BARRIER PAPER

Description

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

Packaging generally refers to the covering or the (partial or complete) wrapping of an object, more particularly for its protection or for better handling. Accordingly, a packaging material comprises the material that forms such packaging.

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

The main requirements for packaging materials of any origin are to protect the packaged goods from external influences and to prevent leakage of the packaged goods, and to function as an advertising and information medium. For this purpose, the packaging material should fulfill different criteria depending on the packaged goods and packaging process. That is, in addition to so-called barrier properties against water, fat, oxygen or mineral oil, for example, suitable packaging materials should also meet mechanical and process-specific requirements. A packaging material, especially a flexible packaging material should have, depending on the packaging equipment, sufficient tear resistance, a suitable coefficient of friction and flexibility; it should be heat-sealable as well as printable from the outside, and should not lose its protective effect during the entire conversion and packaging process.

Known paper-based, coated packaging materials often include compounds such as polyvinylidene chloride (containing halogen) or are composites of paper and metal or plastic films, have a tear resistance that could be improved, which can lead to running problems on packaging equipment, and/or are often not recyclable due to an excessively high proportion of adhesive parts in the coating or the formation of so-called stickies via the paper fiber stream.

Polyvinyl alcohols, in particular cross-linked polyvinyl alcohols are widely known as linear. water-soluble, biodegradable barrier coatings, also suitable for paper. Such coatings present good barriers against oil, fat, oxygen, solvents and other non-polar gases, liquids, or solids. Due to their hydrophilicity, however, polyvinyl alcohols are highly permeable to polar compounds such as water. This can also influence the barrier effect against non-polar migrants, since polyvinyl alcohols absorb moisture very well, swell, and thus create pathways through the barrier coating at the molecular level.

In order to solve this problem, mixtures of all types of polymer dispersions and wax emulsions are offered. However, when testing papers produced in laboratory and pilot tests, it was observed that such known mixtures of polymer dispersions and wax emulsions have the disadvantage that fat can penetrate the coating, which in turn leads to an increase in water vapor permeability. As a result, there is a risk that the water vapor permeability increases in direct contact with greasy food. When transferring laboratory formulas to a pilot coater, it was also observed that the heat sealability deteriorated. Furthermore, with increasing storage time, a decrease in heat sealability was frequently observed when such coatings were produced on a pilot scale. This refers to the ability of the material to produce a stable seal seam by heat sealing, and not the stability of an existing seal seam.

The object of the present invention is to eliminate the disadvantages of the known materials and to provide a material which is suitable as a packaging material, in particular for moisture-sensitive foodstuffs, and which, even when it comes into contact with fat, retains a low-level water vapor permeability or only allows as little increase in it as possible. It must also be suitable for heat-sealing applications. In particular, a sealed-seam strength of more than 4 N/15 mm and a water vapor transmission rate (WVTR) with target values of <20 g/m²/d (38° C., 90% RH) and <8 g/m²/d (23° C., 50% RH) are aimed for.

Furthermore, the material according to the invention should be producible as easy as possible, make do with the lowest possible application weights and, if possible, should allow for recyclability via the paper fiber stream.

This problem is solved by a barrier paper according to claim 1, i.e. By a barrier paper comprising a base paper and at least one coating color layer S1 applied directly or indirectly to the base paper, wherein the coating color layer S1 comprises at least one polymer binder and at least one wax, and wherein the coating color layer S1 has at least one of the following features:

• • a) change in surface tension of not more than +10 mN/m, preferably not more than +6 mN/m,
  • b) change of the polar component of the surface tension of not more than −0.65 mN/m, preferably not more than −0.60 mN/m,
  • c) change in the polar component of the surface tension of not more than −3.0% pts, preferably not more than −1.5% pts,
  • wherein the respective change is determined by measuring and comparing the measured values of the surface tension of the polar component of the surface tension before and after a temperature treatment of the barrier paper at 105° C. for 3 min.

Preferred embodiments are defined in the dependent claims.

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

Furthermore, such a barrier paper can be used to achieve the reference values defined above with regard to heat sealability and water vapor permeability.

Finally, the barrier paper according to the invention can be produced relatively easily and with low application weights, and can be recycled via the waste paper cycle.

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

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

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

In the present description and claims, the terms “include”, “comprise”, and/or “comprising” may also mean “consisting of”, i.e., the presence or addition of one or more other features, steps, operations, elements, components, and/or groups is excluded.

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

Unless otherwise stated, indications in “%” in the context of formulations and/or compositions refer to “% (w/w)”, in particular in relation to the respective total weight of the respective formulations and/or compositions.

As mentioned above, the barrier paper according to the invention comprises a base paper and at least one coating color layer S1 applied directly or indirectly to the base paper, wherein the coating color layer S1 comprises at least one polymer binder and at least one wax, and wherein the coating color layer S1 has at least one of the following features:

• • a) change in surface tension of not more than +10 mN/m, preferably not more than +6 mN/m,
  • b) change of the polar component of the surface tension of not more than −0.65 mN/m, preferably not more than −0.60 mN/m,
  • c) change in the polar and disperse component of the surface tension of not more than −3.0% pts, preferably not more than −1.5% pts,
  • wherein the respective change is determined by measuring and comparing the measured values of the surface tension of the polar component of the surface tension before and after a temperature treatment of the barrier paper at 105° C. for 3 min.

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

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

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

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

The cohesion of atoms and molecules, which determines the surface tension of a substance, is due to different types of interactions. In particular, a distinction can be made between dispersive and polar interactions. The interactions due to temporal fluctuations in the charge distribution of the atoms/molecules are called dispersive interactions (Van der Waals interactions). Polar interactions include Coulomb interactions between permanent dipoles or between permanent and induced dipoles (e.g. hydrogen bonds). Accordingly, the surface tension is also composed additively of a dispersive component and a polar component.

If the ratio of the dispersive to the polar component of the surface tension are compared for each of the two phases, predictions about the adhesion of two phases to each other can be derived. The more the dispersive and polar components match, the more interaction possibilities exist between the phases and the stronger the adhesion can be expected.”

If the comparison of the measured values shows that a) no significant change in the surface tension, i.e. of no more than +10 mN/m, and/or b) or c) no significant change in the polar component of the surface tension, i.e. of no more than −0.65 mN/m or of no more than −3.0% pts., could be determined, the barrier paper has the advantageous properties.

The inventors assume that in a coating color layer comprising or consisting of at least one polymer binder and at least one wax, the drying of the coating color layer also causes at least partial segregation and/or partial film formation of the coating color layer and may also result in an uneven distribution of wax within the coating color layer. For one and the same composition of the coating color layer, different properties of the coating color layer and thus also of the barrier paper result, depending on how the drying parameters are selected.

The inventors have transferred these findings to the coating color layer S1, wherein at least one of the following features of the dried coating color layer S1:

• • a) change in surface tension of not more than +10 mN/m, preferably not more than +6 mN/m,
  • b) change of the polar component of the surface tension of not more than −0.65 mN/m, preferably not more than −0.60 mN/m,
  • c) change in the polar component of the surface tension of not more than −3.0% pts, preferably not more than −1.5% pts,
    can be regarded as an indicator of the quality of the coating color layer S1 with regard to the properties mentioned in the problem, in particular with regard to whether there is partial segregation and/or partial filming of the coating color layer S1 or whether there is an uneven distribution of wax within the coating color layer S1.

In other words, the properties of a barrier paper mentioned in the problem definition depend not only on the composition of a coating color layer S1, but also on how this coating color layer S1 was dried. In addition to the composition, the dried coating color layer S1 must therefore have at least one of the following structural characteristics:

• • a) change in surface tension of not more than +10 mN/m, preferably not more than +6 mN/m,
  • b) change of the polar component of the surface tension of not more than −0.65 mN/m, preferably not more than −0.60 mN/m,
  • c) change in the polar and disperse component of the surface tension of not more than −3.0% pts, preferably not more than −1.5% pts,
    wherein the respective change is determined by measuring and comparing the measured values of the surface tension of the polar component of the surface tension before and after a temperature treatment of the barrier paper at 105° C. for 3 min.

