ES2698846T3 - Packaging of paper and cardboard with barrier coating - Google Patents

Abstract

Paper or cardboard packaging, where the packaging is manufactured at least partially from recycled paper, contaminated with mineral oil and the packaging has at least one barrier layer which can be prepared by applying an aqueous polymer dispersion containing at least one copolymer that can be be prepared by emulsion polymerization of (a) one or more major monomers that are selected from the group consisting of (meth) C1 to C4 alkyl acrylates, (b) 0.1 to 5% by weight of one or more monomers acids, (c) 0-20% by weight of acrylonitrile and (d) 0 to 10% by weight of monomers other than monomers (a) to (c), where the glass transition temperature of the copolymer is in the range of +10 to +45 ° C, in which case the copolymer is composed of at least 70% by weight of the main monomers (a) and the barrier layer can be found on at least one of the packing surfaces a layer of barrier can form at least one of v Several layers of a multilayer coating of the packaging.

Description

DESCRIPTION

Packaging of paper and cardboard with barrier coating

The invention relates to a paper or cardboard packaging made from recycled paper, contaminated with mineral oil, having a barrier layer, which can be prepared by applying an aqueous polymer dispersion containing a copolymer which can be prepared by of emulsion polymerization from C 1 to C 4 alkyl (meth) acrylates, acidic monomers and optionally acrylonitrile and other monomers, in which case the glass transition temperature of the copolymer is from 10 to 45 ° C. The barrier layer may be on one of the surfaces of the package or form one of several layers of a multi-layer coating of the package.

Cardboard packaging is usually made from recycled paper. In the case of printed paper, mainly newspaper, the recycled paper may contain mineral oil residues from the printing inks commonly used for newspaper printing. Already at room temperature, the volatile fractions of these residues evaporate and, in the case of food packaging, are deposited on the packaged foods in the box, for example, pasta, semolina, rice or corn flakes. Even most of the internal bags used today, made of polymeric films, do not offer sufficient protection in this case. In Zurich cantonal laboratory studies, mineral oil residues have been detected at a considerable level in foods that were packed in packages made from recycled paper. The volatile mineral oil components are preponderantly paraffinic or naphthenic hydrocarbons, which are harmful to health, and aromatic hydrocarbons, mainly those with 15-25 C atoms.

Therefore, there is a need to decrease the risk of contamination of food products with mineral oil residues. One possibility would be to dispense with newspaper recycling in the manufacture of cardboard for food packaging. This is not desirable for ecological reasons and is not practicable due to insufficiently available amounts of virgin cellulose. Another solution would be to dispense with mineral oils in printing inks for newspaper printing. However, this faces technological obstacles, first and foremost with respect to resistance to remove the print on the surface of the paper. In the packaging sector, barrier coatings against fats and oils are known. WO 2006/053849 discloses, for example, coatings based on water-based polymeric compositions for paper and paperboard. Although the polymers show good barrier properties against liquid greasy substances, however, it has been shown that in this way there is not necessarily a good barrier effect against substances that penetrate in gaseous form, since the transport mechanisms are different for penetrating substances. In the case of fats and oils, transport is carried out through the fibers, where capillary forces and surface wetting play a role. In the case of problems with substances that pass in gaseous form, it is not the capillary effect and the humidification that play a role, but the absorption, diffusion and porosity. In addition, fats and oils differ from hydrocarbons, that is, from the components of mineral oil in their polarity and, as a consequence of this, in their diffusion behavior through layers of barriers.

The fundamental objective of the invention is to provide packaging that reduces the risk of contamination of products packaged with volatile components of mineral oil, despite the use of recycled paper contaminated with mineral oil.

