Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
  • D21H21/16—Sizing or water-repelling agents
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
  • D21H17/30—Alginic acid or alginates
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/10—Coatings without pigments
  • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
  • D21H19/20—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/10—Coatings without pigments
  • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
  • D21H19/20—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H19/22—Polyalkenes, e.g. polystyrene
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/80—Paper comprising more than one coating
  • D21H19/82—Paper comprising more than one coating superposed
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H19/00—Coated paper; Coating material
  • D21H19/80—Paper comprising more than one coating
  • D21H19/84—Paper comprising more than one coating on both sides of the substrate
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/10—Packing paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
  • D21H27/30—Multi-ply

Definitions

• the present invention relates to a paper-based composite as a food packaging material with a barrier function and to the production and use of the composite.
• the barrier performance can be increased for polymeric substrate films by applying e.g. B. metal oxides can be increased by physical vapor deposition (PVD). PVD coating is also widely used on paper substrates, but is mainly used for decorative purposes. One reason for this is that such coatings can only increase barrier performance as long as the coatings are virtually defect-free. However, since paper has a very rough surface, inorganic coatings always contain some defects that allow small amounts of gas to penetrate. The roughness of the paper can be reduced by pre-coatings.
• a hybrid polymer layer made of inorganic-organic polymers based on silanes can serve as a smooth planarization layer.
• the low viscosity of the paints and the effects of drying result in very smooth surfaces that are very suitable for the subsequently applied inorganic coatings.
• PVD coating takes place under dry conditions that cause the paper to shrink. After the coating process, the paper absorbs moisture and thereby expands, which can lead to tension in the inorganic layer and therefore defects through cracks. In addition, the metal oxide layer must be very thin to avoid the formation of cracks and chips.
• the object was achieved by providing the composite according to the invention, which has a primer based on an aqueous polymer dispersion directly on the paper substrate.
• Primer or sealing varnishes known in the prior art based on an aqueous polymer dispersion can be used as primer varnishes.
• the composite according to the invention is flexible, so that the barrier performance is largely retained under mechanical stress.
• aqueous polymer dispersion By using an aqueous polymer dispersion, their properties can be adjusted. For example, the viscosity can be adjusted by varying the water content of the aqueous polymer dispersion.
• the aqueous polymer dispersions do not require reactive diluents that adversely affect the mechanical properties of polymers. The absence of reactive diluents makes the aqueous polymer dispersion more environmentally friendly and results in a less sticky primer.
• the substrate Due to the excellent barrier performance of these combined layers, the substrate as such does not have to have a barrier performance, so that there are no particular restrictions with regard to the compositions and properties of the substrate. Therefore, both original paper substrates and recyclates or other fiber-based materials (fiber casting compounds) can be used as substrates.
• the composite according to the invention is ideally suited as a food packaging material.
• the composite according to the invention contains a paper substrate, a primer applied thereon based on an aqueous polymer dispersion and a barrier layer on the primer.
• the barrier layer is a metal oxide layer and/or a hybrid polymer layer.
• the composite according to the invention can hereinafter simply be referred to as “the composite”. become.
• the aqueous polymer dispersion-based primer can simply be referred to as “the primer.”
• the barrier layer of metal oxide layer and/or hybrid polymer layer may simply be referred to as "the barrier layer”.
• the composite is a sheet having a preferred thickness of 1 mm or less, more preferably less than 300 ⁇ m.
• the composite is preferably so flexible that it can be folded and folded over without cracking and is therefore suitable for packing and wrapping objects, especially food.
• the composite can be folded to form a folded edge, with no cracks occurring in the paper substrate, in the primer and in the barrier layer.
• the composite not only the paper substrate and the primer, but preferably all components, including the one or more layers of the barrier layer, are directly on top of one another, i.e. H. arranged without an intermediate layer or adhesive or the like.
• the sequence of layers can depend on the drying process of one layer on top of an underlying layer.
• the increased temperature during drying can lead to expansion, shrinkage or change in viscosity of the layer.
• the density of defects can be reduced.
• the primer used can also be used as a sealing layer in the resulting packaging and as a finishing layer to protect the underlying metal oxide layer.
