additives are preferably contained in an amount of 0 to 2% by weight, preferably 0 to 1% by weight, relative to the total weight of the dry paint color layer S1. It is preferred here to directly exclude the value of 0% by weight as a lower limit.

[0091] The smoothness of the painted color layer S1 (according to ISO 5627, 1995-03) is preferably 400s to 2500s, preferably 500 to 2000s.

[0092] The roughness of the painted color layer S1 (according to Parker Printing Surface (PPS) DIN ISO 8791-4, 2008-05) is preferably 0.8 to 2.0 μm, preferably 1.0 to 1.8 μm.

[0093] The application amount of the paint color layer S1 (ISO 536, 2020-05) is preferably 4 to 20 g / m 2 , preferably 6 to 15 g / m 2 And particularly preferably 8 to 12 g / m 2 This amount relates to the dry painted color layer S1 in the final product.

[0094] In one embodiment, the barrier paper of the present invention is preferably characterized in that the at least one wax in the painted color layer S1 is enriched at the side facing away from the base paper.

[0095] Here, "enrichment" should be understood in particular as meaning that the local concentration of the wax in the painted color layer S1 on the side facing away from the base paper is greater than the local concentration of the wax in the painted color layer S1 on the side facing the base paper, which is indirectly demonstrated by the fact that the polar part of the surface energy is not substantially further reduced during subsequent drying.

[0096] A further demonstration of the wax enrichment can be carried out with the aid of electron spectroscopy (ESCA, also referred to as XPS for short). The wax enrichment in the overprint color layer S1 on the side facing away from the base paper was also demonstrated by the following experiment.

[0097] In the coating experiments on the pilot coating equipment, the lower water vapor transmission rate that could be achieved due to the laboratory coating of the individual sheets was not achieved. In order to test whether the cause was poor quality of the coating (defects, bubbles, wetting disturbances) or simply just insufficient drying and film formation, a number of individual paper sheets were post-dried gently but sufficiently long (3 minutes, 105° C.) in a drying oven. The water vapor transmission rate of the post-dried papers (Comparative Examples 1 and 2) was improved and the polar part of the surface tension was reduced. Since no chemical reaction is expected in the coating, it can be concluded that the non-polar wax has migrated to the interface by post-drying.

[0098] The base paper used in the barrier paper according to the present invention is theoretically not limited.

[0099] Preferably, the base paper has a g / m 2 , preferably 40 to 100 g / m 2 Weight per unit area.

[0100] It is also preferred that the base paper has a long fiber proportion of 10 to 80 wt. %, preferably 20 to 50 wt. %, and a short fiber proportion of 20 to 90 wt. %, preferably 50 to 80 wt. %, relative to the total weight of the base paper, wherein long fibers are fibers having a fiber length of 2.6 to 4.4 mm, and short fibers are fibers having a fiber length of 0.7 to 2.2 mm.

[0101] The long fiber fraction is responsible in particular for achieving strength in relatively thin papers, while the short fiber fraction makes the paper in particular denser and more closed and provides the paper with a uniform appearance. By further increasing the long fiber proportion, the paper may become too stiff. The lower price of short fiber materials relative to long fiber materials also plays a role.

[0102] In addition, 0 to 20% by weight, preferably 0 to 5% by weight, of fillers, wherein the value of 0% by weight is preferably excluded, such as GCC (ground calcium carbonate), for example known under the trade name Hydrocarb 60 or Hydroplex 60, PCC (precipitated calcium carbonate), for example known under the trade name Precarb 105, natural kaolin and / or talc.

[0103] Furthermore, customary auxiliaries such as retention agents and / or sizing agents may be present.

[0104] The advantages of such base papers are, on the one hand, their high flexibility and, on the other hand, their good processability on existing packaging equipment for flexible materials such as plastic foils, maintaining high machine availability and achieving the necessary penetration resistance.

[0105] In particular for contact with foods, the base paper comprises at least 60% by weight, preferably at least 75% by weight of fiber material, up to 25% by weight, preferably up to 10% by weight of fillers and up to 15% by weight of auxiliaries. In addition, unavoidable or necessary traces of processing auxiliaries (e.g., reagents, dispersants, release agents, etc.) may be present in the base paper.

[0106] In one embodiment, the barrier paper is characterized in that it has at least one additional painted color layer S2 applied indirectly or directly between the base paper and the painted color layer S1, and the painted color layer S2 includes at least one hydrophilic polymer, in particular for forming a mineral oil and / or fat barrier layer and / or an oxygen barrier layer.

[0107] If the priming color layer S2 is applied directly between the base paper and the priming color layer S1 , this means that the priming color layer S2 is in contact with the base paper on one side and with the priming color layer S1 on the other side.

[0108] If the painted color layer S2 is applied indirectly between the base paper and the painted color layer S1, this means that the painted color layer S2 must exist between the base paper and the painted color layer S1, but does not necessarily have to be in direct contact with them; therefore, other intermediate layers are not excluded.

[0109] The paint layer S2 is preferably used to form a mineral oil barrier layer and / or a fat barrier layer and comprises at least one hydrophilic polymer.

[0110] The preferred target value for the mineral oil barrier is <30 g / m 2 A preferred target value for the fat sealing value of food products not to be consumed immediately is the palm kernel fat test according to DIN 53116 Class 1 (no penetration even after a test duration of more than 24 hours).

[0111] Hydrophilic polymers are usually crosslinked and thus less flexible. Coatings are preferably selected for coating the flexible packaging such that they bend up to 180°, projecting inwards (coating to coating) and ideally also projecting outwards without fat penetration.