The objective is achieved according to the invention by means of a packaging made of paper or cardboard; wherein the package is made at least in part from recycled paper contaminated with mineral oil, and the package has at least one barrier layer which can be manufactured by applying an aqueous polymer dispersion containing at least one copolymer which can be prepared by emulsion polymerization

(a) one or more main monomers which are selected from the group consisting of alkyl (meth) acrylates of C1 to C4,

(b) 0.1 to 5% by weight of one or more acid monomers, for example, selected from acrylic acid and methacrylic acid,

(c) 0-20% by weight of acrylonitrile and

(d) 0 to 10% by weight of monomers other than monomers (a) to (c),

wherein the glass transition temperature of the copolymer is in the range of 10 to 45 ° C, where the copolymer is made up of at least 70% by weight of the main monomer (a), and where the barrier layer can be found in at least one of the packaging surfaces, or the barrier layer can form at least one of several layers of a multilayer packaging covering. The packagings are suitable mainly for food.

Contaminated with mineral oil means that the paper contains quantities of volatile hydrocarbons that are detectable by standard analytical procedures, mainly volatile paraffins, volatile naphthenes and / or volatile aromatic hydrocarbons having up to 25 carbon atoms. Volatile hydrocarbons are those that they have up to 25 C atoms, for example, from 5 to 22 C atoms. In one embodiment of the invention, the mineral oil contamination comes from printing inks and comprises volatile paraffins, volatile naphthenes and / or volatile aromatic hydrocarbons. .

Hereinafter, the designation "(met) acryl ..." and similar designations are used as abbreviated notation for "acryl ... or methacryl ...".

The polymer dispersions that can be used according to the invention are dispersions of polymers in aqueous medium. These are, for example, completely demineralized water or even mixtures of water and a solvent miscible with it, such as methanol, ethanol or tetrahydrofuran. Preferably, organic solvents are not used. The solids contents of the dispersions are preferably from 15 to 75% by weight, preferably from 40 to 60% by weight, in particular from more than 50% by weight. The solids content can be established by the corresponding adjustment of the amount of water and / or monomer amounts that are employed during the emulsion polymerization. The average particle size of the polymer particles dispersed in the aqueous dispersion is preferably less than 400 nm, mainly less than 300 nm. Particularly preferably, the average particle size is between 70 and 250 nm and between 80 and 150 nm. By "average particle size" is meant here the value d ⁵⁰ of the particle size distribution, ie 50% by weight of the entire mass of all the particles have a particle diameter smaller than the value d ⁵⁰ . The distribution of particle sizes can be determined in a known manner by the analytical ultra centrifuge (W. Machtle, Makromolekulare Chemie 185 (1984), pages 1025-1039). The pH value of the polymer dispersion is preferably adjusted to a pH of more than 4, mainly at a pH value between 5 and 9.

The copolymers that can be used according to the invention are emulsion polymerized materials, which can be prepared by emulsion polymerization of free radical polymerizable monomers. The copolymer is formed from one or several main monomers (a), which are selected from the group consisting of alkyl (meth) acrylates of C1 to C4. The main monomers (a) are preferably used in at least 70% by weight, preferably in at least 75% by weight, for example, from 79.5 to 99.5% by weight, based on the sum of all the monomers . Particularly preferred main monomers (a) are selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate and n-butyl acrylate.

The copolymer is formed from one or more acidic monomers (b). The acidic monomers are ethylenically unsaturated, free radical polymerizable monomers which have at least one acid group, for example monomers having carboxylic acid, sulfonic acid or phosphonic acid groups. Carboxylic acid groups are preferred. Mention may be made, for example, of acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid. The acid monomers (b) are preferably selected from acrylic acid and methacrylic acid. The acidic monomers (b) are used in 0.1 to 5% by weight, preferably in 0.5 to 5% by weight, based on the sum of all the monomers.

The copolymer can optionally be formed from acrylonitrile, like other monomer (c), from 0 to 20% by weight, with respect to the sum of all the monomers. In one embodiment of the invention, the copolymer is formed of acrylonitrile at 1-20% by weight, preferably 2-20% by weight.