• the composite according to the invention not only offers a barrier against water vapor and oxygen, but also against other molecules that can migrate, such as aromas from the packaged food or unwanted foreign odors from outside. There is also a certain barrier against other substances such as foreign substances contained in printed packaging materials or recycled materials.
• the metal oxide layer and the hybrid polymer layer can independently cover the underlying layers completely or partially.
• the respective thicknesses of the layers are not particularly limited. They can vary and be flexibly adapted depending on the application method of the hybrid polymer layer, the nature of the surface of the substrate and the use of the coating.
• the composite according to the invention contains a combination that consists of a precoating, a metal oxide layer and a hybrid polymer layer in this order.
• This combination results in good adhesion between the precoating and the metal oxide layer and good adhesion between the metal oxide layer and the inorganic groups of the hybrid polymer.
• a possible explanation for the resistance to folding stresses could be the laminate theory. Laminate theory explains the forces acting on a laminate when it is bent. Tensile stress acts on the outer layer and compressive stress on the inner layer. The fragile layer is the brittle metal oxide layer. It should be in the middle, i.e. in the neutral plane, where the strains and stresses that occur during bending have the least influence.
• the precoating and the hybrid polymer layer act as buffer layers, which improve the fracture properties of the brittle film.
• a hybrid polymer layer can improve crack resistance.
• the more flexible pre-coating and the stiffer hybrid polymer layer act as optimal buffer layers. Changing the order of shifts is also possible and may have certain advantages. If the metal oxide layer is applied directly to the primer and the hybrid polymer layer as a top layer, defects (e.g.
• Hybrid polymer layers are chemically inert and also highly abrasion resistant and can protect the brittle and delicate metal oxide structure.
• the metal oxide is applied to the hybrid polymer layer, the very flat surface of the hybrid polymer layer can reduce the number of defects in the metal oxide.
• the paper substrate is provided with the primer on one of its surface sides.
• the other side of the surface can be free of a coating or have a coating, for example also the primer or a planarization layer or a barrier layer.
• a recyclate is used as a paper substrate, it must be sealed towards the food, i.e. on the inside, so that no unwanted substances migrate into the food.
• the base substrate can be coated with a planarization layer to smooth its surface so that it can be printed, for example.
• a planarization layer can also be used if a barrier layer, for example made of metal oxide layer and / or hybrid polymer layer is provided.
• the composite according to the invention is suitable for use as a food packaging material. However, he is not limited to this. With the properties shown here, a composite according to the invention is suitable for numerous applications in which flexible, paper-based packaging with high barrier performance is required. Examples of such applications are cosmetic items such as individually packaged care products or disinfectant wipes, but also cleaning products such as detergent in tab or powder form. In addition, the composite is suitable for contact with food, for example powdered nutritional supplements, instant coffee, portioned ketchup or tea bags.
• the composite according to the invention can also be referred to as follows: “Composite as packaging material, in particular for food, cosmetics or cleaning products.”
• the composite according to the invention is based on a paper substrate.
• the paper substrate is suitable as a base material for the barrier food packaging material.
• Paper is a cellulose-based fabric.
• the term “paper” or “paper substrate” is intended to include all cellulose-based fabrics, including thicker papers such as cardboard or cardboard.
• the paper can be a thin sheet with a mass per unit area of less than 150 g/m 2 , but also a cardboard in the range of 150 g/m 2 to 600 g/m 2 . Cardboard can be even heavier than cardboard.
• a paper is preferred, e.g. B. a calendered paper, precoated paper, release paper or the like, with a basis weight of 20-120 g/m 2 , preferably 35-90 g/m 2 and more preferably 50-70 g/m 2 .
• the thickness of the paper substrate is preferably more than 10 ⁇ m, for example 10 ⁇ m
• the paper substrate is a thin sheet having a thickness of 10 ⁇ m to 1 mm, even more preferably 10 ⁇ m to 200 ⁇ m.
• the paper substrate is preferably flexible.
• the surface of the paper substrate coated with the primer is preferably smooth. This surface preferably has an average roughness Ra of less than 2 ⁇ m or from 0.1 to 10 ⁇ m. In addition, it preferably has a roughness Rq of 1 to 10 ⁇ m and Rz of 5 to 20 ⁇ m.
