Packaging material

Abstract

Packaging material (2) especially for liquid or moisture-sensitive foods with a layered structure (4) which has - a support layer (6) consisting of a paper material, - a SiO2 impregnation (8, 14) wherein the SiO2 impregnation is designed as an internal impregnation (14) and is introduced into the carrier layer (6) and / or is applied as a SiO2 barrier layer (8), - an O2 barrier layer (10).

Description

[0001] The present invention relates to a packaging material.

[0002] Due to the desired elimination of plastic packaging, packaging based on paper and cardboard is increasingly coming into focus.

[0003] Compared to plastic, however, such packaging proves difficult to use for liquids or moisture-sensitive products. Furthermore, transparency is often desirable in product packaging, which is only partially achievable with paper and cardboard packaging.

[0004] US patent 12 005 672 B2 describes a process for manufacturing, for example, a paper cup, in which a silicon-based sol-gel is applied to a paper material, which is then treated at 200°C and thereby forms a SiO2 coating.

[0005] EP 2 234 494 B1 describes a silicon-based sol-gel process for coating plant seeds.

[0006] Based on this, the invention aims to provide a paper-based packaging material that is particularly suitable for packaging liquid, moist or moisture-sensitive products, or that enables transparent packaging, especially of such products.

[0007] According to a first aspect, the problem relating to the packaging material is solved according to the invention by a packaging material having the features of claim 1.

[0008] The packaging material is particularly suitable for packaging liquid or moisture-sensitive foods. The packaging material has a layered structure consisting of - a carrier layer consisting of a paper material, - a SiO2 impregnation, wherein the SiO2 impregnation is designed as an internal impregnation and is introduced into the substrate, i.e., into the paper material, and / or is applied as a SiO2 barrier layer, as well as with - an O2 barrier layer.

[0009] Studies have shown that this type of layered structure, with a paper-based substrate, SiO2 impregnation, and an O2 barrier layer, is particularly suitable for the long-term storage of liquid, moist, or moisture-sensitive products, especially food. The combination of SiO2 impregnation and the O2 barrier layer creates a moisture-proof and gas-tight coating on a paper base, making it ideal for long-term product packaging. It is particularly noteworthy that the O2 barrier layer enables gas-tight packaging that can replace conventional plastic packaging. This provides reliable and long-lasting protection, especially for sensitive foods that react with oxygen and may discolor.

[0010] When the term "paper material" is used here, it generally refers to paper or cardboard. Paper is generally a sheet-like product consisting primarily of fibers of plant origin. The fibers used are usually pulp, wood pulp, or, in the case of recycling, waste paper. Additionally, fillers and other additives may be present in a manner known per se.

[0011] The term "paper material" specifically includes cardboard and paperboard, which differ from standard paper primarily in their higher basis weight and / or multi-ply construction. The term "paper" specifically refers to a sheet-like paper material with a basis weight of 7 g / m². 2 up to 225 g / m² 2Cardboard or paperboard, as used here, refers to a sheet-like paper material with a basis weight greater than 225 g / m². 2 exhibits.

[0012] The term O2 barrier layer generally refers to a layer that is gas-tight, at least for oxygen.

[0013] Preferably, the SiO2 impregnation forms a barrier layer that is applied directly or indirectly to the O2 barrier layer. Alternatively or additionally, the SiO2 barrier layer forms an outermost layer of the layer structure.

[0014] SiO2 impregnation generally provides good protection against moisture and liquids. Therefore, a SiO2 barrier layer is preferably applied as the outermost layer, which comes into contact with the product / foodstuff (especially liquid). This layer protects the underlying O2 barrier layer from moisture. Preferably, the SiO2 barrier layer is applied directly to the O2 barrier layer.

[0015] In a preferred further development, the layer structure additionally includes a primer layer. The primer layer is applied as a first layer to the substrate. It serves primarily as an adhesion promoter layer upon which a subsequent layer, specifically a SiO2 barrier layer, is applied. The primer layer ensures good adhesion of the SiO2 barrier layer to the substrate. Therefore, the primer layer is primarily an adhesion promoter layer. Together with the primer layer, the SiO2 barrier layer forms a particularly effective, moisture-resistant layer structure.

[0016] The primer layer is specifically a so-called bioprimer. This primer layer acts as a barrier against water and water vapor (i.e., it is impermeable to water vapor or exhibits a very low water vapor transmission rate (WVTR)). In combination with the SiO2 barrier layer, this creates an overall barrier with a water vapor transmission rate comparable to that of a plastic film.

[0017] In addition, the primer layer also forms a grease barrier.

[0018] In a preferred embodiment, at least one SiO2 barrier layer is generally arranged between the primer layer and the O2 barrier layer.

[0019] In particular, the layer structure comprises several and preferably exactly two SiO2 barrier layers.

