Method for producing a coated packaging material, and packaging material having at least one barrier layer for hydrophobic compounds

Abstract

The invention relates to a method for producing a coated packaging material (10), wherein at least the following steps are carried out: a) providing a substrate (12), which has a base material (14) made of cellulose, an outside (16) to face away from a good to be packaged, and an inside (18) to face the good to be packaged; b) coating the inside (18) of the substrate with at least one layer of an aqueous composition, which comprises at least polyvinyl alcohol and a cross-linking agent and has a solid content of at most 25 wt %; and c) drying the layer and cross-linking the polyvinyl alcohol by means of the cross-linking agent in order to form a barrier layer (22a, 22b) for hydrophobic compounds. The invention further relates to a packaging material (10) having at least one barrier layer (22a, 22b) for hydrophobic compounds.

Claims

1. A method for producing a coated packaging material, comprising the steps of: a) providing a substrate having a base material of cellulose, an outside to face away from a packaging good as well as an inside to face the packaging good, wherein the base material is selected from the group consisting of: coated or uncoated paper, coated or uncoated cardboard, and coated or uncoated paperboard; b) coating the inside of the substrate with at least one layer of an aqueous composition including at least polyvinyl alcohol and a cross-linking agent and having a solid content of at most 25% by wt., wherein as the cross-linking agent at least an alkyl orthosilicate and/or at least one olefinically saturated and/or unsaturated bi-, tri- or multi-functional compound with at least two functional groups selected from carboxylic acid and acid anhydride is used; and adjusting a pH value of the aqueous composition to a value between 1 and 7 before applying the aqueous composition to the substrate; c) drying the layer and cross-linking the polyvinyl alcohol with the aid of the cross-linking agent with formation of a barrier layer for hydrophobic compounds; drying the substrate with the aqueous composition coated thereon to a residual humidity between 3% and 10% by weight in the base material; and wherein the cross-linking agent contributes to the formation of a three-dimensional network by reaction with polyvinyl alcohol.

2. The method according to claim 1, wherein the aqueous composition has a solid content between 3% by wt. and 25% by wt., and/or a water content of at least 75% by wt.

3. The method according to claim 1, wherein, as the cross-linking agent, tetraethyl orthosilicate, malonic acid, glutaric acid, adipic acid, citric acid, butane tetracarboxylic acid, maleic acid, polyacrylic acid, polymethacrylic acid, polyethyl acrylic acid or any mixtures hereof and/or polymerizates hereof and/or copolymerizates hereof is used.

4. The method according to claim 1, wherein the aqueous composition includes between 0.01 and 55 parts by weight of cross-linking agent related to 100 parts by weight of polyvinyl alcohol and/or between 1 and 60 parts by weight of a filler and/or a pigment related to 100 parts by weight of polyvinyl alcohol.

5. The method according to claim 4, wherein the filler and/or a pigment are acid-stable and/or have at least substantially spherical and/or platelet-shaped particle geometries.

6. The method according to claim 1, wherein the aqueous composition is applied to the substrate such that an area-related dry mass between 1 g/m.sup.2 and 20 g/m.sup.2 results and/or that the aqueous composition is applied to the substrate such that the layer has a wet film thickness between 1 m and 1000 m.

7. The method according to claim 1, wherein the aqueous composition is applied to the substrate by means of an equalizing coating method blade and/or film press, and/or by means of a contour coating method.

8. The method according to claim 1, wherein the coated substrate is dried by infrared irradiation and/or by convection and/or under UV irradiation in step c).

9. The method according to claim 1, wherein a substrate is provided in step a), which includes a base material, the outside and/or inside of which is provided with a conditioning layer and/or a covering layer.

10. The method according to claim 1, wherein the substrate is coated with a further composition before step a) and/or after step c), wherein the further composition includes at least polyvinyl alcohol, has a solid content of at most 15% by wt. and is free of cross-linking agents.

