Use of aqueous polyanion-polyethyleneimine solutions for producing polymer films with oxygen-barrier properties

ES 2 594 776 T3

DESCRIPTION

Use of aqueous polyanion-polyethyleneimine solutions to produce polymeric films with oxygen barrier properties

The invention relates to the use of an aqueous solution comprising at least one polymeric polyanion and at least one high molecular weight polyethyleneimine to provide oxygen barrier properties to a polymer film.

When packaging products that are susceptible to oxidation or that are sensitive to oxygen, it is important that the packaging materials used have oxygen barrier properties, that is, that they have minimal oxygen transmission or minimal oxygen permeability. Polymeric films used as packaging materials and made of, for example, polyolefins, such as polyethylene, or of oriented polypropylene, or of polyesters, for example, polyethylene terephthalate, in general have relatively high oxygen permeability when used in the form of not coated. Therefore, various measures have been proposed to increase the oxygen barrier properties of these packaging materials.

WO 07/002322 describes coated polymeric films with oxygen barrier properties. The coating composition is a solution of a maleic acid / acrylic acid copolymer and a vinyl alcohol / vinylamine copolymer. After the coating process, the two copolymers of the coating composition are crosslinked in the polymeric film.

WO 98/31719 describes coating compositions for barrier coatings. The compositions comprise an ethylenically unsaturated acid monomer and a polyamine, which comprise an incorporated crosslinking agent. After the coating procedure, crosslinking is carried out through the initiation of a free radical induced polymerization reaction.

WO 2008/042748 describes the use of certain polyelectrolyte hydrogels for the controlled release of bioactive agents.

WO 2011/023587 describes the use of specific polyelectrolyte complexes to provide an oxygen barrier to packaging materials made from polymeric films. The polymeric film is coated with an aqueous dispersion comprising a previously dispersed polyelectrolyte complex produced by water-in-water emulsion polymerization, or the polymeric film is coated with a composition comprising a polyelectrolyte complex produced from anionic polymer and cationic surfactant, or the polymeric film is coated with at least three alternating layers, in which, respectively, one of the two adjacent layers comprises an anionic polyelectrolyte component and the other of two adjacent layers comprises a cationic polyelectrolyte component, and polyelectrolyte complexes are formed at the opposite adjacent interfaces of the alternate layers. Hitherto known packaging films with oxygen barrier properties are still not entirely satisfactory, especially when used in high atmosphere of high humidity. For example, the barrier coating described in WO 2011/023587 needs an additional moisture protection system to protect the barrier against moisture.

It was an object of the present invention to provide additional compositions and processes that allow the production of polymeric films with good oxygen barrier properties, in particular good oxygen barrier properties in high humidity environments without the need for protective coatings. additional.

The invention provides the use of an aqueous solution comprising at least one polyanion and at least one polyethyleneimine to provide oxygen barrier properties to a polymeric film, wherein the polyanion is a polymer comprising acid groups neutralized with at least one base selected from the group consisting of inorganic bases and monovalent organic bases and said polymer comprising acid groups having a weight average molecular weight of at least 10,000 g / mole before neutralization;

and in which said polyethyleneimine has a weight average molecular weight of at least 25,000 g / mol.

The invention also provides a coated polymeric film comprising an oxygen barrier coating obtainable by use in accordance with the invention as described herein, wherein at least one side of the polymeric film has been coated with an aqueous solution comprising at least one polyanion and at least one polyethyleneimine, wherein the polyanion is a polymer comprising acid groups neutralized with at least one monovalent base and said polymer comprising acid groups having a weight average molecular weight of at least 10,000 g / mol prior to neutralization;

and wherein said polyethyleneimine has a weight average molecular weight of at least 25,000 g / mol. Molecular weight can be determined by gel permeation or light scattering chromatography.