[0112] The paint layer S2 should preferably be coatable in the dry state with the (aqueous) coating material of the paint layer S1 .

[0113] To this end, the paint color layer S2 should preferably not absorb water or swell as much as possible during the coating process, so that on the one hand it does not affect its own barrier effect (mineral oil, fat and in special cases also oxygen), and on the other hand it can also achieve an optimal defect-free coating of the paint color layer S1.

[0114] Since polymer-based oxygen barriers (and also always mineral oil barriers and fat barriers) are generally hydrophilic, they can only be applied if at least a portion of the free hydrophilic groups are covalently crosslinked when the coating is dried. For this purpose, reactive additives such as bifunctional or polyfunctional aldehydes, carboxylic acids, epoxides or inorganic crosslinkers, for example zirconates or borates, are preferably used. Another possible group of crosslinkers are PAE resins (polyamidoamine epichlorohydrin) which are also used as wet strength agents for base papers. For contact with foods, the use of these additives is prohibited or restricted.

[0115] Therefore, the choice when searching for raw materials for mineral oil and fat barriers generally does not fall on water-soluble polymers, but rather preferably on polymer dispersions that are designed by the manufacturer through functionalization to have a corresponding barrier effect without being significantly soluble in water, or by the addition of insufficient amounts of water-soluble polymers that are responsible for achieving or enhancing the overall oleophobic effect.

[0116] Examples of suitable polymers are copolymers from polyvinyl alcohol and polyvinyl acetate, acrylate (co)polymers, acrylonitrile copolymers.

[0117] Likewise suitable is the use of crosslinked or partially hydrophobized polyvinyl alcohol, ethylene vinyl alcohol or other copolymers of vinyl alcohol (such as those described in EP 4041548 A1), carbohydrates and / or proteins.

[0118] Preferred polymers (according to EP 4041548 A1) are partially saponified polyvinyl alcohol and / or partially saponified polyvinyl alcohol copolymers, each having an onset temperature determined by means of DSC of less than 210° C. and an average molecular weight (M) of preferably less than 100,000 g / mol. W ), wherein the onset temperature according to DIN EN ISO 11357-1:2010-03 is defined as the intersection of the extrapolated baseline and the inflection tangent line at the beginning of the melting peak or crystallization peak by means of DSC.

[0119] Due to its high surface tension (surface energy), polyvinyl alcohol is suitable in particular for the additional application of a thin metal layer which has a significantly lower and substantially dispersive surface tension.

[0120] The barrier paper of the invention can preferably contain at least one further layer, which consists of or includes a metal, in particular aluminum. This can further improve the barrier effect. This further layer can be formed as an intermediate layer or a cover layer. This layer formed as an intermediate layer is preferably located directly below or above the heat-sealable layer, for example the color coating layer S1.

[0121] Particularly preferred here are polyacrylates which preferably contain protective colloids based on starch. Suitable polyacrylates are known under the trade name Epotal SP 101D.

[0122] Additionally suitable are polyacrylates known, for example, under the trade name Rhobarr 214 or polyacrylonitriles.

[0123] The advantage of such polymers is that they swell less when exposed to water, since, if they swell, the layer applied onto them does not achieve its optimum water vapor barrier effect.

[0124] In one embodiment, the hydrophilic polymer is preferably contained in an amount of 30 to 100 wt %, or 50 to 100 wt %, relative to the total weight of the paint color layer S2.

[0125] Other possible components of the paint layer S2 include, for example, pigments, in particular inorganic pigments such as calcium carbonate (GCC or PCC), talc, kaolin, natural and / or synthetic silicates.

[0126] Such pigments are preferably contained in an amount of 0 to 70% by weight, particularly preferably 0 to 50% by weight, relative to the total weight of the paint color layer S2. The value of 0% by weight is preferably directly excluded as a lower limit.

[0127] Preferably, flake pigments can be selected, since flake pigments can contribute to an improved barrier effect in the case of lamellar orientation parallel to the coating. The particle size can preferably be selected such that in the case of lamellar orientation the particles are completely contained in the layer. The aspect ratio (ratio of average diameter to thickness, also referred to as shape factor) should be greater than 10, preferably greater than 100 and particularly preferably greater than 1000.

[0128] In one embodiment, the color coating layer S2 further comprises other additives, such as thickeners, surfactants, crosslinking agents and / or rheology modifiers.

[0129] Such additives are preferably contained in an amount of 0 to 2% by weight, particularly preferably 0 to 1% by weight, relative to the total weight of the paint layer S2. The value of 0% by weight is preferably directly excluded as a lower limit.

[0130] The paint color layer S2 preferably does not contain glyoxal.

[0131] The surface tension of the paint color layer S2 is preferably 45 to 70 mN / m, in particular 50 to 65 mN / m and very particularly 57 to 61 mN / m.

[0132] The polar portion of the surface tension of the paint layer S2 is preferably 60 to 95%, in particular 70 to 90% and particularly preferably 78 to 84%.

[0133] The dispersion fraction of the surface tension of the paint color layer S2 is preferably 5 to 40%, in particular 10 to 30%, and particularly preferably 16 to 22%.

[0134] The surface tension and the corresponding parts are determined here in the manner defined above.

[0135] The surface tension of the paint color layer S2 is preferably at least 5 mN / m greater than the surface tension of the paint color layer S1, generally 20 to 30 mN / m greater, and preferably has a significantly higher polar portion, because this polar portion can be a maximum of 12% due to the wax proportion in the paint color layer S1, as obtained by measurement.