11. A method for producing a coated packaging material, comprising at least the steps of: a) providing a substrate having a base material of cellulose, an outside to face away from a packaging good as well as an inside to face the packaging good, wherein the base material is coated or uncoated paper, coated or uncoated cardboard or coated or uncoated paperboard; b) coating the inside of the substrate with at least one layer of aqueous compositions including at least polyvinyl alcohol and a cross-linking agent and having a solid content between 3% by wt. and 25% by wt.; and adjusting a pH value of the aqueous composition to a value between 1 and 7 before applying the aqueous compositions to the substrate; c) drying the layer and cross-linking the polyvinyl alcohol with the aid of the cross-linking agent with formation of a barrier layer for hydrophobic compounds, wherein the cross-linking agent contributes to the formation of a three-dimensional network by reaction with polyvinyl alcohol; drying the substrate coated with the aqueous compositions to a residual humidity between 3% and 10% by weight in the base material; wherein the steps b) and c) are repeated to form two barrier layers; the two barrier layers including polyvinyl alcohols with different cross-linking levels and/or polyvinyl alcohols with different degrees of hydrolysis and/or polyvinyl alcohols cross-linked with different cross-linking agents than each other; and/or wherein the substrate after step c) is coated with a further composition, wherein the further composition includes at least polyvinyl alcohol, has a solid content of between 1% by wt. and 15% by wt. and is free of cross-linking agents.

12. The method according to claim 11, wherein the at least one layer of aqueous compositions have a solid content between 3% by wt. and 25% by wt., and/or a water content of at least 75% by wt.

13. The method according to claim 11, wherein, as the cross-linking agent, at least one olefinically saturated and/or unsaturated compound with at least one functional group selected from aldehyde, carboxylic acid, acid anhydride and amino group, and/or ferric chloride and/or an alkyl orthosilicate, in particular tetraethyl orthosilicate, and/or a urea formaldehyde resin is used.

14. The method according to claim 11, wherein the at least one layer of aqueous compositions include between 0.01 and 55 parts by weight of cross-linking agent related to 100 parts by weight of polyvinyl alcohol and/or between 1 and 60 parts by weight of a filler and/or a pigment related to 100 parts by weight of polyvinyl alcohol.

15. The method according to claim 14, wherein the filler and/or the pigment are acid-stable and/or have at least substantially spherical and/or platelet-shaped particle geometries.

16. The method according to claim 11, wherein the at least one layer of aqueous compositions are applied to the substrate such that an area-related dry mass between 1 g/m.sup.2 and 20 g/m.sup.2 results and/or that the at least one layer of aqueous compositions are applied to the substrate such that the layer has a wet film thickness between 1 m and 1000 m.

17. The method according to claim 11, wherein the at least one layer of aqueous compositions are applied to the substrate (12) by means of an equalizing coating method, and/or by means of a contour coating method.

18. The method according to claim 11, wherein the coated substrate is dried by infrared irradiation and/or by convection and/or under UV irradiation in step c).

19. The method according to claim 11, wherein a substrate is provided in step a), which includes a base material (14), the outside and/or inside of which is provided with a conditioning layer and/or a covering layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features of the invention are apparent from the claims, the embodiments as well as based on the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the embodiments are usable not only in the respectively specified combination, but also in other combinations without departing from the scope of the invention. There shows:

(2) FIG. 1 a schematic lateral sectional view of a packaging material according to the invention according to an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

(3) FIG. 1 shows a schematic lateral sectional view of a packaging material 10 according to the invention according to an embodiment. The packaging material includes a substrate 12 composed of a base material 14 and having an outside 16 to face away from a packaging good as well as an inside 18 to face the packaging good. The base material 14 is cardboard with an area-related mass of 400 g/m.sup.2 in the present embodiment. On the inside 18 of the substrate 12, a layer system 20 is formed, which is produced by generating a first barrier layer 22a, a second barrier layer 22b as well as a layer 24 functioning as a covering layer. The barrier layers 22a, 22b include cross-linked polyvinyl alcohol. The barrier layer 22a moreover includes platelet-shaped or spherical particles or mixtures thereof as a filler and/or pigment. The barrier layers 22a, 22b make impossible or prevent thereby at least largely the migration of hydrophobic compounds through the layer system 20. Therein, the cross-linking of the polyvinyl alcohol described in more detail below ensures increased mechanical stability and prevents swelling of the barrier layers 22a, 22b if they come in contact with humidity.