The copolymer can optionally be formed from other monomers (d) different from the monomers (a) to (c). The amount of other monomers (d) is in this case from 0 to 10% by weight or 0 to 5% by weight, with respect to the sum of all the monomers. In one embodiment, other monomers than the monomers (a) to (c) are not used.

The other monomers (d) can be selected from the group consisting of C ⁵ -C ²⁰ alkyl (meth) acrylates, vinyl esters of carboxylic acids containing up to 20 C atoms, vinyl aromatic compounds up to 20 C atoms, ethylenically unsaturated nitriles, other than acrylonitrile, vinyl halides, vinyl ethers of alcohols containing 1 to 10 carbon atoms, aliphatic hydrocarbons with 2 to 8 carbon atoms and one or two double bonds or mixtures of these monomers. Mention may be made, for example, of (meth) acrylic acid alkyl esters having a C ⁵ -C ¹⁰ alkyl residue, such as 2-ethylhexyl acrylate. Mixtures of the (meth) acrylic acid alkyl esters are also particularly suitable. The vinyl esters of carboxylic acids having 1 to 20 C atoms are, for example, vinyl laurate, vinyl stearate, vinyl propionate, versic acid vinyl ester and vinyl acetate. Suitable vinyl aromatic compounds are vinyltoluene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene. An example of nitriles is methacrylonitrile. Vinyl halides are ethylenically unsaturated compounds, substituted with chlorine, fluorine or bromine, preferably vinyl chloride and vinylidene chloride. As vinyl ethers, there may be mentioned, for example, vinyl methyl ether or vinyl isobutyl ether. Vinyl ether is preferred from alcohols containing 1 to 4 carbon atoms. As hydrocarbons with 4 to 8 carbon atoms and two olefinic bonds, butadiene, isoprene and chloroprene can be mentioned. As other monomers (d), C ⁵ to C ¹⁰ alkyl acrylates and methacrylates and aromatic vinyl compounds, mainly styrene and mixtures thereof, are preferred. Particularly preferred are n-hexyl acrylate, octyl acrylate and 2-ethylhexyl acrylate, 2-propylheptyl acrylate, styrene, as well as mixtures of these monomers. Other monomers (d) are also, for example, monomers containing hydroxyl groups, in particular C ¹ -C ¹⁰ hydroxyalkyl (meth) acrylates as well as (meth) acrylamide. As other monomers (d), phenyloxyethyl glycol mono- (meth) acrylate, glycidyl acrylate, glycidyl methacrylate, (meth-) amino acrylates such as 2-aminoethyl (meth) acrylate. Like other monomers (d), crosslinking monomers may also be mentioned.

In an embodiment of the invention, the copolymer can be prepared from

(a) 79.5 to 99.5% by weight of one or more main monomers which are selected from the group consisting of C ¹ to C ⁴ alkyl (meth) acrylates,

(b) 0.5 to 5% by weight of one or more acidic monomers selected from acrylic acid and methacrylic acid,

(c) 0-20% by weight of acrylonitrile and

no other monomer than the monomers (a) to (c).

The type of the copolymer monomer amounts are adapted in such a way that the glass transition temperature of the polymerized emulsion material is in the range of 10 to 45 ° C, preferably 15 to 40 ° C. The glass transition temperature can be determined by differential scanning calorimetry (ASTM D 3418-08, called "midpoint temperature" or midpoint temperature).

