EP2714990B1 - Paper and cardboard packaging with barrier coating - Google Patents

Description

The invention relates to a paper or cardboard packaging from mineral oil loaded, recycled paper with a barrier layer, which can be prepared by applying an aqueous polymer dispersion containing a copolymer which can be prepared by emulsion polymerization of C1 to C4 alkyl (meth) acrylates, acid monomers and optionally acrylonitrile and other monomers, wherein the glass transition temperature of the copolymer is in the range of +10 to +45 ° C. The barrier layer may be on one of the packaging surfaces or form one of several layers of a multilayer packaging coating.

Cardboard packaging is usually made from recycled paper. In the case of printed paper, in particular newsprint, the recycled paper may contain residual mineral oil from printing inks commonly used for newspaper printing. Even at room temperature, volatiles of these residues evaporate and, in the case of food packaging, beat on the box-packed foodstuffs, e.g. Noodles, grits, rice or cornflakes down. Also, most of the inner bag made of polymer films used today do not provide adequate protection. Studies by the Cantonal Laboratory of Zurich have revealed significant levels of residual oil in food packaged in recycled paper packaging. The volatile mineral oil constituents are predominantly health-hazardous paraffin and naphthenic hydrocarbons and aromatic hydrocarbons, in particular those having 15-25 C atoms.

There is therefore a need to reduce the risk of contamination of foods with mineral oil residues. One possibility would be to refrain from recycling newsprint in the manufacture of cardboard packaging for food packaging. This is undesirable for environmental reasons and not practical because of insufficient available amounts of fresh cellulose. Another solution would be to dispense with mineral oils in the printing inks for newspaper printing. However, this encounters technological obstacles, especially with regard to the wiping resistance of the printing on the paper surface. In the packaging sector, barrier coatings against grease and oils are known. In the WO 2006/053849 For example, coatings based on water-based polymer compositions for paper and board are described. Although the polymers show good barrier properties against liquid fatty substances. However, it has been shown that this does not necessarily give a good barrier effect to gaseous substances passing through, since it is different transport mechanisms for the substances passing through. In the case of liquid fats and oils, transport takes place via the fibers, whereby capillary forces and surface wetting play a role. In the case of problems with gaseous substances, capillary action and wetting are not important, but rather sorption, diffusion and porosity. In addition, fats and oils differ from hydrocarbons, ie of mineral oil constituents in their polarity and thus in their diffusion behavior through barrier layers.

It is an object of the present invention to provide packages which reduce the risk of contamination of the packaged product with volatile mineral oil constituents despite the use of recycled paper contaminated with mineral oil.

1. (a) einem oder mehreren Hauptmonomeren, welche ausgewählt sind aus der Gruppe bestehend aus C1- bis C4-Alkyl(meth)acrylaten,
2. (b) 0,1 bis 5 Gew.% eines oder mehreren Säuremonomeren, z.B. ausgewählt aus Acrylsäure und Methacrylsäure,
3. (c) 0-20 Gew.% Acrylnitril und
4. (d) 0 bis 10 Gew.% weiteren, von den Monomeren (a) bis (c) verschiedenen Monomeren,

wobei die Glasübergangstemperatur des Copolymers im Bereich von +10 bis +45 °C liegt, wobei das Copolymer zu mindestens 70 Gew.% aus den Hauptmonomeren (a) aufgebaut ist, und wobei sich die Barriereschicht auf mindestens einer der Verpackungsoberflächen befinden kann oder die Barriereschicht mindestens eine von mehreren Schichten einer mehrschichtigen Verpackungsbeschichtung bilden kann. Die Verpackungen eignen sich insbesondere für Lebensmittel.The object is achieved according to the invention by a packaging made of paper or cardboard, wherein the packaging is made at least in part from mineral oil loaded, recycled paper and wherein the package has at least one barrier layer which can be produced by applying an aqueous polymer dispersion comprising at least one copolymer which can be produced is characterized by emulsion polymerization

1. (a) one or more major monomers selected from the group consisting of C1 to C4 alkyl (meth) acrylates,
2. (b) from 0.1 to 5% by weight of one or more acid monomers, for example selected from acrylic acid and methacrylic acid,
3. (c) 0-20% by weight of acrylonitrile and
4. (d) 0 to 10% by weight of other monomers other than monomers (a) to (c),

wherein the glass transition temperature of the copolymer is in the range of +10 to +45 ° C, wherein the copolymer is at least 70% by weight of the major monomers (a), and wherein the barrier layer may be on at least one of the packaging surfaces or the barrier layer can form at least one of several layers of a multilayer packaging coating. The packaging is particularly suitable for food.