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

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

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

The polar component of the surface tension of the coating color layer S1 is preferably 0 to 12%, in particular 0 to 6%, preferably 0 to 3% and particularly preferably 0 to 1%, wherein in a preferred embodiment the values 0% are just excluded as the lower limit.

The dispersive component of the surface tension of the coating color layer S1 is preferably 88 to 100%, in particular 94 to 100%, preferably 97 to 100% and particularly preferably 99 to 100%.

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

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

Measuring liquids used and origin of the material constants entered:

Water and diiodomethane (according to Buscher) and 1,5-pentanediol (according to Gebhardt).

In contrast to DIN EN ISO 19403-2 (2020-04), 1,5-pentanediol is used as the 3rd measuring liquid, as it still allows measurable contact angles on paper surfaces before the liquid is absorbed by the paper, unlike other non-polar measuring liquids.

The temperature treatment of the barrier paper at 105° C. for 3 minutes is preferably carried out in a hot-air oven (drying oven), wherein it is preferable to ensure that the paper is actually exposed to 105° C. for a period of 3 minutes. For this purpose, the oven should preferably be preheated and have a sufficient internal volume (e.g. >100 dm³, e.g. width×height×depth 60 cm×48 cm×37 cm) so that there is no significant drop in temperature when the front door is opened briefly (2-3 s) to place the paper inside. The barrier paper is preferably placed on a metal grid located at the middle height of the drying oven, on which a cardboard is preferably placed as a support. The metal grid and cardboard should already have reached the oven temperature and have been placed in the oven, which has already been preheated to 105° C., for at least 15 minutes before starting the temperature treatment. It should be noted that the duration of the temperature treatment was preferably set at 3 minutes in order to ensure that the barrier paper has enough time to really reach 105° C. and that the treatment of the paper does not last too long so that no decomposition processes occur. After removing the barrier papers from the oven, they were stored for at least 12 hrs. at 23° C. and 50% RH (conditioned) before further measurements were performed.

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

“Waxes are substances that today are defined by their mechanical and physical properties. Their chemical composition and origin, however, are very different. A substance is described as a wax if it is kneadable at 20° C., solid to brittle hard, has a coarse to fine crystalline structure, is translucent to opaque in color, but not glassy, melts above 40° C. without decomposition, is slightly liquid (low viscosity) slightly above the melting point, has a strongly temperature-dependent consistency and solubility and can be polished under slight pressure.” If more than one of the properties listed above is not fulfilled, the substance is not a wax within the meaning of the DGF (DGF unit method M-I 1 (75)).

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

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

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

The following correlations were determined in laboratory tests: The lower the wax content, the better the heat sealability, especially the hot tack. However, a low wax content results in a higher water vapor permeability and a comparatively high sensitivity of the water vapor barrier to fat contact. If it is intended to make do with little wax, the aqueous coating should be dried in such a way that wax migrates to the surface in order to obtain a good, less fat-sensitive water vapor barrier.

In one embodiment, the wax content of the coating color layer S1 is selected such that the barrier paper has at least one of the following features:

• • a) a sealed-seam strength (cold tack) of the coating color layer S1 against the coating color layer S1 of ≥4 N/15 mm, generated with the heat sealing parameters T=130 to 150° C., sealing time=0.3 sec, sealing pressure=3.3 bar or with ultrasonic sealing parameters that cause a T of 130 to 150° C. and a sealing time of 0.3 sec and a sealing pressure of 3.3 bar
  • b) a water vapor transmission rate (WVTR)≤20 g/m²/d (38° C., 90% r.h.),
  • c) a water vapor transmission rate (WVTR)≤8 g/m²/d (23° C., 50% r.h.),
  • d) an increase in water vapor permeability (38° C., 90% r.h.) after carrying out the palm kernel fat test according to DIN 53116 2003-02 (under the test conditions 10 min exposure time and pressure load of 2000 N/m²) of not more than 70 g/m²/d, preferably of not more than 60 g/m²/d,
  • e) an increase in water vapor permeability after carrying out the palm kernel fat test in accordance with DIN 53116 2003-02 (under the test conditions 60 min exposure time and 2000 N/m²) of no more than a factor of 6,
  • f) a static coefficient of friction (coating color layer S1 against coating color layer S1) of <0.9
  • g) a kinetic coefficient of friction (coating color layer S1 against coating color layer S1) of <0.6
  • wherein the values for a) to g) are determined for a basis weight of the coating color layer S1 of ≤12 g/m².

Herein, the basis weight of the coating color layer S1 is not limited to values of ≤12 g/m², but the above-mentioned parameters only have to be fulfilled for such basis weights. For higher basis weights, the parameters must be adjusted accordingly.

The parameter a), a sealed-seam strength (cold tack) of coating color layer S1 against coating color layer S1, is preferably understood to mean that a sheet of barrier paper is folded in such a way that the coating color layer S1 comes to coincide with itself in the seal seam area or that two sheets of barrier paper are placed on top of each other in such a way that the coating color layers S1 of the two sheets come to coincide in the seal seam area.

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

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

In one embodiment, the barrier paper according to the invention is preferably characterized in that the at least one wax is a

• • wax based on mixtures or pure substances of fossil or natural short- to medium-chain hydrocarbons, their acids, esters, amides and diamides, hydrogenated vegetable oils; waxes and/or metal soaps produced by hydrogenation or partial hydrogenation of vegetable oils and animal oils or fats, preferably heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, Triacontane, hentriacontane, dotriacontane, tritriacontane, tetratriacontane, pentatriacontane, hexatriacontane, heptatriacontane, octatriacontane, nonatriacontane, montan waxes, carnauba wax, beeswax, candelilla wax, rice bran wax, sugar cane wax, wax obtained from sunflower seed press cake, particularly preferably beeswax and/or wax obtained by hydrogenation of soybean oil, and/or paraffin waxes with an average molecular weight of at least 500 Daltons and a viscosity of at least 11 cSt at 100° C.

Beeswax and/or paraffin wax are particularly preferred, as these are approved for direct food contact according to BfR XXVI of 01.04.2021, Chapter C, Section IV, Point 2 with reference to BfR. XXV. of 01.06.2019, German Federal Institute for Risk Assessment of the Federal Ministry of Food and Agriculture, Germany.

When using paraffin waxes, those that belong to FCM substance no. 94 in the EU Commission Regulation No. 10/2100 of Jan. 14, 2011 “on plastic materials and articles intended to come into contact with food” are particularly preferred.

In one embodiment, the barrier paper according to the invention is preferably characterized in that the at least one wax is present therein in an amount of from 0.01 to 10% (w/w), preferably from 0.01 to <8.0% (w/w), preferably from 0.01<6.0% (w/w), particularly preferably from 0.01 to <5.0% (w/w), and most particularly preferably from 0.01≤2.0% (w/w), and preferably the lower limit is at least 0.1% (w/w), particularly preferably at least 0.2% (w/w) based on the total weight of the coating color layer S1.

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

In one embodiment, the barrier paper according to the invention is preferably characterized in that the at least one polymer binder is present therein in an amount of 99.9 to >92% (w/w), particularly preferably >95% (w/w) and most preferably >98% (w/w) based on the total weight of the coating color layer S1.

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

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

Other possible components of the coating color layer S1 comprise, for example, pigments, in particular inorganic pigments such as Ca-carbonate (GCC or PCC), talc, kaolins, natural and/or synthetic silicates.