(4) As fillers and/or pigments, basically, organic, inorganic as well as organic-inorganic modified particles are suitable, which are equipped with or without swelling power in water. In the present embodiment, the barrier layer 22a includes kaolin. Therein, kaolin offers the advantage that it is acid-stable and does not swell in water. Moreover, the used kaolin is composed of platelet-shaped particles, which form a mechanical barrier and hereby additionally impede or make impossible the migration of compounds through the barrier layer 22a. In contrast, the second barrier layer 22b is composed exclusively of cross-linked polyvinyl alcohol, wherein polyvinyl alcohols with different degrees of hydrolysis and polymerization are used and have been cross-linked with different cross-linking agents for producing the two barrier layers 22a, 22b. However, of course, the two barrier layers 22a, 22b can basically also include the same cross-linked polyvinyl alcohol. In contrast, the terminating layer 24, which is in contact with the packaging good in a later packaging formed of the packaging material 10 is composed of non-cross-linked polyvinyl alcohol and in particular increases the flexibility and extensibility of the layer system 20. Alternatively or additionally, it can be provided that the layer 24 is immediately formed on the substrate 12 and/or between the barrier layers 22a, 22b.

(5) The outside 16 of the substrate 12 is not coated in the shown embodiment. However, basically, one or more layers can also be provided on the outside 16 in order to achieve certain properties of the packaging material 10, for example a better printability or a gas and/or humidity barrier effect.

(6) In the following, various embodiments for the production of the packaging material 10 according to the invention with barrier properties with respect to nonpolar chemical compounds are cited.

1. Production of an Aqueous Polyvinyl Alcohol Solution

(7) If the polyvinyl alcohol is not already present dissolved in water, the production of the polyvinyl alcohol solution is performed as follows:

(8) First, a defined amount of cold water is presented. Subsequently, a defined amount of an optionally finely ground polyvinyl alcohol powder with a degree of hydrolysis, which is preferably between 80% and 99.9%, is stirred in with vigorous stirring (2000 rpm) at a temperature of 75 C. to 80 C. within 30 to 45 minutes with an intensive or dissolver stirrer. The dissolution process is terminated as soon as the solution is clear. The still warm solution is cooled to 25 C. Before further use, the exact solid content of the solution is determined for example by means of a thermobalance and optionally adjusted to a value between 5% by wt. and 15% by wt. The determined or adjusted solid content serves as a basis for the further course of the procedure and in particular for determining the layer thickness to be applied to the substrate as well as for amount determination of the cross-linking reagents to be added. The pH value of the obtained polyvinyl alcohol solution is neutral.

(9) After the cooling operation is terminated, the pH value of the freshly prepared polyvinyl alcohol solution is adjusted if needed. The adjustment of the pH value is effected in a manner known per se by addition of a suitable acid or base. For example, mineral acids such as concentrated hydrochloric acid or bases such as sodium hydroxide are suitable.

2. Production of an Aqueous Composition

2.1 Glyoxal as a Cross-Linking Agent

(10) To the polyvinyl alcohol prepared according to item 1., a 40% glyoxal solution is added at room temperature (25 C.) with vigorous stirring within about 15 minutes with simultaneous adjustment of the pH value of the solution to pH=3 to obtain an aqueous composition for coating the substrate 12. The amount of the added glyoxal is between 5 and 40% by wt. related to 100% by wt. of polyvinyl alcohol.

(11) After 15 minutes, the aqueous composition is degassed at an initial negative pressure of 200 mbar, which is slowly increased to 500 mbar to 600 mbar in the following. If the vacuum is further increased (e.g. to over 800 mbar, i.e. to a pressure of about 200 mbar), the water begins to boil and condensate deposits on the walls of the vacuum container. Finally, the aqueous composition is degassed at a pressure of about 100 mbar without further stirring.

(12) After termination of the degassing, the aqueous composition can be applied to the substrate 12, wherein the polyvinyl alcohol is cross-linked by the glyoxal.