Mineral oil contamination means that the paper contains detectable amounts of volatile hydrocarbons by conventional analytical methods, in particular volatile paraffins, volatile naphthenes and / or volatile aromatic hydrocarbons having up to 25 carbon atoms. Volatile hydrocarbons are those having up to 25 C atoms, e.g. from 5 to 22 carbon atoms. In one embodiment of the invention, the mineral oil load is derived from printing inks and includes volatile paraffins, volatile naphthenes and / or volatile aromatic hydrocarbons.

In the following, the term "(meth) acrylic ..." and similar terms will be used as a shorthand notation for "acrylic ... or methacrylic ...".

The polymer dispersions to be used according to the invention are dispersions of polymers in an aqueous medium. This may be, for example, completely desalinated water or mixtures of water and a miscible solvent such as methanol, ethanol or tetrahydrofuran. Preferably, no organic solvents are used. The solids contents of the dispersions are preferably from 15 to 75 wt .-%, preferably from 40 to 60 wt .-%, in particular greater than 50 wt.%. The solids content can be adjusted, for example, by appropriate adjustment of those used in the emulsion polymerization Amount of water and / or the amount of monomers done. The mean particle size of the polymer particles dispersed in the aqueous dispersion is preferably less than 400 nm, in particular less than 300 nm. Particularly preferably, the mean particle size is between 70 and 250 nm or between 80 and 150 nm. Here, the average particle size is the d ₅₀ value Understood particle size distribution, ie 50 wt .-% of the total mass of all particles have a smaller particle diameter than the d ₅₀ value. The particle size distribution can be determined in a known manner with the analytical ultracentrifuge ( W. Mächtle, Macromolecular Chemistry 185 (1984), page 1025-1039 ). The pH of the polymer dispersion is preferably adjusted to pH greater than 4, in particular to a pH of between 5 and 9.

The copolymers to be used according to the invention are emulsion polymers preparable by emulsion polymerization of free-radically polymerizable monomers. The copolymer is formed from one or more major monomers (a) selected from the group consisting of C1 to C4 alkyl (meth) acrylates. The main monomers (a) are preferably at least 70% by weight, preferably at least 75% by weight, e.g. from 79.5 to 99.5 wt.%, Based on the sum of all monomers used. 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 acid monomers (b). Acid monomers are ethylenically unsaturated, radically polymerizable monomers having at least one acid group, e.g. Monomers with carboxylic acid, sulfonic acid or phosphonic acid groups. Preferred are carboxylic acid groups. Called z. For example, acrylic acid, methacrylic acid, itaconic acid, maleic acid or fumaric acid. Preferably, the acid monomers (b) are selected from acrylic acid and methacrylic acid. The acid monomers (b) are used at 0.1 to 5 wt.%, Preferably at 0.5 to 5 wt.%, Based on the sum of all monomers.

The copolymer can optionally be formed as further monomer (c) to 0 to 20 wt.%, Based on the sum of all monomers, of acrylonitrile. In one embodiment of the invention, the copolymer is formed to 1-20 wt%, preferably 2-20 wt% of acrylonitrile.

The copolymer may optionally be formed from other monomers (d) other than the monomers (a) to (c). The amount of further monomers (d) is 0 to 10 wt.% Or 0 to 5 wt.%, Based on the sum of all monomers. In one embodiment, 0.1 to 10 wt.% Or 0.1 to 5 wt.% Of further monomers (d) are used. In another embodiment, no further monomers other than monomers (a) to (c) are used.

