MINERAL OIL BARRIER

Abstract

The present invention relates to packaging material comprising a plastic substrate comprising at least one surface, and a barrier layer for hydrophobic substances, wherein the barrier layer is in contact with the at least one surface of the plastic substrate, wherein the barrier layer comprises a copolymer, a surface-reacted calcium carbonate, and a mineral material selected from natural ground calcium carbonate and/or precipitated calcium carbonate, as well as a method for producing the same and its use.

Claims

1. A packaging material comprising a plastic substrate comprising at least one surface, and a barrier layer for hydrophobic substances, wherein the barrier layer is in contact with the at least one surface of the plastic substrate, and wherein the barrier layer comprises (I) a copolymer obtainable by emulsion polymerization of (i) one or more principal monomers selected from the group consisting of C.sub.1-C.sub.4 alkyl (meth)acrylates, and (ii) 0.1 to 5 wt.-% of one or more acid monomers, wherein the glass transition temperature T.sub.g of the copolymer is from −10 to 70° C., and the emulsion polymerization is carried out in an aqueous medium in the presence of at least one carbohydrate compound, (II) a surface-reacted calcium carbonate, wherein the surface-reacted calcium carbonate is a reaction product of natural ground calcium carbonate or precipitated calcium carbonate with carbon dioxide and one or more H.sub.3O.sup.+ ion donors, wherein the carbon dioxide is formed in situ by the H.sub.3O.sup.+ ion donors treatment and/or is supplied from an external source, and (III) a mineral material selected from natural ground calcium carbonate and/or precipitated calcium carbonate, wherein the weight ratio of the surface-reacted calcium carbonate to the mineral material is from 1:10 to 1:0.01.

2. The packaging material of claim 1, wherein the plastic substrate is a plastic film, a plastic sheet, a plastic foil, a semi-rigid plastic container, or a rigid plastic container.

3. The packaging material of claim 1, wherein the plastic substrate comprises a polyethylene, a polypropylene, a polyester, a polyvinylchloride, a poly(tetrafluoro ethylene), a polyalkylene terephthalate, a polyalkylene furandicarboxylate, a polycarbonate, a polystyrene, a melamine formaldehyde, a polylactic acid, a plastarch material, a polyhydroxyalkanoate, a polybutylene succinate, a polycaprolactone, a polyanhydride, a polyvinyl alcohol, a cellophane, a cellulose ester, a silicone, or a mixture thereof.

4. The packaging material of claim 1, wherein the glass transition temperature T.sub.g of the copolymer is from 0 to 60° C.

5. The packaging material of claim 1, wherein the barrier layer comprises the copolymer in an amount from 40 to 99.9 wt.-%, based on the total weight of the barrier layer.

6. The packaging material of claim 1, wherein the copolymer is obtainable by emulsion polymerization of (i) one or more principal monomers selected from the group consisting of C.sub.1-C.sub.4 alkyl (meth)acrylates, (ii) 0.1 to 5 wt.-% of one or more acid monomers, based on the total weight of all monomers, (iii) 0 to 20 wt.-% of acrylonitrile, based on the total weight of all monomers, and (iv) 0 to 10 wt.-% of further monomers other than the monomers (i) to (iii), based on the total weight of all monomers.

7. The packaging material of claim 6, wherein the one or more principal monomers (i) are selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, and mixtures thereof, and/or the one or more acid monomers (ii) are selected from acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and mixtures thereof, and/or, the further monomers (iv) are selected from the group consisting of C.sub.5-C.sub.20 alkyl (meth)acrylates, vinyl esters of carboxylic acids comprising up to 20 carbon atoms, vinylaromatics having up to 20 carbon atoms, ethylenically unsaturated nitriles other than acrylonitrile, vinyl halides, vinyl ethers of alcohols comprising 1 to 10 carbon atoms, aliphatic hydrocarbons having 2 to 8 carbon atoms and one or two double bonds, and mixtures thereof.

8. The packaging material of claim 1, wherein the surface-reacted calcium carbonate has a specific surface area of from 20 m.sup.2/g to 200 m.sup.2/g, measured using nitrogen and the BET method according to ISO 9277.

9. The packaging material of claim 1, wherein the surface-reacted calcium carbonate is in form of particles having a volume median particle size d.sub.50 from 0.1 to 50 μm.