The coating produced according to the invention using the aqueous polymer solution has oxygen barrier properties. Barrier properties can be measured by the permeability test described in the examples. The term "oxygen barrier property" means that the oxygen transmission rate (TTO) has been reduced compared to an uncoated substrate. The oxygen transmission rate of the

ES 2 594 776 T3 polymeric films coated according to the invention is preferably less than 20%, in particular less than 10%, or less than 5%, for example 1 to 3%, of the value of the non-polymeric film coated measured at 23 ° C and 0% relative humidity; and preferably less than 30% or less than 20% or less than 10% measured at 23 ° C and 85% relative humidity.

The aqueous solution of the polymers preferably contains 10 to 90% by weight, more preferably 20 to 80% by weight of the polyanion, based on the solids content.

The aqueous solution of the polymers preferably contains 10 to 90% by weight, more preferably 20 to 80% by weight of the polyethyleneimine, based on the solids content.

The weight ratio between polyanion (calculated without neutralizing agent) and polyethyleneimine is preferably 10: 1 to 10: 9, more preferably 10: 2 to 10: 5 or 10: 3 to 10: 4.

The concentration of the sum of polyanion and polyethyleneimine in the aqueous solution is preferably at least 1% by weight, in particular at least 5% by weight and up to 50% by weight or up to 60% by weight, for example 1 at 50% by weight or from 5 to 40% by weight.

The amount of polyethyleneimine used to produce the aqueous solution is preferably selected such that, per mole of the amino groups of the polyethyleneimine, the amount of anionic groups of at least one anionic polymer is, for example, up to 400% in mole or up to 250 mole%, preferably 150 to 380 mole% or 180 to 250 mole%.

Polyanion is a polymer that comprises neutralized acid groups, also called an anionic polymer. Anionic polymers are polymers having anionic or acid groups, in particular organic polymers having carboxylate, phosphate or sulfate groups or the corresponding acid groups. The term anionic polymer also encompasses the corresponding polymers with acid groups, provided they are at least partially neutralized by monovalent bases when used in the aqueous solution according to the invention.

Examples of suitable anionic polymers are those formed by free radical polymerization of ethylenically unsaturated anionic monomers capable of free radical polymerization. The term anionic monomer comprises monomers with at least one anionic or acidic group, in which the acidic group can be neutralized by a base. The group of anionic polymers also comprises copolymers made of at least one anionic monomer and one or more of a different non-acidic non-ionic copolymerizable monomer. The polyanion can also be synthesized by polymerization of one or more nonionic monomers, such as acid derivatives, such as, for example, ethylenically unsaturated acid esters, followed by hydrolysis to obtain an anionic polymer. Suitable nonionic monomers can be alkyl acrylates, alkyl methacrylates (eg tert-butyl acrylate, ethyl acrylate, etc.) or ethylenically unsaturated acid anhydrides such as maleic anhydride.

Examples of ethylenically unsaturated anionic monomers that can be used are C3 to C10 or C3 to C5 monoethylenically unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid, vinyl sulfonic acid, acid styrenesulfonic, acrylamidomethylpropanesulfonic acid, vinylphosphonic acid, itaconic acid, and salts of these acids such as the alkali metal salts, alkaline earth metal salts, or ammonium salts of these acids. Among the preferably used anionic monomers are acrylic acid, methacrylic acid, maleic acid and 2-acrylamido-2-methylpropanesulfonic acid. Particular preference is given to aqueous solutions of acrylic acid-based polymers. Anionic monomers can be polymerized alone to give homopolymers, or else they can be polymerized in a mixture with each other, to give copolymers. Examples of these are homopolymers of acrylic acid, homopolymers of methacrylic acid, copolymers of acrylic acid and maleic acid, copolymers of acrylic acid and methacrylic acid, and copolymers of methacrylic acid and maleic acid. Preferably, the polyanion is selected from polymers that can be produced from monomers selected from the group consisting of C3 to C10 monoethylenically unsaturated carboxylic acids, vinyl sulfonic acid, styrene sulfonic acid, acrylamidomethylpropanesulfonic acid, vinyl phosphonic acid, and salts of these acids, preferably acrylic acid, methacrylic acid, maleic acid, itaconic acid. Most preferably, the polyanion is a polyacrylic acid or a copolymer of acrylic acid and maleic acid.