The further 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 carbon atoms, vinylaromatics having up to 20 carbon atoms, ethylenically different from acrylonitrile unsaturated nitriles, vinyl halides, vinyl ethers of alcohols containing 1 to 10 carbon atoms, aliphatic Hydrocarbons having 2 to 8 carbon atoms and one or two double bonds or mixtures of these monomers. Examples include (meth) acrylic acid alkyl esters having a C ₅ -C ₁₀ alkyl radical, such as 2-ethylhexyl acrylate. In particular, mixtures of (meth) acrylic acid alkyl esters are also suitable. Vinyl esters of carboxylic acids having 1 to 20 carbon atoms are, for. As vinyl laurate, vinyl stearate, vinyl propionate, vinyl versatate and vinyl acetate. Suitable vinylaromatic compounds are vinyltoluene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene. Example of nitriles is methacrylonitrile. The vinyl halides are chloro, fluoro or bromo substituted ethylenically unsaturated compounds, preferably vinyl chloride and vinylidene chloride. To name as vinyl ethers are, for. As vinyl methyl ether or vinyl isobutyl ether. Vinyl ether is preferably from 1 to 4 C-containing alcohols. As hydrocarbons having 4 to 8 carbon atoms and two olefinic double bonds may be mentioned butadiene, isoprene and chloroprene. Preferred further monomers (d) are the C ₅ - to C ₁₀ -alkyl acrylates and -methacrylates and vinylaromatics, in particular styrene and mixtures thereof. Very particular preference is given to n-hexyl acrylate, octyl acrylate and 2-ethylhexyl acrylate, 2-propylheptyl acrylate, styrene and mixtures of these monomers. Further monomers (d) are z. As well as hydroxyl-containing monomers, in particular C ₁ -C ₁₀ hydroxyalkyl (meth) acrylates and (meth) acrylamide. Further monomers (d) which may also be mentioned are phenyloxyethylglycol mono- (meth) acrylate, glycidyl acrylate, glycidyl methacrylate, amino (meth) acrylates such as 2-aminoethyl (meth) acrylate. Other monomers (d) which may also be mentioned are crosslinking monomers.

1. (a) 79,5 bis 99,5 Gew.% eines oder mehreren Hauptmonomeren, welche ausgewählt sind aus der Gruppe bestehend aus C1- bis C4-Alkyl(meth)acrylaten,
2. (b) 0,5 bis 5 Gew.% eines oder mehreren Säuremonomeren ausgewählt aus Acrylsäure und Methacrylsäure,
3. (c) 0-20 Gew.% Acrylnitril und

keinen weiteren, von den Monomeren (a) bis (c) verschiedenen Monomeren.In one embodiment of the invention, the copolymer is produced from

1. (a) 79.5 to 99.5% by weight of one or more major monomers selected from the group consisting of C1 to C4 alkyl (meth) acrylates,
2. (b) from 0.5 to 5% by weight of one or more acid monomers selected from acrylic acid and methacrylic acid,
3. (c) 0-20% by weight of acrylonitrile and

no further, different from the monomers (a) to (c) monomers.

Type and amounts of the monomers of the copolymer are adjusted so that the glass transition temperature of the emulsion polymer in the range of +10 to +45 ° C, preferably from +15 to +40 ° C. The glass transition temperature can be determined by differential scanning calorimetry (ASTM D 3418-08, so-called "midpoint temperature").