Such pigments are preferably contained in the coating color layer S1 in an amount of 0 to 70% (w/w), based on the total weight thereof. To ensure that the heat sealability of the coating color layer S1 is not impaired too much, quantities of 0 to 50% (w/w), preferably 0 to 30% (w/w) and particularly preferably 0 to 10% (w/w) should be selected. Preferably, the value 0% (w/w) is just excluded as the lower limit.

Preferably, platelet-shaped pigments should be selected, as these can contribute to improving the barrier when aligned in laminar direction parallel to the coating. The particle size should preferably be selected so that the particles are completely enclosed in the layer in laminar orientation. The aspect ratio (ratio of average diameter to thickness, also known as the form factor) should be higher than 10, preferably higher than 100 and particularly preferably higher than 1000.

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

These additives are preferably present in the coating color layer S1 in an amount of 0 to 2% (w/w), preferably 0 to 1% (w/w), based on the total weight of the dry coating color layer. Preferably, the value 0% (w/w) is just excluded as the lower limit.

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

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

The application quantity (ISO 536, 2020-05) of the coating color layer S1 is preferably 4 to 20 g/m², preferably 6 to 15 g/m² and particularly preferably 8 to 12 g/m². The quantity refers to the dried coating color layer S1 in the final product.

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

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

Further evidence of wax accumulation can be provided by electron spectroscopy (ESCA, also abbreviated to XPS).

The accumulation of wax in the coating color layer S1 on the side facing away from the base paper was also detected by the following tests.

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

In principle, the base paper used for the barrier paper according to the invention is not limited.

It is preferred that the base paper has a basis weight of 20 to 120 g/m², preferably 40 to 100 g/m².

It is further preferred that the base paper has a long fiber content of 10 to 80% (w/w), preferably from 20 to 50% (w/w), and a short fiber content of 20 to 90% (w/w), preferably from 50 to 80% (w/w), based on the total weight of the base paper, wherein a long fiber is a fiber with a fiber length of 2.6 to 4.4 mm and a short fiber is a fiber with a fiber length of 0.7 to 2.2 mm.

The long-fiber content in particular ensures the strength of the comparatively thin paper, while the short-fiber content, in particular, makes the paper denser and more compact and gives it a uniform appearance. A further increase in the long fiber content would make the paper too stiff. The lower price of short-fiber pulp compared to long-fiber pulp also plays a role.

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

Additionally, conventional additives such as retention agents and/or sizing agents may be present.

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

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

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

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

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

Preferably, the coating color layer S2 is used for forming a barrier layer for mineral oil and/or fat and comprises at least one hydrophilic polymer.

Preferred target values for the mineral oil barrier are n-hexane permeabilities of <30 g/m²/d. The preferred target value for fat resistance for foods that are not consumed immediately is passing the palm kernel fat test according to DIN 53116 Cat. 1 (no passages even after more than 24 hours of testing).

Hydrophilic polymers are often cross-linked and therefore not very flexible. For the coating of flexible packaging, it is preferable to select coatings that can withstand creases of up to 180° inwards (coating to coating) and ideally also outwards without any passage of fat.

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

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

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

The use of these additives is either prohibited or limited for contact with food.

Therefore, when looking for raw materials for barriers for mineral oil and fat, water-soluble polymers are usually not the first choice, but preferably polymer dispersions that are adjusted by the manufacturers by functionalization so that they have the appropriate barrier effect without being appreciably water-soluble, or by adding an insufficient amount of water-soluble polymers that provide or enhance the overall oleophobic effect.

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

The use of cross-linked or partially hydrophobized polyvinyl alcohols, ethylene vinyl alcohols or other copolymers of vinyl alcohol (for example those described in EP 4041548 A1) carbohydrates and/or proteins is also suitable.

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

Due to their high surface tension (surface energy), polyvinyl alcohols are particularly suitable for additionally applying thin metal layers, which have a much lower and predominantly disperse surface tension.

Preferably, the barrier paper according to the invention may comprise at least one further layer consisting of or comprising metals, in particular aluminum. In particular the barrier effect can thus be further improved. This additional layer can be designed as an intermediate layer or as a top layer. If designed as an intermediate layer, this layer is preferably located directly below or above a heat-sealable layer, for example the coating color layer S1.

For this, polyacrylates preferably containing a starch-based protective colloid are particularly preferred. A suitable polyacrylate is known under the trade name Epotal SP 101 D.

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

Such polymers have the advantage that they swell less when they come into contact with water, as a coating applied to them does not achieve its optimum water vapor barrier when it swells.

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

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

Such pigments are preferably present in the coating color layer S2 in an amount of 0 to 70% (w/w), particularly preferably 0 to 50% (w/w), based on the total weight thereof. Preferably, the value 0% (w/w) is just excluded as the lower limit.

Preferably, platelet-shaped pigments should be selected, as these can contribute to improving the barrier when aligned in laminar direction parallel to the coating. The particle size should preferably be selected so that the particles are completely enclosed in the layer in laminar orientation. The aspect ratio (ratio of average diameter to thickness, also known as the form factor) should be higher than 10, preferably higher than 100 and particularly preferably higher than 1000.

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

Such additives are preferably present in the coating color layer S2 in an amount of 0 to 2% (w/w), particularly preferably 0 to % (w/w), based on the total weight thereof. Preferably, the value 0% (w/w) is just excluded as the lower limit.

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

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

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

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

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

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

The application quantity (ISO 536, 2020-05) of the coating color layer S2 is preferably 3 to 12 g/m², and particularly preferably 8 to 10 g/m². The quantity refers to the dried coating color layer S2 in the final product.

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

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

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

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

The aspect ratio (ratio of average diameter to thickness, also known as the form factor) should be around 7 to 40 to 1, preferably around 15 to 30 to 1.

The particle size of the platelet-like pigment is preferably adjusted such that at least about 70%, preferably at least about 85%, of the particles have a particle size of about ≤2 μm (sedigraph). The pH value of the platelet-like pigment in aqueous solution preferably is 6 to 8.

As suitable polymer binders, acrylate-based or styrene/butadiene-based binders can be named in particular. In principle, all polymers that can be used as binders for pigment coatings in the paper industry are suitable. Starch-based binders (solutions of modified starches, dispersions of cross-linked starches, so-called biolatices) and polymer-starch hybrid latices may be employed as well.

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

The polymer binder preferably comprises a styrene-acrylate copolymer, preferably a styrene-butyl acrylate copolymer, in particular a styrene-n-butyl acrylate copolymer.

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

All in all, the coating color layer S3 may be a hydrophobic precoat.

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

The coating color layer S3 preferably contains 5 to 50% (w/w), preferably 10 to 30% (w/w), of a polymer binder. The quantity refers to the dried coating color layer in the final product.

The coating color layer S3 also preferably contains 50 to 95% (w/w), preferably 70 to 90% (w/w), of an inorganic pigment. The quantity refers to the dried coating color layer in the final product.

Additionally, the coating color layer S3 may contain additives such as thickeners, e.g. acrylate-based thickeners, surfactants, and/or rheology modifiers. The use of crosslinkers is also conceivable. Preferably, the coating color layer contains a zirconium-based crosslinker and is itself crosslinked with formaldehyde.

These additives are preferably each present in an amount of 0 to 2% (w/w), preferably of more than 0 to 2% (w/w), wherein the value 0% (w/w) is preferably excluded. The quantity refers to the dried coating color layer S3 in the final product.

The application quantity (ISO 436, 2020-05) of the coating color layer S3 is preferably 1 to 10 g/m², and particularly preferably 2 to 6 g/m². The quantity refers to the dried coating color layer in the final product.

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

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

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

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

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

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

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

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

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

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

For example, the non-coated side of the paper can be provided with one or more coatings that are easier to print on than the surface of the base paper, which only is only provided with a starch film.