However, anionic monomers can also be polymerized in the presence of at least one other ethylenically unsaturated monomer. These monomers can be non-ionic or they can carry a cationic charge. Examples of nonionic comonomers are acrylamide, methacrylamide, N-C1 to C3 alkylacrylamides, N-vinylformamide, acrylic esters of monohydric alcohols having 1 to 20 carbon atoms, for example, in particular, methyl acrylate, ethyl acrylate, isobutyl acrylate and n-butyl acrylate, methacrylic esters of monohydric alcohols having 1 to 20 carbon atoms, for example methyl methacrylate and ethyl methacrylate, and also vinyl acetate and vinyl propionate.

Suitable cationic monomers that can be copolymerized with the anionic monomers are dialkylaminoethyl acrylates, dialkylaminoethyl methacrylates, dialkylaminopropyl acrylates, dialkylaminopropyl methacrylates, dialkylaminoethylacrylamides, dialkylaminoethylmethaacrylamides, dialkylaminopropylacrylamides, dialkylaminopropylacrylamides

ES 2 594 776 T3 dialkylaminopropylmethacrylamides, diallyldimethylammonium chloride, vinylimidazole, and also the respective acid-neutralized and / or quaternized basic monomers. Individual examples of cationic monomers are dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminopropyl acrylate, methacrylate, dimethylaminopropyl acrylate, diethylaminopropyl methacrylate diethylaminopropyl, dimethylaminoethylacrylamide, dimethylaminoethylmethacrylamide, dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, diethylaminoethylacrylamide and diethylaminopropylacrylamide .

The basic monomers may have been completely, or only partially, neutralized or quaternized, for example in a proportion of 1 to 99% in each case. The preferred quaternizing agent used for the basic monomers is dimethyl sulfate. However, the monomers can also be quaternized with diethyl sulfate or with alkyl halides, such as methyl chloride, ethyl chloride, or benzyl chloride. The amount of cationic monomers used is at most such that the resulting polymer has a net charge that is anionic at pH <6.0 and a temperature of 20 ° C. The resulting excess anionic charge in the amphoteric polymers is, for example, at least 5% by mole, preferably at least 10% by mole.

The amounts of the non-acidic non-anionic comonomers used in the production of the anionic polymers are such that the resulting polymers are water soluble when diluted with water at a pH above 7.0 and at a temperature of 20 ° C, and have a net anionic charge. Examples of the amount of non-acidic non-anionic comonomers, based on the total amount of monomers used in the polymerization reaction, are 0 to 99% by weight, preferably 1 to 75% by weight, and mostly an amount in the range of 1 to 25% by weight.

Examples of preferred copolymers are copolymers made from 25 to 90% by weight of acrylic acid and 75 to 10% by weight of acrylamide. It is preferable to polymerize at least one ethylenically unsaturated C3 to C5 carboxylic acid in the absence of other monoethylenically unsaturated monomers. gives particular preference to homopolymers of acrylic acid, obtainable by free radical polymerization of acrylic acid in the absence of other monomers; or copolymers of acrylic acid and maleic acid.

In one embodiment, the anionic polymer comprises 2-acrylamido 2-methylpropanesulfonic acid (AMPS). It is preferable to copolymerize acrylic acid with AMPS. The amount of AMPS here can be, for example, 0.1 to 15% by mole or 0.5 to 10% by mole, based on the amount of all monomers.