2.2 Adipic Acid (AS), Glutaric Acid (GS) and/or Maleic Acid (MS) as Cross-Linking Agents

(13) The addition of the mentioned dicarboxylic acids can be divided in two sub-categories:

(14) The AS and GS belong to the group of the saturated dicarboxylic acids, wherein the AS is poorly soluble (24 g/l) and the GS is easily soluble (640 g/l) in cold water (20 C. The condensation reactions of both acids with polyvinyl alcohol are preferably catalytically supported by addition of mineral acids (e.g. hydrochloric acid) by adjusting the pH value of the aqueous composition to pH=3.

(15) The MS is an unsaturated dicarboxylic acid, which is very well soluble in water (788 g/l, 20 C.) and reacts highly acidic in aqueous solution. The MS is present in cis form. By UV radiation and longer heating at 150 C., it converts to the trans form (fumaric acid), which optionally can be taken into account in the cross-linking reaction. In use of the MS, therefore, additional pH adjustment of the aqueous composition is usually not required. The pH value is between 1.6 and 3.2 according to the used amount, depending on the amount of MS dissolved in the aqueous polyvinyl alcohol solution. The added overall amount of dicarboxylic acid is basically between 5 and 25% by wt. related to 100% by wt. of polyvinyl alcohol.

(16) The aqueous composition including polyvinyl alcohol and one or more of the mentioned dicarboxylic acids, is subsequently heated to 70 C., 15 minutes intensively stirred at 70 C., and then cooled to 25 C. Now, the pH value can be adjusted corresponding to the respectively employed dicarboxylic acid if needed. After pH value adjustment of the aqueous composition, preferably, the above described degassing step is effected.

2.3 Ferric Chloride (FeCl3) as a Cross-Linking Agent

(17) The addition of FeCl.sub.3 to the polyvinyl alcohol solution is preferably effected at 25 C. with vigorous stirring. FeCl.sub.3 can be present as a solid or already dissolved in water. The added amount of FeCl.sub.3 is between 1 and 15% by wt. related to 100% by wt. of polyvinyl alcohol. The mixing time is 15 minutes at 25 C. A pH value adjustment is not required if further cross-linking agents are not provided. Before applying to the substrate 12 to be coated, here too, a degassing step is advisable.

2.4 Polyacrylates as a Cross-Linking Agent

(18) Within the scope of the present invention, by polyacrylates, derivatives of the polyacrylic acid with the general formula

(19) ##STR00002##
are understood, wherein R denotes hydrogen or unsubstituted or substituted alkyl group, in particular methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl and/or tert-butyl. Preferably, polyacrylic acids in the molecular weight range of 2000 to 1500000 g/mol, in particular from 50000 to 500000 g/mol, are used, since this class is comparatively well soluble in cold water (20 C.). The added amount of polyacrylic acid is between 0.01 and 10% by wt. The mixing time is approximately 15 min. at 25 C. to 60 C. The pH value of the mixture can be increased if needed by addition of basic additives such as KOH, NaOH or the like. Before application, a degassing step is advisable.

2.5 Mixtures of Polyvinyl Alcohol with the Cross-Linking Agents Described Under 2.1 to 2.4

(20) The above mentioned cross-linking agent can basically be arbitrarily mixed, e.g. FeCl.sub.3 with di- and/or polycarboxylic acids and/or dialdehydes.

2.6 Incorporation of Fillers and/or Pigments

(21) Fillers and/or pigments with preferably spherical and/or platelet-shaped particles are added to the aqueous composition in a weight percent range of 5-60% related to 100% by wt. of polyvinyl alcohol (PVOH). Basically, organic, inorganic and/or organic-inorganic modified particles equipped with or without swelling power in water are suitable as fillers and/or pigments.

(22) Spherical particles such as silica particles with specific surfaces of 200-500 g/m.sup.2 can be employed. The silica particles are present in solid form or in aqueous dispersions. The size of the particles is between 5 and 10 nm. Unmodified as well as (hydrophilic) modified particles can be employed. Particles are added in the range of 10-60% related to 100% by wt. of PVOH.

(23) Alternatively, mixtures of spherical and platelet-shaped particles can be added. Platelet-shaped particles such as kaolins and sheet silicates (partially or completely anodized) can be employed unmodified or modified. Sheet silicates can be functionalized with alkoxy silanes, which carry amino, epoxy or mercapto groups. Besides kaolin, montmorillonite, bentonite, vermiculite, hectorite, saponite, laponite etc. or mixtures thereof can be employed. In employment of kaolin, a so-called hyperplaty, nano-scaled type with a shape factor of at least 40 is used. A shape factor between 60 and 100 and a size of max. 1 m are preferred.

