Barrier paper

Abstract

The invention relates to a barrier paper comprising at least:-a base paper,-at least one coated pigmented layer S1 applied directly or indirectly to the base paper,-at least one barrier layer B1 applied directly or indirectly to the coated pigmented layer S1,-a coating B2 applied directly or indirectly to the barrier layer B1.

Description

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

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

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

[0004] The main requirements for packaging materials of any origin are to protect the packaged goods from external influences and to prevent the packaged goods from leaking. For this purpose, the packaging material should meet different criteria depending on the packaged goods and the packaging process. Therefore, in addition to the so-called barrier properties against, for example, water, grease, oxygen or mineral oil, suitable packaging materials should also meet mechanical and process-specific requirements. Depending on the packaging equipment, the packaging material should have sufficient tear resistance, appropriate friction values ​​(friction coefficient) and flexibility; it should be sealable, in particular heat-sealable and ultrasonically sealable or compatible with cold-seal adhesives, as well as printable from the outside and should not lose its protective effect during the entire conversion and packaging process.

[0005] Depending on the composition and basis weight, paper can meet many mechanical requirements, but due to its physical properties and porous structure it requires additional coatings, for example to provide it with heat sealability or barrier properties.

[0006] Known coated packaging materials based on paper usually contain compounds such as polyvinylidene chloride (containing halogens) or composite materials of paper and plastic foil with improved tear resistance, which can lead to running problems on packaging equipment and / or are usually not recyclable due to excessively high coating content, adhesive components, optical inhomogeneities or formation of so-called adhesive impurities (sticky matter) via paper fiber flow and / or are not sufficiently resistant to buckling due to their metallic surface coating and / or are ineffective in humid climates due to their respective polymers. In addition, coatings deposited via vacuum deposition usually require particularly smooth and chemically suitable surfaces, which are usually produced by pre-coating.

[0007] Polyvinyl alcohol is widely known as a linear water-soluble, biodegradable barrier coating, which is also used for paper. In this case, such a coating has good barrier properties to oils, fats, oxygen, solvents and other non-polar gases, liquids or solids. However, due to its hydrophilicity, polyvinyl alcohol has a very high permeability to polar compounds such as water. This may also affect the barrier effect against non-polar migrants, because polyvinyl alcohol absorbs water very well, swells and thus creates pathways through the barrier coating at the molecular level.

[0008] There have been many attempts to achieve a deterioration in barrier properties above 50% or 60% relative humidity by adding pigments (e.g. disclosed in WO 2010 / 129032) or crosslinking polymer chains (e.g. disclosed in WO 2020 / 109401 or US 6,444,750). However, not only these microscopic defects are detrimental to the use of polyvinyl alcohol as a barrier; the occurrence of macroscopic defects due to mechanical stresses in packaging and conversion equipment also and primarily impairs the scope of use of polyvinyl alcohol.

[0009] Polyvinyl alcohol is understood to be completely saponified polyvinyl acetate, which is a (thermoplastic) plastic of the following formula (I) and is usually synthesized by free-radical polymerization of vinyl acetate.

[0010]

[0011] The ester groups in polyvinyl acetate are relatively easy to saponify under alkaline conditions, thereby converting the polymer into polyvinyl alcohol, making it hydrophilic and water sensitive.

[0012] Partially saponified polyvinyl acetate is also referred to as partially saponified polyvinyl alcohol.

[0013] In the present invention, the term "partially saponified polyvinyl acetate" may be used synonymously with the term "partially saponified polyvinyl alcohol".

[0014] The degree of saponification here refers to the proportion of ester groups which have been saponified and are now present as -OH groups. For example, polyvinyl alcohol with a degree of saponification of 90% is a vinyl acetate polymer in which 90% of the ester groups originally present have been saponified. Thus, 90% OH groups and 10% ester groups are present in this polyvinyl alcohol. In the case of a degree of saponification of 100%, only OH groups are present, since all ester groups originally present have been saponified.

[0015] In addition to the pure homopolymers, many copolymers of polyvinyl alcohol are also of great technical importance. Copolymers are understood to be all polymers whose main proportion (>50%) consists of vinyl alcohol or vinyl acetate units, regardless of the number of different monomers used for the synthesis.

[0016] Such polyvinyl alcohol copolymers preferably include polyethylene vinyl alcohol.

[0017] In a narrow sense, saponification is understood here to be the hydrolysis of esters by aqueous hydroxide solutions, for example by sodium hydroxide, or by special enzymes (esterases). In contrast to the hydrolysis of acidic esters (the reverse reaction of esterification), they are irreversible, since the protons required for esterification are missing in the carboxylic acid. The products of the reaction are understood to be the alcohols that constitute the esters and the salts of the acids (carboxylation). In a broader sense, any hydrolysis of esters can be described as saponification.

[0018] Furthermore, metallized barrier papers are known, for example from document WO 2021 / 023661 A1, which have a relative humidity of less than 5 g / m 2 / d low water vapor transmission rate (WVTR).

[0019] From document WO2021 / 251449A1, a paper substrate for metal vapor deposition is known, which comprises a base paper and a layer containing a polyvinyl alcohol resin on the base paper. Preferably, the paper substrate comprises another layer containing a water vapor barrier resin as a filling layer, wherein the layer preferably contains a flat pigment. Examples of metal vapor deposition layers include aluminum, tin, nickel, copper, gold, platinum, silver, cobalt, chromium, etc.; aluminum is preferred due to its high light-shielding properties and its low cost.

[0020] WO 2021 / 260043 A1 likewise describes metallizable barrier papers.

[0021] The object of the present invention is to eliminate the disadvantages of known materials and to provide a material suitable as a packaging material, which is particularly suitable for moisture- and oxidation-sensitive and fat-containing foods and which can be used to prepare packages, such as tubular bags, by means of heat-sealing or cold-sealing methods. In addition, the material should not contain any barrier layer based on halogen-containing compounds. In addition, compared with known packaging materials, the material according to the invention should have one or more of the following properties:

[0022] Improved oxygen barrier, improved fat barrier, improved mineral oil barrier, improved buckling resistance and flexibility of the barrier paper (equivalent to no or minimal loss of barrier properties due to buckling or folding of the barrier paper or the packaging produced therefrom), recyclability through waste paper recycling, improved heat seal properties, improved cold seal properties (compatible with sealing media, such as water-based cold seal adhesives), high tear resistance, no change in the taste of the package contents, aroma seal, the outside and the inside should be printable. The material should also have improved water vapor barrier, and the sealed seams should be as moisture-proof as possible. Finally, the material should be as economical to produce as possible.

[0023] Furthermore, the object of the present invention is to improve other application properties of metallized barrier papers, to find a method for producing improved barrier papers and to indicate their use.

[0024] This object is achieved by the barrier paper according to claim 1, which has the following characteristics:

[0025] Barrier paper comprising at least

[0026] -Base paper,

[0027] - at least one coating coloring layer S1 applied directly or indirectly to the base paper,

[0028] at least one barrier layer B1 applied directly or indirectly on the coated color layer S1,

[0029] - A coating B2 applied directly or indirectly to the barrier layer B1 .

[0030] Surprisingly, it has been shown that the inventive structure of such a barrier paper can decisively improve its application properties. In particular, as an environmentally friendly and sustainable alternative to plastic packaging for consumer goods and foods, at least equivalent properties can now be achieved while retaining the excellent recycling properties of paper packaging, especially in the waste paper cycle. In addition to the arrangement of the coating color layer S1, its properties are particularly important for the subsequent barrier layer B1 and for the properties of the barrier paper as a flexible packaging material.

[0031] It has thus been shown that the barrier paper according to the invention can be used without problems in conventional packaging machines for plastic packaging and can be formed into conventional packaging, such as heat-sealed tubular bags for sensitive foods such as potato chips and chocolate or liners for tobacco products welded by means of ultrasound, and can also be closed sufficiently tightly.

[0032] Preferred embodiments of the barrier paper according to the present invention are listed below:

[0033] Preferred is a barrier paper, wherein the coated colored layer S1 has at least one of the following properties:

[0034] a) Water vapor barrier properties,

[0035] b) Oxygen barrier properties,

[0036] c) Mineral oil barrier properties,

[0037] d) Fat barrier properties,

[0038] e) Fragrance barrier,

[0039] f) resistance to buckling of at least one property,

[0040] g) fat resistance,

[0041] h) Sealing,

[0042] i) A Bekk smoothness of at least 200 Bekk seconds.

[0043] The fat resistance of the barrier paper according to the invention is here tested based on palm kernel fat and has in particular at least one of the following values ​​listed under a) to f) (penetration number with diameter <1 mm / penetration number with diameter >1 mm):

[0044] a) Display paper (AP): <5 / <5, preferably <2 / <2, especially 0 / 0

[0045] b) Test paper (PP): <5 / <5, preferably <2 / <2, especially 0 / 0

[0046] c) Display paper (AP) - inner flexure: <5 / <5, preferably <2 / <2, especially 0 / 0

[0047] d) Test paper (PP) - inner flexure: <5 / <5, preferably <2 / <2, especially 0 / 0

[0048] e) Display paper (AP) - outer flexure: <5 / <5, preferably <2 / <2, especially 0 / 0

[0049] f) Test paper (PP) - outer flexure: <5 / <5, preferably <2 / <2, especially 0 / 0

[0050] Palm kernel fat test: Similar to DIN 53116. In the case of bent specimens, a 180° bend is produced with a roller which applies a load of 330 g / cm to the produced bend, and wherein the coating can be located on the inside (inner bend) or on the outside (outer bend).

[0051] Display paper: Evaluation of display paper as mentioned in DIN 53116. Here, fat penetration points with a diameter (d) <1 mm (first value in the table) and >1 mm (second value in the table) are counted.

[0052] Test strips: Evaluation of the back side of the test strips as mentioned in DIN 53116. This is not part of the standard but is done for better differentiation.

[0053] Barrier paper, wherein the coated color layer S1 comprises or consists of at least one water-soluble polymer and / or water-dispersible polymer.

[0054] Preferred are barrier papers wherein the at least one water-soluble polymer and / or the at least one water-dispersible polymer is selected from the group consisting of:

[0055] a) polyvinyl alcohol, in particular partially saponified or fully saponified;

[0056] b) copolymers of polyvinyl alcohol, in particular with ethylene, polyvinylamine or acrylic acid derivatives, partially or fully saponified;

[0057] c) modified fully or partially saponified polyvinyl alcohol or copolymers, in particular modified with acyl groups, alkyl groups, acrylamide, silanol, diacetone, acetoacetyl, itaconic acid;

[0058] d) polymers having an onset temperature of less than 210° C. as determined by DSC;

[0059] e) acrylic-based polymers;

[0060] f) polyester-based polymers;

[0061] g) polymers based on nitrocellulose;

[0062] h) Polymers based on polyvinyl acetate.

[0063] Within the scope of the present disclosure, unless stated otherwise, the onset temperature is determined by means of DSC in accordance with DIN EN ISO 11357-1:2010-03 as the intersection of the extrapolated baseline with the tangent of the inflection point at the onset of the melting or crystallization peak.