[0020] Overall, the layer structure preferably has a layer sequence of carrier layer - primer layer - SiO2 barrier layer - O2 barrier layer - SiO2 barrier layer and is in particular formed by this layer sequence.

[0021] Alternatively, the SiO2 impregnation is introduced into the substrate layer and forms an internal SiO2 impregnation, i.e. the paper material already has the SiO2 impregnation as an integral component, so that an impregnated substrate layer is formed.

[0022] The previously mentioned layer structure, primer layer - SiO2 barrier layer - O2 barrier layer - SiO2 barrier layer, is then applied to this impregnated carrier layer with the internal impregnation.

[0023] Alternatively, the primer layer and possibly also the (first) SiO2 barrier layer can be omitted following the carrier layer with the internal impregnation, and the O2 barrier layer with subsequent SiO2 barrier layer is applied directly to the carrier layer impregnated with the internal impregnation.

[0024] The packaging material preferably consists of one of the aforementioned layer structures, optionally supplemented by further printing on an outside of a (product) packaging formed by the packaging material.

[0025] The following sections describe in detail the SiO2 impregnation, the O2 barrier layer, and the primer layer, as well as their production. The production process utilizes compositions / mixtures of several components, also referred to as formulations. Unless otherwise stated, the volume percentages of the individual components specified below refer to the entire formulation. Each of the formulations described below is considered inventive in itself. The filing of one or more divisional applications based on these formulations remains reserved. SiO2 impregnation and SiO2-generating substance

[0026] When the term SiO2 impregnation is used here, it refers to the formation of a silicon-based protective impregnation using a sol-gel process. In this process, a silicon dioxide-forming liquid precursor is introduced into the substrate or applied as a coating to create the SiO2 barrier layer. Subsequent heat treatment, particularly drying, then results in the desired inorganic, silicon-based protective effect. The production of such a silicon-based protective effect using a sol-gel process is generally known and is described, for example, in US 12,005,672 B2, cited at the beginning. The resulting SiO2 barrier layer is therefore specifically a silicon-based sol-gel layer containing SiO2 as an inorganic solid.

[0027] In such a sol-gel process, a precursor containing alkoxysilanes, such as TEOS (tetraethyl orthosilicate) and / or MTES (methyl triethoxysilane), is generally provided first. This is prepared / dissolved in a liquid, especially water, and in this form either introduced or applied to the support layer.

[0028] A subsequent hydrolysis and condensation reaction leads to aggregation, resulting in a three-dimensional network of SiO2 molecules. This process forms a gel, primarily aqueous.

[0029] This solution with the precursor contained therein, namely the (aqueous) gel formed after the hydrolysis and condensation reaction, is also referred to as a SiO2-generating substance within the meaning of the present application.

[0030] This SiO2-generating substance (aqueous gel) preferably has a solid content of SiO2 in the range of 0.5 vol% to 28 vol%, based on the aqueous gel.

[0031] Subsequent drying removes the solvent, resulting in the formation of a solid substance. In the case of the SiO2 barrier layer, this solid, silicon-based, inorganic protective layer containing SiO2 is formed. The SiO2 barrier layer is subsequently referred to simply as the SiO2 layer, particularly when combined with a transparent substrate.

[0032] For the sol-gel process, and thus for the SiO2-generating substance used for SiO2 impregnation, a preferably aqueous solution containing alkoxysilanes in the range of 2 to 10 vol%, and particularly in the range of 3 to 7 vol%, is used as the starting material. The alkoxysilanes form the aforementioned SiO2 precursor, which ultimately forms a protective SiO2 layer at the end of the sol-gel process. When introduced into the matrix of the substrate, this protective SiO2 layer adheres to the paper fibers.

[0033] To initiate and control the hydrolysis and condensation reaction, the solution further contains, in a preferred embodiment (optional, not mandatory), a so-called acid catalyst, such as HCL (hydrogen chloride), preferably with a proportion of less than 1 vol% and particularly in the range between 0.1 and 0.5 vol%.

[0034] The pH range of the solution is preferably generally adjusted to 3 to 5, particularly by means of the acid catalyst.

[0035] Optionally, the solution can contain a wetting agent as an additional component, which supports the wetting of the substrate layer and also the stability of the SiO2 barrier layer. The proportion of the optional wetting agent is, for example, less than 3 vol% and, in particular, in the range between 0.5 vol% and 1.5 vol%.

[0036] Various well-known wetting agents can be used, such as siloxane-based wetting agents like polydimethylsiloxanes (PDMS) or silanol-modified siloxanes. Alternatively or additionally, EO / PO copolymers are used, in particular fluorine-free surfactants such as PEG-based or polyglyceride surfactants, or acetylenic diol wetting agents.