• the average roughness value of the paper substrate coated with the primer can be determined, for example, using scanning electron microscopy (SEM), laser scanning microscopy (LSM) or atomic force microscope (AFM).
• a smooth surface can be obtained by mechanical treatment, for example calendering, and/or coating.
• smooth paper include supercalendered kraft (SCK) such as glassine, clay coated kraft (CCK), PE coated paper (polyethylene coated kraft, PCK), machine glazed (MG), fiber mold, Release liner or similar.
• the paper substrate can be, for example, original paper or a recyclate, i.e. waste paper.
• Original paper contains no or only small amounts of impurities.
• a paper-based recyclate may contain undesirable short-chain sugar chains, paint or printing ink as contaminants that are not necessary for the desired function of the composite or can even be disadvantageous.
• An example of impurities is a content of at least 5% of low molecular weight substances with a molecular weight of less than 1000 Da.
• the paper substrate is provided on at least one of its surface sides with a primer based on an aqueous polymer dispersion.
• an aqueous polymer dispersion is a composition containing water as a main phase and a polymer as a secondary phase, and includes dispersions of a liquid in another liquid immiscible therewith, and colloidal solutions of polymer particles in water.
• the aqueous polymer dispersion is referred to as a primer and is preferably highly flexible.
• a primer varnish is for example an aqueous polymer dispersion of a high molecular weight propylene copolymer, a modified polyvinyl alcohol or a modified vinyl acetate copolymer.
• An aqueous polymer dispersion of an ethylene-acrylic acid (EAA) copolymer is preferred.
• sealing layers for packaging systems can be used as primer coatings.
• the primer is applied directly to the paper substrate so that the primer and the paper substrate lie directly on top of each other in the composite.
• the primer reduces surface roughness, serves as a water vapor barrier, increases surface energy and seals the surface so that later applied layers cannot penetrate the paper structure.
• the primer creates a stronger adhesion between the paper substrate and the metal oxide and therefore a higher resistance of the metal oxide during bending or folding, so that fewer cracks occur.
• Particularly strong adhesion occurs when the precoating material contains acrylic acid, which leads to good adhesion to the hydroxy groups of the paper and the hybrid polymer.
• the metal oxide SiO x can be covalently bonded to polymers via CO-Si and/or C-Si.
• the alkyl content influences the properties of the primer. Higher alkyl content results in better adhesion between substrate and polymer resin, higher overall stiffness, lower melting temperature and more flexibility, which is important for sealability.
• the primer can smooth the rough surface of the paper substrate. It is therefore preferably at least thick enough to cover all surface roughness of the paper substrate. The result is preferably a surface that consists exclusively of primer material.
• the primer can be applied using reverse gravure printing, blade coating, curtain coating or slot die coating.
• the paper substrate can be corona treated.
• the primer is preferably applied in a thickness of 1-30 g/m 2 or 3-10 g/m 2 , preferably 4-8 g/m 2 , more preferably 5-7 g/m 2 and is applied at 80-110° C dried and, if necessary, hardened.
• the average thickness of the primer is preferably 1 ⁇ m to 20 ⁇ m, more preferably 2 ⁇ m to 10 ⁇ m.
• the thickness of the layer is determined using scanning electron microscopy.
• the primer When producing the composite, the primer is applied to the paper substrate.
• the aqueous primer partially penetrates the paper substrate, resulting in an intimate bond between the two components. After the primer has dried, this results in a strong adhesion between the paper substrate and the primer.
• a very thin layer of metal oxide can be created Thickness of, for example, 20 to 60 nm have a high barrier performance.
• the primer makes the barrier layer structure independent of the nature of the paper-fiber substrate to be coated. This means that recycled materials can also be used as paper substrates because possible migration of monomers or residues (MOSH/MOAH) from the paper can be prevented and the coating creates defined surfaces.
• the aqueous polymer dispersion contains a polymer.
• polymer includes both a fully polymerized polymer and a prepolymer that is elongated into the polymer after application to the paper substrate.