(24) Further fillers such as natural and/or synthetic aluminosilicates with defined pore volumes of 3-10 , 8-13 and 10-15 or more angstrom can be added alone or in combination with spherical or platelet-shaped fillers or added as mixtures from them.

(25) Furthermore, natural organic fillers such as cellulose fibers and/or cellulose regenerate fibers, in particular micro- and nanofibrilled celluloses, can be used as fillers. These fillers can be used alone or in combination with one or more other fillers.

(26) In a further development, it is provided that the aqueous composition is basically formed free of boron compounds such as for example borax, free of silicates swellable in water, in particular of swellable sheet silicates, and/or free of hydrogen sulfite adducts in order to ensure a high chemical and mechanical stability with high food compatibility of the resulting barrier layer 22 at the same time.

3. Application of the Aqueous Composition

(27) An aqueous composition prepared according to the above described recipes is applied to the coated or preferably uncoated substrate 12. The base material 14 of the substrate 12 is composed of cardboard and has a surface weight between 200 g/m.sup.2 and 800 g/m.sup.2.

3.1 Application Possibilities and Layer Arrangement

3.1.1 One-Layer Wet Film Application

(28) For producing a single barrier layer 22, the substrate 12 can be coated with aqueous compositions consisting of: polyvinyl alcohol+glyoxal; polyvinyl alcohol+dicarboxylic acids; polyvinyl alcohol+polyacrylic acids; polyvinyl alcohol+dicarboxylic acids+fillers and/or pigments; polyvinyl alcohol+polyacrylic acids+dicarboxylic acids+fillers and/or pigments; polyvinyl alcohol+FeCl.sub.3; or polyvinyl alcohol+mixture of different cross-linking agents; polyvinyl alcohol+mixture of different cross-linking agents+fillers and/or pigments;
wherein the wet film application can be 3 to 15 g/m.sup.2. Therein, it is to be emphasized that the substrate 12 alternatively can basically already consist of a base material 14 coated with non-cross-linked polyvinyl alcohol, wherein fillers and/or pigments can be admixed with the non-cross-linked polyvinyl alcohol if needed.

(29) Further embodiments for the aqueous composition usable within the scope of the invention are indicated in table 1. Therein, it is again to be emphasized that the solid content of each aqueous composition is at most 25% by wt. inclusive possibly present fillers and/or pigments. Preferably, the solid content of each aqueous composition is at most 15% if the aqueous composition is formed free of fillers and/or pigments. The amounts of polyvinyl alcohol indicated in table 1 are always to be considered as 100 parts. The amount of the cross-linking agent is always related to the 100 parts of polyvinyl alcohol.

(30) TABLE-US-00001 TABLE 1 Ingredients of the aqueous composition Main component Parts Parts Parts PVOH Degree of hydrolysis: 80->99% 100 100 100 Cross-linking Parts- Parts- agent/compound Chem. Structural min. max. Parts class compound formula number number preferred Dialdehydes unsaturated aldehydes Glyoxal 1 50 10-30 Glutaraldehyde 1 50 5-25 Acrylaldehyde 1 50 5-20 Polycarboxylic acids, unsaturated polycarboxylic acids, carboxylic acid esters Malonic acid 1 50 10-30 Glutaric acid 1 50 10-30 Adipic acid 1 50 10-30 Citric acid 0 1 50 2-10 Butane tetracarboxylic acid anhydride 0.1 25 1-10 Acrylic acid 0.1 25 1-10 Methacrylic acid 0.1 25 1-10 Maleic acid 0.1 25 1-10 Methacryl methyl ester 0.1 25 5-20 Hydroxyethyl methacrylate 0.1 25 5-20 FeCl.sub.3 FeCl.sub.3 0.1 20 1-10 Silanes TEOS 0.1 10 1-10 Urea formaldehyde 0.1 20 1-10 resin (e.g. Urecoll) Polyacrylic acid 0.01 25 0.1-10

3.1.2 Multi-Layer Application

(31) On demand, multi-layer layer systems 20 with two, three, four or five consecutively applied barrier layers 22 can be produced. An aqueous polyvinyl alcohol solution without cross-linking agent can also be used as a first conditioning streak or as a primer in this case. Alternatively or additionally, the non-cross-linked polyvinyl alcohol layer can be applied between two barrier layers 22 and/or as a terminating layer 24 as shown in FIG. 1. The non-cross-linked or cross-linked polyvinyl alcohol layer can be filled with fillers and/or pigments. The dry weight of each layer 24 and/or barrier layer 22 in turn can be 3 to 15 g/m.sup.2.