[0037] A particular advantage of the wetting agents listed here is their good environmental compatibility and, in particular, their SUPD compliance (compliant with the EU Single-Use Plastics Directive 2019 / 904).

[0038] In addition to these components (precursor, acid catalyst, optional wetting agent), the formulation may contain further additives, such as (metal) oxides like Al₂O₃, TiO₂, ZrO₂, MgO, V₂O₅, and / or antimicrobial agents. Such additives are present, for example, in the SiO₂-containing substance for coating seeds, as described in the aforementioned EP 2 234 494 B1, particularly in paragraphs 13, 17, and 18. The proportion of these further additives is preferably a maximum of 20% by weight, based on the proportion of alkoxysilanes in the solution.

[0039] Quaternary ammonium compounds (QACs), particularly functionalized organosilane derivatives, are preferably added. Alternatively or additionally, chitosan, for example, is added. The addition is preferably in a volume fraction of 0.5 vol% to 5 vol%, more preferably 1 vol% to 3 vol% (based on the solution / formulation), depending on the desired properties of the coating. In specific applications, the proportion is increased, for example, to up to 10 vol% to achieve a particularly strong antimicrobial effect or improved chemical bonding to the substrate.

[0040] The remainder of the solution (formulation) consists of solvents. The proportion of at least one solvent, or even several solvents, in the solution is typically between 90% and 95% by volume.

[0041] Water is preferably used as the sole or at least the main solvent.

[0042] In a preferred embodiment, the solution preferably contains, in addition to water as the main solvent, alcohol, in particular ethanol, preferably in the range of less than 5 vol% and particularly in the range of 1-3 vol%. The alcohol acts as a co-solvent to complement the water, thereby counteracting, for example, undesirable phase separation in the solution.

[0043] The formula is composed as follows, for example: ingredient Vol % Vol % (preferred) Precursor alkoxysilane 1-10 3-7 Acid catalyst (optional) HCL 0,05-1 0,1-0,5 Wetting agent (optional) e.g. siloxanes 0,1-3 0,5-1,5 Additive (optional) e.g. QAVs or chitosan 0,5-10 1-3 Additional solvent (optional) alcohol 0,5-1 1-3 solvent Water rest rest

[0044] The individual components of the solution are mixed together and, for example, at room temperature (especially 20°C) for usually several hours (e.g., 5 hours), primarily by stirring. This process then produces the aqueous sol-gel already described, which is the SiO2-generating substance.

[0045] The production of a SiO2-generating substance is, for example, also known in principle from the aforementioned EP 2 234 494 B1.

[0046] The formulation described here for the SiO2-generating substance utilizes the hydrolysis and condensation of alkoxysilanes to create a three-dimensional network of SiO2 molecules. This network ensures high cohesion and homogeneity of the resulting SiO2 barrier layer, enabling a uniform and highly adhesive coating. The formulation is water-based and preferably contains alcohol as a co-solvent and acid catalysts to control the reaction. The addition of optional wetting agents improves the wetting properties and allows for optimal adaptation to various substrate materials. The formulation is SUPD-compliant and free of synthetic polymers. By varying the different components and / or their proportions, the formulation can be adapted to different applications. O2 barrier layer

[0047] The O2 barrier layer is preferably a layer formed by a crosslinking reaction, particularly based on silicates, especially alkali silicates. The layer is therefore particularly a silicate layer, which additionally preferably contains SiO2.

[0048] For production, a liquid composition / formula is provided, the main component of which is bio-based silicate polymers (e.g., alkali silicates). Their proportion is preferably between 30 vol% and 40 vol%, particularly 35 vol%. These form a dense inorganic network for oxygen blocking. They are, in particular, completely petroleum-free and produced from quartz sand and alkaline solutions.

[0049] As an optional additional component, the composition contains polysiloxanes, the proportion of which is preferably in the range of 1 vol% - 20 vol% and particularly at 7 vol%. These serve to increase flexibility, improve adhesion and reduce brittleness.

[0050] The entire class of polysiloxanes is generally suitable; however, functionalized polysiloxanes are preferred, such as aminofunctionalized polysiloxanes, hydrophobic polysiloxanes (e.g., polydimethylsiloxanes), and hydrophobic polysiloxanes (e.g., polydimethylsiloxanes). Depending on the requirements, different polysiloxanes or a mixture of several polysiloxanes are used.

[0051] Another essential component is a SiO2 film former with a concentration of preferably 15 vol% - 20 vol%, particularly 18 vol%. This ensures a dense, mechanically stable protective layer with a barrier effect against oxygen and, to some extent, also against moisture.