The preparation of the copolymers can be carried out by emulsion polymerization, then it is a polymerized emulsion material. In the emulsion polymerization, ionic and / or nonionic emulsifiers and / or protective colloids or stabilizers are usually used as surfactant compounds in order to support the dispersion of the monomers in the aqueous medium. Protective colloids are polymeric compounds that bind large amounts of water in solvation and are capable of stabilizing dispersions of water-insoluble polymers. In contrast to emulsifiers, these usually do not reduce the surface tension between polymer particles and water. A detailed description of suitable protective colloids is found in Houben-Weyl, Methoden der organischen Chemie [Procedures of organic chemistry], volume XIV / 1, Makromolekulare Stoffe [Macromolecular substances], Georg-Thieme-Verlag, Stuttgart, 1961, pages 411 to 420. Suitable protective colloids are, for example, amphiphilic polymers, ie polymers with hydrophobic and hydrophilic groups. They can be natural polymers such as starches or synthetic polymers. Suitable emulsifiers are both anionic and nonionic surfactants whose number average molecular weight is usually below 2000 g / mol or preferably below 1500 g / mol, while the number average molecular weight of the protective colloids is below 2000 g / mol, for example, from 2000 to 100000 g / mol, mainly from 5000 to 50000 g / mol. Preferably, anionic and nonionic emulsifiers are used as surfactants. Suitable emulsifiers are, for example, C ^s to C ³⁶ fatty alcohols, ethoxylates having an ethoxylation degree of 3 to 50, mono-, di- and tri-alkyl (C ⁴ to C ¹² ) ethoxylated phenols having an degree of ethoxylation from 3 to 50, alkali metal salts of dialkyl esters of sulfosuccinic acid, alkali metal salts and ammonium salts of C ⁸ -C ¹² alkyl sulfates, alkali metal salts and ammonium salts of alkyl acids ( from C ¹² to C ^1s ) sulphonic and alkali metal and ammonium salts of alkyl (from C ⁹ to C ^1s ) arylsulfonic acids. If emulsifiers and / or protective colloids are used together as adjuvants for dispersing the monomers, the amounts used thereof are, for example, from 0.1 to 5% by weight, based on the monomers. The commercial names of emulsifiers are, for example, Dowfax® 2 A1, Emulan® NP 50, Dextrol® OC 50, Emulgator 825, ^{Emulgator 825 S, Emulan® OG, Texapon® NSO, Nekanil® 904 S, Lumiten®} I-rA , ^{Lumiten E 3065, Lumiten® ISC,} Disponil® NLS, Disponil LDBS 20, Disponil FES 77, Lutensol AT 18, Steinapol VSL, Emulphor NPS 25. The surfactant is usually used in amounts of 0.1 to 10% by weight, with respect to the monomers that are to be polymerized.

The emulsion polymerization is usually carried out at 30 to 130, preferably 50 to 90 ° C.

The polymerization medium can be composed only of water, as well as mixtures of water and liquids miscible with it, such as methanol. Preferably only water is used. The emulsion polymerization can be carried out either as a batch process or as a continuous feed process, including step or gradient procedures. The feed method is preferred in which a part of the mixture is initially charged for polymerization, the polymerization temperature is heated, polymerized, and then the remainder of the polymerization mixture is introduced continuously or stepwise. , usually by means of several, spatially separated feed channels, of which one or more contain the monomers in pure or emulsified form.

The customary and known adjuvants, for example, water-soluble initiators and regulators, can be used in the emulsion polymerization. Water-soluble initiators for the emulsion polymerization are, for example, ammonium and alkali metal salts of peroxydisulfuric acid, for example, sodium peroxodisulfate, hydrogen peroxide or organic peroxides, for example, tert-butyl hydroperoxide. Initiating systems called reduction-oxidation (redox) are also suitable. The redox initiator systems are composed of at least one generally inorganic reducing agent and an inorganic or organic oxidation agent. Oxidation components are, for example, the initiators mentioned above for emulsion polymerization. The reducing components are, for example, alkali metal salts of sulphurous acid, such as, for example, sodium sulphite, sodium hydrosulfite, alkali salts of disulphuric acid such as sodium disulfite, bisulphite addition compounds of aliphatic aldehydes and ketones, such as acetone bisulfite or reducing agents such as hydroxymethanesulfinic acid and its salts, or ascorbic acid. The redox initiator systems can be used, using together soluble metal compounds, whose metal components can occur in various valence states. Typical redox initiator systems are, for example, ascorbic acid / iron (II) sulfate / sodium peroxodisulfate, tert-butyl hydroperoxide / sodium disulfite, tert-butyl hydroperoxide / Na-hydroxymethanesulfinic acid or tert-butyl hydroperoxide / ascorbic acid. The individual components, for example, the reduction components, can also be mixtures; for example, a mixture of the sodium salt of hydroxymethanesulfinic acid and sodium disulfite. The mentioned compounds are generally used in the form of aqueous solutions, in which case the lower concentration is determined by the amount of water acceptable in the dispersion; and the higher concentration is determined by the water solubility of the compound in question. In general, the concentration is from 0.1 to 30% by weight, preferably from 0.5 to 20% by weight, particularly preferably from 1.0 to 10% by weight, based on the solution. The amount of the initiators is generally 0.1 to 10% by weight, preferably 0.5 to 5% by weight, with respect to the monomers to be polymerized. Several different initiators can also be used in the emulsion polymerization. To eliminate the residual monomers, initiator is also added after the end of the emulsion polymerization itself.