3.2 Application Systems

(32) The layer systems 20 described under 3.1.1. and 3.1.2. can be applied with application tools usual in the coating and paper industry by means of spraying, coating with doctor blade, casting or an equivalent contour coating method. Suitable parameter values are for example:

(33) Rolling doctor blade: 10, 20, 40, 60, 80 m wet film thickness

(34) Film drawing frame: variable gap setting, 0-1000 m wet film thickness

(35) Film drawing frame: fixed gap: 60, 120 m wet film thickness

(36) These application tools are employed by means of a motor-controlled application system with a maximum speed of the substrate 12 of up to 1000 m/min for uniform application.

(37) Alternatively or additionally, a nozzle application system is used, which at the same time applies at least one barrier layer 22 or layer 24 and a maximum of four layers to the cardboard substrate 12 movable in horizontal direction. The mixing of the aqueous compositions can be effected in the nozzle chamber, in the nozzle gap (gap width e.g. 0.1-1.0 mm) or outside of the nozzle on the substrate 12. Wet film layer thicknesses above 200 m are possible with this application method. From the parameters of layer thickness and maximum speed of the linear drive, the required delivery amount of the aqueous composition results.

4. Drying and Cross-Linking the Wet Films by Means of IR Radiation (IR), Convection Drying (KV) and/or UV Radiation (UV)

(38) The solvent (water) of the aqueous composition applied to the substrate 12 is removed with infrared and/or convection driers. Both drier types can be used individually, collectively, successively or independently of each other. The drier temperatures of both dryer types can for example be chosen between 60 C. and 200 C. Supply and exhaust air, respectively, and temperature settings of the dryers or the dryer combination are preferably selected such that a bubble-free layer system 20 arises. A residual humidity of 5-7% by wt. in the substrate 12 can be taken as a criterion for the exact temperature setting.

(39) All of the barrier layers 22 or layers 24 are preferably first dried with IR and/or KV. In aqueous compositions containing dialdehydes and/or dicarboxylic acids, polyacids and/or mixtures thereof as cross-linking agents (see 2.1 to 2.5), the thus supplied heat is sufficient to virtually quantitatively perform the cross-linking of the polyvinyl alcohol.

(40) The cross-linking reaction with FeCl.sub.3 is a two-step process. After the at least predominant removal of the solvent, the at least largely dry coating is irradiated with UV light. Hereto, for example, a Hg vapor high-pressure lamp can be used. The exposure of the UV active polyvinyl alcohol layer takes approximately 10 s at a power of about 0.4 W/cm.sup.2 with an intensity specification of 75%.

(41) Basically, it is advisable to irradiate all of the aqueous compositions containing UV active cross-linking agents with UV light before, during and/or after thermal drying.

5. Examination Method

5.1 Measurement of the Barrier Effect with Respect to Hydrophobic Hydrocarbons

(42) The packaging material 10 shown in FIG. 1 was subjected to a migration examination with the food stimulant Tenax based on the test standards DIN EN 1186-13 and DIN EN 14338, wherein the Tenax was applied to the layer system 20 of the packaging material 10. After incubation of the migration formulation at a defined temperature and time, the migrated substances were eluted from Tenax by means of n-hexane and the mineral oil hydrocarbons were separated specifically in two different fractions by means of liquid chromatography, namely the fraction of the saturated (mineral oil saturated hydrocarbons, MOSH) and the fraction of the aromatic hydrocarbons (mineral oil aromatic hydrocarbons, MOAH). The two thus obtained fractions were analyzed by gas chromatography and acquired as a sum parameter, wherein deuterated n-nonadecane or diethyl naphthalene were employed for the evaluation of the signal area sums. With respect to the extractable starting amount of mineral oil hydrocarbons from the raw packaging material, which defines the sum of all of the components capable of migrating, less than 1% of the substances capable of migrating were detected in the Tenax eluate. The migration of the hydrophobic hydrocarbons is therefore prevented more than 99% and therefore is always below a value of 0.6 mg/kg of packaged food for mineral oils.