In order to improve the barriers of a paper in total, smooth surfaces can be vaporized with metals or metal oxides (e.g. via phase deposition in vacuum).

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

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

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

The barrier paper can be used as a heat-sealable barrier paper, but it is also possible to apply cold seal adhesive to one of the two sides, especially if the paper is to be used on a packaging machine designed for cold seal adhesion.

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

In one embodiment, the barrier paper comprises the coating color layers S1 and S3 as defined above.

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

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

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

It is preferred, however, to obtain the barrier paper according to the invention by a process in which an aqueous suspension or solution comprising the starting materials of the respective coating color layer S1 or coating color layers S2+S1, is applied to the base paper, which is preferably coated with a coating color layer S3, wherein the aqueous application suspension or solution has a solids content of 15 to 55% (w/w), preferably of 20 to 45% (w/w), and is applied by means of a curtain coating process; in the case of the coating color layers S2+S1, both coatings may be applied successively with intermediate drying or preferably by means of a double curtain coating process with an operating speed of the coating system of at least 100 m/min, preferably ≥200 m/min.

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

This process is more particularly advantageous from an economic point of view and due to the even application over the paper web.

If the solids content falls below a value of around 15 wt %, the economic efficiency deteriorates because a large amount of water has to be removed in a short time by gentle drying, which has a detrimental effect on the coating speed. If, on the other hand, the value of 55% (w/w) is exceeded, the only effect is an increased technical effort to ensure the stability of the coating color curtain during the coating process and the drying of the applied film, since the machine has to run very quickly again in this case.

In the curtain coating process, a free-falling curtain of a coating dispersive is formed. The coating dispersion in the form of a thin film (curtain) is “poured” onto a substrate by free fall in order to apply the coating dispersion to the substrate. DE 10 196 052 T1 discloses the use of the curtain coating process in the production of information recording materials, wherein multilayer recording layers are realized by applying the curtain, which consists of several coating dispersion films, to substrates.

In a preferred embodiment of the process according to the invention, the aqueous, deaerated application suspension has a viscosity of about 100 to about 400 mPas (Brookfield, 100 rpm, 20° C.). If the value drops below about 80 mPas or exceeds about 500 mPas, this leads to poor runnability of the coating mass on the coating unit. Particularly preferably, the viscosity of the aqueous, deaerated application suspension is about 150 to about 300 mPas.

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

The individual coatings can be formed on-line on a paper machine with a coating unit or in a separate coating process off-line on a coating machine. For development purposes and for the production of prototypes, the paper can also be produced on a laboratory scale by means of a squeegee and subsequent drying in a drying cabinet. Drying can, e.g., be carried out in the same way as the temperature treatment described above, for 3 minutes at 90° C. in a drying cabinet. As the risk of boiling bubbles forming is lower with this slow drying process, a temperature of more than 100° C. can also be set, preferably 105° C.

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

A coating color layer can be applied to the base paper and/or to already existing coating color layers using a printing process (e.g. flexo printing and gravure printing).

The coating color layer can be applied to the base paper and/or to already existing coating color layers water free as a melt by means of extrusion.

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

The coating color layer can be applied by laminating or lining paper, e.g. in the form of plastic films, on the base paper and/or on existing coating color layers.

The coating color layers can also be applied one after the other over a number of application steps.

The present invention further relates to a barrier paper obtainable by the process described above.

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

The barrier paper according to the invention can be used on all standard packaging machines. By way of example, vertical and horizontal form-fill-seal machines for the production of stand-up pouches, flowpacks or pillow packs, bubble bags or cushions as a replacement for plastic air pillow bags or cushions; machines that bring together two webs of the same or different materials and join them by heat sealing, e.g. also tray sealers, chamber belt machines (also with vacuum), pouch filling and sealing machines, thermoforming packaging machines, linear filling machines that apply lids by heat sealing for sealing, wrapping machines with a final heat sealing step, blister packaging machines, and X-fold packaging machines could be mentioned here.

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

The present invention further relates to a packaging material, in particular a heat-sealable packaging material, consisting of or comprising a barrier paper as described above.

The invention is explained in detail below with reference to non-limiting examples.

EXAMPLES

Base papers from one production line were used for comparative examples 1 to 3 and examples 1 to 5.

The pure base paper was produced on the associated paper machine (38% (w/w) long fiber, 57% (w/w) short fiber, 5% (w/w) calcium carbonate as filler, fully sized with alkyl ketene dimer on water cobb 25 g/m²), smoothed by means of a smoothing unit, and on both sides, enzymatically partially degraded, cationically modified potato starch (approx. 1 g/m²) was applied with a film press.

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

In a second step, this paper was coated on a production coating machine with a coating color layer S3, which was applied by means of a blade coater to the less smooth side, which was on the side facing away from the smoothing cylinder during the smoothing process (comparative examples 1 to 3 and examples 1 to 3).

For examples 4 and 5, the coating color S3 was applied in two steps. 4 g/m² were already applied online on the paper machine to the less smooth side, while a further 4 g/m² were applied directly to it using a blade coater, as in the previous examples and comparative examples.

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

In comparative example 1a and examples 4 and 5, the coating color layer S1 was applied directly to the coating color layer S3 in the same way.

The drying unit consists of a series of electric infrared dryers, followed by a block of air hoods (hot air drying).

The information on the length of the drying sections, the web temperature of the paper surface and the residence time in the respective drying area can be taken from Tables 1 and 2a, wherein the production parameters are only given for the application of the coating color layer S1.

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

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

Production of the coating color S1 (comparative examples 1 to 3 and examples 1 to 3) (formulation from pilot plant, scaled up identically for production plant) Aqueous application suspension with a solids content of 20 to 60%: 38.1 kg of water is provided and mixed with 452.8 kg of styrene acrylate/methyl acrylate/butyl acrylate/ethylhexyl acrylate 97.8% (w/w) and beeswax 2.0% (w/w), in the case of comparative example 3 styrene acrylate/methyl acrylate/butyl acrylate/ethylhexyl acrylate 91.82% (w/w) and beeswax 8.0% (w/w). As additives, 0.523 kg of the extensional rheology aid Sterocoll DF 4 (BASF SE, polyacrylamide, W/O emulsion) and 0.188 kg of the defoamer Genapol PF 10 (Clariant Produkte (Germany) GmbH, polymerization product of propylene oxide and ethylene oxide) are added subsequently. This results in a pH value of approx. 8.5 and a viscosity (Brookfield) of approx. 160 mPas.

Production of Coating Color S1 (Examples 4 and 5)

Aqueous application suspension with a solids content of 20 to 60%: 16 kg of water is provided and mixed with 267 kg of an aqueous suspension consisting of 90 parts of a carboxylated styrene-butadiene polymer and 10 parts of a paraffin wax with chain lengths C21-C38. Solutions of 6.5 kg of polyvinyl alcohol type 8-88 and 15.6 kg of polyvinyl alcohol type 28-99 are added subsequently as thickeners. As additives, 0.2 kg of the extensional rheology aid Sterocoll DF 4 (BASF SE, polyacrylamide, W/O emulsion) and 0.7 kg of the defoamer Genapol PF 10 (Clariant Produkte (Germany) GmbH, polymerization product of propylene oxide and ethylene oxide) are added subsequently. The surfactant added is 1.7 kg Dynawet 2050 (CTP GmbH), a non-ionic surfactant preparation with CAS-#160875-66-1 as the main active ingredient. This results in a viscosity of 230 mPas and a pH value of 6.5.

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

77 kg of water is provided and mixed with 228.6 kg of Epotal SP 101 D (BASF SE, polyacrylate with starch-based protective colloid). In the following, 0.957 kg of the thickener Texturecel 100 GA (DDP Specialty Products Germany GmbH, carboxymethyl cellulose), 0.081 kg of the extensional rheology aid Sterocoll DF 4 and 0.210 kg of the defoamer Genapol PF 10 are admixed as additives. A pH value of 8.8 is set by adding sodium hydroxide solution, resulting in a viscosity (Brookfield) of approx. 200 mPas.