In the polymerization, regulators can be used, for example, in amounts of 0 to 0.8 parts by weight, based on 100 parts by weight, of the monomers to be polymerized, whereby the molecular mass is decreased. Suitable are, for example, compounds with a thiol group, such as tert-butyl mercaptan, mercaptoethyl propionate, 2-ethylhexyl thioglycolate, thioglycolic acid ethyl ester, mercaptoethanol, mercaptopropyltrimethoxysilane, ndodecylmercaptan, or tert-dodecyl mercaptan. In addition, thiol group regulators such as, for example, terpinolene can be used. In a preferred embodiment, the emulsion polymerized material is prepared using 0.05 to 0.5% by weight, based on the amount of monomers, of at least one molecular weight regulator.

The polymer dispersion used for coating packages for the use according to the invention can be composed only of the polymerized emulsion material, dispersed in water. But it can also contain other additives, for example, fillers, antiblocking agents, dyes, flow control agents or thickeners.

In one embodiment of the invention, the at least one copolymer is used in combination with up to 1 part by weight of pigments in the form of plates, with respect to 1 part by weight of copolymer. Examples of platelet-shaped pigments are talc, clay or mica. Talc is preferred. Preferred shape factors (ratio between length and thickness) are greater than 10.

The polymer dispersion forms a barrier layer after coating the substrate. A barrier layer occurs mainly if a copolymer is used which causes a coating with the copolymer to have a permeability for gaseous n-hexane of less than 50 g / m2 d, preferably less than 10 g / m2 d, particularly preferred of less than 5 g / m2 or less than 1 g / m2 gives 23 ° C and an application weight of 20-25 g / m2 on paper (see measurement procedures in the examples described below).

The content of the at least one copolymer in the dispersion used for the coating is preferably at least 1% by weight, in particular at least 5% by weight and up to 60 or up to 75% by weight. The content of the at least one copolymer in the aqueous dispersion is preferably 15 to 75% by weight, or 40 to 60% by weight. Preferred aqueous dispersions of the copolymers have at pH values of 4 and a temperature of 20 ° C a viscosity of 10 to 150,000 mPas, or 200 to 5000 mPas (measured with a Brookfield viscometer at 20 ° C, 20 rpm, spindle 4) . The average particle size of the copolymer particles dispersed in the aqueous dispersion is, for example, from 0.02 to 100 gm, preferably from 0.05 to 10 gm. It can be determined, for example, with the aid of optical microscopy, light scattering or freeze fracture electron microscopy.

According to the invention, the carrier substrates are coated with an aqueous dispersion of at least one of the copolymers described above. Suitable substrates are mainly paper and cardboard. The dispersions used for the coating may contain other additives and adjuvants, for example, thickeners for adjusting the rheology, wetting aids or binders.