The preparation of the copolymers can be carried out by emulsion polymerization, it is then an emulsion polymer. In the emulsion polymerization, ionic and / or nonionic emulsifiers and / or protective colloids or stabilizers are generally used as surface-active compounds in order to assist in the dispersion of the monomers in the aqueous medium. Protective colloids are polymeric compounds which upon solvation bind large quantities of water and are capable of stabilizing dispersions of water-insoluble polymers. In contrast to emulsifiers, they usually do not lower the interfacial tension between polymer particles and water. A detailed description of suitable protective colloids can be found in Houben-Weyl, Methods of Organic Chemistry, Volume XIV / 1, Macromolecular Materials, Georg Thieme Verlag, Stuttgart, 1961, pages 411-420 , Suitable as protective colloids z. B. amphiphilic polymers, ie polymers with hydrophobic and hydrophilic groups. They may be natural polymers such as starch 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 above 2000 g / mol, for example 2000th to 100,000 g / mol, in particular from 5000 to 50,000 g / mol. Anionic and nonionic emulsifiers are preferably used as surface-active substances. Suitable emulsifiers are, for example, ethoxylated C ₈ - to C ₃₆ fatty alcohols having a degree of ethoxylation of 3 to 50, ethoxylated mono-, di- and tri-C ₄ - to C ₁₂ -alkylphenols having a degree of ethoxylation of 3 to 50, alkali metal salts of dialkyl esters of Sulfosuccinic acid, alkali metal and ammonium salts of C ₈ - to C ₁₂ -alkyl sulfates, alkali metal and ammonium salts of C ₁₂ - to C ₁₈ -alkylsulfonic acids and alkali metal and ammonium salts of C ₉ - to C ₁₈ -alkylarylsulfonic acids. If emulsifiers and / or protective colloids are used as auxiliaries for dispersing the monomers, the amounts used thereof are, for example, from 0.1 to 5% by weight, based on the monomers. Trade names of emulsifiers are z. Dowfax® A1, Emulan® NP 50, Dextrol® OC 50, Emulsifier 825, Emulsifier 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 wt .-%, based on the monomers to be polymerized.

The emulsion polymerization is generally carried out at 30 to 130, preferably 50 to 90 ° C.
The polymerization medium may consist of water only, as well as of mixtures of water and thus miscible liquids such as methanol. Preferably, only water is used. The emulsion polymerization can be carried out both as a batch process and in the form of a feed process, including a stepwise or gradient procedure. Preferably, the feed process in which one submits a portion of the polymerization, heated to the polymerization, polymerized and then the rest of the polymerization, usually over several spatially separate feeds, one or more of which monomers in pure or in emulsified form, continuously or gradually supplied.

In the emulsion polymerization, the customary and known auxiliaries, such as water-soluble initiators and regulators can be used. Water-soluble initiators for the emulsion polymerization are, for example, ammonium and alkali metal salts of peroxodisulfuric acid, eg. For example, sodium peroxodisulfate, hydrogen peroxide or organic peroxides, z. B. tert-butyl hydroperoxide. Also suitable are so-called reduction-oxidation (red-ox) initiator systems. The redox initiator systems consist of at least one mostly inorganic reducing agent and one inorganic or organic oxidizing agent. The oxidation component is z. B. to the above-mentioned initiators for emulsion polymerization. The reduction components are, for. B. to alkali metal salts of sulfurous acid, such as. For example, sodium sulfite, sodium hydrogen sulfite, alkali metal salts of the desulfurous acid such as sodium disulfite, bisulfite addition compounds aliphatic aldehydes and ketones such as acetone bisulfite or reducing agents such as hydroxymethanesulfinic acid and salts thereof, or ascorbic acid. The red-ox initiator systems can be used with the concomitant use of soluble metal compounds whose metallic component can occur in multiple valence states. Usual Red Ox initiator systems are z. As ascorbic acid / iron (II) sulfate / sodium peroxydisulfate, tert-butyl hydroperoxide / sodium disulfite, tert-butyl hydroperoxide / Na-hydroxymethanesulfinic acid or tert-butyl hydroperoxide / ascorbic acid. The individual components, eg. As the reduction component, mixtures may also be z. B. a mixture of the sodium salt of hydroxymethanesulfinic acid and sodium disulfite. The compounds mentioned are usually used in the form of aqueous solutions, the lower concentration being determined by the amount of water acceptable in the dispersion and the upper concentration by the solubility of the compound in question in water. In general, the concentration is 0.1 to 30 wt .-%, preferably 0.5 to 20 wt .-%, particularly preferably 1.0 to 10 wt .-%, based on the solution. The amount of initiators is generally 0.1 to 10 wt .-%, preferably 0.5 to 5 wt .-%, based on the monomers to be polymerized. It is also possible to use a plurality of different initiators in the emulsion polymerization. To remove the residual monomers, initiator is usually also added after the end of the actual emulsion polymerization.