[0064] Particularly in the case of polymers selected from this group, the barrier layer B1 can therefore be applied directly to the coating color layer, ie for example without intermediate layers, without adhesion promoters or pretreatment of the coating color layer, for example by means of corona or plasma treatment.

[0065] Furthermore, due to the special suitability of polyvinyl alcohol, it is possible to omit a pre-coating and still apply the barrier layer B1 , in particular a metallization, simply and reliably.

[0066] Preferred are barrier papers wherein the at least one water-soluble polymer and / or the at least one water-dispersible polymer comprises at least partially saponified polyvinyl alcohol and / or at least partially saponified polyvinyl alcohol copolymers, each having an onset temperature determined by means of DSC of less than 210°C.

[0067] Preferred is a barrier paper in which the at least one water-soluble polymer and / or the at least one water-dispersible polymer comprises a partially saponified polyvinyl alcohol having a degree of saponification of 30% to 95%, an average molecular weight of greater than 0 and less than 100,000 g / mol, and an onset temperature determined by means of DSC of less than 200° C.

[0068] Preferred are barrier papers in which the at least one water-soluble polymer and / or the at least one water-dispersible polymer comprises a partially saponified polyvinyl alcohol having a degree of saponification of greater than 95% to 100%, an average molecular weight of greater than 70,000 g / mol, and an onset temperature determined by means of DSC of less than 200° C.

[0069] Preferred are barrier papers in which at least one polymer comprises a partially saponified polyvinyl alcohol copolymer, preferably partially saponified polyethylene vinyl alcohol, having a degree of saponification of 95% to 100%, an average molecular weight of more than 60,000 g / mol, and an onset temperature determined by DSC of less than 210° C.

[0070] Preference is given to barrier papers in which the partially saponified polyvinyl alcohol and / or the partially saponified polyvinyl alcohol copolymer has a viscosity of less than 30 mPas, particularly preferably less than 20 mPas and very particularly preferably less than 15 mPas at a dry content of 4%.

[0071] Preferred are barrier papers wherein the at least one polymer comprises a mixture of the water-soluble polymers and / or water-dispersible polymers mentioned previously as preferred.

[0072] Preferred is a barrier paper in which the coated color layer S1 has a surface tension in the range of 25 to 80 mN / m, in particular 25 to 75 mN / m. A particularly preferred range is 45 to 70 mN / m. Preferably, the polar part of the surface tension is in the range of 55 to 80%.

[0073] These surface tensions (surface energies) are advantageous, in particular for the direct application of the barrier layer B1, in particular in the case of metallization (wetting, nucleation, growth). Conventional coatings, for example based on BOPP or PET, must first be treated, for example with the aid of a corona plasma, to achieve a surface tension of at least 25 mN / m, preferably at least 35 mN / m.

[0074] Polyvinyl alcohol is suitable as a suitable polymer for the coating color layer S1 due to its high surface tension (surface energy) of about 50 to 70 mN / m, which in particular in this case also contains about 70% to 80% of highly polar parts, so that in particular the thin metal layer has a significantly lower and mainly dispersed surface tension. Therefore, we determined a surface tension of 27.6 mN / m in the case of a polyvinyl alcohol-based coating color layer S1 evaporated with Al by means of physical vapor deposition with only 3.6% polar part. Pure aluminum has a very high surface tension of 1200 mN / m. In fact, aluminum is covered with an oxide layer, resulting in about 40 mN / m. As a result, the metal layer (barrier layer B1) not only adheres via weak forces as on most non-polar plastics (polyolefins, polyesters, acrylic copolymers, etc.), but is also more firmly anchored, resulting in a high composite strength, which also proves to be an advantage when bending the barrier paper, because even in the case of more demanding external bending parts, the metal layer (barrier layer B1) will not separate during bending.

[0075] In addition, there are also other preferred water-soluble and therefore polar polymers, which have certain oxygen barrier properties and are particularly suitable for coating coloring layer S1, but are also suitable for coating B2. It can be mentioned that natural and modified starch, partially degraded starch, modified soluble cellulose, nanocellulose and other polymeric carbohydrates, such as chitosan, amylopectin, curdlan, xanthan gum, hemicellulose, pectin, dextran, gum arabic, gum karaya, guar gum, gellan gum etc. Because many carbohydrates tend to be brittle, it is recommended to be added in the smaller molecules that act as plasticizers in hydrophilic polymers. Examples for this are sugar alcohols such as glycerol and sorbitol, poly (ethylene) glycol. As other natural polymers, protein can be used, such as casein, zein, keratin, collagen, gelatin, whey protein, wheat gluten, rapeseed protein, soy protein, sorghum alcohol-soluble protein, oat protein, rice bran protein, lupin protein, cotton protein or peanut protein. Water-insoluble polymers may also be used, particularly those which do not form an oxygen barrier but do form a barrier to fat and mineral oil vapors. These also have high, predominantly polar, surface energies.

[0076] Pigments which improve the barrier effect can be added to all the polymers mentioned. However, it should be noted that these do not significantly impair the smoothness of the individual layers. This can be achieved by selecting flake-shaped pigments with a high shape factor (aspect ratio), whose thickness is less than the thickness of the individual layers and whose proportion does not exceed 50% by weight of the layer. Examples of such pigments are kaolin, natural and synthetic phyllosilicates (mica), talc, precipitated calcium carbonate.

[0077] The coating color layer S1 can be applied to one side of the base paper or to both sides. A plurality of coating color layers S1 can be arranged on one side of the base paper, wherein in particular the composition or layer thickness or unit area weight can be the same or different. The coating layer B2 and the coating color layer S1 can be the same or different, wherein in particular the composition or layer thickness or unit area weight can be the same or different.

[0078] Preferred are barrier papers, in which the barrier layer B1 contains a metal, in particular Al, Cu, Sn, Zn, Ag, Au, Ti, In, Si, a metal alloy, a metal oxide, in particular Al2O3, SiO2, a mixed oxide or a combination thereof, or consists of them.

[0079] Preferred is a barrier paper, wherein the barrier layer B1 is applied by means of vacuum deposition or other known or conventional methods.

[0080] Preferred is a barrier paper, wherein the barrier layer B1 has at least one of the following characteristics:

[0081] a) Optical density ≥1.5 and ≤6.0,

[0082] b) Layer thickness ≥5 nm, preferably ≥10 nm, particularly preferably ≥15 nm, in particular 5 nm to 150 nm.

[0083] The barrier layer B1 can be applied to one side of the base paper or to both sides. A plurality of barrier layers B1 can be arranged on one side of the base paper, wherein in particular the composition or the layer thickness can be identical or different.

[0084] Preferred are barrier papers in which the coating B2 comprises or consists of at least one polymer, in particular a polymer selected from the group consisting of:

[0085] a) polyethylene-acrylic acid copolymer,

[0086] b) polyolefins,

[0087] c) polyvinyl alcohol,

[0088] d) cellulose nitrate,

[0089] e) Bio-based polymers

[0090] f) Non-bio-based polymers

[0091] g) styrene-butadiene latex,

[0092] h) Acrylate latex.

[0093] Preferred are barrier papers in which the coating B2 has at least one of the following properties:

[0094] a) protecting the barrier layer B1 against external influences, in particular mechanical influences such as buckling in the packaging equipment, for example when closing the package (for example sealing a seam) or against abrasion or chemical influences,

[0095] b) sealable, in particular heat-sealable, ultrasonically sealable and cold-sealable,

[0096] c) fat resistance,

[0097] d) Water resistance,

[0098] e) Moisture resistance,

[0099] f) Printability,

[0100] g) additional barrier properties,

[0101] h) Optimization of existing barrier properties.

[0102] Preferred is a barrier paper, wherein the barrier paper has at least one of the following features:

[0103] a) At 23°C and 50% relative humidity, WVTR ≤ 5g / m 2 / d

[0104] b) At 23°C and 50% relative humidity, WVTR inner flexure ≤ 5g / m 2 / d

[0105] c) At 23°C and 50% relative humidity, WVTR outer flexure ≤ 5g / m 2 / d

[0106] d) At 38°C and 90% relative humidity, WVTR ≤ 15g / m 2 / d

[0107] e) At 38°C and 90% relative humidity, WVTR inner flexure ≤ 15g / m 2 / d

[0108] f) At 38°C and 90% relative humidity, WVTR outer flexure ≤ 15g / m 2 / d

[0109] g) At 23°C and 50% relative humidity, OTR ≤ 10 cm 3 / m 2 / d

[0110] h) At 23°C and 50% relative humidity, the inner buckling portion of OTR is ≤10cm 3 / m 2 / d

[0111] i) At 23°C and 50% relative humidity, OTR outer flexure ≤ 10cm 3 / m 2 / d

[0112] j) buckling resistance of at least one barrier property, in particular in the region of the inner and / or outer buckling,

[0113] k) at least 2.5% by weight, in particular at least 3.0% by weight, of residual moisture, based on the total weight of the barrier paper.

[0114] Preferred is a barrier paper, wherein the barrier paper has at least one of the following features:

[0115] a) At 23°C and 50% relative humidity, WVTR ≤ 3g / m 2 / d

[0116] b) At 23°C and 50% relative humidity, WVTR inner flexure ≤ 3g / m 2 / d

[0117] c) At 23°C and 50% relative humidity, WVTR outer flexure ≤ 3g / m 2 / d

[0118] d) At 38°C and 90% relative humidity, WVTR ≤ 10g / m 2 / d

[0119] e) At 38°C and 90% relative humidity, WVTR inner flexure ≤ 10g / m 2 / d

[0120] f) At 38°C and 90% relative humidity, WVTR outer flexure ≤ 10g / m 2 / d

[0121] g) At 23°C and 50% relative humidity, OTR ≤ 5 10cm 3 / m 2 / d

[0122] h) At 23°C and 50% relative humidity, OTR ≤ 5 cm 3 / m 2 / d

[0123] i) At 23°C and 50% relative humidity, OTR ≤ 5cm 3 / m 2 / d

[0124] j) buckling resistance of at least one barrier property, in particular in the region of the inner and / or outer buckling,

[0125] k) at least 2.5% by weight, in particular at least 3.0% by weight, of residual moisture, based on the total weight of the barrier paper.

[0126] At least one barrier property, in particular resistance to buckling in the region of the inner or outer buckling means that at least one barrier property deviates from the barrier property of the barrier paper in the region of the buckling or in the buckling by less than maximum 100%, preferably maximum 75%, particularly preferably maximum 50% and very particularly preferably maximum 25%. For example, if the measured value of the WVTR of the barrier paper according to the invention = 1.5 g / m 2 / d (at 38°C and 90% relative humidity), the measured value of WVTR in the region of the inner flexure (i.e., the inner flexure is in the measurement surface) or directly at the inner flexure is between 0 and 3 g / m 2 / d range (less than the maximum 100%).

[0127] Preferred is a barrier paper in which the coating color layer S1, the barrier coating layer B1 and the barrier coating layer B2 are removable in the waste paper cycle.