[0136] The application amount of the paint color layer S2 (ISO 536, 2020-05) is preferably 3 to 12 g / m 2 And particularly preferably 8 to 10 g / m 2 This amount relates to the dry painted color layer S2 in the final product.

[0137] The smoothness of the painted color layer S2 (according to ISO 5627, 1995-03) is preferably 80s to 500s, preferably 100 to 200s.

[0138] The roughness of the painted color layer S2 (according to Parker Printing Surface (PPS) DIN ISO 8791-4, 2008-05) is preferably 2 to 4 μm, preferably 2.5 to 3.5 μm.

[0139] In one embodiment, the barrier paper of the invention is characterized in that a further color layer S3 is directly present on the base paper, in particular a color layer comprising or consisting of at least one inorganic pigment and a polymeric binder.

[0140] The inorganic pigments are preferably flake-shaped and comprise, in particular, talc, precipitated calcium carbonate or silicates, preferably phyllosilicates and very particularly preferably kaolin.

[0141] The aspect ratio (ratio of average diameter to thickness, also known as shape factor) should be about 7 to 40 to 1, preferably about 15 to 30 to 1.

[0142] The particle size of the flake pigments is preferably configured such that at least about 70%, preferably at least about 85%, of the particles have a particle size of about <2 μm (sedimentogram particle size analysis). The pH value of the flake pigments in aqueous solution is preferably 6 to 8.

[0143] As suitable polymeric adhesives, in particular, adhesives based on acrylates or based on styrene / butadiene can be mentioned. In theory, all polymers that can be used as adhesives for pigment painting in the paper industry are suitable. It is also possible to use adhesives based on starch (solvent-modified starch, starch cross-linked by dispersion, so-called bio-latex) and polymer-starch mixed latexes.

[0144] The polymeric binder preferably comprises a polyacrylate-based polymeric binder.

[0145] The polymeric binder preferably comprises a styrene-acrylate copolymer, preferably a styrene-butyl acrylate copolymer, in particular a styrene-n-butyl acrylate copolymer.

[0146] A suitable styrene-n-butyl acrylate copolymer is known, for example, under the trade name Acronal S305FD.

[0147] The paint color layer S3 may be generally a hydrophobic pre-coating layer.

[0148] In another embodiment, the paint color layer S3 is generally hydrophilic.

[0149] The paint layer S3 preferably contains 5 to 50% by weight, preferably 10 to 30% by weight, of a polymeric binder. This amount relates to the dry paint layer in the final product.

[0150] The paint layer S3 preferably also contains 50 to 95% by weight, preferably 70 to 90% by weight, of inorganic pigments. This amount relates to the dry paint layer in the final product.

[0151] In addition, the color layer S3 may contain additives such as thickeners (e.g., acrylate-based thickeners), surfactants and / or rheology modifiers. It is also conceivable to use a crosslinking agent. The color layer preferably contains a zirconium-based crosslinking agent and is itself crosslinked with formaldehyde.

[0152] These additives are preferably contained in an amount of 0 to 2% by weight, preferably greater than 0 to 2% by weight, wherein a value of 0% by weight is preferably excluded. This amount relates to the dry paint layer S3 in the end product.

[0153] The application amount of the paint color layer S3 (ISO 436, 2020-05) is preferably 1 to 10 g / m 2 And particularly preferably 2 to 6 g / m 2 This amount relates to the dry painted color layer in the final product.

[0154] If such a paint color layer S3 (also called pre-coat or primer) is applied, it has the following advantages: the paper surface is sealed and other paint color layers applied thereto migrate only slightly into the paper. In addition, this paint color layer reduces the average roughness depth of the base paper and provides a favorable paint color support (holdout), which is unique in that the application method of the covering surface and the defined surface energy make it possible for the applied paint color layer to be formed optimally and to form an optimal barrier layer with as little application as possible, which has a favorable impact on the cost structure. In addition, the pre-coat is produced in such a way that the sub-layer adhesion between the base paper and the paint color layer is not significantly reduced, which can play an important role for the later sealing application.

[0155] The surface tension of the paint color layer S3 is preferably 15 to 40 mN / m, in particular 22 to 30 mN / m.

[0156] The polar portion of the surface tension of the paint color layer S3 is preferably 10 to 50%, in particular 15 to 30%.

[0157] The dispersive fraction of the surface tension of the paint color layer S3 is preferably 50 to 90%, in particular 70 to 85%.

[0158] The surface tension and the corresponding parts are determined here in the manner defined above.

[0159] For good wetting and sub-layer adhesion, the surface tension of the pre-coat should be greater or at least more polar than the surface tension of the layer located above it.

[0160] If there is an embodiment with layer S2, this cannot be guaranteed in some cases, because the paint color layer S2 itself already has a high surface tension and a highly polar part. The highly polar paint color layer S3 may swell too much when applied with an aqueous paint formulation, which may lead to cracking after drying. Therefore, the data given about the surface tension of the paint color layer S3 have been proven to be a universal basis for the direct application of the paint color layer S1 or the paint color layer S2.

[0161] The smoothness of the painted color layer S3 (according to ISO 5627, 1995-03) is preferably 80s to 200s, preferably 90 to 120s.

[0162] The roughness of the painted color layer S3 (according to Parker Printing Surface (PPS) DIN ISO 8791-4, 2008-05) is preferably 2.8 to 4.0 μm, preferably 3.2 to 3.6 μm.