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

Production of the Coating Color S3:

The composition is given in Table 1: For the person skilled in the art, these specifications are sufficient to produce a spreadable coating mass.

The composition of the respective coating color layers, the drying parameters and the determined properties of the barrier papers are summarized in the following Table 1.

Description of measurement methods for which no standard is known or for which own procedures have been developed:

Heat sealability: While testing the sealed-seam strength of an existing seal seam is clearly defined by DIN 55529:2012-09, for example, there is no standardized method for testing the suitability of a material for heat sealing. This is obviously due to the fact that packers prefer to develop their own incoming inspections for heat-sealable films or papers adapted to their packaging systems.

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

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

Palm kernel fat test according to DIN 53116: Test condition I (pressure 2000 N/m² and exposure time >24 hrs., in practice 25 hrs.) was selected. The print side of a C1S paper of the brand NexCoat-Smart 60 g/m² (Koehler Paper SE) is used as the display paper.

Testing the palm kernel fat test on a creased paper: For folded samples, a 180° fold is produced with a roller that exerts a load of 330 g/cm on the resulting fold, and wherein the coating can be on the inside (inside fold) or the outside (outside fold).

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

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

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

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

Note for Tables 1, 2 and 2a

The columns marked with * contain the measured values of the paper indicated on the left after a 3-minute treatment in the hot air drying oven at 105° C. A Binder type E 115 drying oven with the following internal dimensions width×height×depth was used: 60×48×40 cm (internal volume 115 dm³), drying oven temperature range: 0-250° C., natural convection, no circulating air fan). In the oven, there is a metal grid at medium height and a cardboard of approx. 2 mm thickness lying on it. The oven is now preheated to 105° C. for at least 30 minutes. During the brief opening of the door (<2 s), the test specimen is placed on the cardboard. After 3 minutes, the test specimen is removed and conditioned for at least 12 hrs. at 23° C. and 50% r.h. before further measurements are taken.

TABLE 1
Comparative examples

			Comparative	Comparative	Comparative	Comparative
	Measuring		example	example	example	example
Specification	method	Unit	1	1*	1a	1a*
Smoothness Bekk	ISO 5627	s	2093	2371	2114	2423
Roughness PPS	DIN ISO	μm	1.3	1.2	1.4	1.0
	8791-4
Coefficient of	ISO 8295	—	0.41	0.42	0.43	0.46
friction [CoF value
in itself (static)]
Coefficient of	ISO 8295	—	0.31	0.32	0.32	0.35
friction [CoF value
in itself (kinetic)]
Heat sealability:
Sealing condition	T		0.3 s/	0.3 s/	0.3 s/	0.3 s/
for producing the	variable		3.33 bar	3.33 bar	3.33 bar	3.33 bar
sealing seam to be
tested
Cold seal seam	DIN	N/15	3.0/150° C.	3.2/150° C.	3.3/150° C.	3.5/150° C.
strength (cold	55529:	mm
tack) at optimum	2012 September
sealing
temperature
Hot seal seam	DIN	N/15	1.5/150° C.	2.2/150° C.	1.6/150° C.	1.9/150° C.
strength (hot-tack)	55571-2	mm
	Method C
Water vapor
transmission
rate (WVTR) and
its dependence
on fat contact:
WVTR (38° C., 90%	ISO/FDIS	g/m2/d	44	35.5	62	33
r.h.)	2528
Decrease (change)		g/m2/d		8.5		29
due to post-drying
Decrease (change)		%		19.3		46.7
due to post-drying
Treatment with	DIN	g/m2/d	250-320	52-81	180	62
PKFT (10 min,	53116
2000 N/m2) and	ISO/FDIS
Determination	2528
WVTR (38° C., 90%
r.h.)
Treatment with	DIN	g/m2/d	350	136	320	150
PKFT (1 hr.,	53116
2000 N/m2) and	ISO/FDIS
Determination	2528
WVTR (38° C., 90%
r.h.)
WVTR (23° C., 50%	ISO/FDIS	g/m2/d	11	7	n.d.	n.d.
r.h.)	2528
Decrease (change)				4
due to post-drying
Treatment with	DIN	g/m2/d	85	57	n.d.	n.d.
PKFT (10 min,	53116
2000 N/m2) and	ISO/FDIS
Determination	2528
WVTR (23° C., 50%
r.h.)
Mineral
oil barrier:
Mineral oil barrier	own	g/m2/d	14	15	**	**
(HVTR)	method
Palm kernel fat	DIN	Fat	0/0	0/0	**	**
test (display	53116: >24 hrs.	passages <1
paper)		mm/>1 mm
Palm kernel fat	own	Fat	0/0	n.d.	**	**
test (inside fold)	method	passages <1
(display paper)		mm/>1 mm
Palm kernel fat	own	Fat	0/0	n.d.	**	**
test (outside fold)	method	passages <1
(display paper)		mm/>1 mm
Sensory	DIN EN	Grade	3 (ammonia)	2	3 (ammonia)	1.5 (ammonia)
Assessment (odor)	1230-1:	1-4
	2010 February
	Part 1: Odor
Base paper:
Basis weight	ISO 536	g/m2	62		62
Coating color
layer S3):
Basis weight	ISO 536	g/m2	4
Binder	Chemistry	share	styrene-n-		styrene-n-
	(trade	100%	butyl acylate		butyl acylate
	name)		(Acronal S		(Acronal S
			305 FD) 22.8%		305 FD) 22.8%
Inorganic pigment	Chemistry	share	kaolin		kaolin
	(trade	100%	(Capim		(Capim
	name)		NP) 75.8%		NP) 75.8%
Crosslinking agent	Chemistry	share	ammonium		ammonium
	(trade	100%	zirconium		zirconium
	name)		carbonate		carbonate
			(Alicross		(Alicross
			AZC) 1.1%		AZC) 1.1%
Other additives		share	0.3%		0.3%
		100%
Surface tension of	DIN EN	mN/m	26		26
the layer	ISO
	19403-2
Polar part of the		%	21		21
surface tension
Dispersed part of		%	79		79
the surface
tension
Coating color
layer S2:
Basis weight	ISO 536	g/m2	10		**
Polymer binder	Chemistry	share	polyacrylate		**
	(trade	100%	with starch-
	name)		based
			protective
			colloid
			(Epotal SP
			101 D) 98.3%
Other additives		share	1.70%		**
		100%
Surface tension of	DIN EN	mN/m	57-61		**
the layer	ISO
	19403-2
Polar part of the		%	80-82		**
surface tension
Dispersed part of		%	20-18		**
the surface
tension
Coating color
layer S1
Basis weight	ISO 536	g/m2	10		10
Polymer binder	Chemistry	share	styrene		styrene
		100%	acrylate/methyl		acrylate/methyl
			acrylate/butyl		acrylate/butyl
			acrylate/		acrylate/
			ethylhexyl		ethylhexyl
			acrylate 97.8%		acrylate 97.8%
Wax	Chemistry	share	beeswax		beeswax
		100%	2.0%		2.0%
Other additives		share	0.20%		0.20%
		100%
Surface tension of	DIN EN	mN/m	21	33	20	35
the coating	ISO
	19403-2
Increase (change)		mN/m		+12		+15
due to post-drying
Polar part of the		%	11	0.2	14	0.6
surface tension
Decrease (change)		% pts.		−10.8		−13.4
due to post-drying
Dispersed part of		%	89	99.8	86	99.4
the surface
tension
Polar part		mN/m	2.3	0.1	2.8	0.2
(absolute)
Decrease (change)		mN/m		−2.2		−2.6
due to post-drying
Dispersed part		mN/m	18.7	32.9	17.2	34.8
(absolute)
Coated paper
Basis weight	ISO 536	g/m2	87		75
Residual moisture		%	4.3		4.2
		(w/w)
Drying of the coating
color layer S1
Coating machine		m/min	250		250
speed
web temperature	IR sensor	° C.	32-68		33-70
range
Length of the		m	1.6		1.6
drying section
(IR drying)
Residence time in		s	0.38		0.38
drying section
Web temperature	IR sensor	° C.	81		83
after air hoods
Length of the		m	12		12
drying section air
hoods
Average web		° C.	74.5		76.5
temperature in the
air hood area
Residence time in		s	2.9		2.9
the air hood area