The application can be effected, for example, in coating machines in the manner in which the coating composition is applied on paper or cardboard. If materials in the form of tapes are used, the polymer dispersion is applied from a tank usually on an application roller and leveled with the help of an air brush. Other possibilities of applying the coating are achieved, for example, with the aid of the reverse engraving process, by spray methods or a roller blade and other coating methods known to the skilled worker. In this case, the support substrate is coated on at least one side; that is to say that in can it is covered on one side or on both sides. Preferred application methods for paper and paperboard are curtain coating, air knife, banding or doctoring. Preferred methods of application for the coating of sheets are doctor blade, wire doctor, air brushes, application methods with counter-rotating rolls, anti-rotation engraving, casting head or nozzle.

The amounts applied to the flat materials are preferably 1 to 10 g (polymer, solid) per m2, preferably 2 to 7 g / m2 in films or preferably 5 to 30 g / m2 in the case of paper or cardboard. After applying the coating compositions on the carrier substrates, the solvent or water is evaporated. For this, for example, in the case of a continuous operation, it is possible to conduct the material through a dryer channel that is equipped with an infrared irradiation device. Then, the coated and dried material is led through a cooling roller and finally rolled up. The thickness of the dry coating is preferably at least 1 gm, in particular from 1 to 50 gm, particularly preferably from 2 to 30 gm or 5 to 30 gm.

The barrier layer is on at least one of the packaging surfaces. It can also form at least one of several layers of a multilayer packaging covering. The barrier coating can be applied directly on a surface of the support material, between the support and the barrier coating, although other layers can also be found, for example, primer layers, other barrier layers or layers of color printing inks. or in black and white. The barrier layer is preferably inside, on the side of the package facing the packaged product.

The inner bag is preferably manufactured from a polymer film. The material of the inner bag is preferably selected from polyolefins, preferably oriented polyethylene or polypropylene, in which case the polyethylene may have been manufactured according to the high pressure polymerization process, but also according to the low pressure polymerization process of ethylene . To further improve the adhesion on a film, the support film has previously been subjected to corona treatment. Other suitable support films are, for example, polyester films such as polyethylene terephthalate, polyamide films, polystyrene and polyvinyl chloride. In one embodiment, the support material is biodegradable films, for example, of biodegradable aliphatic-aromatic copolyesters and / or poly (lactic acid), for example, Ecoflex® or Ecovio® films. Suitable polyesters are, for example, comprised of alkanediols, especially C ² to alkanediols C ^s, for example, 1,4-butanediol, aliphatic dicarboxylic acids, dicarboxylic acid mainly C ² to C ^s, such , adipic acid and aromatic dicarboxylic acids such as, for example, terephthalic acid.

The thickness of the support films is generally in the range of 10 to 200 gm.

To obtain special surface or coating properties of films and packaging products, for example, a good printability, barrier or blocking behavior to a better, good water resistance, it may be advantageous to coat the coated substrates with cover layers that confer these desired properties further or subjecting the barrier coating to corona treatment. The pre-coated substrates according to the invention show a good coating capacity. It can be recoated according to a procedure set forth above or coated several times simultaneously in a continuous process without an intermediate winding and unwinding, for example, of the film or paper using, for example, a curtain coater. The barrier layer according to the invention is thus found inside the system; the cover layer then determines the properties of the surface. The cover layer has a good adhesion for the barrier layer.

The invention also provides a method for preparing a package, in which a composition in the form of an aqueous polymer dispersion described above is provided and applied to a packaging substrate and dried, in which case the aqueous polymer dispersion contains at least one of the polymers described above.

It is also an object of the invention to use an aqueous polymer dispersion containing at least one of the copolymers described above for the manufacture of a barrier layer against the volatile components of a mineral oil, mainly for the manufacture of packaging, mainly of packaging for food.

The coated substrates according to the invention show an extraordinary barrier effect against the volatile components of a mineral oil. The coated substrates can be used as such as a packaging medium. The coatings have very good mechanical properties and show, for example, a good blocking behavior.