[0163] In one embodiment, the base paper of the present invention may further include other layers in addition to the coloring layers S1, S2 and S3 described above.

[0164] Thus, for example, the uncoated side of the paper can be provided with one or more coatings which can be printed better than a base paper surface which is provided only with a starch film.

[0165] In order to improve the barrier effect of the paper overall, the smooth surface can be vapor-coated with metals or metal oxides (for example by vacuum vapor deposition).

[0166] A prerequisite for this is preferably a smooth surface, such as in this case the color layer S2 or also the color layer S1 or also a smooth printed color layer on the uncoated side of the base paper.

[0167] Barrier lacquers are also known, which can also be applied over the entire surface or only in certain areas by further processing devices, for example.

[0168] An example is the product HYDRO-LAC GA oxygen barrier varnish from the manufacturer Hubergroup Print Solutions. This varnish can be applied to the paint color layer S1 or to the uncoated side of the barrier paper, but is still better applied to the smooth printed paint layer.

[0169] The barrier paper can be used as a heat-sealable barrier paper, but there are other possibilities for applying a cold seal adhesive to one of the two sides, in particular when the paper is to be used on packaging equipment designed for cold seal gluing.

[0170] Preferably, one of the two sides, preferably the printed side, can also be provided with an additional heat sealant, the purpose of which is to create a seal between the front and back sides (A / B seal).

[0171] In one embodiment, the base paper comprises the painted color layers S1 and S3 as defined above.

[0172] In one embodiment, the base paper comprises the painted color layers S1, S2 and S3 as defined above.

[0173] Here, the above-described paint color layer S3 can also be applied in two or more coating layers.

[0174] The barrier layer according to the invention can be obtained economically with all known papermaking and paper coating processes (film press with or without pre-dosing, roll application, doctor blade, knife, curtain coater, spray coater).

[0175] However, it is preferred that the barrier paper of the present invention is obtained by the following method, wherein an aqueous suspension or solution of the starting material comprising the corresponding brush color layer S1 or brush color layer S2+S1 is applied to the base paper (preferably coated with the brush color layer S3), wherein the aqueous application suspension or solution has a solid content of 15 to 55% by weight, preferably 20 to 45% by weight, and is applied by curtain coating (in the case of brush color layers S2+S1, the two coatings can be applied successively with intermediate drying or preferably by double curtain coating) at a coating equipment running speed of at least 100 m / min, preferably >200 m / min.

[0176] The barrier paper is then preferably dried, wherein the drying should be carried out gently so that the web temperature never exceeds 90° C., since otherwise bubbles can form which deteriorate the quality of the barrier layer or, in extreme cases, destroy it. Contactless drying consisting of a bank of infrared dryers, whose drying power can be set individually, and subsequent hot air hoods, which can also be set individually, has proven useful. Optionally, a second stage with an IR dryer can be installed subsequently to achieve better film formation.

[0177] This method is advantageous especially from an economic point of view and due to the uniform application on the paper web. If the solid content value is below about 15% by weight, the economic efficiency is poor, because a large amount of water must be removed in a short time by gentle drying, which has a negative impact on the coating speed. On the other hand, if the value of 55% by weight is exceeded, this only leads to increased process complexity in order to ensure the stability of the coating color curtain film during the coating process and the drying of the applied film, because in this case the machine must be operated very quickly again.

[0178] In the curtain coating method, a free-falling curtain of the coating dispersion is formed. Due to the free fall, the coating dispersion in the form of a thin film (curtain) is "cast" onto the substrate to apply the coating dispersion to the substrate. DE 10196 052 T1 discloses the use of the curtain coating method in the preparation of information recording materials, wherein a multi-layer recording layer is achieved by applying a curtain composed of a plurality of coating dispersion films to the substrate.

[0179] In a preferred embodiment of the method according to the invention, the degassed aqueous application suspension has a viscosity of about 100 to about 400 mPas (Brookfield, 100 rpm, 20° C.). If values ​​below about 80 mPas or values ​​above about 500 mPas result in a lack of flowability of the coating material at the coating device. The viscosity of the degassed aqueous application suspension is particularly preferably about 150 to about 300 mPas.

[0180] In a preferred embodiment, in order to optimize the process, the dynamic surface tension of the aqueous application suspension is set to about 35 to about 55 mN / m, preferably about 38 to about 52 mN / m (measured according to the standard for air blowing pressure tensiometer (ASTM D 3825-90) 50 ms after bubble formation, as described below). When the dynamic surface tension of the painting color is determined and is set specifically by selecting a suitable surfactant and by obtaining the required amount of surfactant, a better control of the painting process is obtained.

[0181] The formation of the individual coatings can be carried out in-line on a paper machine with a coating tool or offline on a coating machine in a separate coating process. For development purposes and for the production of prototypes, the paper can also be produced on a laboratory scale by means of a manual doctor blade and subsequent drying in a drying cabinet. For example, similar to the temperature treatment described above, drying can be carried out in a drying cabinet at 90° C. for 3 minutes. Since the risk of bubble formation is lower in such a slow drying process, temperatures of more than 100° C., preferably 105° C., can also be set.

[0182] In other embodiments, the individual paint color layers can also be applied to the base paper by means of the following method:

[0183] The paint layer can be applied to the base paper and / or to an already existing paint layer by means of a printing method, such as flexographic printing and gravure printing.

[0184] The color layer can be applied in a waterless manner as a melt to the base paper and / or to an already existing precoat layer by means of extrusion.