[0128] Preference is given to barrier papers in which the following deinkability scores are achieved according to the evaluation of the recyclability of the printed product after processing the barrier paper according to INGEDE method 11:

[0129] a) Brightness Y is the maximum 35 points,

[0130] b) The color coefficient a* in the CIELAB system is a maximum of 20 points,

[0131] c) Dirt points A in two different size classes A50 with a maximum of 15 points and A250 with a maximum of 10 points,

[0132] d) the dye elimination (printing ink elimination) degree IE is a maximum of 10 points, and

[0133] e) The filtrate darkens ΔY to a maximum of 10 points,

[0134] The sum of all point values ​​is in the range from 0 to 100, preferably in the range from 51 to 70, particularly preferably in the range from 71 to 100, and / or preferably no individual point value is negative.

[0135] Preferred are barrier papers in which a precoat layer comprising at least one inorganic pigment and a polymer binder is present between the base paper and the applied color layer S1, wherein the inorganic pigment is preferably flake-shaped and preferably comprises talc, precipitated calcium carbonate, silicate, preferably phyllosilicate or kaolin, and / or the polymer binder comprises a polymer binder based on polyacrylate.

[0136] Preferably, the precoat layer comprises at least one polymeric binder and at least one organic and / or one inorganic pigment and optionally also additional customary amounts of coating coloring components.

[0137] Pigments: Phyllosilicate.

[0138] Polymer binder: styrene-acrylate latex, butadiene latex.

[0139] Rheology modifiers such as acrylate based thickeners and / or zirconium based crosslinkers.

[0140] Preferred is a barrier paper in which the weight per unit area of ​​the coating color layer S1 and the coating layer B2 is between 4 and 20 g / m 2 , preferably 8 to 15 g / m 2 In the range of 500 ℃ and 1000 ℃, based on the dried final product (air drying).

[0141] Preference is given to barrier papers, wherein the barrier papers contain no halogen-containing compounds except for unavoidable traces.

[0142] Preferred is a barrier paper wherein the base paper has a g / m 2 , preferably 40 to 100 g / m 2 Weight per unit area.

[0143] Preferred are barrier papers in which the base paper has a long fiber content of 10 to 80% and a short fiber content of 20 to 90% by weight, the long fibers being fibers with a fiber length of 2.6 to 4.4 mm and the short fibers being fibers with a fiber length of 0.7 to 2.2 mm.

[0144] Preferred are barrier papers wherein the base paper comprises or consists of 100% virgin fiber pulp and up to 100% recycled fibers, or comprises or consists of a mixture of both.

[0145] Preferred are barrier papers wherein the base paper comprises up to 90% recycled fibers.

[0146] It is preferred that the base paper has a starch precoat or a starch-containing precoat, preferably on one side or on both sides, in particular to improve printability.

[0147] The present invention also relates to a method for producing barrier paper, characterized in that an aqueous suspension containing starting materials for coating the color layer S1 is applied indirectly or directly to the base paper, wherein the aqueous application suspension has a solid content of 5 to 50% by weight, preferably 10 to 30% by weight, and is applied by a curtain coating method (curtain coating), preferably a double curtain coating method (double curtain coating) at a running speed of the coating device of at least 200 m / min.

[0148] Preferably, after conventional drying of the coating color layer S1, the barrier paper is re-moistened with a moistening unit or a steam bellows to achieve a moisture content of between 2.5 and 7%, preferably between 3.5 and 5%, particularly preferably between 4 and 4.5%, based on the total mass. This is ideal for the barrier coating B1, especially if metallization is involved, in order to maintain the flexibility of the coating color layer S1 and the base paper, but too much moisture should also be prevented from entering the coating chamber (e.g., vacuum chamber).

[0149] Preferably, after conventional remoistening of the applied color layer S1, the barrier paper is remoistened with a moistening unit or steam bellows to achieve a moisture content of between 2.5 and 7%, preferably between 3.5 and 5%, particularly preferably between 4 and 4.5%, based on the total mass.

[0150] Preferably, after conventional rewetting of the applied color layer S1, the surface of the applied color layer S1 is smoothed / polished with one or more roll smoothing units, calenders or shoe calenders to a smoothness value of minimum 200 Becquerel seconds, in particular 500 Becquerel seconds.

[0151] Preferably, after conventional smoothing of the coated color layer S1 , the barrier layer B1 is applied directly or indirectly on the coated color layer S1 by conventional methods.

[0152] The coating B2 can subsequently be applied directly or indirectly to the barrier layer B1 by means of customary methods and, if desired, dried by means of customary methods.

[0153] After coating B2, a full-surface or partial sealing lacquer, in particular a hot or cold sealing lacquer, can be applied directly or indirectly on coating B2 and / or on the opposite outer side of the barrier paper by conventional methods and dried directly or indirectly by conventional methods.

[0154] After coating B2, full-surface or partial printing can be applied directly or indirectly by conventional methods on coating B2 and / or on the opposite outer side of the barrier paper to make the packaging identifiable and provide information, and dried directly or indirectly by conventional methods.

[0155] The invention also relates to the use of a barrier paper according to the invention or a barrier paper produced according to the method as packaging material for foods, consumer goods, tobacco products or as a component of a packaging material, in particular a component of a packaging material based on cardboard or paperboard, in particular as packaging material for foods, in particular sausages, cheese, coffee, granola bars, chocolate, chocolate-containing products or potato chips.

[0156] The present invention also relates to a package comprising the barrier paper according to the present invention or the barrier paper prepared according to the method, wherein the package is preferably a cold-sealed package, a heat-sealed package, an ultrasonic-sealed package, in particular a tubular bag package.

[0157] In a preferred embodiment, in the case of packaging, the coated side (inner side) faces the inside (inner side of the packaging) and the outer side faces the outside. This allows, in particular, the packaging of moist and / or greasy items. In this case, the outer side is printed and the inner side is sealed to the inner side (A:A sealing) and / or the inner side is sealed to the outer side (A:B sealing).

[0158] In particular, there are embodiments of packaging in which the coated side (inner side) faces the outside (outer side of the packaging) and the outer side faces the inside. This makes it possible to prevent the packaged goods, which are particularly sensitive to moisture, from drying out. In this case, the inner side is printed and the outer side is sealed to the outer side (A:A sealing) and / or the outer side is sealed to the inner side (A:B sealing).

[0159] The quality of the barrier paper according to the invention, in particular as regards its resistance to buckling, can be determined in particular by dynamic mechanical thermal analysis (DMTA).

[0160] Dynamic Mechanical Thermal Analysis (DMTA) / DMTA Measurement:

[0161] Dynamic Mechanical Thermal Analysis (DMTA) is a method used to measure the viscoelastic properties of a polymer or material system. By applying cyclic sinusoidal stress / strain forces to cause deformation without destruction, the phase angle can be calculated by shifting the sinusoidal response of the material. The phase angle of a viscoelastic material is defined as a value greater than = 0° (pure elastic material) and less than = 90° (pure viscous material). Therefore, the tan value is a value representing the ratio between the elastic modulus (G') and the viscosity modulus (G"), which is given by the following equation:

[0162]

[0163] The tan value (quantifying the loss attenuation effect), elastic modulus (G') and viscosity modulus (G") of packaging materials that retain their barrier properties after buckling or folding can be compared with packaging materials that lose their predetermined barrier properties. We obtained the tan for materials that retain their barrier properties after buckling or folding and the tan for materials that lose their barrier properties after folding. The tan (loss factor) is within the acceptable range for viscoelastic materials (tan = 0-1.0).

[0164] Furthermore, the barrier paper according to the invention is preferably characterized in that the value of the loss factor tan δ measured as a function of temperature by means of dynamic mechanical thermal analysis (DMTA) of the barrier paper passes through a maximum value at temperature Tg and a first inflection point at temperature Tw with increasing temperature.

[0165] Preferably, the temperature Tg is lower than the temperature Tw.

[0166] Barrier papers having a value of the loss factor tan δ measured as a function of temperature which with increasing temperature is a maximum at temperature Tg and a first inflection point at temperature Tw, preferably with Tg below Tw, are characterized in that they retain the barrier properties in an advantageous manner after buckling.

[0167] Preferably, the magnitude of the difference between tan δ at temperature Tg and tan δ at temperature Tw is >0.013, preferably >0.014 and particularly preferably >0.015.

[0168] In particular, in the case of such values ​​of the difference between tan δ at temperature Tg and tan δ at temperature Tw, the barrier properties are advantageously maintained after buckling.

[0169] As described above, the onset temperature is determined by means of DSC as follows:

[0170] The (extrapolated) onset temperature (according to DIN EN ISO 11357-1:2010-03) is the intersection of the extrapolated baseline and the inflection point tangent at the start of the melting or crystallization peak in the DSC measurement. The baseline and the inflection point tangent are determined by the temperature-dependent heat flow signal. In the case of pure and homogeneous materials, the initial temperature can be designated as the melting temperature. In contrast to the peak temperature, the onset temperature is less dependent on the heating rate and the sample mass. In addition, the onset temperature is often used for the temperature calibration of the DSC.

[0171] The barrier paper according to the invention is particularly characterized in that it is particularly well suited as a packaging material for moisture- and oxidation-sensitive and greasy objects, in particular foods, and can be used to produce sachets by means of a hot seal or cold seal application, wherein for the cold seal application a water-based cold seal adhesive can be used. Furthermore, the presence of a layer based on a halogen-containing compound or a barrier layer is not necessary.

[0172] Compared with fully saponified polyvinyl alcohol (PVOH) or polyethylene vinyl alcohol (EVOH), the advantage of partially saponified polyvinyl alcohol is that they have significantly lower optimal sealing temperatures during heat sealing. This has no negative impact on the strength of the sealed seam. In addition, in the case of otherwise identical concentrations, partially saponified polyvinyl alcohol has a slightly lower viscosity. High viscosity is quite disadvantageous because in this case the PVOH solution must be diluted to a greater extent, which is why a larger amount of water must be dried during the coating process. This not only consumes energy and therefore requires a coating device with a higher drying capacity, but also may be difficult to achieve in terms of application technology depending on the desired applied weight. In addition, the diffusion of water molecules at high viscosity and therefore the drying itself are slowed down. In addition, it is easier to accumulate gaseous water in the coating, resulting in the formation of macroscopic coating defects.

[0173] Therefore, partially saponified polyvinyl alcohol or partially saponified polyvinyl alcohol copolymers, such as polyethylene vinyl alcohol, are preferred over the fully saponified variants.

[0174] Especially in the case of water-sensitive and moisture-sensitive coating color layers S1, for example based on polyvinyl alcohol, they must be protected from humid environments. This can be achieved by vacuum depositing the metal with minimal application. Vacuum deposition also requires high smoothness or minimal roughness.

[0175] Due to its minimum thickness, the vacuum deposited layer must in turn be protected from scratches, abrasion, oxidation and tearing. In addition, for specific packaging preparations, an additional sealing layer is required to prepare a pouch or similar packaging form. This is achieved by applying the coating B2 to the barrier layer B1 (e.g. the vacuum deposited layer). In addition, the coating B2 can additionally improve the oxygen or water vapor barrier properties.