The polymerization reaction to make the polymer anionic can also be carried out in the presence of at least one crosslinking agent. This then gives copolymers with higher molar mass than when anionic monomers are polymerized in the absence of any crosslinking agent. The crosslinking agents used can comprise any of the compounds that have at least two ethylenically unsaturated double bonds in the molecule. Examples of crosslinking agents are triallylamine, pentaerythritol triallyl ether, pentaerythritol tetraallyl ether, methylenebisacrylamide, N, N'-divinylethyleneurea, allyl ethers comprising at least two allyl groups, or vinyl ethers having at least two vinyl groups , in which these ethers are derived from polyhydric alcohols, for example sorbitol, 1,2-ethanediol, 1,4-butanediol, trimethylolpropane, glycerol, diethylene glycol, and from sugars, such as sucrose, glucose, mannose; other examples are dihydric alcohols having 2 to 4 carbon atoms and which have been fully esterified with acrylic acid or methacrylic acid, for example, ethylene glycol dimethacrylate, ethylene glycol diacrylate, butanediol dimethacrylate, butanediol diacrylate, diacrylates or polyethylene glycols dimethacrylates with molecular weights from 300 to 600, ethoxylated trimethylenepropane triacrylates or ethoxylated trimethylenepropane trimethacrylates, 2,2-bis (hydroxymethyl) butanol trimethylacrylate, pentaerythritol triacrylate, pentaerythritol tetracrylate, and triallylmethylammonium chloride. If crosslinking agents are used in the production of the solutions of the invention, examples of the respective amounts used of the crosslinking agent are 0.0005 to 5.0% by weight, preferably 0.001 to 1.0% by weight, referred to the sum of all the monomers used in the polymerization reaction, provided that the polymer remains water-soluble at pH> 7. The preferred crosslinking agents used are pentaerythritol triallyl ether, pentaerythritol tetraallyl ether, N, N'-divinylethyleneurea, allyl ethers of sugars such as sucrose, glucose or mannose, in which these ethers comprise at least two allyl groups, and triallylamine, and also mixtures of these compounds.

If at least one anionic monomer is polymerized in the presence of at least one crosslinking agent, it is preferable to produce crosslinked copolymers of acrylic acid and / or methacrylic acid by polymerizing acrylic acid and / or methacrylic acid in the presence of the triallyl ether of pentaerythritol, the tetraallyl ether of pentaerythritol, N, N'-divinylethyleneurea, allyl ethers of sugars such as sucrose, glucose or mannose, in which these ethers comprise at least two allyl groups, and triallylamine, and also mixtures of these compounds. Preferably, the amounts of crosslinking agents used in the polymerization reaction are limited to some extent so that the resulting anionic polymers are soluble in aqueous solution at pH> 7.0.

The weight average molecular weight of the polymer comprising acid groups before neutralization is at least 10,000 g / mol, more preferably at least 30,000 g / mol, for example 10,000 to 200,000 g / mol or 30,000 to 150,000 g / mol.

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The acidic groups of the polyanion are partially or totally neutralized with at least one base selected from the group consisting of inorganic bases and monovalent organic bases. A monovalent organic base is an organic compound with a single basic group, for example, a single amino group. The bases are, for example, NaOH, KOH, Ca (OH) 2, Ba (OH) 2, sodium carbonate, potassium carbonate, trisodium phosphate, ammonia or primary, secondary or tertiary organic amines. The preferred bases are ammonia, sodium hydroxide, and triethanolamine. Most preferred are volatile bases such as ammonia.

The degree of neutralization of the polyanion is preferably 30 to 100%, more preferably 50 to 100%, based on the total molar amount of acid groups in the anionic polymer.

The aqueous solution comprises at least polyethyleneimine. Polyethyleneimines are polymers that comprise ethyleneimine units. They are preferably branched. The polyethyleneimines can be used neutralized as the salts with suitable acids, but are preferably used in the non-neutralized form.

In one embodiment of the invention, the polyethyleneimine is selected from highly branched or dendritic polyethyleneimines. Highly branched polyethyleneimines are characterized by their high degree of branching (GR). GR can be determined by NMR of¹³C-spectroscopy, preferably in D2O and is defined as:

GR = D + T / (D + T + L) in which D (dendritic) correlates with the amount of tertiary amine groups, L (linear) correlates with the amount of secondary amine groups and T (terminal) correlates with the number of primary amine groups. The highly branched polyethyleneimines according to the invention have a GR of preferably 0.1 to 0.95, or 0.25 to 0.9, more preferably 0.30 to 0.80 and especially preferably at least 0, 5. Dendritic polyethyleneimines have a uniform structural and molecular constitution (GR = 1).