In the polymerization regulators can be used, for. B. 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 weight is reduced. Suitable z. B. Compounds having a thiol group such as tert-butyl mercaptan, mercaptoethyl propionate, 2-ethylhexyl thioglycolate, thioglycolic acid ethyl ester, mercaptoethanol, mercaptopropyltrimethoxysilane, n-dodecyl mercaptan, or tert-dodecyl mercaptan. Furthermore, regulators without a thiol group can be used, e.g. Terpinolene. In a preferred embodiment, the emulsion polymer is prepared using from 0.05 to 0.5% by weight, based on the amount of monomer, of at least one molecular weight regulator.

The polymer dispersion used for the coating of the packagings can consist solely of the emulsion polymer dispersed in water for the use according to the invention. However, it may also contain other additives, e.g. Fillers, antiblocking agents, dyes, leveling 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 platelet-shaped pigments, based on 1 part by weight of copolymer. Examples of platelet-shaped pigments are talc, clay or mica (mica). Preference is given to talc. Preferred form factors (length to thickness ratio) are greater than 10.

The polymer dispersion forms a barrier layer after coating the substrate. A barrier layer is particularly present when a copolymer is used which causes a coating with the copolymer to have a permeability to gaseous n-hexane less than 50 g / m ² d, preferably less than 10 g / m ² d, more preferably less than 5 g / m ² d or less than 1 g / m ² d at 23 ° C and a weight of 20-25 g / m ² on paper (see measuring method in the examples below).

The content of the at least one copolymer in the dispersion used for the coating is preferably at least 1 wt .-%, in particular at least 5 wt .-% and up to 60 or up to 75 wt.%. Preferably, the content of the at least one copolymer in the aqueous dispersion is 15 to 75% by weight, or 40 to 60% by weight. Preferred aqueous dispersions of the copolymers have 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) at a pH of 4 and a temperature of 20 ° C. ). The mean particle size of the copolymer particles dispersed in the aqueous dispersion is, for example, from 0.02 to 100 μm, preferably from 0.05 to 10 μm. You can z. Example by means 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 in particular paper and cardboard. The dispersions used for coating may contain other additives or adjuvants, e.g. Thickener for adjusting the rheology, wetting aids or binders.

The application can be carried out, for example, on coating machines in such a way that the coating composition is applied to paper or board. If web-shaped materials are used, the polymer dispersion is usually applied from a trough over an applicator roll and leveled with the aid of an air brush. Other ways of applying the coating succeed, for example. with the aid of the reverse gravure method, with a spray method or with a roller blade or with other coating methods known to the person skilled in the art. The carrier substrate is coated on at least one side, i. it can be coated on one side or on both sides. Preferred application methods for paper and board are curtain coating, air knife, bar brushing or knife coating. Preferred application methods for film coating are doctor blade, wire bar, air brush, reverse roll coating method, countergraduate coating, pouring head or die.

The amounts applied to the sheet-like materials are preferably 1 to 10 g (polymer, solids) per m ² , preferably 2 to 7 g / m ² for films, or preferably 5 to 30 g / m ² for paper or board. After applying the coating compositions to the support substrates, the solvent or water is evaporated. For this purpose, for example, when working continuously, the material can pass through a dryer channel, which can be equipped with an infrared irradiation device. Thereafter, the coated and dried material is passed over a cooling roll and finally wound up. The thickness of the dried coating is preferably at least 1 μm, in particular 1 to 50 μm, particularly preferably 2 to 30 μm or 5 to 30 μm.

The barrier layer may be located on at least one of the packaging surfaces. It may also form at least one of several layers of a multilayer packaging coating. The barrier coating may be applied directly to a surface of the substrate, however, other layers may be present between the substrate and the barrier coating, e.g. B. primer layers, other barrier layers or colored or black and white ink layers. The barrier layer is preferably located on the inner, the packaged goods facing side of the package.