[0176] Furthermore, the barrier paper according to the invention is characterized by improved oxygen barrier properties, improved fat barrier properties, improved mineral oil barrier properties and improved water vapor barrier properties.

[0177] The barrier paper according to the invention also has an improved resistance to buckling, without impairing the barrier effect, and is furthermore characterized by a high resistance to tearing.

[0178] In addition, the barrier paper according to the present invention can be recycled through waste paper.

[0179] If the barrier paper according to the invention is used as packaging material for foods, it is particularly characterized in that it does not influence and / or change the taste of the packaged foods.

[0180] Furthermore, the barrier paper according to the invention is heat sealable and exhibits improved cold seal properties (compatible with sealing media, such as water-based cold seal adhesives), wherein the sealed seams each have sufficient moisture barrier properties.

[0181] Furthermore, the barrier paper according to the invention is easy to print on the uncoated side (outer side) and on the coated side (inner side).

[0182] Finally, the barrier paper according to the invention can be produced relatively easily and at a low applied weight and can be recycled via waste paper.

[0183] Hereinafter, the term "includes / comprising" may also mean "consisting of."

[0184] "Hydrophobic / water-repellent" refers to substances that cannot be mixed with water or can be wetted by water only using surfactants. "Hydrophilic / hydrophilic" refers to substances that can be mixed with water or can be wetted by water without the use of surfactants. Hydrophobic polymers are also called non-polar polymers, and hydrophilic polymers are also called polar polymers.

[0185] For example, the logP value can be used to define hydrophobicity or hydrophilicity. ow The log P value is the n-octanol-water partition coefficient K (also spelled as octanol / water partition coefficient, which is common and correct) and is a dimensionless partition coefficient known to those skilled in the art, which indicates the ratio of the concentrations of a chemical in a two-phase system consisting of n-octanol and water and is therefore a measure of the hydrophobicity or hydrophilicity of a substance. ow The base 10 logarithm of . In this case it applies:

[0186] and

[0187] where c o Si = concentration of chemical in the octanol-rich phase, c w Si = concentration of chemical in the water-rich phase.

[0188] If the substance is better soluble in a fat-like solvent such as n-octanol, then K ow greater than 1, if the substance dissolves better in water, then K ow Less than 1. Therefore, log P is positive for hydrophobic / lipophilic substances and negative for hydrophilic / lipophobic substances.

[0189] The low permeability of polyvinyl alcohols to oxygen, mineral oils, fats and other non-polar migrants is due to their relatively high hydrophilicity.

[0190] Furthermore, ethylene-containing polymers, such as (saponified) polyethylene vinyl alcohol, have a relatively low water vapor permeability due to the ethylene content and the associated low hydrophilicity.

[0191] In principle, the base paper used for the coated paper according to the invention is not restricted.

[0192] However, it is preferred that the base paper has a g / m 2 , preferably 40 to 100 g / m 2 Weight per unit area.

[0193] Furthermore, it is preferred if the base paper has a composition with 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.

[0194] The long fibers refer to fibers having a fiber length of 2.6 to 4.4 mm, and the short fibers refer to fibers having a fiber length of 0.7 to 2.2 mm.

[0195] Furthermore, fillers may be present in amounts of 0% to 20%, preferably 0% to 5%, preferably not including the value of 0%, such as GCC (ground calcium carbonate) known under the trade names Hydrocarb 60 or Hydroplex 60, PCC (precipitated calcium carbonate) known, for example, under the trade name Precarb 105, natural kaolin and / or talc and customary auxiliaries, such as retention aids and / or sizes.

[0196] Such base papers are advantageous on the one hand for their high flexibility or their low stiffness and on the other hand for their good processability on existing packaging equipment for flexible materials such as plastic foils, maintaining high machine availability and achieving the necessary puncture resistance, bursting strength and tear propagation work.

[0197] Common packaging machines are, for example, vertical and horizontal tubular bag machines (Form-Fill-Seal) for producing stand-up bags, flow packs, pillow packs, etc., machines which bring together two webs of the same or different materials and join them by heat sealing, cold sealing or ultrasonic sealing, for example also tray sealers, chamber belt machines (Kammerbandmaschinen, also with vacuum), sachet filling and welding machines, deep-draw packaging machines, linear filling machines which apply lids by heat sealing for sealing, packaging machines with a final heat sealing step, blister packaging machines and X-fold packaging machines.

[0198] The barrier paper according to the present invention is also preferably characterized in that a pre-coating layer comprising at least one inorganic pigment and a polymer binder is present between the base paper and the coating color layer S1.

[0199] The inorganic pigments are preferably flake-form and include in particular talc, precipitated calcium carbonate or silicates, preferably phyllosilicates, and very particularly preferably kaolin.

[0200] As suitable polymeric binders, particular mention is made of binders based on acrylates or on styrene / butadiene. In principle, all polymers that can be used as binders for pigment coatings in the paper industry are suitable. Binders based on starch (solutions of modified starch, dispersions of cross-linked starch, so-called bio-latexes) and polymer-starch hybrid latexes are also possible.

[0201] The polymer binder preferably comprises a polyacrylate-based polymer binder.

[0202] In general, the pre-coat layer may be a hydrophobic pre-coat layer.

[0203] In another embodiment, the pre-coat layer is entirely hydrophilic.

[0204] The precoat layer preferably contains 1 to 70% by weight, preferably 5 to 50% by weight, of polymeric binder. This amount is relative to the dried precoat layer in the final product.

[0205] The precoat layer also preferably contains 50 to 95% by weight, preferably 80 to 90% by weight, of inorganic pigments. This amount is based on the dried precoat layer in the final product.

[0206] Furthermore, the pre-coat layer may contain additives such as thickeners, for example acrylate-based thickeners, surfactants and / or rheology modifiers. The use of cross-linking agents is also contemplated. Preferably, the pre-coat layer contains a zirconium-based cross-linking agent and is itself cross-linked with formaldehyde.

[0207] These additives are preferably contained in an amount of 0 to 2% by weight, preferably more than 0 to 2% by weight, wherein a value of 0% is preferably excluded. The amounts are based on the dried precoat layer in the end product.

[0208] The application amount of the pre-coat is preferably 1 to 10 g / m 2 , particularly preferably 2 to 6 g / m 2 The amount is based on the dried pre-coat layer in the final product.

[0209] If such a precoat (also called a primer) is applied, this has the advantage that the paper surface is sealed and the additional coating color layer 1 applied thereon migrates only slightly into the paper and thus produces sufficient layer adhesion. In addition, the precoat reduces the average roughness depth of the base paper and provides an advantageous "holdout", which is characterized by application covering the entire surface and a defined surface energy, so that the applied coating color layer 1 can be formed optimally. In addition, the precoat imparts layer adhesion between the base paper and the coating color layer 1, which may be important for subsequent sealing applications.

[0210] The coating color layer 1 applied in the precoat layer preferably comprises at least partially saponified polyvinyl alcohol and / or at least partially saponified polyvinyl alcohol copolymers. The preparations used for processing preferably have a polymer content of 10 to 100% by weight, particularly preferably 50 to 99.8% by weight.

[0211] The coated color layer 1 may further contain additives such as thickeners, for example acrylate-based thickeners; surfactants, for example sulfosuccinates; extensional rheological aids, for example polyacrylamide, carboxymethylcellulose, polyvinyl alcohol; and / or crosslinking agents, such as aldehydes and polyvalent aldehydes, zirconates, polyvalent epoxides, epichlorohydrin resins and / or hydrazides.

[0212] These additives are preferably each contained in an amount of 0.1 to 1% by weight based on the total weight of the coated color layer 1 .

[0213] In one embodiment, the barrier paper according to the invention is further preferably characterized in that the at least partially saponified polyvinyl alcohol and / or the at least partially saponified polyvinyl alcohol copolymer has an average molecular weight of less than 100 000 g / mol.

[0214] In a further embodiment, the barrier paper according to the invention is further preferably characterized in that the at least partially saponified polyvinyl alcohol and / or the at least partially saponified polyvinyl alcohol copolymer has an average molecular weight of greater than 30,000 g / mol or greater than 40,000 g / mol or greater than 50,000 g / mol or greater than 60,000 g / mol or greater than 70,000 g / mol.

[0215] In one embodiment, the barrier paper according to the invention is further preferably characterized in that the at least partially saponified polyvinyl alcohol and / or the at least partially saponified polyvinyl alcohol copolymer has a degree of saponification of 30% to 100%.

[0216] In a further embodiment, the barrier paper according to the invention is additionally preferably characterized in that the at least partially saponified polyvinyl alcohol and / or the at least partially saponified polyvinyl alcohol copolymer has a degree of saponification of 30% to less than 100%.

[0217] In a further embodiment, the barrier paper according to the invention is additionally preferably characterized in that the at least partially saponified polyvinyl alcohol and / or the at least partially saponified polyvinyl alcohol copolymer has a degree of saponification of less than 95% or from 30% to 95%.

[0218] In a further embodiment, the barrier paper according to the invention is additionally preferably characterized in that the at least partially saponified polyvinyl alcohol and / or the at least partially saponified polyvinyl alcohol copolymer has a degree of saponification of 95% to 100%.

[0219] In a further embodiment, the barrier paper according to the invention is additionally preferably characterized in that the at least partially saponified polyvinyl alcohol and / or the at least partially saponified polyvinyl alcohol copolymer has a degree of saponification of 95% to less than 100%.

[0220] In a further embodiment, the barrier paper according to the invention is additionally preferably characterized in that the at least partially saponified polyvinyl alcohol and / or the at least partially saponified polyvinyl alcohol copolymer has an onset temperature determined by means of DSC of less than 200° C.

[0221] The barrier paper according to the invention is further preferably characterized in that at least one polymer comprises a partially saponified polyvinyl alcohol having a degree of saponification of less than 95% or from 30% to 95%, an average molecular weight of greater than 0 and less than 100,000 g / mol, and an onset temperature determined by means of DSC of less than 200° C.

[0222] In another embodiment, the barrier paper according to the invention is further preferably characterized in that at least one polymer comprises a partially saponified polyvinyl alcohol having a degree of saponification of 95% to 100%, an average molecular weight of more than 70,000 g / mol, and an onset temperature determined by means of DSC of less than 200° C.

[0223] In another embodiment, the barrier paper according to the invention is further preferably characterized in that at least one polymer comprises a partially saponified polyvinyl alcohol copolymer, preferably partially saponified polyethylene vinyl alcohol, having a degree of saponification of 95% to 100%, an average molecular weight of more than 60,000 g / mol, and an onset temperature determined by means of DSC of less than 210° C.

[0224] It has been shown that partially saponified polyvinyl alcohol copolymers, such as polyethylene vinyl alcohol, are generally more flexible than polyvinyl alcohol.