[0185] The advantage of this technology is that significantly more material can be applied thereby, but this is only meaningful if the total product does not need to be recycled as paper. On the other hand, the disadvantages are the lower application speed, the higher energy consumption and the higher minimum application weight.

[0186] The paint layer can be applied, for example in the form of a plastic foil, to the base paper and / or to an already existing paint layer by means of paper lamination or stacking.

[0187] The paint layers can also be applied in a plurality of application steps one after the other.

[0188] The invention also relates to a base paper obtainable according to the above-mentioned method.

[0189] Finally, the invention also relates to the use of a barrier paper as described above as a packaging material or as a component of a packaging material, the packaging material being in particular a heat-sealable packaging material, but also by applying a cold seal lacquer or other medium for closing flexible packaging, preferably for food, in particular for packaging fatty and moisture-sensitive foods, luxury foods such as tobacco, coffee, tea, medicinal herbs, as well as household items, cosmetic products, other moisture-sensitive consumer goods such as washing powder, coffee pods, sanitary napkins, baby diapers and facial tissues, and for protecting them from mineral oil vapors from the environment.

[0190] The barrier paper according to the invention can be used in all common packaging machines. Mention may be made, for example, of vertical or horizontal tube bag machines (make-fill-seal) for producing, in particular, stand-up bags, blister packs or pillow packs, airbags or airbags as a substitute for plastic airbags or airbags, machines for bringing together two paper webs of the same or different materials and connecting them by heat sealing, for example also tray sealers, box conveyor machines (also with vacuum), bag filling and closing machines, deep-draw packaging machines, linear filling machines for closing the bag opening by heat sealing, film wrapping machines with a final heat sealing step, blister packaging machines and X-fold packaging machines.

[0191] In a further preferred embodiment of the invention, the coated paper according to the invention is applied to cardboard or paperboard, in particular by lamination, stacking or bonding.

[0192] The present invention furthermore relates to a packaging material, in particular a heat-sealable packaging material, which comprises or consists of a barrier paper as described above.

[0193] The invention will be explained in detail below with the aid of non-limiting examples. Example

[0194] The base paper from the production line was used for Comparative Examples 1 to 3 and Examples 1 to 5.

[0195] A pure base paper (38 wt. % long fibers, 57 wt. % short fibers, 5 wt. % calcium carbonate as filler, sized with alkyl ketene dimer to an absorbency of 25 g / m 2 ), polished by means of a calender, and partially enzymatically degraded cationic modified potato starch (about 1 g / m 2 ).

[0196] The paper machine is equipped with a polishing cylinder (Yankee cylinder) and can thereby produce paper which is smooth on one side.

[0197] As a second step, a coating color layer S3 is provided for this paper on a production coating machine, and the coating color layer S3 is applied to the less smooth side by means of a blade coater, which is located on the side facing away from the polishing cylinder during the polishing process (Comparative Examples 1 to 3 and Examples 1 to 3).

[0198] For Examples 4 and 5, the paint color S3 was applied in two steps. 4 g / m 2 was applied online on the paper machine to the less smooth side. 2 , while an additional 4 g / m 2 .

[0199] For Comparative Examples 1, 2 and 3, in separate coating experiments, the coating color layer S2 was applied on a pilot coating device and subsequently the coating color layer S1 was applied separately directly onto the coating color layer S2, both by means of a curtain coater.

[0200] In comparative example 1a and examples 4 and 5, the paint color layer S1 is applied directly onto the paint color layer S3 in the same manner.

[0201] The drying unit consists of a series of electric infrared dryers followed by an air hood module (hot air drying).

[0202] The length of the drying section, the web temperature at the paper surface and the residence time in the respective drying zone can be seen from Tables 1 and 2a, in which only the production parameters for applying the overprint color layer S1 are given.

[0203] Examples 1, 2 and 3 were also produced on a production coater by means of a curtain coater. Here, the drying unit also consists of an infrared dryer module, but this is operated with natural gas, followed by a module consisting of an air hood. Example 2 does not contain the paint color layer S2. The paint color layer S1 is applied directly to the paint color layer S3. Examples 1 and 3, however, still retain the paint color layer S2.

[0204] The length of the drying section, the web temperature at the paper surface and the residence time in the respective drying zone can be seen from Table 2, where only the production parameters for applying the coating color layer S1 are given. The drying requirements for the coating color layer S2 are so low that no difference is made between the production on the pilot coating plant and the production coating plant for mineral oil and fat barriers.

[0205] Preparation of the painting color S1 (Comparative Examples 1 to 3 and Examples 1 to 3) (pilot plant formulation, scaled up in the same way for the production plant) Aqueous application suspension with a solids content of 20 to 60%:

[0206] 38.1 kg of water were placed and mixed with 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). This was followed by 0.523 kg of the extensional rheological agent Sterocoll DF 4 (BASF SE, polyacrylamide, oil-in-water emulsion) and 0.188 kg of the defoamer Genapol PF 10 (Clariant Produkte (Deutschland) GmbH, polymerization product of propylene oxide and ethylene oxide) as additives. A pH value of about 8.5 and a viscosity of about 160 mPas (Brookfield) were obtained.