The inner bag is preferably made of a polymer film. The material of the inner bag is preferably selected from polyolefins, preferably polyethylene or oriented polypropylene, which polyethylene may have been produced by both high pressure and low pressure polymerization of ethylene. In order to improve the adhesion to a film even further, the carrier film may be previously subjected to a corona treatment. Other suitable carrier films are, for example, films of polyester, such as polyethylene terephthalate, films of polyamide, polystyrene and polyvinyl chloride. In one embodiment, the support material is biodegradable films, e.g. from biodegradable aliphatic-aromatic copolyesters and / or polylactic acid, for example Ecoflex® or Ecovio® films. Suitable copolyesters are e.g. formed from alkanediols, in particular C 2 to C 8 alkanediols, e.g. 1,4-butanediol, from aliphatic dicarboxylic acids, in particular C 2 to C 8 dicarboxylic acids, such as e.g. Adipic acid and from aromatic dicarboxylic acids such as e.g. Terephthalic acid.

The thickness of the carrier films is generally in the range of 10 to 200 μm.

In order to obtain special surface or coating properties of the films and packaging materials, for example a good printability, even better barrier or blocking behavior, good water resistance, it may be advantageous to coat the coated substrates with cover layers which additionally impart these desired properties or the barrier coating subject to a corona treatment. The substrates precoated according to the invention show good overcoatability. It may be overcoated again according to a method mentioned above or in a continuous process without intermediate winding and unwinding e.g. the film or paper are coated at the same time several times, e.g. using a curtain coater. As a result, the barrier layer according to the invention is located inside the system, the surface properties are then determined by the cover layer. The cover layer has good adhesion to the barrier layer.

The invention also provides a process for producing a packaging, wherein a composition in the form of an aqueous polymer dispersion described above is provided and applied to a packaging substrate and dried, wherein the aqueous polymer dispersion contains at least one of the above-described copolymers.

The invention also provides the use of an aqueous polymer dispersion comprising at least one of the copolymers described above for producing a barrier layer against volatile mineral oil constituents, in particular for producing packaging, in particular packaging for foodstuffs.

The coated substrates according to the invention show an excellent barrier effect against volatile mineral oil constituents. The coated substrates can be used as such as packaging. The coatings have very good mechanical properties, and show e.g. good block behavior.

Examples

Unless otherwise stated in the context, the percentages always indicate percent by weight. The indication of a content refers to the content in aqueous solution or dispersion.

DINP

Diisononylphtalat

MMA

Methylmethacrylat

MA

Methylacrylat

AS

Acrylsäure

S

Styrol

nBA

n-Butylacrylat

AN

Acrylnitril

Bu

Butadien

The following starting materials were used:

DINP

diisononyl phthalate

MMA

methyl methacrylate

MA

methyl acrylate

AS

acrylic acid

S

styrene

nBA

n-butyl acrylate

AT

acrylonitrile

Bu

butadiene

Test for fat barrier

1. 1. Donor: Papier von 30g/m² beladen mit 1 % Gravex 913 (Shell, Mineralöl für Druckfarben)
2. 2. Spacer-Papier zum Ausschluss eines benetzenden Kontaktes, 30g/m²
3. 3. Das zu testende Barrierematerial
4. 4. Akzeptor: handelsübliche PE-Folie 20µm, LLDPE mit Dichte 0.915 g/cm³

Dieses Paket (Grundmaße 10x10cm) wurde allseitig mit Aluminiumfolie umhüllt.To examine the fat barrier, a 10 × 10 cm blotter paper sheet was coated with the respective polymer and contacted with a test fat or test oil (eg, 2 ml of oleic acid). The area of the greased field is rated after up to 16 hours at 60 ° C. Depending on the quality, the breakdown is evaluated after x hours.
Barrier test against gaseous mineral oil constituents (test method 1)
In a test setup were packed on top of each other:

1. 1. Donor: paper of 30g / m ² loaded with 1% Gravex 913 (Shell, mineral oil for printing inks)
2. 2. Spacer paper to exclude a wetting contact, 30g / m ²
3. 3. The barrier material to be tested
4. 4. acceptor: commercially available PE film 20 μm, LLDPE with density 0.915 g / cm ³

This package (basic dimensions 10x10cm) was wrapped on all sides with aluminum foil.