The weight average molecular weight of the polyethyleneimines is at least 25,000 g / mol, more preferably at least 10,000 g / mol, for example 25,000 to 3,000,000 g / mol or 100,000 to 2,000,000 g / mol. The charge density of the polyethyleneimines is preferably 1 to 35 meq / g, more preferably 5 to 25 meq / g. Charge density can be measured by titration of aqueous solutions of polyethyleneimine with potassium polyvinyl sulfate (KPVS) at pH 4.5 with toluidine blue as an indicator.

Suitable cationic polymers are ethyleneimine polymers that are produced by polymerization of ethyleneimine in aqueous medium in the presence of small amounts of acids or acid-forming compounds, examples being halogenated hydrocarbons, for example, chloroform, carbon tetrachloride, tetrachloroethane, or ethyl chloride, or are condensates of epichlorohydrin and compounds comprising amino groups, examples being mono- and polyamines, for example dimethylamine, diethylamine, ethylenediamine, diethylenetriamine, and triethylenetetramine, or ammonia. By way of example, they have molecular weights Mw of 25,000 to 3 million, preferably 100,000 to 2,000,000 g / mol.

This group of cationic polymers also includes graft polymers of ethyleneimine on compounds having a primary or secondary amino group, examples being polyamidoamines made from dicarboxylic acids and polyamines. The ethyleneimine-grafted polyamidoamines can also react with bifunctional crosslinking agents, for example with epichlorohydrin or with bischlorohydrin ethers of polyalkylene glycols.

In one embodiment, the polyethyleneimine is cross-linked. Any crosslinking agent with at least two functional groups capable of forming covalent bonds with the amine groups of polyethyleneimine can be used for crosslinking. Suitable crosslinking agents are, for example, alkyldialdehydes with preferably 3 to 20 carbon atoms, such as glutaraldehyde (1,5-pentanedial).

The aqueous solution may comprise water as the sole solvent or it may comprise a mixture of water and water-miscible organic solvents, such as methanol, ethanol, acetone, or tetrahydrofuran. Preferably, water is the only solvent. The pH is preferably 6 to 12, more preferably 7 to 10.

One embodiment of the invention is a polymeric film comprising an oxygen barrier coating obtainable by using an aqueous solution of polymer as described above, wherein at least one side of the polymeric film has been coated with a solution. aqueous comprising at least one polyanion and at least one polyethyleneimine, wherein the polyanion is a polymer comprising acid groups neutralized with at least one monovalent base and said polymer comprising acid groups having a weight average molecular weight of at least 10,000 g / mol prior to neutralization;

and wherein said polyethyleneimine has a weight average molecular weight of at least 25,000 g / mol.

Aqueous polymer solutions used for the coating process may comprise additional additives or auxiliaries, for example thickeners for adjusting rheology, wetting aids, or binders. Preferred polymeric film substrates are polymeric films that are suitable for packaging.

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Preferred polymeric films are made of oriented polypropylene or polyethylene, wherein the polyethylene may have been produced from ethylene, either by the high pressure polymerization process or by the low pressure polymerization process. Examples of other suitable polymeric films are made of polyester, such as polyethylene terephthalate, and films made of polyamide, polystyrene, and polyvinyl chloride. In one embodiment, the polymeric film is biodegradable, for example made from biodegradable aliphatic-aromatic copolyesters and / or polylactic acid, an example being Ecoflex® films or Ecovio® films. Examples of suitable copolyesters are those formed from alkanediols, in particular C2 to C8 alkanediols, for example 1,4-butanediol, and from aliphatic dicarboxylic acids, in particular C2 to C8 dicarboxylic acids, for example acid adipic, and from aromatic dicarboxylic acids, eg terephthalic acid. Preferred polymeric film materials are selected from polyethylene terephthalate, oriented polypropylene, cast polypropylene, polyethylene, biodegradable aliphatic-aromatic copolyesters, metallized polyethylene terephthalate, metallized oriented polypropylene, and polyamide.