[0207] Preparation of Paint Color S1 (Examples 4 and 5):

[0208] Aqueous application suspensions with a solids content of 20 to 60%:

[0209] 16 kg of water was placed in advance and mixed with 267 kg of an aqueous suspension, which was mixed with 90 parts of a carboxylated styrene-butadiene polymer and 10 parts of paraffin wax with a chain length of C21-C38. This was followed by a solution of 6.5 kg of 8-88 type polyvinyl alcohol and 15.6 kg of 28-99 type polyvinyl alcohol as a thickener. This was followed by 0.2 kg of an extensional rheological aid Sterocoll DF 4 (BASF SE, polyacrylamide, oil-in-water emulsion) and 0.7 kg of a defoamer Genapol PF 10 (Clariant Produkte (Deutschland) GmbH, a polymer of propylene oxide and ethylene oxide) as an additive. 1.7 kg of Dynawet 2050 (CTP GmbH) was added as a surfactant, a nonionic surfactant preparation as a main active ingredient, CAS number 160875-66-1. A viscosity of 230 mPas and a pH value of 6.5 were obtained.

[0210] Preparation of paint color S2: (pilot plant recipe, scale up in the same way for production equipment)

[0211] 77 kg of water were placed in advance and mixed with 228.6 kg of Epotal SP 101D (BASF SE, polyacrylate with starch-based protective colloid). This was followed by 0.957 kg of thickener Texturecel 100GA (DDP Specialty Products Germany GmbH, carboxymethylcellulose), 0.081 kg of extensional rheology aid Sterocoll DF 4 and 0.210 kg of defoamer Genapol PF 10 as additives. A pH value of 8.8 was set by adding caustic soda and a viscosity of about 200 mPas was obtained (Brookfield).

[0212] Both coating colors are suitable for use in curtain coaters and are degassed by vacuum in the working container of the coater before coating.

[0213] Prepare the paint color S3:

[0214] The composition is found in Table 1: This information is sufficient for the person skilled in the art to produce a paintable coating material.

[0215] The composition of the corresponding painted color layer, the drying parameters and the properties of the obtained barrier paper are summarized in Table 1 below.

[0216] Description of measurement methods for which no standard is known or an appropriate process has not yet been developed:

[0217] Heat sealability: Although the test of the seal seam strength of an already produced seal seam is clearly defined by, for example, DIN 55529:2012-09, there is no standardized method available for testing the suitability of a material for heat sealability. The reason for this is obviously that packagers preferably develop their own input controllers suitable for heat sealable foils or papers adapted to their packaging equipment.

[0218] Based on industry information, relatively strict sealing conditions were used (sealing time 0.3s, sealing pressure 3.33 bar, smooth sealing jaws). The sealability was tested as follows, with two sealable coatings of the paper sealed against themselves. In order to obtain the optimal sealing temperature, test samples were prepared, which were sealed at different sealing jaw temperatures (100-200°C).

[0219] Hot tack (hot seam strength): performed in accordance with DIN 55571-2 Method C. It should also be noted that the same sealing conditions as for the heat sealability test apply. The cooling time between sealing and force measurement was chosen to be 80 ms. The force measurement was performed over a tensile length of 80 mm.

[0220] Palm kernel fat test according to DIN 53116: Select test condition I (pressure 2000 N / m 2 and >24 hours of action time, 25 hours in practice). Use NexCoat-Smart 60g / m 2 The printed side of C1S paper of the trademark (Koehler Paper SE) was used as the display paper.

[0221] The palm kernel fat test was carried out on folded paper: a 180° bend was produced on the folded sample with a roller which applied a load of 330 g / cm to the produced bend and in which the coating could be present on the inside (inner bend) or outside (outer bend).

[0222] Hexane transmission rate (HVTR, hexane vapor transmission rate): Here, n-hexane is filled into a (solvent-resistant) beaker, hermetically closed with the test sample and the weight loss is followed over time. The test is carried out at 23° C. and 50% air humidity. The coated side faces inwards towards the hexane vapor atmosphere. Corresponding beakers with PTFE seals are available in specialized shops.

[0223] Water vapor transmission rate was determined according to ISO / FDIS 2528: Also note that the coated side of the test specimen was facing the desiccant.

[0224] Dependence of the water vapor transmission rate of the coating on fat contact: First, the test specimens were subjected to the palm kernel fat test analogously to DIN 53116 2003-02. The corresponding test conditions are given. At the end of the exposure time, after wiping off the fat from the paper, the water vapor transmission rate (WVTR) was determined according to ISO / FDIS 2528. After wiping off the fat (which contains red dye according to the standard), a certain portion remains in or on the water vapor barrier coating. However, this does not lead to a further change in the WVTR, since a constant water vapor transmission rate is set in the measurement process.

[0225] The determination of the dynamic surface tension of dried paper coatings is explained in the specification.

[0226] Regarding Tables 1, 2 and 2a:

[0227] The columns marked with * contain the measured values ​​of the paper given on the left in each case after treatment in a hot air drying oven at 105° C. for 3 minutes. A Binder drying oven of the type E 115 with the following internal dimensions of width x height x depth was used: 60 x 48 x 40 cm (internal volume 115 dm 3), drying oven temperature range: 0-250°C, natural convection, no circulation around the blower). In the oven, the metal grid is located at the middle height and a cardboard of about 2 mm thickness is placed on it. The oven is now preheated to 105°C for at least 30 minutes. The test sample is placed on the cardboard during a short door opening (<2s). After 3 minutes, the test sample is removed and tempered at 23°C and 50% relative humidity for at least 12 hours before further measurements are carried out.

[0228]

[0229]

[0230]

[0231]

[0232]

[0233]

[0234]

[0235]

[0236]

[0237]

[0238]

[0239]

[0240]

[0241]

[0242]

[0243]

[0244] Example 2: (Example 2 from Table 1)

[0245] Another heat sealable paper of the invention was tested having a water vapor barrier for use in flexible packaging.