• the prepolymer can be an oligomer or polymer with a weight average molecular weight Mw of at least 2000 g/mol or even more than 5000 g/mol. A lower Mw results in a lower viscosity.
• the primer is prepared using an aqueous dispersion of a polymer as a starting material.
• the dispersibility of the polymer in water requires hydrophilic components, e.g. B. acidic or ionic residues in the molecule of the polymer. Hydrophilic components would interfere with non-aqueous, e.g. purely organic, compositions and are therefore not contained in polymers of such compositions. Therefore, the aqueous polymer dispersion used according to the invention differs from conventional non-aqueous primer paints. Consequently, the resulting primers also differ.
• the aqueous polymer dispersion preferably contains 10 to 90% water and 90 to 10% polymer, more preferably 40 to 80% water and 20 to 60% polymer.
• the total of the water content and the polymer content constitutes 80 to 100% of the aqueous polymer dispersion.
• the dispersion is aqueous, meaning it is based on water. It is preferably solvent-free, i.e. free from solvents other than water. In some embodiments, a small amount of solvent, e.g. B. 0.01% to 10% or 0.1% to 5% may be contained in the aqueous polymer dispersion. After application to the paper substrate, the aqueous polymer dispersion is dried. The water in the aqueous polymer dispersion can be removed by heating and/or air convection. As used herein, the term "drying" includes a process for partially or completely removing water. A dried dispersion may contain small amounts of water or no water, e.g. B. 0 to 5% or 0.1 to 5%, preferably 0 to 2% water.
• the dispersion may contain other components such as a reactive diluent, colorant or photoinitiator.
• the photoinitiator can be selected from the group of thioxanthones, ketosulfones, (alkyl)benzoylphenylphosphine oxides, 1-hydroxyalkylphenyl ketones or 2,2-dimethoxy-1,2-diphenylethan-1-one.
• the photoinitiator can be contained in an amount of 0.1% to 10%, in particular 0.5% to 5%, on a dry matter basis.
• a percentage on a "dry matter basis” means the percentage based on the solids content, i.e. H. without water and any other solvents that may be present.
• the viscosity of the aqueous polymer dispersion can be adjusted by varying the water and/or reactive diluent content.
• the dispersion preferably has a viscosity of 0.01 to 10 Pa.s, particularly preferably 10 to 3000 mPa.s. A viscosity within this range leads to good flowability of the aqueous polymer dispersion and a uniform coating of the substrate surface. Since the viscosity of the aqueous polymer dispersion depends on its water content, the viscosity increases upon drying. In the present invention, the viscosity is measured at 23°C according to DIN EN ISO 2555 (Brookfield method).
• a reactive diluent is reactive because it is polymerizable and becomes part of the molecule of the cured polymer structure, and it is a diluent because it reduces the viscosity of the dispersion.
• the reactive diluent preferably has a weight-average molecular weight Mw of less than 500 g/mol and thus differs from the prepolymer with a weight-average molecular weight Mw of more than 2000 g/mol.
• the reactive diluent can be selected from aliphatic (meth)acrylates or polyether (meth)acrylates. Since the viscosity can be adjusted by varying the water content, a reactive diluent is not necessary.
• the aqueous polymer dispersion preferably does not contain any reactive diluent.
• a reactive diluent may be included.
• the dispersion may contain 0 to less than 2%, preferably less than 0.1%, more preferably 0% of a reactive diluent on a dry matter basis.
• the aqueous polymer dispersion contains a water-dispersible prepolymer which, for example, has at least one polymerizable carbon-carbon double bond. It can be cured, that is, polymerized, resulting in a cured polymer.
• the aqueous polymer dispersion may contain the prepolymer as the only polymerizable component.
• the aqueous polymer dispersion may contain the prepolymer and other copolymerizable components, e.g. B. a chain extender, which can be monomeric. In this case the finished polymer is created e.g. B. by chain extension and by hardening the polymerizable CC double bonds.
• the precoat is preferably obtainable in a process consisting of reducing the water content of the aqueous polymer dispersion, e.g. B. by heating and curing the dried dispersion.
• the prepolymer is curable by heating or irradiation, ie treatment with UV light or electron beams.