The experimental system was stored at 60 ° C and examined by periodically cutting a strip of the acceptor sheet, extracting with n-hexane 2h / 25 ° C, and measuring the content of 15-25 carbon number mineral oil ingredients by on-line HPLC-GC. It was the breakthrough time for the breakthrough of mineral oil components by the barrier material certainly. The breakthrough time is the time after which mineral oil constituents above the detection limit are detected for the first time in the extract.

Barrier test against gaseous mineral oil constituents (test method 2)

9 ml of hexane are placed in a container with a sponge and closed with a lid which has an opening and a sealing ring (inner diameter 63 mm). The opening is tightly closed with the barrier material being tested, with the barrier material not touching the hexane-soaked sponge. The weight loss of the vessel is measured. The weight loss is a measure of the gas phase through the barrier material escaping hexane and thus a measure of the quality of the barrier effect against gaseous mineral oil components. The weight loss in grams is converted to 1 m ² paper surface and then expressed as g / m ² d (per day).

Example 1:

Comparison test fat barrier / barrier against gaseous mineral oil components

For the polymers listed in Table 1, the barrier effect against fats and oils, ie against fatty acids and fatty acid esters (fat barrier) and the barrier against gaseous mineral oil constituents, ie against volatile hydrocarbons (hereinafter mineral oil barrier) according to Test 1 were investigated. The results are summarized in Table 1. Table 1: Barrier effects of certain polymers polymer Test fat / oil fat barrier mineral oil barrier aromatic / aliphatic, amorphous polyester-polyurethane DINP + no penetration - breakthrough <4d aliphatic, partially crystalline polyester-polyurethane DINP + no penetration - breakthrough <4d MMA / MA / AS Copolymer Tg about 50 ° C DINP oleic acid - Partially greased area + no penetration aromatic / aliphatic, partially crystalline polyester-polyurethane DINP + no penetration - breakthrough <4d polyethylene film DINP oleic acid + no penetration - breakthrough <1d S / nBA / AN / AS copolymer, Tg 5 ° C oleic acid + no penetration - breakthrough <4d S / butadiene / AS copolymer, Tg 20 ° C oleic acid - Fully greased - no hexane barrier (test 2)

The results show that coatings with a fat barrier effect can not be concluded to be effective as a barrier to gaseous mineral oil constituents. Although the tested MMA / MA / AS copolymer has a mineral oil barrier, for example when it is coated on polyethylene. However, it was found that this polymer is probably due to the high glass transition temperature on paper is not good enough to form a film and the coating has defects through which the test oil can penetrate.

Example 2: Preparation of polymer dispersions

After rinsing with nitrogen, place 450.0 g of demineralised water and 3.0 g of emulsifier (Disponil® LDBS 20, 20% in water) into a reactor. The mixture in the original is heated to 70-90 ° C. Subsequently, 21.43 g of sodium peroxodisulfate (7%) are added and stirred for 50 minutes. Within 2 hours the emulsion feed consisting of 240.0 g of water, 26.67 g emulsifier (Dowfax 2A1, 45% in water) and 600.0 g of monomer mixture according to Table 2 in the reactor. After the end of the emulsion feed polymerize for 45 min. Then the reactor is cooled to room temperature.
Solids content: approx. 45% Table 2: Copolymer compositions, amounts in% by weight example monomers Tg [° C] d ₅₀ [nm] ¹⁾ B 1 74% EA / 10% MMA / 15% AN / 1% AS 10 104 B 2 65% EA / 19% MMA / 15% AN / 1% AS 19 107 B 3 80% MA / 19% MMA / 1% AS 36 97 B 4 90% MA / 9% AN / 1% AS 29 132 B 5 55% EA / 44% MMA / 1% AS 30 110 B 6 65% MA / 19% MMA / 15% AN / 1% AS 47 B 7 65% MA / 19% MMA / 15% AN / 1% AS 47 B 8 54% EA / 44% MMA / 2% AS 33 (calculated) 119 B 9 52% EA / 44% MMA / 4% AS 36 (calculated) 120 ¹⁾ Weight average particle size d ₅₀