10. The packaging material of claim 1, wherein the mineral material is natural ground calcium carbonate.

11. The packaging material of claim 1, wherein the mineral material is in form of particles having a weight median particle size d.sub.50 from 0.01 to 15 μm.

12. The packaging material of claim 1, wherein the barrier layer comprises the combination of the surface-reacted calcium carbonate and the mineral material in an amount of from 0.1 to 60 wt.-%, based on the total weight of the barrier layer.

13. The packaging material of claim 1, wherein the weight ratio of the surface-reacted calcium carbonate to the mineral material is from 1:10 to 1:1.

14. The packaging material of claim 1, wherein the barrier layer has a layer weight of least 2 g/m.sup.2.

15. The packaging material of claim 1, wherein the hydrophobic substances comprise mineral oils, plasticizers, hydrophobic contaminants, bisphenol A (BPA), bis (2-ethylhexyl) phthalate (DEHP), nonylphenol monoethoxylate (NMP), nonylphenol diethoxilate (NDP), diisopropylnaphthalene, mineral oil saturated hydrocarbons (MOSH), polyolefine oil saturated hydrocarbons (POSH), mineral aromatic hydrocarbons (MOAH), alkanes, naphthenes, or mixtures thereof.

16. The packaging material of claim 1, wherein the packaging material is a food packaging, a medical device packaging, a pharmaceutical packaging, a flexible packaging, a pallet, a shrink wrap, a plastic wrap, an overwrap, a freezer bag, a vacuum bag, a fast food wrapper, a food bag, a snack bag, a grocery bag, an ovenable food container, a cup, a tray, a box, a folding box, a clamp, a can, a bottle, a liquid container, a beverage container, a rigid medical thermoform, a protective medical packaging, a pouch, a bag, a tray, a lid, a blister pack, a skin pack, or an insert.

17. A method for producing a packaging material, comprising the steps of: A) providing a plastic substrate comprising at least one surface, B) providing a liquid barrier layer composition, C) applying the liquid barrier layer composition onto the at least one surface of the plastic substrate to form a barrier layer for hydrophobic substances, and D) drying the barrier layer, wherein the liquid barrier layer composition comprises (I) a copolymer obtainable by emulsion polymerization of (i) one or more principal monomers selected from the group consisting of C.sub.1-C.sub.4 alkyl (meth)acrylates, and (ii) 0.1 to 5 wt.-% of one or more acid monomers, wherein the glass transition temperature T.sub.g of the copolymer is from −10 to 70° C., and the emulsion polymerization is carried out in an aqueous medium in the presence of at least one carbohydrate compound, (II) a surface-reacted calcium carbonate, wherein the surface-reacted calcium carbonate is a reaction product of natural ground calcium carbonate or precipitated calcium carbonate with carbon dioxide and one or more H.sub.3O.sup.+ ion donors, wherein the carbon dioxide is formed in situ by the H.sub.3O.sup.+ ion donors treatment and/or is supplied from an external source, and (III) a mineral material selected from natural ground calcium carbonate and/or precipitated calcium carbonate, wherein the weight ratio of the surface-reacted calcium carbonate to the mineral material is from 1:10 to 1:0.01.

18. The method of claim 17, wherein in step C) the liquid barrier layer composition is applied using a spray technique, a printing technique, spray coating, screen printing, flexographic printing, inkjet printing, offset printing, rotogravure printing, tampon printing, and combinations thereof.

19. The method of claim 17, wherein step C) is carried out at a surface temperature of the plastic substrate from 10 to 100° C.

20. The method of claim 17, wherein the liquid barrier layer composition of step B) is an aqueous liquid barrier layer composition.

21. The packaging material of claim 1, wherein the packaging material is suitable for use in food packaging applications, medical device packaging applications, or pharmaceutical packaging applications.