Examples

Provided that the context does not turn out to be something different, the data in percentage always means percentage in weight. The indication of a content refers to the content in the aqueous solution or dispersion.

The following raw materials were used:

DINP diisononyl phthalate

MMA methyl methacrylate

MA methyl acrylate

AS acrylic acid

S styrene

nBA n-butyl acrylate

AN acrylonitrile

Bu butadiene

Fat barrier test

To investigate the grease barrier, a blotting paper sheet with a size of 10x10 cm was coated with the respective polymer and contacted with a test fat or test oil (for example, 2 ml of oleic acid). The field area impregnated with the fat is evaluated after up to 16 hours at 60 ° C. According to the quality after x hours, the discharge is evaluated.

Barrier test against gaseous components of a mineral oil (test procedure 1)

In an experimental assembly they were packed on top of each other:

1. Donor: 30g / m2 paper loaded with 1% Gravex 913 (Shell, mineral oil for printing inks) 2. Spacer paper to exclude a wetting contact, 30g / m2

3. The barrier material to be tested

4. Acceptor: commercial polyethylene film of 20 gm, LLDPE with density of 0.915 g / cm3

This package (basic dimension of 10x10 cm) was wrapped with aluminum foil on all sides.

The experimental system was stored at 60 ° C and was investigated by periodically cutting a strip of the receiving film, extracting with n-hexane for 2 hours / 25 ° C and measuring the content of mineral oil components having a carbon number of 15. -25 by means of HPLC-GC online. The penetration time for the penetration of the mineral oil components through the barrier material was determined. Penetration time is the time after which, for the first time, mineral oil components in the extract are detected above the detection limit.

Barrier test against gaseous components of mineral oil (test procedure 2)

In a container with a sponge, 9 ml of hexane are placed and closed with a lid having an opening and a sealing ring (internal diameter 63 mm). The opening is hermetically sealed with the barrier material to be tested, while the barrier material does not come into contact with the sponge soaked with hexane. The weight decrease is a measure for the hexane leaving through the barrier material by the gas phase and, therefore, a measure for the quality of the barrier effect against gaseous components of the mineral oil. The weight reduction in grams is recalculated to 1 m2 of paper area and then indicated as g / m2 d (per day). Example 1: Comparison test of grease barrier / barrier against gaseous components of mineral oil For the polymers listed in table 1 the barrier effect against fats and oils, ie against fatty oils and fatty acid esters (fat barrier) was investigated. ) and the barriers against gaseous components of mineral oil, that is against volatile hydrocarbons (hereinafter, mineral oil barrier) according to the test 1, were investigated. The results are compiled in table 1.

Table 1: Barrier effects of certain polymers

The results show that of the coatings with a fat barrier effect it is not possible to conclude on an effectiveness as a barrier against gaseous components of mineral oil. While the tested MMA / MA / AS copolymer exhibits a barrier to mineral oil, for example, if it is coated on polyethylene, however, it has been found that this polymer does not form film sufficiently well on paper, probably due to the high glass transition temperature and the coating presents defective sites through which the test oil can penetrate.

Example 2: Preparation of polymer dispersions

In a reactor, after purging with nitrogen, 450.0 g of demineralized water and 3.0 g of emulsifier (Disponil® LDBS 20, 20% in water) are charged initially. The mixture in the initial charge is heated to 70-90 ° C. Then, 21.43 g of sodium peroxodisulfate (7%) are added and the mixture is stirred for 50 minutes. For 2 hours, the emulsion feed is metered into the reactor which is composed of 40.0 g of water, 26.67 g of emulsifier (Dowfax 2A1, 45% in water) and 600.0 g of monomer mixture according to the Table 2. After finalizing the emulsion feed, polymerization is continued for 45 minutes then the reactor is cooled to room temperature.

Solids content: approximately 45%

Table 2: Copolymer compositions, amounts in% by weight

Example 3: Comparative test of barrier against gaseous components of mineral oil

Different barrier materials were tested with test procedure 2 for the quality of the barrier effect against gaseous components of mineral oil. The results are compiled in table 3.