[0225] In another embodiment, the barrier paper according to the invention is preferably characterized in that at least one polymer comprises a mixture consisting of: a partially saponified polyvinyl alcohol having a degree of saponification of 1% to 95%, an average molecular weight of greater than 0 and less than 100,000 g / mol and an onset temperature determined by means of DSC of less than 200° C., a partially saponified polyvinyl alcohol having a degree of saponification of 95% to 100%, an average molecular weight of greater than 70,000 g / mol and an onset temperature determined by means of DSC of less than 200° C., and / or a partially saponified polyvinyl alcohol copolymer having a degree of saponification of 95% to 100%, an average molecular weight of greater than 60,000 g / mol and an onset temperature determined by means of DSC of less than 210° C., preferably partially saponified polyethylene vinyl alcohol.

[0226] The degree of saponification is determined according to DIN EN ISO 3681 as follows:

[0227] Distilled water (70 mL) and neutralized ethanol (30 mL) were added to polyvinyl alcohol (PVOH) (1 g) and heated under reflux until completely dissolved. After cooling, the solution was neutralized with caustic potash solution (0.1 M). In the case of partially saponified PVOH types, additional caustic potash solution (50 mL, 0.1 M) was added and heated under reflux (60 min). In the case of fully saponified PVOH types, in order to avoid carbon dioxide absorption in excess alkali solution, additional caustic potash solution (25 mL, 0.1 M) of reduced amount was used, while also reducing the reflux time (30 min). The excess alkali solution was then back-dripped with hydrochloric acid (0.1 M) relative to phenolphthalein as an indicator. A blank test was carried out in parallel.

[0228] The saponification degree (%) can be calculated according to Equation 1:

[0229]

[0230] The esterification value is determined according to Equation 2:

[0231]

[0232] (Equation 2)

[0233] The average molecular weight was determined by size exclusion chromatography (GPC) under the following conditions:

[0234] Eluent: DMSO / +0.1M LiCl; Pre-column: 10μm, protection, ID 8.00mm x50.00mm; Column: 10μm, ID 8.00mm x 300.00mm; 10μm, ID 8.00mm x 300.00mm; 10μm, ID8.00mm x 300.00mm; Pump: 1260HPLC pump; Flow rate: 1.0mL / min; Injector: 1260 autosampler; Injection volume: 200μL; Sample concentration: 5.0g / L; Temperature: 80℃; Detector: SECurity 2 Refractive index detector (RI) - WEG eta1001HT viscometer; Calculation: WinGPC UniChrom version 8.33.

[0235] The sample was dissolved in a solvent (5 mg / mL) at a temperature of 80° C. for 3 hours and injected by an automatic sampler.

[0236] To determine the calibration curve, several PMMA standards with different molecular weights were measured. The calibration curve was converted into a universal calibration curve by measuring the intrinsic viscosity.

[0237] The barrier paper according to the invention is further preferably characterized in that the polyvinyl alcohol has a viscosity of less than 30 mPas or less than 20 mPas, particularly preferably less than 15 mPas, at a dry content of 4%.

[0238] The viscosity was measured at 23°C using a Brookfield viscometer at 100 rpm.

[0239] The advantage of a viscosity in this range is that, in the case of application, a higher solids content can be used and therefore less energy must be used for drying, and a higher processing speed can be achieved. In addition to the economic advantages, this is also reflected in the use of a larger drying window on the coating equipment.

[0240] As mentioned above, the quality of the barrier paper according to the invention, in particular as regards its resistance to buckling, can be determined by dynamic mechanical thermal analysis (DMTA).

[0241] Using dynamic mechanical thermal analysis (DMTA), the glass transition temperature (Tg) can also be determined - the temperature at which the polymer chains change from a solid frozen state to a mobile state, but before the polymer chains slide over each other, which corresponds to the melting point (Tm). Advantageously, a viscoelastic state exists in the packaging material in order to maintain barrier properties after bending or folding - therefore, a Tg below the operating and use temperature is ideal. Tg is determined in DSC by the temperature of the sample during firing. Preferred polymers have a glass transition temperature, Tg, corresponding to a tan maximum.

[0242] The barrier paper according to the invention preferably has a breaking force in the running direction of >80 N / 15 mm, preferably >90 N / 15 mm, and perpendicularly to the running direction of the paper of >40 N / 15 mm, preferably >50 N / 15 mm.

[0243] The barrier paper according to the invention also preferably has a dynamic coefficient of friction (CoF) of <0.7, preferably <0.6, particularly preferably <0.5. This refers to the friction of coated side on coated side (coating on coating).

[0244] The barrier paper according to the invention is further preferably characterized in that the weight per unit area of ​​the individual layers is 4 to 20 g / m 2 , preferably 4 to 15 g / m 2 , based on the dried final product (air dry).

[0245] The barrier paper according to the invention is further preferably characterized in that the coating B2 can be wetted with conventional water-based cold sealing adhesives. For this purpose, the surface energy of the coating B2 is >35 mN / m, >40 mN / m, preferably >50 mN / m, particularly preferably >55 mN / m.

[0246] Such wettability of the coating B2 is advantageous in that no uncoated areas are formed during the application and drying of the cold sealing adhesive and that sufficient adhesion is also imparted during application.

[0247] The barrier paper according to the invention is further preferably characterized in that the barrier paper has an oxygen transmission rate (OTR) of less than 10, preferably less than 5 10cm 3 / m 2 / d (23°C, 0% relative humidity).

[0248] The barrier paper according to the invention is further preferably characterized in that the barrier paper has an oxygen transmission rate (OTR) of less than 10, preferably less than 5 10cm 3 / m 2 / d (23°C, 50% relative humidity).

[0249] The barrier paper according to the invention is further preferably characterized in that the barrier paper has an oxygen transmission rate (OTR) 10 cm of less than 20, preferably less than 15. 3 / m 2 / d (23°C, 70% relative humidity).

[0250] The barrier paper according to the invention is further preferably characterized in that the barrier paper has an oxygen transmission rate (OTR) 10 cm of less than 50, preferably less than 40. 3 / m 2 / d (23°C, 80% relative humidity).

[0251] The barrier paper according to the invention preferably also does not lose the oxygen barrier properties due to mechanical stress of the 180° bend by applying a load of 330 g / cm with a roller pair on the resulting bend, and the coating can be located on the inside (inner bend) or outside (outer bend).

[0252] Oxygen transmission rate (or also oxygen transmission rate-OTR) is measured according to ISO 15105-2.

[0253] The barrier paper according to the invention is further preferably characterized in that it has a fat barrier property in accordance with test condition I according to DIN 53116.

[0254] The barrier paper according to the invention preferably also does not lose the fat barrier properties due to mechanical stress of the 180° bend by applying a load of 330 g / cm with a roller pair on the resulting bend, and the coating can be located on the inside (inner bend) or outside (outer bend).

[0255] The barrier paper according to the invention is further preferably characterized in that the barrier paper has a g / m 2 / d of mineral oil barrier properties (hexane).

[0256] The barrier paper according to the invention preferably also does not lose the mineral oil barrier (hexane) due to mechanical stress of the 180° bend with a roller pair applying a load of 330 g / cm on the resulting bend, and the coating can be located on the inside (inner bend) or outside (outer bend).

[0257] The mineral oil barrier property was determined by filling hexane into a beaker (solvent resistant), closing it tightly with the coated paper, and following the weight loss over time.

[0258] The barrier paper according to the invention is further preferably characterized in that the barrier paper has a water vapor permeability of less than 10, preferably less than 5 g / m 2 / d (23°C, 50% relative humidity).

[0259] The barrier paper according to the invention is further preferably characterized in that the barrier paper has a water vapor permeability of less than 10, preferably less than 5 g / m 2 / d (23°C, 85% relative humidity).

[0260] The barrier paper according to the invention is further preferably characterized in that the barrier paper has a water vapor permeability of less than 10, preferably less than 5 g / m 2 / d (38°C, 50% relative humidity).

[0261] The barrier paper according to the invention is further preferably characterized in that the barrier paper has a water vapor permeability of less than 20, preferably less than 10 g / m 2 / d (38°C, 70% relative humidity).

[0262] The barrier paper according to the invention is further preferably characterized in that the barrier paper has a water vapor permeability of less than 20, preferably less than 10 g / m 2 / d (38°C, 90% relative humidity).

[0263] The barrier paper according to the invention is further preferably characterized in that the barrier paper has a water vapor barrier. This is the case even if the coating is in contact with fat, which is not the case for all water vapor barriers.

[0264] The barrier paper according to the invention is further preferably characterized in that it is buckle-resistant in the absence of buckling, in inner buckling and in outer buckling.

[0265] The coated paper according to the invention is characterized by recyclability through waste paper recycling. Preferably, it is recyclable, preferably conditionally recyclable, by evaluation according to PTS PTS-RH 021.

[0266] The coated paper according to the invention is characterized by its recyclability through the waste paper cycle. Preferably, the evaluation is carried out according to UNI 11743 level C, preferably level B, particularly preferably level A, very particularly preferably level A+.

[0267] The coated paper according to the invention is characterized by biodegradability in a marine environment according to ASTM D7081.

[0268] The barrier paper according to the invention is organoleptically non-irritating and achieves a value of at least ≤2 (according to standard DIN 1230-1:2010-02).

[0269] The barrier paper according to the invention is heat-sealable and preferably produces a sealing seam strength (cold tack) of >3.5 N / 15 mm, particularly preferably >5.0 N / 15 mm at the optimum sealing temperature, wherein the sealing seam strength of the barrier paper is determined as follows:

[0270] The barrier papers were sealed at 3.3 bar for 0.3 seconds in a temperature range of 100° C. to 230° C. perpendicular to the paper running direction and the sealed seam strength (cold tack) was determined in accordance with DIN 55529 (2012).

[0271] "Heat sealing" is preferably understood as joining two layers of barrier paper by means of localized heat action and / or pressure. In other embodiments, the coated side of the paper can also be joined to the opposite side of the paper which is not heat-sealable itself, to the opposite side of the paper which is heat-sealable, or to another paper by heat sealing.

[0272] The barrier paper according to the invention is also cold-sealable due to its compatibility with common cold-sealing media. Cold sealing is generally understood to be the application of a cold-sealing adhesive to the portion of the flat packaging material to be sealed by a pressure method. Cold-sealing adhesives have the property that they produce an adhesive effect only under and after an increased pressure between the sealing jaws of a packaging machine and are otherwise non-sticky or only limitedly sticky.

[0273] Ultrasonic sealing is understood to be the focusing of the energy of ultrasound on the area to be welded and the heat generated by friction, in particular for heat sealing. Typical sealing times are between 100 and 200 milliseconds. In contrast to heat sealing, for example with sealing pliers, the heat required with ultrasonic technology is only generated in the material to be welded. The tool remains cool and helps dissipate heat.

[0274] Heat-sealable barrier papers, cold-sealable barrier papers, and ultrasonically-sealable barrier papers are characterized by the moisture barrier properties of the sealed seams.

[0275] The barrier paper according to the invention is also tear-resistant.

[0276] The barrier paper according to the invention is furthermore characterized in that the taste of the food packaged therein is not affected.