5.2 Layer Structure

(43) For characterizing the layer structure of the layer system 20, a semi-thin section was prepared, based on which the individual layers 22a, 22b and 24 were spectroscopically identified with an optical and an IR or Raman microscope.

6. Further Embodiments

(44) In the following, further embodiments for the packaging material 10 according to the invention are specified. Unless otherwise stated, the production was effected in the above described manner.

6.1. Example 1

(45) In the following, first, the production of a coated substrate 12 is explained:

(46) Base material 14: Cardboard with an area-related mass between 200 and 800 g/m.sup.2, preferably uncoated

(47) Composition (not cross-linking) for coating:

(48) aqueous polyvinyl alcohol solution (Elvanol 90-50 or Elvanol 85-82, Dupont or mixtures thereof) solid content: 10.00% by wt.
Coating the cardboard base material 14 with the composition (40-200 m wet film layer thickness)
Application method: doctor blade, airbrush, nozzle
Speed of the substrate 12: up to 1000 m/min
Drying: IR & convection until achieving 5-7% of residual humidity in the base material 14.

(49) The thus produced substrate 12 can be used as a starting material for the application of one or more barrier layers 22.

6.2. Example 2

(50) Base material 14: Cardboard with an area-related mass between 200 and 800 g/m.sup.2, preferably uncoated

(51) Aqueous composition (cross-linking):

(52) aqueous polyvinyl alcohol solution (Elvanol 90-50 or Elvanol 85-82, Dupont or mixtures thereof), pigments (according to item 2.5) as cross-linking agents, the cross-linking agents listed in item 3.1.1 or mixtures thereof are possible solid content: up to 25.00% by wt.
Coating the cardboard base material 14 with the aqueous composition (40-200 m wet film layer thickness)
Application method: doctor blade, airbrush, nozzle
Speed of the substrate 12: up to 1000 m/min
Drying: IR & convection until achieving 5-7% of residual humidity in the base material 14.

6.3. Example 3

(53) Base material 14: Cardboard with an area-related mass between 200 and 800 g/m.sup.2, preferably uncoated

(54) Composition (not cross-linking):

(55) aqueous polyvinyl alcohol solution (Elvanol 90-50 or Elvanol 85-82, Dupont or mixtures thereof) filled with pigments (cf. item 2.5) solid content: up to 25.00% by wt.
Coating the cardboard base material 14 or the substrate 12 with the composition (40-200 m wet film layer thickness)
Application method: doctor blade, airbrush, nozzle
Speed of the substrate 12: up to 1000 m/min
Drying: IR & convection until achieving 5-7% of residual humidity in the base material 14.

6.4. Example 4

(56) Base material 14: Cardboard with an area-related mass between 200 and 800 g/m.sup.2, preferably uncoated

(57) Composition (physically cross-linking):

(58) aqueous polyvinyl alcohol solution (Elvanol 90-50 or Elvanol 85-82, Dupont or mixtures thereof) filled with aluminosilicates and carboxymethyl cellulose solid content: 12% by wt.
Coating the cardboard base material 14 with the composition (40-200 m wet film layer thickness)
Application method: nozzle, one-layer application
Speed of the base material: up to 1000 m/min
Drying: IR & convection until achieving 5-7% of residual humidity in the cardboard.

6.5. Example 5

(59) Substrate 12: Cardboard with an area-related mass between 200 and 800 g/m.sup.2, coated or preferably uncoated

(60) Aqueous composition (thermally cross-linking or curing):

(61) aqueous PVOH solution, solid content 10% by wt. (Elvanol 85-82 or Elvanol 90-50 and mixtures thereof, Dupont), 100 parts maleic acid, p. a. (Sigma), 5 parts related to 100 parts of PVOH
Coating the substrate with the aqueous composition (1-layer application, 40-200 m wet film layer thickness)
Application method: nozzle, one-layer application
Speed of the substrate 12: up to 1000 m/min
Drying: IR & convection until achieving 5-7% of residual humidity in the base material 14.