		Comparative	Comparative	Comparative	Comparative
		example	example	example	example
	Specification	2	2*	3	3*
	Smoothness Bekk	1394	2427	1100	2254
	Roughness PPS	1.2	1.1	1.4	1.2
	Coefficient of	0.49	0.54	0.44	0.36
	friction [CoF value
	in itself (static)]
	Coefficient of	0.41	0.38	0.32	0.34
	friction [CoF value
	in itself (kinetic)]
	Heat sealability:
	Sealing condition	0.3 s/	0.3 s/	0.3 s/	0.3 s/
	for producing the	3.33 bar	3.33 bar	3.33 bar	3.33 bar
	sealing seam to be
	tested
	Cold seal seam	3.8/140° C.	4.9/140° C.	<1/150° C.	<1/150° C.
	strength (cold
	tack) at optimum
	sealing
	temperature
	Hot seal seam	1.5/150° C.	2.6/150° C.	<1/150° C.	<1/150° C.
	strength (hot-tack)
	Water vapor
	transmission
	rate (WVTR) and
	its dependence
	on fat contact:
	WVTR (38° C., 90%	16.5	8.5	91	26.5
	r.h.)
	Decrease (change)		8		64.5
	due to post-drying
	Decrease (change)		48.5		70.9
	due to post-drying
	Treatment with	129/81	32/19	170-230	61-85
	PKFT (10 min,
	2000 N/m2) and
	Determination
	WVTR (38° C., 90%
	r.h.)
	Treatment with	n.d.	n.d.	290	62
	PKFT (1 hr.,
	2000 N/m2) and
	Determination
	WVTR (38° C., 90%
	r.h.)
	WVTR (23° C., 50%	n.d.	n.d.	20	6
	r.h.)
	Decrease (change)				14
	due to post-drying
	Treatment with	n.d.	n.d.	85	38
	PKFT (10 min,
	2000 N/m2) and
	Determination
	WVTR (23° C., 50%
	r.h.)
	Mineral
	oil barrier:
	Mineral oil barrier	36	39	21	24
	(HVTR)
	Palm kernel fat	0/0	n.d.	0/0	n.d.
	test (display
	paper)
	Palm kernel fat	0/0	n.d.	0/0	n.d.
	test (inside fold)
	(display paper)
	Palm kernel fat	0/0	n.d.	0/0	n.d.
	test (outside fold)
	(display paper)
	Sensory	3 (ammonia)	n.d.	3.5 (ammonia)	2
	Assessment (odor)
	Base paper:
	Basis weight	62		62
	Coating color
	layer S3):
	Basis weight	4		4
	Binder	styrene-n-		styrene-n-
		butyl acylate		butyl acylate
		(Acronal S		(Acronal S
		305 FD) 22.8%		305 FD) 22.8%
	Inorganic pigment	kaolin		kaolin
		(Capim		(Capim
		NP) 75.8%		NP) 75.8%
	Crosslinking agent	ammonium		ammonium
		zirconium		zirconium
		carbonate		carbonate
		(Alicross		(Alicross
		AZC) 1.1%		AZC) 1.1%
	Other additives	0.3%		0.3%
	Surface tension of	26		26
	the layer
	Polar part of the	21		21
	surface tension
	Dispersed part of	79		79
	the surface
	tension
	Coating color
	layer S2:
	Basis weight	8		10
	Polymer binder	polyacrylate		polyacrylate
		with starch-		with starch-
		based		based
		protective		protective
		colloid		colloid
		(Epotal SP		(Epotal SP
		101 D) 98.3%		101 D) 98.3%
	Other additives	1.70%		1.70%
	Surface tension of	57-61		57-61
	the layer
	Polar part of the	80-82		80-82
	surface tension
	Dispersed part of	20-18		20-18
	the surface
	tension
	Coating color
	layer S1
	Basis weight	12		10
	Polymer binder	styrene		styrene
		acrylate/methyl		acrylate/methyl
		acrylate/butyl		acrylate/butyl
		acrylate/		acrylate/
		ethylhexyl		ethylhexyl
		acrylate 97.8%		acrylate 91.82%
	Wax	beeswax		beeswax
		2.0%		8.0%
	Other additives	0.20%		0.20%
	Surface tension of	21	23	22	28
	the coating
	Increase (change)		+2		+6
	due to post-drying
	Polar part of the	5	1.9	1.5	0
	surface tension
	Decrease (change)		−3.1		−3.3
	due to post-drying
	Dispersed part of	95	98.1	98.5	100
	the surface
	tension
	Polar part	1.1	0.4	0.8	0
	(absolute)
	Decrease (change)		−0.7		−0.8
	due to post-drying
	Dispersed part	19.9	22.6	21.7	28
	(absolute)
	Coated paper
	Basis weight	87		87
	Residual moisture	n.d.		5.6
	Drying of the
	coating
	color layer S1
	Coating machine	205		230
	speed
	web temperature	34-67		43-47
	range
	Length of the	1.6		1.6
	drying section
	(IR drying)
	Residence time in	0.47		0.42
	drying section
	Web temperature	85		78
	after air hoods
	Length of the	12		12
	drying section air
	hoods
	Average web	76		62.5
	temperature in the
	air hood area
	Residence time in	3.5		3.1
	the air hood area
	*Post-drying: 105° C., 3 min
	** without coating color layer S2

TABLE 2
Examples

	Measuring
Specification	method	Unit	Example 1	Example 1*	Example 2	Example 2*	Example 3	Example 3*