[0246] The paper is suitable for various possible applications as secondary packaging or primary packaging, in particular for products in the food and non-food sectors which require a water vapor barrier.

[0247] The advantages of the paper are:

[0248] - No optical brightener required

[0249] -Water vapor barrier for optimal product protection

[0250] -Good sealability

[0251] -Excellent strength properties

[0252] - Suitable for direct contact with food

[0253] -100% new fiber material

[0254] - Very good running characteristics on converting and packaging equipment

[0255] -Can be recycled in the paper cycle

[0256] - Particularly suitable for flexographic, gravure and digital printing

[0257] The properties of the paper are summarized in Table 3 below.

[0258] Table 3:

[0259]

[0260]

[0261] Example 3: (Example 1 from Table 1)

[0262] Another heat-sealable paper of the invention made of virgin fiber material having a barrier layer against water vapor, fat and mineral oil residues was tested.

[0263] The paper is suitable for a wide variety of possible applications in the tobacco industry, which places particularly high demands on tobacco products.

[0264] The advantages of the paper are:

[0265] -High whiteness

[0266] - No optical brightener required

[0267] - Smooth surface

[0268] -Good sealability

[0269] - Very good aroma barrier

[0270] -High bending-breaking resistance

[0271] -Excellent strength properties

[0272] - Suitable for direct contact with food

[0273] -100% new fiber material

[0274] - Excellent printing and painting position (Druck-und Lackstand)

[0275] - Very good running characteristics on converting and packaging equipment

[0276] - Particularly suitable for flexographic and gravure printing

[0277] The properties of the paper are summarized in Table 4 below.

[0278] Table 4:

[0279]

[0280] Example 4: (Example 1 from Table 1)

[0281] Another heat sealable paper of the invention was tested having a water vapor barrier for use in flexible packaging.

[0282] The paper is suitable for various possible applications as secondary packaging or primary packaging for tobacco products, such as tobacco containment bags with a barrier layer, tobacco pouches and coated cigarette liners.

[0283] The advantages of the paper are:

[0284] - No optical brightener required

[0285] -Water vapor barrier for optimal product protection

[0286] -Good sealability

[0287] -Excellent strength properties

[0288] - Suitable for direct contact with food

[0289] -100% new fiber material

[0290] - Very good running characteristics on converting and packaging equipment

[0291] -Can be recycled in the paper cycle

[0292] - Particularly suitable for flexographic and gravure printing

[0293] The properties of the paper are summarized in Table 5 below.

[0294] Table 5:

[0295]

[0296]

[0297] Example 5: (Example 1 from Table 1)

[0298] Another fat resistant, heat sealable paper of the invention formed from virgin fiber material having a water vapor barrier and a mineral oil barrier was tested.

[0299] In the case of flexible packaging of dry and powdered filled goods from the food and non-food sectors, the papers are suitable for a wide range of possible applications.

[0300] The advantages of the paper are:

[0301] -High whiteness

[0302] - No optical brightener required

[0303] - Smooth surface

[0304] -Good sealability

[0305] -High bending-breaking resistance

[0306] -Excellent strength properties

[0307] - Suitable for direct contact with food

[0308] -100% new fiber material

[0309] - Excellent printing and painting position (Druck-und Lackstand)

[0310] - Very good running characteristics on converting and packaging equipment

[0311] - Particularly suitable for flexographic, gravure and digital printing

[0312] The properties of the paper are summarized in Table 6 below.

[0313] Table 6:

[0314]

Claims

1. A barrier paper comprising a base paper and at least one color coating layer S1 applied indirectly or directly on the base paper, wherein the color coating layer S1 comprises at least one polymeric binder and at least one wax, and wherein the color coating layer S1 has at least one of the following characteristics: a) a surface tension change of not more than +10 mN / m, preferably not more than +6 mN / m, b) a partial change in the polarity of the surface tension of not more than -0.65 mN / m, preferably not more than -0.60 mN / m, c) a change in the polar fraction of the surface tension of not more than -3.0%, preferably not more than -1.5%, The corresponding changes are determined by measuring and comparing the measured values ​​of the surface tension and the polar part of the surface tension before and after the temperature treatment of the barrier paper at 105° C. for 3 minutes.

2. The barrier paper according to claim 1, wherein the proportion of the wax of the color coating layer S1 is selected so that the barrier paper has at least one of the following characteristics: a) a sealing seam strength of ≥ 4N / 15mm for the painted color layer S1 after sealing the painted color layer S1 under heat sealing parameters of sealing temperature of 130 to 150°C, sealing time of 0.3 seconds and sealing pressure of 3.3 bar or ultrasonic sealing parameters of sealing temperature of 130 to 150°C, sealing time of 0.3 seconds and sealing pressure of 3.3 bar (cold adhesion), b)≤20g / m 2 / d (38°C, 90% relative humidity) water vapor transmission rate (WVTR), c)≤8g / m 2 / d (23℃, 50% relative humidity) water vapor transmission rate (WVTR), d) Under test conditions according to DIN 53116 (10 minutes action time and 2000 N / m 2 The water vapor transmission rate (38°C, 90% relative humidity) of palm kernel fat after testing under pressure load) does not increase by more than 70 g / m 2 / d, preferably not more than 60g / m 2 / d, e) Under test conditions according to DIN 53116 (60 minutes action time and 2000 N / m 2 ) after the palm kernel fat test, the water vapor transmission rate is not increased by more than 6 times, f) static friction coefficient of <0.9 (painted color layer S1 against painted color layer S1), g) Dynamic friction coefficient of <0.6 (painted color layer S1 against painted color layer S1), For ≤12g / m 2 The values ​​a) to g) are determined from the weight per unit area of ​​the paint color layer S1.