22. A barrier layer, wherein the barrier layer is suitable for use in a plastic substrate, wherein the barrier layer prevents migration of hydrophobic substances, and wherein the barrier layer comprises (I) a copolymer obtainable by emulsion polymerization of (i) one or more principal monomers selected from the group consisting of C.sub.1-C.sub.4 alkyl (meth)acrylates, and (ii) 0.1 to 5 wt.-% of one or more acid monomers, wherein the glass transition temperature T.sub.g of the copolymer is from −10 to 70° C., and the emulsion polymerization is carried out in an aqueous medium in the presence of at least one carbohydrate compound, (II) a surface-reacted calcium carbonate, wherein the surface-reacted calcium carbonate is a reaction product of natural ground calcium carbonate or precipitated calcium carbonate with carbon dioxide and one or more H.sub.3O.sup.+ ion donors, wherein the carbon dioxide is formed in situ by the H.sub.3O.sup.+ ion donors treatment and/or is supplied from an external source, and (III) a mineral material selected from natural ground calcium carbonate and/or precipitated calcium carbonate, wherein the weight ratio of the surface-reacted calcium carbonate to the mineral material is from 1:10 to 1:0.01.

Description

DESCRIPTION OF THE FIGURES

[0214] FIG. 1 is a photograph of the HpVTR cup that was used for the migration barrier performance analysis.

[0215] FIG. 2 is a photograph of the punch used for cutting the packaging material samples for the migration barrier performance analysis.

EXAMPLES

I. Measurement Methods

[0216] In the following, measurement methods implemented in the examples are described.

Particle Size Distribution (Mass % Particles with a Diameter <X), d.sub.50 (Wt) Value (Weight Median Grain Diameter) and d.sub.98(Wt) Value of a Particulate Material:

[0217] The d.sub.50(wt) and d.sub.98(wt) values were measured using a Sedigraph 5120 from the company Micromeritics, USA. The method and the instrument are known to the skilled person and are commonly used to determine grain size of fillers and pigments. The measurements were carried out in an aqueous solution comprising 0.1 wt.-% Na.sub.4P.sub.2O.sub.7. The samples were dispersed using a high speed stirrer and supersonics.

Particle Size Distribution (Volume % Particles with a Diameter <X), d.sub.50(Vol) Value (Volume Median Grain Diameter) and d.sub.98(Vol) Value of a Particulate Material:

[0218] Volume median grain diameter d.sub.50(vol) was evaluated using a Malvern Mastersizer 2000 Laser Diffraction System. The d.sub.50(vol) or d.sub.98(vol) value, measured using a Malvern Mastersizer 2000 Laser Diffraction System, indicates a diameter value such that 50% or 98% by volume, respectively, of the particles have a diameter of less than this value. The raw data obtained by the measurement was analysed using the Mie theory, with a particle refractive index of 1.57 and an absorption index of 0.005.

Solids Content of an Aqueous Suspension

[0219] The suspension solids content (also known as “dry weight”) was determined using a Moisture Analyser MJ33 from the company Mettler-Toledo, Switzerland, with the following settings: drying temperature of 160° C., automatic switch off if the mass does not change more than 1 mg over a period of 30 s, standard drying of 5 to 20 g of suspension.

Specific Surface Area (SSA)

[0220] The specific surface area was measured via the BET method according to ISO 9277 using nitrogen, following conditioning of the sample by heating at 250° C. for a period of 30 minutes. Prior to such measurements, the sample was filtered within a Büchner funnel, rinsed with deionised water and dried overnight at 90 to 100° C. in an oven. Subsequently, the dry cake was ground thoroughly in a mortar and the resulting powder placed in a moisture balance at 130° C. until a constant weight is reached.

Barrier Performance Analysis

[0221] The barrier performance was evaluated by a modified version of the n-hexan vapour transmission rate test.

[0222] In order to improve the safety at work the testing solvent of n-hexane was replaced by n-heptane, called in the following heptane vapour transmission rate (HpVTR) test. The n-heptane used in the following experiments is commercially available from Merck KGaA, Darmstadt, Germany.

[0223] The gravimetric method serves to determine the HpVTR of materials with planar shape using a gastight cup (e.g. a metal chamber) and a sealable closure which is fixable. The closure itself has a defined opening. The material to be tested was put between the cup (see FIG. 1) and the closure, provided by suitable gaskets on both sides (used testing fluid may not affect the material quality of the gaskets by any means).

[0224] A defined volume of n-heptane (9 ml) was filled into the evaporation chamber. The quantity of n-heptane vapour that passed under controlled conditions through the exposed surface area of a barrier sample was measured on a defined time scale, namely, at one, four, eight, and 24 hours.

[0225] The most convenient way to prepare the barrier samples with a diameter of 10.0 cm was by using a template or a punch (as e.g. can be seen in FIG. 2). Prior to the test it was imminent to check the samples on surface defects like specks, crease, holes or similar irregularities. In order to gain a representative value at least three replicates per trial point were measured.