6.6. Example 6

(62) Base material 14: Cardboard with an area-related mass between 200 and 800 g/m.sup.2, coated or preferably uncoated

(63) Aqueous composition (UV-curable):

(64) aqueous PVOH solution, solid content 10% by wt. (Elvanol 85-82 or Elvanol 90-50, and mixtures thereof, Dupont), 100 parts aqueous FeCl.sub.3 solution (Donau Chemie), solid content 46.33% by wt., 6.7 parts related to 100 parts of PVOH
Coating the substrate with the aqueous composition (1-layer application, 40-200 m wet film layer thickness)
Application method: nozzle, one-layer application
Speed of the base material: up to 1000 m/min
UV-curing with Hg vapor high-pressure lamp, 10 s exposure, 0.4 W/cm.sup.2 power

6.7. Example 7

(65) Base material 14: Cardboard with an area-related mass between 200 and 800 g/m.sup.2, coated or preferably uncoated

(66) Aqueous composition (thermally curing):

(67) aqueous PVOH solution, solid content 10% by wt. (PVOH-8582 or Elvanol 9050 and mixtures thereof, Dupont), 100 parts glyoxal (40% aqueous solution, BASF), 12.6 parts related to 100 parts of PVOH
Coating the substrate with the aqueous composition (1-layer application, 40-200 m wet film layer thickness)
Application method: nozzle, one-layer application
Speed of the base material: up to 1000 m/min
Drying: IR & convection until achieving 5-7% of residual humidity in the cardboard base material 14.

6.8. Example 8

(68) Base material 14: Paper with an area-related mass between 50 and 150 g/m.sup.2, coated or preferably uncoated

(69) Aqueous composition (thermally curing):

(70) aqueous PVOH solution, solid content 10% by wt. (PVOH-8582 or Elvanol 9050 or mixtures thereof, Dupont), 100 parts polyacrylic acid, 0.01-5.0 parts related to 100 parts of PVOH
Coating the substrate with the aqueous composition (1-layer application, 40-200 m wet film layer thickness)
Application method: nozzle, one-layer application
Speed of the base material: up to 1000 m/min
Drying: IR & convection until achieving 5-7% of residual humidity in the base material 14.

6.9. Example 9

(71) Base material 14: Cardboard with an area-related mass between 200 and 800 g/m.sup.2, coated or preferably uncoated

(72) Compositions: combination of example 1 and example 2, example 1 and example 3, example 1 and example 4, example 1 and example 5, example 1 and example 6, example 1 and example 7 or example 1 and example 8

(73) The coating of example 1 is carried as the lowermost layer on the base material, the coating according to the recipe from example 2, 3, 4, 5, 6, 7 or 8 and/or two- or three-fold combinations of these examples are applied thereon.

(74) Multi-layer application, each 80-200 m wet film layer thickness

(75) Speed of the base material: up to 1000 m/min

(76) Application method: doctor blade, nozzle

6.10. Example 10

(77) Base material: Cardboard with an area-related mass between 200 and 800 g/m.sup.2, coated or preferably uncoated

(78) Compositions:

(79) combination of 2 streaks (aqueous compositions) from example 1 and one streak from example 2 to example 8. The streak from example 1 is used as a conditioning and covering streak in this application in order to act leveling on the inside 18 of the substrate 12 and protecting on the outside 16 of the substrate 12 with respect to tension and compression (forces, which occur in grooving and stamping operations). The covering streak is easily printable and bondable.
Multi-layer application, each 80-200 m wet film layer thickness
Application method: doctor blade, nozzle
Speed of the base material: up to 1000 m/min
Drying: IR & convection until achieving 5-7% of residual humidity in the cardboard.

(80) The parameter values specified in the documents for defining process and measurement conditions for the characterization of specific properties of the inventive subject matter are to be considered as encompassed by the scope of the invention even within the scope of deviationsfor example due to measurement errors, system errors, weighing errors, DIN tolerances and the like.