[0277] The barrier paper according to the invention can be obtained economically using known production methods.

[0278] However, it is preferred that the barrier paper according to the invention is obtained by a process in which an aqueous suspension comprising the starting materials for the coating color layer S1 is applied to a base paper, wherein the aqueous application suspension has a solids content of 5 to 50% by weight, preferably 10 to 30% by weight, and is applied by a curtain coating method, preferably a double curtain coating method, at a running speed of the coating device of at least 200 m / min.

[0279] This method is particularly advantageous, particularly from an economic point of view and due to the uniform application to the paper web.

[0280] If the solids content is below values ​​of about 10% by weight, the economy is impaired, since a large amount of water must be removed in a short time by gentle drying, which adversely affects the coating speed. On the other hand, if values ​​of 50% by weight are exceeded, this only leads to increased technical effort to ensure the stability of the coated color curtain during the coating process and drying of the applied film, since in this case the machine must again be run very quickly.

[0281] In the curtain coating method, a free-falling curtain of a coating dispersion is formed. By free falling, the coating dispersion in the form of a thin film (curtain) is "poured" onto the substrate so that the coating dispersion is applied to the substrate. DE 10196 052 T1 discloses the use of curtain coating in the preparation of information recording materials, wherein a multi-layer recording layer is achieved by applying a curtain consisting of a plurality of coating dispersion films to the substrate.

[0282] In a preferred embodiment of the method according to the invention, the degassed aqueous application suspension has a viscosity of about 100 to about 800 mPas (Brookfield, 100 rpm, 20° C.). If this value is below about 100 mPas or if this value exceeds about 800 mPas, this leads to insufficient runnability of the coating composition on the coating apparatus. Particularly preferably, the viscosity of the degassed aqueous application suspension is about 200 to about 500 mPas.

[0283] In a preferred embodiment, in order to optimize the process, the surface tension of the aqueous application suspension can be adjusted to about 25 to about 70 mN / m, preferably about 35 to about 60 mN / m (measured according to the Bubble Pressure Tensiometer Standard (ASTM D 3825-90), as described below). By determining the dynamic surface tension of the coating colorant and purposefully adjusting it by selecting a suitable surfactant and by determining the required amount of surfactant, better control of the coating process is obtained.

[0284] It has been shown that polyvinyl alcohol solutions require significantly less surfactant to generate the same surface tension compared to dispersions, especially dispersions with small particle size and thus high particle surface area.

[0285] The dynamic surface tension is measured with the help of a bubble pressure tensiometer. The maximum internal pressure of a bubble formed in a liquid via a capillary is measured. According to the Young-Laplace equation, the internal pressure p (Laplace pressure) of a spherical bubble depends on the radius of curvature r and the surface tension σ:

[0286]

[0287] If a bubble is generated at the tip of a capillary in a liquid, the curvature first increases and then decreases again, resulting in a pressure maximum. The maximum curvature and therefore the maximum pressure occurs when the radius of curvature corresponds to the radius of the capillary.

[0288] Pressure characteristics during bubble pressure measurement, position of the maximum pressure:

[0289] The radius of the capillary is determined using a reference measurement with a liquid with known surface tension (usually water). Once the radius is known, the surface tension can be calculated from the pressure maximum pmax. Since the capillary is immersed in the liquid, the hydrostatic pressure p0 resulting from the immersion depth and the density of the liquid must be subtracted from the measured pressure (this is done automatically in the case of modern measuring instruments). This leads to the following formula for the bubble pressure method:

[0290]

[0291] The measured values ​​correspond to the surface tension at a specific surface age, from the start of bubble formation until the pressure maximum occurs. By varying the bubble generation rate, the dependence of the surface tension on the surface age can be obtained, resulting in a curve of the surface tension versus time.

[0292] This dependency plays an important role in the use of surfactants, since, due to the sometimes low diffusion and adsorption rates of surfactants, even the equilibrium value of the interfacial tension is not reached in many processes.

[0293] The formation of the individual coatings can be carried out in-line on a paper machine with a coating unit or off-line on a coating machine in a separate coating process.

[0294] In other embodiments, the individual layers can also be applied to the base paper by means of the following methods:

[0295] The paint color layer S1 can be applied to the base paper and / or to an already existing pre-coating layer by means of a printing method.

[0296] The coating color layer S1 can be applied to the base paper and / or to an already existing precoat layer by means of extrusion.

[0297] This technology has the advantage that significantly more material can thus be applied, but this is only interesting if the entire product does not need to be recyclable as paper. On the other hand, it has the disadvantages of lower application speeds, higher energy consumption and higher minimum application weights.

[0298] The coating color layer S1 can be applied by lamination or gluing of the paper, for example in the form of a plastic foil, to the base paper and / or to an already existing pre-coating.

[0299] It is also possible to apply the coating color layer S1 and the precoat layer successively in a plurality of application steps.

[0300] The invention further relates to a barrier paper obtainable by the above process.

[0301] Due to its relatively high polarity, the coating color layer S1 is also suitable for applying additional barriers in the form of aqueous polymer solutions or dispersions by melt extrusion or lamination with films.

[0302] The coated color layer S1 may be smoothed to achieve a Bekker smoothness of at least 200 Bekker seconds, in particular 500 Bekker seconds.

[0303] A further layer is applied to the metallized layer by means of vacuum deposition.

[0304] If necessary, barrier layers B1, in particular ultra-thin metal layers, metal oxide layers or other inorganic compounds, can be applied by vapor deposition or in particular vacuum vapor deposition to improve all barrier properties of the coating coloring layer S1. Such thin barrier layers are only effective when they adhere to a very smooth, flexible substrate that does not contain any particulate matter (e.g., inorganic pigments) and can form a closed layer thereon. The relatively high surface energy of the coating coloring layer S1, in particular the relatively high surface energy of the integrated polymer, is conducive to the adhesion of polar materials such as metal oxides and other inorganic oxides and polarizable conductive materials such as metal layers. The barrier paper thus obtained can be made sealable again by applying a heat seal layer or a cold seal adhesive.

[0305] The further coating layer B2 is applied to the barrier layer B1 deposited by means of vacuum by means of gravure printing (also curtain coating or other printing methods). The advantage of contactless application is that the surface of the material to be coated cannot be damaged or adversely affected.

[0306] The present invention also relates to the use of a barrier paper as described above or obtainable by a process as described above as packaging material.

[0307] Finally, the present invention also relates to the use of a barrier paper as described above or obtainable by a process as described above as a packaging material for foods, in particular for greasy, moisture-sensitive and oxidation-sensitive foods.

[0308] The present invention further preferably relates to the use of a barrier paper as described above or obtainable by the process described above as packaging material for, for example, cereal bars, chocolate, meat, sausages, cheese, chocolate-containing products, butter and margarine, snacks, chips (e.g. potato or lentil chips), products baked in vegetable oils (e.g. potato chips), salty snacks, biscuits, soda crackers, protein bars, sports and fitness bars, nutritional supplements, stock cubes, cosmetics (e.g. face powders and make-up), coffee and tea, animal feed, tobacco products (including as lining), yogurt (as lid). In a further preferred embodiment of the present invention, the barrier paper according to the invention is applied to cardboard or paperboard, in particular by gluing, laminating or bonding.

[0309] Finally, the invention also relates to the use of a composite material in which the barrier paper according to the invention is applied to cardboard or paperboard, in particular by gluing, laminating or bonding, as packaging material for foods, in particular greasy and oxidation-sensitive foods.

[0310] Thus, packaging materials can be produced in a simple and economical manner and method, which packaging materials have the advantages of both material components, such as the increased strength and stiffness of cardboard or paperboard compared to coated paper and the advantages of barrier paper. For example, starch or aqueous dispersion adhesives can be used for application.

[0311] Preferably, the barrier paper may thus be a component of a packaging material based on cardboard or paperboard.

[0312] With these packaging materials according to the invention, in particular heavier foods can be safely packaged and presented in an attractive manner to customers in shops in the form of upright packages.

[0313] These packaging materials preferably have a mass fraction of the homogeneous material type paper, cardboard or paperboard of more than 95% by weight. A further advantage of the invention is that these packaging materials according to the invention are not composite packaging according to §3 (5) of the Packaging Act, so that this embodiment of the invention contributes significantly to reducing the impact of packaging waste on the environment.

[0314] The invention also relates to a package comprising a barrier paper as described above or in combination with a cardboard or paperboard as described above.

[0315] The features of the use according to the invention apply analogously here to the packaging according to the invention.

[0316] The package may be a cold seal package. Cold seal packages are preferably suitable for packaging foods such as chocolate, chocolate-containing products, bars, e.g. granola bars and / or other confectionery. This is due on the one hand to the heat sensitivity of chocolate and on the other hand to the possible higher machine speeds. Packaging machines based on cold seals can run faster, since heating the heat sealing medium is relatively time-consuming.

[0317] The packaging can also be a heat-sealed packaging. The heat-sealed packaging is preferably suitable for use as a secondary packaging or packaging via a metering scale and a filling scale.

[0318] The packaging can also be cold sealed packaging.

[0319] The package may also be a primary or secondary package, in particular a heat-sealed or cold-sealed tubular bag package, pillow pack, stand-up bag, wrapper, 3 and 4 side seal bag, lid.

[0320] The barrier paper can also be used reversed so that the inside faces the outside and the outside faces the inside. This ensures that it can be used in a humid environment very well. In this case, an additional partial or full surface sealing lacquer must be applied, or the package must be sealed via ultrasound. In this case, the coating B2 is applied or printed.

[0321] The coating layer B2 may be opaque to prevent the transmission of the barrier layer B 1. Alternatively, the coating layer B2 may also be printed with an opaque layer.

[0322] Preferably, the barrier paper according to the present invention comprises at least one base paper having two sides (surfaces) of different roughness (rougher side r and smoother side g). Preferably, the rougher side (r) of the base paper is coated (inner side) by means of a pre-coating layer, a coating color layer S1, a barrier layer B1 and a barrier layer B2. Preferably, the less rough side (r) is printed via gravure printing (outer side).

[0323] In a specific embodiment, the smoother side (g) can also be coated with the aid of a pre-coating, a coating color layer S1, a barrier layer B1 and a barrier layer B2 (inner side), while the rougher side (r) is used for printing (outer side). This embodiment has poorer printability, but due to its less rough surface, it leads to an improvement in the barrier properties of the coating color layer S1 or a saving in material of the coating color layer S1, while also maintaining the barrier properties (e.g., the same properties at a lower layer thickness).