Example 3: Comparison test Barrier against gaseous mineral oil components

Various barrier materials were tested by Test Method 2 for the degree of barrier against gaseous mineral oil components. The results are summarized in Table 3. Table 3: Barrier effects of certain polymers example Tg [° C] Hexane permeation [gm ² d] B 1 10 0.2-0.3 B 2 19 0.6 B 3 36 0.5 B 4 29 2 B 5 30 0.3 B 6 47 100-150 B 7 47 120-160 B 8 33 (calculated) 1.8 B 9 36 (calculated) 2.1 55 MA / 44 MMA / 1 AS Copolymer 50 200-270 14 S / 69 nBA / 14 AN / 3 AS copolymer 5 268 30 Bu / 65 S / 5 AS 20 > 300

The results show that the inventive examples B1 to B5, B8 and B9 have very good barrier properties against gaseous mineral oil constituents.

Claims (14)

1. Paper or cardboard packaging produced at least partly from mineral oil contaminated, recycled paper, wherein the packaging includes at least one barrier layer obtainable by applying an aqueous polymeric dispersion comprising at least one copolymer obtainable by emulsion polymerization of

   (a)one or more principal monomers selected from the group consisting of C₁-C₄ alkyl (meth)acrylates,

   (b) 0.1 to 5 wt% of one or more acid monomers,

   (c) 0-20 wt% of acrylonitrile and

   (d) 0 to 10 wt% of further monomers other than the monomers (a) to (c),

   wherein the glass transition temperature of the copolymer is in the range from +10 to +45°C,
   wherein the copolymer is constructed of the principal monomers (a) to an extent of at least 70 wt% ,and wherein the barrier layer may be situated on one or more of the surfaces of the packaging, or the barrier layer may form at least one of multiple layers of a multilayered packaging coating.
2. The packaging according to the preceding claim wherein the amount of acid monomer (b) used is from 0.5 to 5 wt%, based on the sum total of all monomers.
3. The packaging according to either preceding claim wherein the principal monomers (a) are selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl acrylate and n-butyl acrylate.
4. The packaging according to any preceding claim wherein the copolymer is obtainable from

   (a)79.5 to 99.5 wt% of one or more principal monomers selected from the group consisting of C₁-C₄ alkyl (meth)acrylates,

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

   (c) 0-20 wt% of acrylonitrile, and

   no further monomers other than the monomers (a) to (c) .
5. The packaging according to any preceding claim wherein the glass transition temperature of the copolymer is in the range from +15 to +40°C.
6. The packaging according to any preceding claim wherein the copolymer is 1-20 wt% obtainable from acrylonitrile.
7. The packaging according to any preceding claim wherein the further monomers (d) are selected from the group consisting of C₅-C₂₀ alkyl (meth)acrylates, vinyl esters of carboxylic acid 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 according to any preceding claim wherein the copolymer is used in combination with up to 1 part by weight of platelet-shaped pigments per 1 part by weight of copolymer.
9. The packaging according to any preceding claim wherein the coating with the copolymer has a permeability to gaseous n-hexane of less than 50 g/m² d at 23°C and a coat weight of 20 to 25 g/m² on paper.
10. The packaging according to any preceding claim wherein the copolymer is comprised in the aqueous polymer dispersion in an amount of 15 to 75 wt% and preferably of 40 to 60 wt%.
11. The packaging according to any preceding claim wherein the mineral oil contamination comes from printing inks and comprises volatile paraffins, volatile naphthenes and/or volatile aromatic hydrocarbons.
12. The packaging according to any preceding claim wherein the barrier layer is from 2 to 30 µm in thickness.
13. A process for producing packaging according to claim 1, which process comprises a composition in the form of an aqueous polymeric dispersion being provided and applied to a packaging substrate and dried, wherein the aqueous polymeric dispersion comprises at least one copolymer having the polymeric dispersion features according to one or more of claims 1 to 10.
14. The use of an aqueous polymeric dispersion comprising at least one copolymer having the polymeric dispersion features according to one or more of claims 1 to 10 for producing a barrier layer against volatile mineral oil constituents.