[0226] Necessary devices to conduct the HpVTR-test were a balance with a weighting accuracy of 0.1 or 1 mg and an evaporation chamber.

[0227] The test was performed in a climate controlled environment at 23° C., 50% humidity in a laboratory hood. The container was filled with n-heptane, sealed and immediately weighed, then subsequently re-weighed after one, four, eight, and 24 hours.

[0228] The data was collected as a weight loss from the starting weight, which is then calculated as loss of weight per area and time e.g. as [g/m.sup.2/d]. The heptane vapour transmission rate (HpVTR) of interest was calculated once a steady state of transmission was achieved. For most packaging materials tested it can be observed that steady state is reached in between 4 hours and 1 day.

[0229] After reaching aforementioned steady state conditions, a stable and reproducible level of the heptane vapour transmission rate (HpVTR) can be measured.

Weight Analysis

[0230] The weight of the evaporation chambers within the HpTVR evaluation was determined with a lab scale an accuracy of +/−0.0001 g). In this case the lab balance “Mettler AE260 Delta Range” from Mettler Toledo (Schweiz) AG, Nanikon, Switzerland was used.

Thickness Analysis

[0231] The thickness of the samples was measured according “Thickness” (DIN EN 20 534). The samples were conditioned for 48 hours. The thickness was determined by using a micrometer with a test pressure of 10 N/cm.sup.2. The test result was found by taking the average of 10 measurements. The measured thickness value is indicated in μm. For this purpose the thickness measuring instrument “LTM” from the company ABB Automation, Mannheim, Germany was used.

II. Materials

Substrate

[0232] BOPP: Biaxially oriented polypropylene film, translucent, thickness 20 μm, corona surface treated and having a surface tension of 40 mN/m (available from Jakob Benn & Söhne GmbH, Hanau, Germany).

[0233] PE: Polyethylene film, translucent, thickness 40 μm, corona surface treated and having a surface tension of 40 mN/m (available from Constantia Folien+Druck GmbH, Fernwald-Steinbach, Germany).

Surface-Reacted Calcium Carbonate (SRCC)

[0234] SRCC: Surface-reacted calcium carbonate that is commercially available from Omya AG, Switzerland. SRCC has a rose type structure and the following properties: d.sub.50(vol)=1.3 μm; d.sub.98(vol)=5 μm; BET SSA=45 m.sup.2/g; The intra-particle intruded specific pore volume is 0.18 cm.sup.3/g (for the pore diameter range of 0.004 to 0.09 μm).

Mineral Material (MM)

[0235] MM: Natural ground calcium carbonate (marble): d.sub.50(wt)=1.5 μm; d.sub.98(wt)=10 μm; solids content 78 wt.-% (available from Omya AG, Switzerland).

Copolymer

[0236] The copolymer used in the following experiments was prepared according to Example 4 of WO 2013/083504 A1.

[0237] A reactor was purged with nitrogen and 427.1 g of demineralized water and maltodextrin (C Dry MD 01915 (94.7% strength); Cargill) was added in an amount of 30 pphm (weight parts per hundred weight parts of monomers). The mixture in the initial charge was heated to 86° C. Then, 3.2 g of sodium peroxodisulphate (7% strength) were added before stirring for 5 minutes. The emulsion feed consisting of 180.0 g of water, 20.0 g of emulsifier (Dowfax® 2A1, 45% strength) and 450.0 g of a monomer mixture of 55 wt.-% ethyl acrylate, 44 wt.-% methyl methacrylate, and 1 wt.-% acrylic acid was metered into the reactor over 2 hours. Concurrently with the emulsion feed the initiator feed was started (12.9 g of sodium peroxodisulphate, 7% strength) and likewise metered in over 2 hours. After the emulsion feed has ended, the system was allowed to polymerize for 45 min. The reactor was then cooled down to room temperature.

[0238] The resulting dispersion had a solids content of 47 wt.-% and the obtained polymer had a T.sub.g of 30° C.

Defoamer

[0239] The defoamer “Foamaster® WO 2310” used in the following experiments is commercially available from BASF, Ludwigshafen, Germany. The formulation is based on white oil and non-ionic surfactants.