The thickness of the polymeric film can be in the range from 5 to 200 pm, in the case of polyamide films from 5 to 50 pm in the case of films made of polyethylene terephthalate from 10 to 100 pm, in the case of polypropylene oriented from 10 to 100 pm, in the case of polyvinyl chloride films about 100 pm, and in the case of films made of polystyrene about 30 to 75 pm.

Preferably, the oxygen barrier coating on the polymeric film is free of pores, which can be analyzed by atomic force microscopy (AFM) or by scanning electron microscopy (SEM).

One embodiment of the invention is a process of forming a polymeric film with improved oxygen barrier properties, comprising:

- apply an aqueous solution to at least one side of the polymeric film,

- the aqueous solution comprising at least one polyanion and at least one polyethyleneimine, in which the polyanion is a polymer comprising acid groups neutralized with at least one monovalent base and said polymer comprising acid groups having a weight average molecular weight of at least 10,000 g / mol before neutralization;

and wherein said polyethyleneimine has a weight average molecular weight of at least 25,000 g / mol.

The aqueous coating composition can be applied by typical coating machinery for a backing film made of a plastic. If mesh materials are used, the aqueous polymer solution is generally applied from a channel by means of an applicator roll and made uniform with the help of an air knife. Other suitable possibilities for applying the coating use the reverse gravure process or spraying processes, or a separation system using a roller, or other coating processes known to those skilled in the art.

The aqueous coating can also be applied in a multilayer process, in which a first coating is followed by a second or more coatings.

Other suitable coating methods are the known embossing and embossing processes. Instead of using different inks in the ink printing units, the present method uses by way of example a printing method for the application of the aqueous polymer solution. The printing processes that can be mentioned are the flexographic printing process as a relief printing process known to those skilled in the art, the intaglio process as an example of burin engraving and offset printing, and as an example of embossing printing. flat surface. Modern digital printing, ink jet printing, electrophotography and direct imaging can also be used.

In order to achieve a further improvement in adhesion in a polymeric film, the support film may be previously corona treated. Examples of the amounts applied to sheet materials are preferably 0.2 to 50 g (polymer, solid) per m², preferably 0.5 to 20 g / m² or 1 to 15 g / m².

In order to achieve further improvement in adhesion on a polymeric film, a precoat or primer can be applied on the polymeric film prior to coating the oxygen barrier on the substrate. Such primers can be based on polyurethane dispersions, polyurethane solutions, solvent-free or solvent-based reactive polyurethane, polyethyleneimine, polyacrylates, or other primers known to those skilled in the art.

Once the aqueous coating composition has been applied to the sheet substrates, the solvent is evaporated. For this, by way of example, in the case of continuous operation, the material can be passed through a drying tunnel, which can have an infrared irradiation apparatus. The dried, coated material is then passed over a chill roll and finally rolled up. The thickness of the dry coating is preferably 0.2 to 50 pm, especially preferably 0.5 to 20 pm, most preferably 1 to 15 pm.

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Substrates coated with the aqueous coating composition exhibit excellent oxygen barrier action, particularly in high humidity environments. The coated substrates can be used, for example, as a packaging medium, preferably for food packaging. The coatings have very good mechanical properties and exhibit, for example, good blocking behavior and essentially no cracking.

The oxygen barrier coating can also be used as a barrier coating against other substances. Such substances can be carbon dioxide, nitrogen, bisphenol A (BPA), mineral oil, fats, aldehydes, fat, plasticizer, photoinitiators or aromatic substances.

In order to obtain the specific additional surface properties or the specific coating properties of the coated polymeric films, for example good printability, or improved sealing and non-blocking properties or good water resistance, it may be advantageous to coat the coated substrates with topcoats that provide these additional desired properties. Substrates previously coated with the aqueous coating composition according to the invention can easily be overcoated. For the overcoating process, one of the above-mentioned processes can be repeated, or the coating can be repeated in a continuous process without any intermediate winding and unwinding of the sheet. Therefore, the location of the oxygen barrier layer can be within the system, and the surface properties are determined by the finish layer. The top coat has good adhesion to the oxygen barrier layer. Due to the good moisture resistance, in particular, it is not necessary to apply an additional moisture protection coating to ensure that the oxygen barrier layer is effective even at relatively high humidity levels.