Smoothness	ISO 5627	s	632	1427	549	681	427	1583
Bekk
Roughness PPS	DIN ISO	μm	1.7	1.4	1.8	1.7	1.6	1.5
	8791-4
Coefficient of	ISO 8295	—	0.4	0.35	0.32	0.38	0.35	0.29
friction [CoF
value in itself
(static)]
Coefficient of	ISO 8295	—	0.32	0.29	0.27	0.3	0.31	0.27
friction [CoF
value in itself
(kinetic)]
Heat
sealability:
Sealing	T		0.3 s/	0.3 s/	0.3 s/	0.3 s/	0.3 s/	0.3 s/
condition for	variable		3.33 bar	3.33 bar	3.33 bar	3.33 bar	3.33 bar	3.33 bar
producing the
seam to be
tested
Cold seal seam	DIN	N/15	4.8/140° C.	5.8/150° C.	4.4/140° C.	5.3/160° C.	4.1/150° C.	4.3/160° C.
strength (cold	55529:	mm
tack) at	2012
optimum sealing	September
temperature
Hot seal seam	DIN	N/15	3.1/140° C.	2.4/150° C.	3.8/140° C.	2.0/150° C.	2.2/150° C.	1.8/160° C.
strength (hot-	55571-2	mm
tack)	Method C
Water vapor
transmission
rate (WVTR)
and its
dependence
on fat contact:
WVTR (38° C.,	ISO/FDIS	g/m2/d	18.5	12	17.5	15	15	14
90% r.h.)	2528
Decrease		g/m2/d		−6.5		−2.5		−1
(change) due to
post-drying
Decrease		%		−35.1		−14.3		−7
(change) due to
post-drying
Treatment with	DIN	g/m2/d	62-79	55/82	59-80	45-80	55	48
PKFT (10 min,	53116
2000 N/m2) and	ISO/FDIS
Determination	2528
WVTR (38° C.,
90% r.h.)
Treatment with	DIN	g/m2/d	n.d.	n.d.	n.d.	n.d.	75	64
PKFT (1 hr.,	53116
2000 N/m2) and	ISO/FDIS
Determination	2528
WVTR (38° C.,
90% r.h.)
WVTR (23° C.,	ISO/FDIS	g/m2/d	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.
50% r.h.)	2528
Treatment with	DIN	g/m2/d	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.
PKFT (10 min,	53116
2000 N/m2) and	ISO/FDIS
Determination	2528
WVTR (23° C.,
50% r.h.)
Mineral oil
barrier:
Mineral oil	own	g/m2/d	15	17	**	**	14	17
barrier (HVTR)	method)
Palm kernel fat	DIN	Fat	0/0	n.d.	**	**	0/0	n.d.
test (display	53116: >24	passages <1
paper)	hrs.	mm/>1 mm
Palm kernel fat	own	Fat	0/0	n.d.	**	**	0/0	n.d.
test (inside fold)	method	passages <1
(display paper)		mm/>1 mm
Palm kernel fat	own	Fat	0/0	n.d.	**	**	0/0	n.d.
test (outside	Method	passages <1
fold) (display		mm/>1
paper)		mm
Sensory	DIN EN	Grade	3.5 (ammonia)	n.d.	3 (ammonia)	n.d.	2.5 (ammonia)	n.d
Assessment	1230-1:	1-4
(odor)	2010
	February
	Part 1: Odor
Base paper:
Basis weight	ISO 536	g/m2	62		62		62
Coating color
layer S3):
Basis weight	ISO 536	g/m2	4		4		4
Binder	Chemistry	share	styrene-n-butyl		styrene-n-butyl		styrene-n-butyl
	(trade	100%	acylate (Ac-		acylate (Ac-		acylate (Ac-
	name)		ronal S 305		ronal S 305		ronal S 305
			FD) 22.8%		FD) 22.8%		FD) 22.8%
Inorganic	Chemistry	share	kaolin(Capim		kaolin(Capim		kaolin (Capim
pigment	(trade	100%	NP) 75.8%		NP) 75.8%		NP) 75.8%
	name)
Crosslinking	Chemistry	share	ammonium		ammonium		ammonium
agent	(trade	100%	zirconium		zirconium		zirconium
	name)		carbonate		carbonate		carbonate
			(Alicross		(Alicross		(Alicross
			AZC) 1.1%		AZC) 1.1%		AZC) 1.1%
Other additives		share	0.3%		0.3%		0.3%
		100%
Surface tension	DIN EN	mN/m	26		26		26
of the layer	ISO
	19403-2
Polar part of the		%	21		21		21
surface tension
Dispersed part		%	79		79		79
of the surface
tension
[Barrier coat
(MOB)], coating
color layer S2:
Basis weight	ISO 536	g/m2	8		**
Polymer binder	Chemistry	share	polyacrylate		**		polyacrylate
	(trade	100%	with starch-				with starch-
	name)		based protective				based protective
			colloid (Epotal				colloid (Epotal
			SP 101 D) 98.3%				SP 101 D) 98.3%
Other additives		share	1.70%		**		1.70%
		100%
Surface tension	DIN EN	mN/m	57-61		**		57-61
of the layer	ISO
	19403-2
Polar part of the		%	80-82		**		80-82
surface tension
Dispersed part		%	20-18		**		20-18
of the surface
tension
[Barrier coat
(WVTR/sealing:
Coating
color layer S1
Basis weight	ISO 536	g/m2	12		10		10
Polymer binder	Chemistry	share	styrene		styrene		styrene
		100%	acrylate/methyl		acrylate/methyl		acrylate/methyl
			acrylate/butyl		acrylate/butyl		acrylate/butyl
			acrylate/ethyl-		acrylate/ethyl-		acrylate/ethyl-
			hexyl acry-		hexyl acry-		hexyl acry-
			late 97.8%		late 97.8%		late 91.82%
Wax	Chemistry	share	beeswax 2.0%		beeswax 2.0%		beeswax 8.0%
		100%
Other additives		share	0.20%		0.20%		0.20%
		100%
Surface tension	DIN EN	mN/m	20	29	20	21	20	24
of the coating	ISO
	19403-2
Increase		mN/m		+9		+1		+4
(change) due to
post-drying
Polar part of the		%	3	0.1	2.3	2.2	2	0
surface tension
Decrease		% pts.		−2.9		0/−0.1, 2		−2
(change) due to
post-drying
Dispersed part		%	97	99.1	97.7/98.4	97.7/97.2	98	100
of the surface
tension
Polar part		mN/m	0.6	0.03	0.6	0.6	0.4	0
(absolute)
Decrease		mN/m		−0.57		0		−0.4
(change) due to
post-drying
Dispersed part		mN/m	19.8	29.4	20.9	19.9	19.6	24
(absolute)
Coated paper
Basis weight	ISO 536	g/m2	85		75		87
Residual		%	n.d.		n.d.		n.d.
moisture		(w/w)
Drying of the
coating color
layer S1
Coating machine		m/min	450		450		450
speed
Web	IR sensor	° C.	50		50		50
temperature
range
Length of the		m	1.8		1.8		1.8
drying section
(IR drying)
Residence time		s	0.24		0.24		0.24
in drying section
Web	IR sensor	° C.	83		83		83
temperature
after air hoods
Length of the		m	34.8		34.8		34.8
drying section
air hoods
Average web		° C.	66.5		66.5		66.5
temperature in
the air hood
area
Residence time		s	11.1		11.1		11.1
in the air hood
area
*Post-drying: 105° C., 3 min
** No 2nd coating color layer