[0324] The invention is explained in detail hereinafter with reference to non-limiting examples and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0325] Figure 1 Two basic configurations a) and b) of barrier papers according to the invention are shown with the following reference numerals:

[0326] 1: Base paper

[0327] g: The smoother surface of the base paper

[0328] r: Rough surface of base paper

[0329] 2: Apply coloring layer S1

[0330] 3: Barrier layer B1

[0331] 4: Coating B2

[0332] 5: Pre-coating, optionally for better coating color retention to prevent the coated color layer S1 from penetrating into the base paper

[0333] 6: Starch coating, optionally for better printability

[0334] 7: Barrier paper according to the present invention

[0335] A: Sealing surface A of barrier paper

[0336] B: Sealing surface B of barrier paper

[0337] A / A-Seal

[0338] A / B-Seal

[0339] 8: Another coating color layer S1, whose composition / layer thickness is the same as or different from 2

[0340] Not shown: Printing of the barrier paper by means of conventional printing methods, in particular by means of flexographic printing, gravure printing or digital printing methods.

[0341] Figure 2 Two REM surface images of Comparative Example V3 (inner buckling) at different resolutions are shown. Top view of the top coating (B1). It can be seen that this is destroyed in the surface due to the buckling strain.

[0342] Figure 3 Two REM surface images of Example B1 (inner buckling) at different resolutions are shown. Top view of the top coating (Coating B2). It can be seen that although the coating is strained due to the buckling stress, it does not tear.

[0343] Figure 4 Two REM surface images of comparative example V5 (inner buckling) are shown. Top view of the top coating (B2). The applied color layer S1 is missing here. It can be seen that the coating is torn in the surface due to the buckling strain.

[0344] Figure 5Two images of comparative example V1 after the palm kernel fat test are shown (inner flexure on the left, outer flexure on the right). Top view of the top coating (coating color layer S1). In this case, the layer thickness is halved. It can be seen that this halving does not cause any problems with the flat grease barrier (on the right and left side of the flexure), but does cause problems with the flex resistance (grease seepage in the crease and in the edge area of ​​the crease).

[0345] Figure 6 Two images of comparative example V2 after the palm kernel fat test are shown (inner bend on the left, outer bend on the right). Top view of the top coating (coating color layer S1). In this case, the preferred layer thickness was chosen. It can be seen that there are no problems with the flat grease barrier (on the right and left side of the bend) or the bend resistance (no fat penetration in the bend and in the edge area of ​​the bend).

[0346] Figure 7 Various packaging forms according to the invention are shown with A:A sealing.

[0347] Figure 8 A sleeve package according to the invention is shown with an A:B seal on the front side.

[0348] Fig. 9 A schematic diagram showing a typical DMTA measurement chart of a barrier paper according to the present invention is shown. The measured values ​​of the loss factor tan δ are plotted as a function of temperature. As the temperature increases, a maximum value is initially shown at temperature Tg, and then a first inflection point is shown at temperature Tw.

[0349] Fig.10 DMTA measurements of Examples 9 and 10 according to the invention compared to Comparative Example V2 according to Table 2 are shown.

[0350] The present invention is explained in more detail below in a number of examples. The examples are only used to illustrate the present invention, rather than to limit the present invention. Example

[0351] The following coating was applied to a 60 g / m 2 or 70g / m 2 On a base paper with a basis weight of 40% long fibers and 60% short fibers, 100% virgin fiber pulp is used.

[0352] Pre-coating:

[0353] In all examples, the pre-coating contained 75.9% pigment (layered silicate), 22.8% latex (styrene-acrylate latex), and 1.3% rheology modifier (0.2% acrylate-based thickener, 1.1% zirconium-based crosslinker).

[0354] The precoat material is applied to the base paper with the aid of a doctor blade.

[0355] Coating coloring layer S1:

[0356] In Examples 1 to 5, polyvinyl alcohol was used as the polymer. In Examples 6 to 8, partially saponified polyethylene vinyl alcohol was used as the polymer.

[0357] The coated color layer S1 of Examples 1 to 5 comprises a pure polymer coating. Example 1′ comprises a coating having 99.8% polyvinyl alcohol as a polymer (Example 1; saponification degree: 87%; M w : 50900) and 0.2% rheology modifier (docusate sodium) polymer coating.

[0358] The coated colored layer S1 of Examples 9 and 10 and Comparative Examples 1, 2, 3 and 5 corresponded to the coated colored layer S1 of Example 1. Use of the coated colored layer S1 of Example 1' resulted in comparable results.

[0359] Barrier layer B1:

[0360] In Examples 9 and 10 and Comparative Examples 1, 2, 3 and 5, an approximately 40 nm to 80 nm thick barrier layer B1 was applied directly to the coating color layer S1 or the precoat layer by means of vacuum deposition of aluminum.

[0361] Coating B2:

[0362] An embodiment by means of gravure printing and an embodiment by means of curtain coating.

[0363] Investigate the following properties:

[0364] Weight per unit area or applied weight: g / m 2 The applied weight of the coating is calculated. This is determined by weighing the coated and uncoated paper differently.

[0365] Viscosity: The viscosity was measured at a dry content of 4% using a Brookfield viscometer at 23°C and a speed of 100 rpm.

[0366] WVTR: Water Vapor Transmission Rate, measured according to ASTM D 1653.

[0367] In the case of the bent samples, a 180° bend was produced with a roller applying a load of 330 g / cm on the produced bend, and the coating could be located either on the inside (inner bend) or on the outside (outer bend).

[0368] OTR: Oxygen transmission rate, measured according to DIN 15105-2

[0369] In the case of the bent samples, a 180° bend was produced with a roller applying a load of 330 g / cm on the produced bend, and the coating could be located either on the inside (inner bend) or on the outside (outer bend).

[0370] HVTR: Hexane vapor transmission. Here, n-hexane is filled into a beaker (solvent resistant), tightly closed with the test specimen, and the weight loss is followed over time. In the case of curved samples, a 180° curve is produced with a roller that applies a load of 330 g / cm to the resulting curve, and the coating can be located on the inside (inner curve) or on the outside (outer curve).

[0371] Palm kernel fat test: similar to DIN 53116. In the case of bent samples, a 180° bend is produced with a roller applying a load of 330 g / cm on the produced bend, and wherein the coating can be located on the inside (inner bend) or on the outside (outer bend).

[0372] Display paper: Evaluation of the display paper mentioned in DIN 53116. In this case, fat penetration points with a diameter (d) of <1 mm (first value in the table) and >1 mm (second value in the table) were counted.

[0373] Test strips: Evaluation of the back side of the test strips as mentioned in DIN 53116. This is not part of the standard but is carried out for better differentiation.

[0374] Sealing seam strength: The sealing seam strength was determined according to DIN 55529 (2012) by sealing the sample at 3.3 bar for 0.3 seconds in a temperature range of 100° C. to 220° C. perpendicular to the paper running direction. For comparison, the optimum sealing temperature and the sealing force at 150° C. (the optimum sealing temperature of Example 1) are given.

[0375] Friction coefficient: The static and dynamic friction coefficients were determined according to ISO 8295.

[0376] Back-to-back friction coefficient: Align two specimens with their functionally coated sides and measure their friction coefficient (inside / inside)

[0377] Coefficient of Friction Back Side to Barrier Side: Measurements were made of the functionally coated side of the barrier paper (barrier side) versus the metal surface of the device (inside side / barrier side).

[0378] DSC melting temperature / onset temperature:

[0379] The DSC curves were recorded with a Mettler DSC 20S in a cold-welded aluminum crucible and perforated lid. The heating rate was 10 K / min in the range between 30°C and 280°C. The melting temperature was determined via the peak minimum of the melting process. Necessary?

[0380] Surface tension (surface energy):

[0381] Contact angle measuring instrument OCA 20 with software SCA 20 (DataPhysics)

[0382] Measuring principle: OWRK method (Owens, Wendt, Rabel, Kaelble)

[0383] The measurement fluid used and the source of the material constants entered are:

[0384] Water and diiodomethane (according to Buscher) and 1,5-pentanediol (according to Gebhardt)

[0385] Friction sensitivity 1) Measures the barrier properties of the upper barrier paper

[0386] Oser test 2) Place the release papers on top of each other in the Oser tester (release side facing down), press with a weight of 500 g, and turn the instrument on for 60 seconds. Then lift the weight again

[0387] 3) Measure the barrier properties of the upper barrier paper.

[0388] The obtained barrier paper was examined. The results are shown in the following table.

[0389] Table 1 shows the results for intermediate products having only applied color layer S1 but not yet having barrier layer B1 and not yet having coating layer B2 (Examples Bsp. 1 to Bsp. 8).

[0390] Table 2 shows the results for barrier papers according to the invention, in particular with a coated color layer S1 , a barrier layer B1 and a coating B2 (Examples Bsp. 9 and Bsp. 10), and comparative examples V1 to V5.

[0391] The partially saponified polyvinyl alcohols used have very low hexane and oxygen permeabilities. This is probably due to their relatively high hydrophilicity.

[0392] Polyvinyl alcohols with a higher degree of saponification are characterized in terms of coating coloration by a higher viscosity at the same dry content. This only makes sense from a chemical point of view, since a higher polarity means a stronger interaction of each molecule with the surrounding solvent (water).

[0393] This must be considered quite disadvantageous, since a large amount of water has to be dried out during the coating process at low dry contents. This not only consumes energy but can also be difficult to achieve in terms of application technology, depending on the desired application weight. Furthermore, the diffusion of water molecules and thus the drying itself is slowed down. Furthermore, the accumulation of gaseous water in the coating is more likely to occur as a result, leading to the formation of macroscopic coating defects.

[0394] The water vapor permeability of the polyethylene vinyl alcohols considered is lower than that of polyvinyl alcohol, which is probably due to the ethylene content and the lower hydrophilicity associated therewith.

[0395] Generally, fully saponified polyvinyl alcohols (PVOH) are more brittle than partially saponified PVOH due to the fact that they can form a greater number of hydrogen bonds.

[0396] In particular, in order to maintain substantial or all barrier properties after buckling of the barrier paper even in the buckling crease or buckling area, the barrier paper according to all embodiments of the present invention has the following features:

[0397] a) In the case of all barrier papers according to these examples, the values ​​of the loss factor tan δ measured as a function of temperature by means of dynamic mechanical thermal analysis (DMTA) of the barrier papers pass through a maximum value at temperature Tg and a first inflection point at temperature Tw with increasing temperature.

[0398] b) In the case of all barrier papers according to these examples, the temperature Tg is also lower than the temperature Tw.

[0399] c) In the case of all barrier papers according to these examples, the magnitude of the difference between tan δ at temperature Tg and tan δ at temperature Tw is > 0.013.

[0400] Without being bound by this theory, the inventors consider the following:

[0401] Dynamic mechanical thermal analysis (DMTA) shows that barrier papers according to the invention can maintain barrier properties after buckling if the barrier paper has a large amount of viscoelastic components. The so-called "rubber elastic state" state can be explained by quantifying the change in tan delta value (tan delta at the glass transition temperature (Tg) to the first inflection point of the tan delta curve (Tw)) with increasing temperature. Barrier materials (which surprisingly can also include metal-coated layers) that maintain barrier properties after buckling have a tan delta change of >0.013.