Table 3: Barrier effects of certain polymers

The results show that examples B1 to B5, B8 and B9 according to the invention have very good barrier properties against gaseous components of mineral oil.

Claims (14)

1. Packing of paper or cardboard, where the packaging is made at least partially from recycled paper, contaminated with mineral oil and the packaging has at least one barrier layer which can be prepared by applying an aqueous polymer dispersion containing at least one copolymer which can be prepared by emulsion polymerization of (a) one or more main monomers which are selected from the group consisting of alkyl (meth) acrylates of C1 to C4, (b) 0.1 to 5% by weight of one or more acidic monomers, (c) 0-20% by weight of acrylonitrile and (d) 0 to 10% by weight of monomers other than monomers (a) to (c), wherein the glass transition temperature of the copolymer is in the range of 10 to 45 ° C, in which case the copolymer is it comprises at least 70% by weight of the main monomers (a) and the barrier layer can be on at least one of the packaging surfaces a barrier layer can form at least one of several layers of a multilayer coating of the packaging. Packing according to the preceding claim, characterized in that the amount of acid monomer used (b) is from 0.5 to 5% by weight with respect to the sum of all monomers. Packaging according to one of the preceding claims, characterized in that the main monomers (a) are selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate and n-butyl acrylate. Packaging according to one of the preceding claims, characterized in that the copolymer can be prepared from (a) 79.5 to 99.5% by weight of one or more main monomers which are selected from the group consisting of alkyl (meth) acrylates of C1 to C4, (b) 0.5 to 5% by weight of one or more acid monomers selected from acrylic acid and methacrylic acid, (c) 0-20% by weight acrylonitrile and no other monomer than the monomers (a) to (c). Packaging according to one of the preceding claims, characterized in that the glass transition temperature of the copolymer is in the range of 15 to 40 ° C. Packaging according to one of the preceding claims, characterized in that the copolymer can be prepared in 1-20% by weight of acrylonitrile. Packaging according to one of the preceding claims, characterized in that the other monomers (d) are selected from the group consisting of C5 to C20 alkyl (meth) acrylates, vinyl esters of carboxylic acids containing up to 20 C atoms, vinyl aromatics with up to 20 C atoms, ethylenically unsaturated nitriles other than acrylonitrile, vinyl halides, vinyl ethers of alcohols containing 1 to 10 C atoms, aliphatic hydrocarbons with 2 to 8 C atoms and one or two double bonds and mixtures of these monomers. Packaging according to one of the preceding claims, characterized in that the copolymer is used in combination with up to 1 part by weight of plate-shaped pigments per 1 part by weight of copolymer. Packaging according to one of the preceding claims, characterized in that the coating with the copolymer has a permeability for gaseous n-hexane of less than 50 g / m2 at 23 ° C and an application weight of 20 to 25 g / m2 on paper . Packaging according to one of the preceding claims, characterized in that the copolymer in the aqueous polymer dispersion is contained in an amount of 15 to 75% by weight, preferably 40 to 60% by weight. Packaging according to one of the preceding claims, characterized in that the contamination with mineral oil comes from printing inks and comprises volatile paraffins, volatile naphthenes and / or volatile aromatic hydrocarbons. Packaging according to one of the preceding claims, characterized in that the barrier layer comprises a thickness of 2 to 30 μm. 13. Process for manufacturing a package according to claim 1, wherein a composition is provided in the form of an aqueous polymer dispersion is applied to the packaging substrate and dried, in whose case the aqueous polymer dispersion contains at least one copolymer with the characteristics referred to the polymer dispersion according to at least one of claims 1 to 10. 14. Use of an aqueous polymer dispersion containing at least one copolymer with the characteristics referred to the polymer dispersion according to at least one of claims 1 to 10 for the production of a barrier layer against volatile components of mineral oil.