In one embodiment, a polymeric film of the invention comprises, in addition to the oxygen barrier coating layer at least one additional layer made of materials selected from the group consisting of polyacrylates, polyvinylidene chloride (PVDC), waxes, epoxy resins , UV-curable acrylates and polyurethanes.

In one embodiment of the invention, a polymeric film of the invention as described above is laminated with at least one additional material, wherein the at least one additional material is selected from polyethylene terephthalate, oriented polypropylene, polyethylene, cast polypropylene. , biodegradable aliphatic-aromatic copolyesters, metallized polyethylene terephthalate, metallized oriented polypropylene, polyamide, paper and cardboard.

Another embodiment of the invention is a package comprising a polymeric film according to the invention as described above.

Examples

Measurement of the barrier action against oxygen:

Oxygen transmission is determined on coatings on polymeric films at a relative humidity (RH) level of 85%. Measurements are carried out with 100% oxygen gas at a temperature of 23 ° C. Support material: boPP polymeric film (biaxial oriented polypropylene) with a thickness of 40 pm.

The oxygen transmission rate of the uncoated film at 85% RH / 23 ° C: about 975cm³/ (m²* d). The determination procedure is based on the ASTM D3985 standard, using a coulometric sensor. Each sample was measured twice and the mean result is calculated.

The transmission of a multilayer system is calculated according to the equation _ 1 1 TR_lalal ~ TR_to⁺TR_or'

Where TRtolal is the multilayer film oxygen transmission and TRa and TRb are the oxygen transmissions of layer A and layer B, respectively.

Polymer samples:

PEI1 aqueous solution of polyethyleneimine, Mw = 750,000 g / mol; charge density 17 meq / g, pH = 11 PEI2 aqueous polyethyleneimine solution, Mw = 1,300 g / mol; charge density 16 meq / g, pH = 11 aqueous solution of polyvinylamine PVA, Mw = 340,000 g / mol; charge density 13 meq / g, pH = 7-9 PAS1 copolymer of polyacrylic acid and maleic acid (75: 25), Mw = 80000 g / mol PAS2 polyacrylic acid, Mw = 3000 g / mol

PAS1 and PAS2 samples are pre-neutralized with ammonia before combining with polyethyleneimine or polyvinylamine.

The boPP-film is covered with a single polymer solution according to table 1 to generate a single layer (examples 2-6) or with 4 solutions for the generation of a 4-layer film (example 1). Compositions and results are summarized in Table 1.

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Table 1: Results of the measurement of the oxygen transmission rate; amounts in parts by weight

<td>Example 1</td><td>Composition</td><td>Layer thickness [pm]</td><td>Oxygen Transmission Rate (85% RH) [cm³/ (m²* d)]</td>

<td>1 (comparative)</td><td>Layer structure: 1) PEI1 2) PAS1 (+ NH3) 3) PEI1 4) PAS1 (+ NH3)</td><td>about 10</td><td> 421</td>

<td> 2</td><td>100 PAS1 25 NH3 40 PEI1</td><td> 4</td><td> 32</td>

<td>3 (comparative)</td><td>100 PAS1 25 NH3 40 PVA</td><td> 2</td><td> 950</td>

<td>4 (comparative)</td><td>100 PAS1 25 NH3 40 PEI2</td><td> 8</td><td> 227</td>

<td>5 (comparative)</td><td>100 PAS2 25 NH3 40 PEI1</td><td> 5</td><td> 529</td>

<td>6 (comparative)</td><td>100 PAS2 25 NH3 40 PEI2</td><td> 4</td><td> 540</td>

The data shows that Example 2 according to the invention shows the best oxygen barrier properties at high humidity.