[0402] Dynamic mechanical thermal analysis (DMTA) also provides the glass transition temperature (Tg) - the temperature at which the macromolecular polymer chains change from a solid frozen state to a mobile state, but before the macromolecular polymer chains slide over each other, which is the melting point (Tm). It is advantageous if an elastic state exists in the barrier paper so that the barrier properties are maintained after folding or buckling - therefore, a Tg below the operating and use temperature is ideal. In DSC, Tg is determined by the temperature at which tan δ reaches a maximum. One of the embodiments has a glass transition temperature Tg = 8.4°C corresponding to a tan δ maximum of 0.099 and a tan δ change of 0.0185.

[0403]

[0404]

[0405]

[0406]

[0407]

[0408]

[0409]

Claims

1. Barrier paper, comprising at least -Base paper, - at least one coating coloring layer S1 applied directly or indirectly to the base paper, at least one barrier layer B1 applied directly or indirectly on the coated color layer S1, - A coating B2 applied directly or indirectly to the barrier layer B1 .

2. The barrier paper according to claim 1, It is characterized in that The coating color layer S1 has at least one of the following properties: - Water vapor barrier properties, -Oxygen barrier properties, -Mineral oil barrier properties, - Fragrance barrier, -Fat barrier properties, - resistance to buckling of at least one property, - Fat resistance, - Sealing, - Baker smoothness of at least 200 Baker seconds.

3. The barrier paper according to claim 1 or 2, It is characterized in that The coating color layer S1 comprises or consists of at least one water-soluble polymer and / or at least one water-dispersible polymer.

4. The barrier paper according to claim 3, It is characterized in that The at least one water-soluble polymer and / or at least one water-dispersible polymer is selected from the group consisting of: - polyvinyl alcohol, in particular partially saponified or fully saponified; - copolymers of polyvinyl alcohol, in particular with ethylene, polyvinylamine or acrylic acid derivatives, partially or fully saponified; - modified fully or partially saponified polyvinyl alcohols or copolymers, in particular with acyl-, alkyl-, acrylamide-, silanol-, diacetone-, acetoacetyl-, itaconic acid-modified; - polymers having an onset temperature determined by means of DSC of less than 210° C., wherein the onset temperature is determined by means of DSC in accordance with DIN EN ISO 11357-1:2010-03 as the intersection of the extrapolated baseline and the tangent of the inflection point at the onset of the melting or crystallization peak; - acrylic-based polymers; - Polyester-based polymers; - polymers based on nitrocellulose; - Polyvinyl acetate based polymers.

5. Barrier paper according to at least one of claims 3 or 4, It is characterized in that The at least one water-soluble polymer and / or the at least one water-dispersible polymer comprises at least partially saponified polyvinyl alcohol and / or at least partially saponified polyvinyl alcohol copolymer, each having an onset temperature determined by DSC of less than 210°C.

6. Barrier paper according to at least one of claims 3 to 5, It is characterized in that The at least one water-soluble polymer and / or at least one water-dispersible polymer comprises a partially saponified polyvinyl alcohol having a degree of saponification of 30% to 95%, an average molecular weight of greater than 0 and less than 100,000 g / mol, and an onset temperature determined by DSC of less than 200° C.

7. Barrier paper according to at least one of claims 3 to 6, It is characterized in that The at least one water-soluble polymer and / or at least one water-dispersible polymer comprises partially saponified polyvinyl alcohol having a saponification degree of more than 95% to 100%, an average molecular weight of more than 70,000 g / mol, and an onset temperature determined by DSC of less than 200° C.

8. Barrier paper according to at least one of claims 3 to 7, It is characterized in that The at least one water-soluble polymer and / or the at least one water-dispersible polymer comprises a partially saponified polyvinyl alcohol copolymer, preferably a partially saponified polyethylene vinyl alcohol, having a degree of saponification of 95% to 100%, an average molecular weight of more than 60,000 g / mol, and an onset temperature determined by means of DSC of less than 210° C.

9. Barrier paper according to at least one of claims 3 to 8, It is characterized in that The partially saponified polyvinyl alcohol and / or partially saponified polyvinyl alcohol copolymer has a viscosity of less than 30 mPas, particularly preferably less than 20 mPas and very particularly preferably less than 15 mPas at a dry content of 4%.

10. Barrier paper according to at least one of claims 3 to 9, It is characterized in that The at least one water-soluble polymer and / or the at least one water-dispersible polymer comprises a mixture of polymers as defined in claims 3 to 8.

11. Barrier paper according to at least one of the preceding claims, It is characterized in that The coating color layer S1 has a surface tension in the range of 25 to 80 mN / m, in particular, 25 to 75 mN / m.

12. Barrier paper according to at least one of the preceding claims, It is characterized in that The barrier layer B1 contains a metal, in particular Al, Cu, Sn, Zn, Ag, Au, Ti, In, Si, a metal alloy, a metal oxide, in particular Al2O3, SiO2, a mixed oxide or a combination thereof, or consists thereof.

13. Barrier paper according to at least one of the preceding claims, It is characterized in that The barrier layer B1 is applied by means of vacuum deposition.

14. Barrier paper according to at least one of the preceding claims, It is characterized in that The barrier layer B1 has at least one of the following characteristics: a) Optical density ≥1.5 and ≤6.0, b) Layer thickness ≥5 nm, preferably ≥10 nm, particularly preferably ≥15 nm, in particular 5 nm to 150 nm.

15. Barrier paper according to at least one of the preceding claims, It is characterized in that The coating B2 comprises or consists of at least one polymer, in particular a polymer selected from the group consisting of: a) polyethylene-acrylic acid copolymer, b) polyolefins, c) polyvinyl alcohol, d) cellulose nitrate, e) bio-based polymers, f) non-bio-based polymers, g) styrene-butadiene latex, h) Acrylate latex.

16. Barrier paper according to at least one of the preceding claims, It is characterized in that The coating B2 has at least one of the following properties: a) protecting the barrier layer B1 from external influences, in particular mechanical or chemical influences, b) sealable, in particular heat-sealable, ultrasonically sealable and cold-sealable, c) fat resistance, d) Water resistance, e) Moisture resistance, f) Printability, g) Additional barrier properties.

17. Barrier paper according to at least one of the preceding claims, It is characterized in that The barrier paper has at least one of the following characteristics: a) At 23°C and 50% relative humidity, WVTR ≤ 5g / m 2 / d b) At 23°C and 50% relative humidity, WVTR medial flexion ≤ 5g / m 2 / d c) At 23°C and 50% relative humidity, WVTR of the outer flexion part ≤ 5g / m 2 / d d) At 38°C and 90% relative humidity, WVTR ≤ 15g / m 2 / d e) At 38°C and 90% relative humidity, WVTR medial flexion ≤ 15g / m 2 / d f) At 38°C and 90% relative humidity, WVTR of the outer flexion part ≤ 15g / m 2 / d g) At 23°C and 50% relative humidity, OTR ≤ 10g / m 2 / d h) At 23°C and 50% relative humidity, OTR inner flexure ≤ 10g / m 2 / d i) At 23°C and 50% relative humidity, OTR outer flexure ≤ 10g / m 2 / d j) buckling resistance of at least one barrier property, in particular in the area of ​​the medial and / or lateral flexure, k) at least 2.5% by weight, in particular at least 3.0% by weight, of residual moisture, based on the total weight of the barrier paper.

18. Barrier paper according to at least one of the preceding claims, It is characterized in that The coating color layer S1, barrier coating B1 and coating B2 are removable in the waste paper recycling.

19. The barrier paper according to claim 18, It is characterized in that The following deinkability scores were achieved according to the evaluation of the recyclability of the printed product after treatment of the barrier paper according to INGEDE method 11: a) Brightness Y is the maximum 35 points, b) The color coefficient a* in the CIELAB system is a maximum of 20 points, c) Dirt points A in two different size classes A50 with a maximum of 15 points and A250 with a maximum of 10 points, d) the dye elimination (printing ink elimination) degree IE is a maximum of 10 points, and e) The filtrate darkens ΔY to a maximum of 10 points, The sum of all point values ​​is in the range from 0 to 100, preferably in the range from 51 to 70, particularly preferably in the range from 71 to 100, and / or preferably no individual point value is negative.

20. Barrier paper according to at least one of the preceding claims, It is characterized in that Between the base paper and the applied color layer S1 there is a precoat layer comprising at least one inorganic pigment and a polymer binder, wherein the inorganic pigment is preferably in the form of flakes and preferably comprises talc, precipitated calcium carbonate, a silicate, preferably a layered silicate or kaolin, and / or the polymer binder comprises a polymer binder based on polyacrylate or styrene-butadiene.

21. Barrier paper according to at least one of the preceding claims, It is characterized in that The weight per unit area of ​​the coating color layer S1 and the coating layer B2 is 4 to 20 g / m 2 , preferably 4 to 15 g / m 2 In the range of 500 ℃ and 1000 ℃, based on the dried final product (air drying).

22. The barrier paper according to any one of the preceding claims, It is characterized in that The barrier paper does not contain halogen-containing organic compounds.

23. Barrier paper according to at least one of the preceding claims, It is characterized in that The base paper has a g / m 2 , preferably 40 to 100 g / m 2 Weight per unit area.

24. Barrier paper according to at least one of the preceding claims, It is characterized in that The base paper has a long fiber content of 10 to 80% and a short fiber content of 20 to 90% by weight, the long fibers being fibers having a fiber length of 2.6 to 4.4 mm and the short fibers being fibers having a fiber length of 0.7 to 2.2 mm.

25. Barrier paper according to at least one of the preceding claims, It is characterized in that The base paper contains up to 90% recycled fibers.

26. Barrier paper according to at least one of the preceding claims, It is characterized in that The value of the loss factor tan δ measured as a function of temperature by means of dynamic mechanical thermal analysis (DMTA) of the barrier paper passes through a maximum value at temperature Tg and a first inflection point at temperature Tw as the temperature increases.

27. The barrier paper according to claim 26, characterized in that The temperature Tg is lower than the temperature Tw.

28. The barrier paper according to claim 26 or claim 27, characterized in that The magnitude of the difference between tan δ at temperature Tg and tan δ at temperature Tw is >0.013, preferably >0.014 and particularly preferably >0.

015.

29. A method for preparing a barrier paper according to any one of the preceding claims, It is characterized in that An aqueous suspension containing the starting materials for coating the color layer S1 is applied to the base paper, wherein the aqueous application suspension has a solid content of 5 to 50% by weight, preferably 10 to 30% by weight, and is applied by a curtain coating method, preferably a double curtain coating method, at a running speed of the coating device of at least 200 m / min.

30. Use of a barrier paper according to any one of claims 1 to 25 or a barrier paper obtainable by a process according to claim 26 as packaging material for foods, consumer goods, tobacco products or as a component of a packaging material, in particular a component of a packaging material based on cardboard or paperboard, in particular as packaging material for foods, in particular sausages, cheese, coffee, granola bars, chocolate, chocolate-containing products, snacks, potato chips.

31. A package comprising a barrier paper according to any one of claims 1 to 28 or a barrier paper obtainable by a process according to claim 29, wherein the package is preferably a cold-sealed package, a heat-sealed package, an ultrasound-sealed package, in particular a tubular bag package.

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