• the prepolymer is UV-curable.
• the radical polymerization can be initiated by the photoinitiator.
• the prepolymer with a polymerizable C-C double bond can be selected from the group consisting of acrylates, methacrylates, vinyl ethers, allyl ethers, propenyl ethers, alkenes, dienes, unsaturated esters, allyl triazines, allyl isocyanates and N-vinyl amides.
• acrylate or “acrylic” is to be understood as including “(meth)acrylate” or “(meth)acrylic”.
• the polymer contained in the aqueous polymer dispersion is dispersible in an aqueous medium, preferably water.
• an aqueous medium preferably water.
• it has a certain degree of hydrophilicity.
• hydrophilic residues which are derived from corresponding hydrophilic compounds and are capable of making the polymer dispersible in an aqueous medium either directly or after reaction with a neutralizing agent to form a salt.
• the hydrophilic compounds are generally selected from polyols. They can contain an ionic or non-ionic hydrophilic group.
• a polyol containing one or more anionic salt groups, such as carboxylate and sulfonate salt groups, or acid groups that can be converted to an anionic salt group, such as carboxylic acid or sulfonic acid groups, may be preferred.
• anionic salt groups such as carboxylate and sulfonate salt groups
• acid groups that can be converted to an anionic salt group such as carboxylic acid or sulfonic acid groups
• examples are hydroxycarboxylic acids of the formula ( HO )
• the aqueous polymer dispersion usually requires the neutralization of the hydrophilic residues into salts. This is usually done by adding an organic or inorganic neutralizing agent or mixtures thereof to the polymer or water.
• the mechanical properties of the resulting primer are also influenced by the respective crosslinking density.
• Higher networking density usually results in a harder and more brittle material, while a lower crosslink density results in a softer and more conformable material.
• the composite according to the invention can contain a “hybrid polymer layer made of an organically modified silica (hetero)polycondensate”.
• This expression means that the hybrid polymer layer consists of the organically modified silica (hetero) polycondensate or consists of at least 50% thereof.
• the inorganic silica (hetero)polycondensate is modified with organic groups, preferably organically polymerized, and is sometimes referred to herein simply as a "hybrid polymer.”
• the hybrid polymer is crosslinked both inorganically and organically.
• the term “hybrid polymer” also includes polymers with biobased and/or biodegradable components.
• An example of a hybrid polymer is ORMOCER ® or bioORMOCER ® (brand name of the Fraunhofer Society for the Promotion of Applied Research eV, Kunststoff).
• the inorganic component of the hybrid polymer consists of silicon cations, optionally in combination with other cations such as aluminum, zirconium, titanium or boron and combinations thereof, which are linked to one another via oxygen bridges and thereby form a network.
• This is an organically modified silica ion or, in the case of the presence of further metal ions, an organically modified silica heteropolycondensate.
• An example of such a heteropolycondensate is a condensate containing silicon and aluminum.
• silica (hetero)polycondensate is used as a common term for the pure silica polycondensates and the polycondensates containing heteroatoms.
• the hybrid polymer is usually produced by hydrolytic condensation of silanes, possibly in combination with co-condensable compounds of other metal ions.
• silanes can carry hydrolyzable groups such as alkoxides or hydroxide groups. But they can also carry organic groups bonded directly to silicon via carbon. These groups remain bound to the respective silicon atoms during the hydrolytic condensation, so that the polycondensate is modified with the organic groups.
• the organic groups can be derivatives of one or more types of natural or synthetic organic polymers. At least the organic groups can partially integrated into the condensate via Si-C bonds.
• the organic groups bound into the condensate via Si-C bonds can be thermally or photochemically organically polymerizable groups, in particular epoxy groups.
• the organic groups can also be bound to silicon via oxygen. They can be biodegradable.
• the hybrid polymer layer is preferably biodegradable.
• Hybrid polymers with good biodegradability are formed by replacing non-biodegradable organic components with biodegradable components.
• the Si-O-Si bonds are usually acid-stable but base-labile, so that the barrier layer can be broken down.
• the base lability can also be exploited when recycling a composite according to the invention by detaching the hybrid polymer from the substrate by alkaline washing.