Rheology Modifier

[0240] The Rheology modifier “Sterocol FS” used in the following experiments is commercially available from BASF, Ludwigshafen, Germany.

III. Experiments

Sample Preparation

[0241] The performance of the prepared barrier layers against the migration of mineral oils was tested by the n-heptane vapour transmission rate (HpVTR) test comparing the loss of testing liquid.

[0242] Two different barrier layer A and B were tested:

[0243] Composition A: 80 wt.-% copolymer, 16 wt.-% MM, 4 wt.-% SRCC, 0.2 wt.-% defoamer, and 0.15 wt.-% rheology modifier, wherein the wt.-% is based on the total weight of composition A.

[0244] Composition B: 40 wt.-% copolymer, 48 wt.-% MM, 12 wt.-% SRCC, 0.2 wt.-% defoamer, and 0.15 wt.-% rheology modifier, wherein the wt.-% is based on the total weight of composition B.

[0245] The corresponding liquid barrier layer compositions were prepared as follows:

[0246] In a 2 litres beaker, the copolymer dispersion was provided at a pH of 8.5, which was adjusted using a 30% NaOH solution. Subsequently, the mixture of surface-reacted calcium carbonate and mineral material was added under vigorous stirring at 500 rpm for 10 min with a Pendraulik laboratory dissolver of the LD 50 type, from Pendraulik GmbH, Springe, Germany.

[0247] Finally, the defoamer and the rheology modifier were incorporated.

[0248] For continuous adding of 0.2 parts (active substance on final dry product) of the defoamer over a period of one minute, the dissolver was set on 930 rpm. At the same stirring speed the blend was homogenized for a period of 1 min after dosage.

[0249] The rheology modifier was added in an amount of 0.15 parts (active substance on final dry product) over a time span of one minute and 930 rpm and homogenized for 2 min at the same speed.

[0250] The resulting composition A was flexo-printed on the plastic substrates with help of the laboratory printing machine “testacolor tfm-157-2” from the company Norbert Schlafli Maschinen, Zofingen, Switzerland.

[0251] The liquid barrier layer compositions were applied by means of two identical printing units, if not otherwise indicated.

[0252] Each of the two printing units was equipped by:

[0253] Anilox roll from Praxair Surface Technologies S.A., Meyrin, Switzerland, with the following general specifications: [0254] Screen: 120 lines/cm [0255] Screen angel: 60° [0256] URMI volume: 15.2 cm.sup.3/m.sup.2

[0257] Flexo sleeve “WS 746 70” from Felix Böttcher GmbH & Co. KG, Cologne, Germany, with the following general specifications: [0258] Material: EPDM (ethylene-propylene-diene-monomer) [0259] Material density: 1.11 g/cm.sup.3 [0260] Hardness Shore A: 70

[0261] The laboratoy print test machine “testacolor tfm-157-2” was designed with the focus to generate results in lab-scale correlating to printing presses in production scale. Solely, the print speed of the lab machine differed significantly.

[0262] The applied quantity of the liquid barrier layer compositions from an anilox roll via the blanket finally to the substrates depended on various factors. Usually, a transfer rate of approximately 50% from the anilox roll to the sleeve and approximately 40% to the substrate can be expected for the first print unit, whereas the transfer to the substrate in the second print unit is typically lower.

TABLE-US-00001 TABLE 1 Printing conditions. BOPP PE Solids [%] 52.0% Solids [%] 52.0% Density [g/cm.sup.3] 1.17 Density [g/cm.sup.3] 1.17 1st Print Unit 1st Print Unit Anilox reel Anilox reel Volume [g/cm.sup.3] 15.2 Volume [g/cm.sup.3] 15.2 Transfer Rate [%] 50.0% Transfer Rate [%] 50.0% Sleeve Sleeve Transfer Rate [%] 37.0% Transfer Rate [%] 60.0% Application Weight [g/m.sup.2] 1.7 Application Weight [g/m.sup.2] 2.8 Film Thickness [μm] 1.5 Film Thickness [μm] 2.4 2nd Print Unit 2nd Print Unit Anilox reel Anilox reel Volume [g/cm.sup.3] 15.2 Volume [g/cm.sup.3] 15.2 Transfer Rate [%] 50.0% Transfer Rate [%] 50.0% Sleeve Sleeve Transfer Rate [%] 30.0% Transfer Rate [%] 3.0% Application Weight [g/m.sup.2] 1.4 Application Weight [g/m.sup.2] 0.1 Film Thickness [μm] 1.2 Film Thickness [μm] 0.1 Final Product Final Product Application Weight [g/m.sup.2] 3.1 Application Weight [g/m.sup.2] 2.9 Film Thickness [μm] 2.6 Film Thickness [μm] 2.5

[0263] With help of said printing machine a homogeneous, flawless and continuous film of the liquid barrier layer composition was applied on the plastic substrates.