3. The barrier paper according to claim 2, characterized in that: The water vapor transmission rate (38°C, 90% relative humidity) has a variation of maximum -40%, preferably less than -30%, wherein the variation is determined by measuring and comparing the measured values ​​of the water vapor transmission rate before and after temperature treatment of the barrier paper at 105°C for 3 minutes.

4. The barrier paper according to any one of the preceding claims, wherein the wax is a wax as defined according to DGF (DGF Unit Method MI 1(75)).

5. The barrier paper according to claim 1 , wherein the at least one wax comprises waxes based on mixtures or pure substances of fossil or natural short-chain to medium-chain hydrocarbons, their acids, esters, amides and diamides, hydrogenated vegetable oils, waxes prepared by hydrogenation or partial hydrogenation of vegetable and animal oils or fats and / or metal soaps, preferably heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, triacontan, triacontan, dotriacontan, trictriacontan, tetratriacontan, pentatriacontan, hexatriacontan, heptatriacontan, octatriacontan, nonacosane, montan wax, carnauba wax, beeswax, candelilla wax, rice bran wax, sugar cane wax, waxes obtained from sunflower kernel presscake, particularly preferably beeswax and / or waxes obtained by hydrogenation of soybean oil, and / or paraffin waxes having an average molecular weight of at least 500 Daltons and a viscosity of at least 11 cSt at 100° C.

6. The barrier paper according to any one of the preceding claims, wherein the at least one wax is contained in the paint color layer S1 in an amount of 0.01 to 10 wt. %, preferably 0.01 to <8.0 wt. %, preferably 0.01 to <6.0 wt. %, particularly preferably 0.01 to <5.0 wt. % and very particularly preferably 0.01 to ≤2.0 wt. %, relative to the total weight of the paint color layer S1, and the lower limit is preferably at least 0.1 wt. %, particularly preferably at least 0.2 wt. %.

7. The barrier paper according to any one of the preceding claims, wherein the at least one polymeric binder in the painted color layer S1 is selected from the group comprising polyacrylates and copolymers with unsaturated hydrocarbons, polyolefins, copolymers consisting of unsaturated hydrocarbons and acrylic acid or its salts, (partially carboxylated) styrene-butadiene copolymers, styrene-butadiene copolymers, styrene-butadiene, polyvinyl acetate, partially saponified polyvinyl acetate, polyesters such as polylactic acid, and polyhydroxyalkanoates prepared from glucose, polyamides, polyurethanes, polyethers, polyethyleneimines, and / or polyvinylamides, preferably selected from The group comprising the following items: polymethyl acrylate, polymethyl methacrylate, polyethyl acrylate, polyethyl methacrylate, poly(n-, iso-, tert-)butyl acrylate, poly(n-, iso-, tert-)butyl methacrylate, polycyclohexyl methacrylate, polyethylhexyl acrylate and copolymers thereof, graft polymers, and copolymers thereof with styrene, acrylonitrile, methylstyrene and / or vinyltoluene, particularly preferably styrene acrylate / methyl acrylate / butyl acrylate / ethylhexyl acrylate copolymers and / or natural polymers, such as polysaccharides or modified polysaccharides, proteins, lignin or lignin derivatives and other natural macromolecules such as shellac.

8. The barrier paper according to any one of the preceding claims, wherein the at least one polymeric binder is contained in the paint color layer S1 in an amount of 99.9 to >92 wt. %, preferably >94 wt. %, particularly preferably >95 wt. % and very particularly preferably >98 wt. %, relative to the total weight of the paint color layer S1.

9. The barrier paper according to any one of the preceding claims, wherein the at least one wax in the painted color layer S1 is enriched at the side facing away from the base paper, which is indirectly evidenced by: The surface tension polarity changes not more than -0.65mN / m, and / or The surface tension polarity fraction changes no more than -3.0%, The corresponding change is determined by measuring and comparing the measured values ​​of the polar part of the surface tension before and after the barrier paper has been subjected to a temperature treatment at 105° C. for 3 minutes.

10. The barrier paper according to any one of the preceding claims, wherein the base paper has a g / m 2 , preferably 40 to 100 g / m 2 Weight per unit area.

11. Barrier paper according to any of the preceding claims, wherein the base paper has a long fiber proportion of 10 to 80% by weight, preferably 20 to 50% by weight, and a short fiber proportion of 20 to 90% by weight, preferably 50 to 80% by weight, wherein long fibers are fibers having a fiber length of 2.6 to 4.4 mm and short fibers are fibers having a fiber length of 0.7 to 2.2 mm.

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

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

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

15. Method for producing a barrier paper according to any one of the preceding claims, characterized in that An aqueous suspension is applied indirectly or directly to the base paper, the aqueous suspension comprising the starting material for the coating color layer S1, wherein the aqueous application dispersion has a solid content of 15 to 55% by weight, preferably 20 to 45% by weight, and is applied by curtain coating at a coating equipment operating speed of at least 100 m / min, and subsequently dried, wherein the drying is preferably carried out with the aid of infrared or thermal radiation and a subsequent air hood area and the paper web temperature in the entire drying area is maintained at <90°C.

16. Barrier paper obtainable by the process according to claim 15.

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

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

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