TABLE 2a
Examples

	Measuring
Specification	method	Unit	Example 4	Example 4*	Example 5	Example 5*

Smoothness Bekk	ISO 5627	s	7200	3100	4400	3200
Roughness PPS	DIN ISO	μm	1.5	1.6	1.5	1.7
	8791-4
Coefficient of	ISO 8295	—	0.95	0.97	1.00	0.92
friction [CoF value in
itself (static)]
Coefficient of	ISO 8295	—	0.43	0.43	0.44	0.46
friction [CoF value in
itself (kinetic)]
Heat sealability:
Sealing condition for	T		0.3 s/	0.3 s/	0.3 s/	0.3 s/
producing the seam	variable		3.33 bar	3.33 bar	3.33 bar	3.33 bar
to be tested
Cold seal seam	DIN	N/15	5.1/120° C.	4.4/130° C.	5.4/130° C.	4.3/130° C.
strength (cold tack)	55529:	mm
at optimum sealing	2012 September
temperature
Hot seal seam	DIN	N/15	4.6/120° C.	2.9/130° C.	4.5/130° C.	3.5/130° C.
strength (Hot-Tack)	55571-2	mm
	Method C
Water vapor
transmission rate
(WVTR) and its
dependence
on fat contact:
WVTR (38° C., 90%	ISO/FDIS	g/m2/d	37	15	52	22
r.h.)	2528
Change due to post-		g/m2/d		−22		−30
drying
Change due to post-		%		−40.5		−42.3
drying
Treatment with PKFT	DIN	g/m2/d	281	296	278	286
(10 min, 2000 N/m2)	53116
and Determination	ISO/FDIS
WVTR (38° C., 90%	2528
r.h.)
Treatment with PKFT	DIN	g/m2/d	468	462	452	442
(1 hr., 2000 N/m2)	53116
and Determination	ISO/FDIS
WVTR (38° C., 90%	2528
r.h.)
Base paper:
Basis weight	ISO 536	g/m2	60		60
Coating color
layer S3):
Basis weight	ISO 536	g/m2	8		8
Binder	Chemistry	share	styrene-n-butyl		styrene-n-butyl
	(trade	100%	acylate (Acronal		acylate (Acronal
	name)		S 305 FD) 22.8%		S 305 FD) 22.8%
Inorganic pigment	Chemistry	share	kaolin (Capim		kaolin (Capim
	(trade	100%	NP) 75.8%		NP) 75.8%
	name)
Crosslinking agent	Chemistry	share	ammonium		ammonium
	(trade	100%	zirconium		zirconium
	name)		carbonate		carbonate
			(Alicross		(Alicross
			AZC) 1.1%		AZC) 1.1%
Other additives		share	0.3%		0.3%
		100%
Surface tension of	DIN EN	mN/m	26		26
the layer	ISO
	19403-2
Polar part of the		mN/m	21		21
surface tension
Dispersed part of		mN/m	19		19
the surface tension
[Barrier coat
(WVTR/sealing:
Coating color
layer S1
Basis weight	ISO 536	g/m2	10		10
Polymer binder	Chemistry	share	styrene		styrene
		100%	butadiene 87.3%		butadiene 87.3%
Wax	Chemistry	share	paraffin (C21-		paraffin (C21-
		100%	C38) 9.7%		C38) 9.7%
Other additives		share	3.00%		3.00%
		100%
Surface tension of	DIN EN	mN/m	23.1	24.7	24.5	25.1
the coating	ISO
	19403-2
Increase (change)		mN/m		+1.6		+0.6
due to post-drying
Polar part of the		%	1.8	0.4	1.8	0.6
surface tension
Decrease (change)		% pts.		−1.4		−1.2
due to post-drying
Dispersed part of		%	98.3	99.6	98.4	99.6
the surface tension
Polar part (absolute)		mN/m	0.42	0.10	0.43	0.15
Decrease (change)		mN/m		−0.32		−0.28
due to post-drying
Dispersed part		mN/m	22.7	24.6	24.1	25.0
(absolute)
Coated paper
Basis weight	ISO 536	g/m2	78		78
Residual moisture		%	4.1		2.8
		(w/w)
Drying of the
coating color
layer S1
Coating machine		m/min	295		295
speed
Web temperature	IR sensor	° C.	45-52		53-63
range
Length of the drying		m	1.6		1.6
section (IR drying)
Residence time in		s	0.33		0.33
drying section
Web temperature	IR sensor	° C.	93		95
after air hoods
Length of the drying		m	12		12
section air hoods
Average web		° C.	70		79
temperature in the
air hood area
Residence time in		s	2.4		2.4
the air hood area
*Post-drying: 105° C., 3 min

Example 2: (Example 2 from Table 1)

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

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

The advantages of the paper are:

• • without optical brighteners
  • water vapor barrier for optimum product protection
  • good sealability
  • outstanding strength properties
  • suitable for direct food contact
  • 100% virgin fiber pulp
  • very good running properties on converting and packaging systems
  • recyclable in the paper cycle
  • particularly suitable for flexo, gravure and digital printing

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

TABLE 3
Specifications	Standard	Unit	Value
Basis weight	ISO 536	g/m2	74 ± 4%
Thickness	ISO 534	μm	77 ± 5%
Opacity	ISO 2471	%	77 ± 4
Whiteness R 457 OS	ISO 2470	%	83 ± 2
Roughness PPC OS/RS	ISO 8791-4	μm	<4.2/<3.8
Breaking resistance	ISO 1924-2	N/15 mm	≥70/≥45
longitudinal/transverse
Elongation at break,	ISO 1924-2	%	≥2.0/≥5.0
longitudinal/transverse
Burst pressure Mullen	ISO 2758	kPa	≥250
Moisture	ISO 287	%	4.5 ± 1.5
KIT	Tappi T 559	—	12
WVTR	30°/90%/r.h.	—	<80
Sealed-seam strength	ASTN	N/15 mm	>3
cold tack

Example 3: (Example 1 from Table 1)

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

The paper is suitable for various applications in the area of the tobacco industry for particularly sophisticated tobacco products.

The advantages of the paper are:

• • high degree of whiteness
  • without optical brighteners
  • smooth surface
  • good sealability
  • very good aroma barrier
  • high resistance to buckling breakage
  • outstanding strength properties
  • suitable for direct food contact
  • 100% virgin fiber pulp
  • outstanding printing and lacquer hold-out
  • very good running properties on converting and packaging systems
  • particularly suitable for flexo and gravure printing

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

TABLE 4
Specifications	Standard	Unit	Value
Basis weight	ISO 536	g/m2	75 ± 4%
Thickness	ISO 534	μm	82 ± 5%
Breaking resistance	ISO 1924-2	N/15 mm	≥70/≥45
longitudinal/transverse
Elongation at break,	ISO 1924-2	%	≥2.0/≥5.0
longitudinal/transverse
Burst pressure Mullen	ISO 2758	kPa	≥250
Sealed-seam strength	ASTM F88	N/15 mm	>4
cold tack
WVTR	ISO 15106-2	—	<8 (23° C./50% r.h.)
			≤20 (38° C./90% r.h.)
HVTR		—	≤10
KIT	Tappi T 559	—	12
Fat permeability	DIN 53116	—	CAT. 1

Example 4: (Example 1 from Table 1)

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

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

The advantages of the paper are:

• • without optical brighteners
  • water vapor barrier for optimum product protection
  • good sealability
  • outstanding strength properties
  • suitable for direct food contact
  • 100% virgin fiber pulp
  • very good running properties on converting and packaging systems
  • recyclable in the paper cycle
  • particularly suitable for flexo and gravure printing

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

TABLE 5
Specifications	Standard	Unit	Value
Basis weight	ISO 536	g/m2	74 ± 4%
Thickness	ISO 534	μm	77 ± 5%
Opacity	ISO 2471	%	77 ± 4
Whiteness R 457 OS	ISO 2470	%	83 ± 2
Roughness PPC OS/RS	ISO 8791-4	μm	<4.2/<3.8
Breaking resistance	ISO 1924-2	N/15 mm	≥70/≥45
longitudinal/transverse
Elongation at break,	ISO 1924-2	%	≥2.0/≥5.0
longitudinal/transverse
Burst pressure Mullen	ISO 2758	kPa	≥250
Moisture	ISO 287	%	4.5 ± 1.5
KIT	Tappi T 559	—	12
WVTR	30°/90%/r.h.	—	<80
Sealed-seam strength	ASTN	N/15 mm	>3
cold tack

Example 5: (Example 1 from Table 1)

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

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

The advantages of the paper are:

• • high degree of whiteness
  • without optical brighteners
  • smooth surface
  • good sealability
  • high resistance to buckling breakage
  • outstanding strength properties
  • suitable for direct food contact
  • 100% virgin fiber pulp
  • outstanding printing and lacquer hold-out
  • very good running properties on converting and packaging systems
  • particularly suitable for flexo, gravure and digital printing

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

TABLE 6
Specifications	Standard	Unit	Value
Basis weight	ISO 536	g/m2	75 ± 4%
Thickness	ISO 534	μm	82 ± 5%
Breaking resistance	ISO 1924-2	N/15 mm	≥70/≥45
longitudinal/transverse
Elongation at break,	ISO 1924-2	%	≥2.0/≥5.0
longitudinal/transverse
Burst pressure Mullen	ISO 2758	kPa	≥250
Sealed-seam strength	ASTM F88	N/15 mm	>4
cold tack
WVTR	ISO 15106-2	—	<8 (23° C./50% r.h.)
			≤20 (38° C./90% r.h.)
HVTR		—	≤10
KIT	Tappi T 559	—	12
Fat permeability	DIN 53116	—	CAT. 1