[0264] Alternatively, the liquid barrier layer compositions A and B, respectively, were applied onto the plastic substrates by means of spraying, whereas spraying means the even distribution of the medium, namely the liquid barrier layer composition, through a nozzle onto the substrate. The application of the liquid barrier layer compositions onto the substrate was conducted in a spray booth from the company “Straumann AG”, 8154 Oberglatt, Switzerland. This spray booth was equipped with a dry dust collector system and heatable fresh air. For the application itself, an airgun from the company “DeVilbiss”, “GTI-G110 Trans-Tech gravity feed cup” and a nozzle of 1.5 mm in diameter and a paint needle of 0.85-1.5 mm and initial pressure of 2.5 bar was used. The solids content of the liquid barrier layer composition was 52 wt.-%.

[0265] After application, the wet barrier layers were dried in a drying oven from the company “Binder”, 78532 Tuttlingen, Germany put on 75° C. for 10 minutes in order to evaporate the inheriting water of the liquid barrier layer composition and to initiate and finalize the film formation of the copolymer.

[0266] The prepared samples are compiled in Table 2 below:

TABLE-US-00002 TABLE 2 Composition of prepared samples. Sample Substrate Barrier Solution [wt %] Application  1 (comparative) BOPP A —  2 BOPP A 1 printing unit  3 BOPP A 2 printing units  4 (comparative) PE A —  5 PE A 1 printing unit  6 PE A 2 printing units  7 BOPP A Spray  8 BOPP B Spray  9 PE A Spray 10 PE B Spray

Results

[0267] The thereof printed/sprayed and dried samples have been cut into round samples for the following barrier performance test (HpVTR).

[0268] The following results have been obtained at the samples whereas values of less than 40 g/m.sup.2/d are commonly accepted as having a sufficient barrier performance

TABLE-US-00003 TABLE 3 Results of barrier performance test. Sample unit 1 2 3 4 5 6 7 8 9 10 Grammage g/m.sup.2 17.9 19.6 21.0 37.4 40.2 40.3 111.0 119.0 135.7 152.9 Barrier layer weight (dry weight) g/m.sup.2 0.0 1.7 3.1 0.0 2.8 2.9 93.1 101.1 98.3 115.5 HpVTR 1 h g/m.sup.2 29.7 5.4 0.7 19.5 0.7 0.4 0.5 0.5 0.4 0.5 HpVTR 4 h g/m.sup.2 125.0 22.9 1.4 78.9 1.9 0.4 0.6 0.7 0.5 0.7 HpVTR 8 h g/m.sup.2 189.7 44.7 3.2 159.9 3.7 0.7 0.6 0.7 0.5 0.7 HpVTR 24 h g/m.sup.2 330.3 128.3 8.2 461.9 10.3 1.6 0.6 0.8 0.5 1.1 Result barrier performance test Failed Failed Passed Failed Passed Passed Passed Passed Passed Passed

CONCLUSION

[0269] As it is clearly shown by the obtained results, the application of the liquid barrier layer composition either by way of spraying or printing creates a functioning barrier layer against the migration of hydrophobic substances, and especially against the migration of mineral oils.

[0270] By applying a dry barrier layer weight by means of printing of more than 2.0 g/m.sup.2, such as of 2.5 g/m.sup.2 (gsm) and more, a sufficient barrier against the migration of hydrophobic substances can be generated on BOPP film as well as on PE film to limit the possible migration to the desired threshold level of less than 40 g/m.sup.2/d of n-heptane. 40 gsm/m.sup.2/d of n-heptane are corresponding to a migration level of less than 2 mg/kg food stuff of MOSH and less than 0.5 mg/kg food stuff of MOAH.

[0271] Furthermore, it was shown that spraying is also a reasonable way to create a functioning barrier layer.