• Biodegradability can also be adjusted by reducing the degree of crosslinking, especially the inorganic degree of crosslinking (i.e. the Si-O-Si or Si-O-metal bonds).
• the coating it is necessary that as large a proportion as possible, preferably at least 10%, of the organic groups that are integrated into the inorganic network of the hybrid material be biodegradable. Therefore, at least some of the organic groups preferably have a hydrocarbon chain with 2 to 8, preferably with 2 to 6 carbon atoms, which is located between two groups selected from ether, ester, amide and urethane groups. In particular, at least some of the organic groups can have at least two hydrocarbon chains with 2 to 8 carbon atoms, which are branched to one another.
• the inorganic, biodegradable groups have the component [O-(CH 2 ) m -C(O)-O]n, where m is an integer between 2 and 8, n 0, 1, 2 or 3 or greater than 3 and, provided that the component mentioned is present multiple times in the organic, biodegradable group, can assume different values, with the proviso that n is 1 or greater than 1 in the only or in at least one of the components mentioned.
• the organic groups can also be selected from the group consisting of polycaprolactone triol (of fossil origin but biodegradable), chitosan, cellulose, cellulose derivatives; Hemicelluloses and cellulose building blocks and other bioorganic resources exist.
• the hybrid polymer layer is created by applying an appropriate coating varnish to the desired substrate. If it contains solvent, this can be removed if necessary. Alternatively or cumulatively, thermal post-treatment or irradiation with light/UV is possible.
• the hybrid polymer layer can be produced by a method which includes applying a composition, optionally in a diluent and/or solvent and containing hybrid polymer, to a metal oxide layer, for example by spraying, slot die, gravure roller and drying and/or curing the composition includes.
• the coating varnish is preferably applied in a thickness of 1-30 g/m 2 or 2-9 g/m 2 , preferably 3-8 g/m 2 , more preferably 4-5 g/m 2 and at 80-120° C thermally hardened.
• the average thickness of the hybrid polymer layer is preferably 500 nm to 30 ⁇ m, more preferably 1.0 to 10 ⁇ m, even more preferably 1.0 to 5.0 ⁇ m.
• the thickness of the layer is determined, for example, using scanning electron microscopy.
• the hybrid polymer layer can contain other polymers and/or fillers in addition to the hybrid polymers.
• the fillers are preferably inert and not chemically reactive. But they can also have an active function (e.g. antimicrobial function, active barrier function). They should be soluble or dispersible in the hybrid sol and not hygroscopic and have a particle size that does not affect the visual appearance of the coating.
• Typical fillers are starch, chemically modified starch, dextrin, microcrystalline cellulose, insoluble cellulose derivatives, as well as inorganic compounds (e.g. talc, TiOz, SiOz, silicates, clay materials, insoluble carbonates and phosphates).
• filler preferably in an amount of 1 - 25% of the coating
• the proportion of filler depends on the material. Starch or dextrin improve the mechanical properties and make it easier to process. Inorganic fillers such as silicates, aerosils, Stöber particles improve the moisture barrier and can be incorporated up to a proportion of 50%.
• the hybrid polymer adheres very well to the neighboring interfaces.
• the organic content preferably predominates in the coatings, so that the flexibility is also increased in the cured coating becomes.
• the use of longer spacers (three or more chain atoms) between the alkoxysilane group and the organic functionality further maximizes flexibility while maintaining barrier performance.
• flexibility can be increased by carrying out the synthesis at pH values below 7, which preferably allows a more linear network to be obtained.
• metal oxide layer means that the metal oxide layer consists of or consists of at least 50% of the deposited metal oxide.
• Metal oxides can be SiOz, SiO, MgO, CaO, TiOz, ZnO, AlOx or MnO or mixtures thereof.
• silicon oxide SiO x which contains silicon monoxide (SiO) and silicon dioxide (SiOz), so that "x" is 1.0 to 2.0. Values of over 2.0 are also possible. The higher the density of the hydroxy functionalities of the deposited SiO x particles measured using XPS, the larger “x” is. In one embodiment, "x" is greater than 2.0, preferably greater than 2.2, even more preferably greater than 2.5.
• the metal oxide layer provides a permeation barrier against both water vapor and oxygen.
• the average thickness of the metal oxide layer is preferably 5 nm to 200 nm, more preferably 10 nm to 100 nm or 20 nm to 100 nm.
• the layer must have a certain minimum thickness for reasons of stability. However, layers that are too thick are more brittle.
• a combination of a vacuum-evaporated barrier layer with a hybrid polymer layer is possible.
• the inorganic or metallic layer is applied in a vacuum as physical deposition from the gas phase (PVD) or by chemical deposition from the gas phase (vacuum chemical vapor deposition, VCVD).
• PVD physical deposition from the gas phase
• VCVD vacuum chemical vapor deposition
• metal oxides such as SiO x to surfaces using flame pyrolysis.
• the process of flame pyrolysis or CCVD belongs to the group of chemical vapor deposition or CVD (chemical vapor deposition) and enables the deposition of functional thin layers at atmospheric pressure, for example when using SiO x as the metal oxide, the content of silanol groups at the Interface, the inner interfaces and surfaces and in the bulk of the metal oxide layer is higher.
• the metal oxide layer can completely or partially cover the underlying layer.
• the Thickness of the layer is not particularly limited. It can vary depending on the application method, the nature of the surface of the substrate and the use of the coating.
• the metal oxide is modified, for example, by CCVD, which creates, among other things, hydroxy groups which are located, among other things, on the surface of the deposited metal oxide particles. These can form covalent bonds with the hybrid polymers of the adjacent layers, so that, for example, in the case of using SiO x as the metal oxide, additional -Si-O-Si bonds are formed.
• the resulting layer of modified metal oxide is simply referred to as a metal oxide layer in the present invention.
• the metal oxide layer produced by CCVD is very rich in surface OH groups, which serve as chemical anchors for adhesive groups of other substances. This enables a simple, large-area and continuous coating of the primer on the paper substrate.
• the flame pyrolytic process enables the combination of two or three chemically related layers, namely metal oxide layer (especially when using silicon oxide), hybrid polymer layer and primer based on hydrophilic polymers.
• the covalent bonds at the interfaces of the layers result in synergy effects for maximum barrier performance.
• Synergy effects at the interface between the two layers result in the formation of covalent bonds (e.g. Si-O-Si), which lead to the compensation of defects and/or porosities in the inorganic layers and stable interlocking of the layers.
• covalent bonds e.g. Si-O-Si
• Thanks to excellent wetting properties and the covalent bonds the microscopic holes (pinholes, cracks) in the metal oxide layers that arise during CCVD application can also be closed.
• metal oxide coating of very temperature-sensitive substrates can be achieved without loss of properties using adapted process technology. This means that substrates for packaging purposes can be produced easily and cost-effectively without using vacuum technology and avoiding batch processes.
• the specified water vapor permeability is determined according to DIN 53 122-1 (23 ° C, 85% r.h., relative humidity).
• the quantitative characterization of the paper coatings was carried out as follows: The damage to the barrier caused by tension on the packaging machine, by folding, by abrasion of the product packaging and the Puncture caused by sharp edges of the packaging was simulated in a FlexCrack resistance test. To do this, the coated substrate is folded inwards by 180° in the machine direction (MD) and in the transverse direction (CD). The fold is created by a 2 kg metal cylinder. The samples treated in this way are referred to as "folded" after folding.
• composites of (i) paper substrate/primer/ SiO Composites of (ii) paper substrate/primer/hybrid polymer layer/SiO x layer showed a similar WVTR as composites (i), with the WVTR increased by folding more than in composites (i).
• the double application of the primer significantly increased the resistance of the water vapor barrier effect against wrinkles in all composites.
• All composites showed excellent barrier effects against water vapor in both directions, i.e. both from the side of the paper substrate to the side of the barrier layer and from the side of the barrier layer to the side of the paper substrate.

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• 2022
  • 2022-03-17 DE DE102022106229.5A patent/DE102022106229A1/de active Pending
• 2023
  • 2023-02-01 EP EP23154363.8A patent/EP4245914A1/fr active Pending

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