[0052] For this film-forming agent, alkoxysilanes (e.g., tetraethoxysilane [TEOS] or methyltriethoxysilane [MTES]) are primarily used, which—as previously explained in the context of SiO2 impregnation—are converted into an inorganic SiO2 layer via a sol-gel reaction during the coating process. In the liquid formulation, these substances are reactive and serve as precursors for the formation of a dense, mechanically stable network. After curing, the film-forming agent forms an inorganic layer that acts as an oxygen and moisture barrier.

[0053] The SiO2 layer former is of particular importance for the O2 barrier layer because the resulting SiO2 layer significantly reduces the permeation of oxygen molecules due to its density and chemical stability.

[0054] Preferably, the formulation includes as a further component a film-forming agent, particularly a bio-based one, which ensures homogeneity and flexibility and contributes to the biodegradability of the O2 barrier layer. The proportion of the film-forming agent is preferably 10–15 vol% and particularly 12 vol%. Functionalized cellulose (e.g., hydroxyethylcellulose, carboxymethylcellulose) is particularly suitable as the film-forming agent.

[0055] The formulation preferably includes a crosslinking agent as a further component, the proportion of which is preferably between 1% and 3% by volume, and particularly 2% by volume. This is, in particular, a mineral or bio-based crosslinking agent, such as citric acid or silica solutions. The crosslinking agent promotes the chemical stabilization and crosslinking of the layer.

[0056] The remainder of the formulation consists of a solvent, preferably water, which is preferably VOC-free (free of volatile organic compounds). The proportion of the solvent, also referred to as the solvent (carrier liquid for the components), is preferably in the range of 30% to 40% by volume.

[0057] To produce the O2 barrier layer, it is applied to the substrate. Cross-linking occurs, and the solvent is subsequently removed by drying, resulting in the formation of the O2 barrier layer as a silicate layer containing SiO2.

[0058] The formed O2 barrier layer therefore preferably has a silicate content in the range of 40 vol% to 55 vol% and additionally a SiO2 content in the range of preferably 20 vol% to 30 vol%.

[0059] Furthermore, the O2 barrier layer preferably also contains the film former in a proportion of preferably 15 vol% to 20 vol%.

[0060] Additionally, the formed O2 barrier layer optionally contains a polysiloxane component, which is formed by the polysiloxanes optionally used in the solution, with this component preferably being in the range between 2 vol% and 20 vol%. primer layer

[0061] For the formation of the primer layer, a solution / formulation based on bio-based polymers, particularly water-based, is preferably used, with a (solid) content in the range of 30 vol% to 60 vol%.

[0062] Bio-based polymers are understood to be, in particular, polymers that are obtained from natural, renewable sources such as starch, cellulose or proteins.

[0063] Common and suitable polymers include, for example, • Starch-based polymer: MaizeGel (a hydrophilic starch derivative) • Cellulose-based polymer: Hydroxyethylcellulose (HEC), e.g., Natrosol • Protein-based polymer: Gelatin hydrolysate or soy protein isolate

[0064] Another component of the formulation is a stabilizer to maintain the pH value, which is preferably adjusted to a range between 5 and 9 to ensure optimal processing. The proportion of stabilizers is, for example, 0.5% to 1% by volume. Citric acid or acetic acid are used as stabilizers, for example.

[0065] Preferably, at least one preservative, preferably biodegradable, is used. The proportion of the one or more preservatives is preferably in the range of 0.1% to 0.5% by volume.

[0066] Examples of biodegradable preservatives used include sorbic acid, potassium sorbate, benzoic acid and / or acetic acid.

[0067] Alternatively, but preferably only as a supplement to biodegradable preservatives, non-biodegradable preservatives are also used, such as methylisothiazolinone (MIT), benzisothiazolinone (BIT), phenoxyethanol, DMDM ​​hydantoin, and / or propylparaben.

[0068] The remainder of the solution / formulation consists of a solvent in the range of approximately 35% to 75% by volume. The main solvent is preferably water in the range of 40% to 70% by volume. Additionally, an alcohol, such as ethanol or isopropanol, is preferably used as a co-solvent to stabilize and optimize the drying properties. Its proportion is preferably in the range of 3% to 5% by volume.

[0069] To form the primer layer, the solution is applied and then dried to remove the solvent (water, alcohol). The resulting primer layer therefore consists essentially, and in particular more than 95% by volume, of the bio-based polymer. Other components are the stabilizers and preservatives mentioned previously.

[0070] In a preferred embodiment, each SiO2 barrier layer has a thickness in the range of 5 nm to 50 nm. When several barrier layers are applied, they have the same thickness or, alternatively, different thicknesses. In particular, the outermost SiO2 barrier layer has a greater thickness than an inner SiO2 barrier layer.

[0071] In a preferred embodiment, the O2 barrier layer may additionally or alternatively have a layer thickness of at least several hundred nm and in particular between 300 nm and 500 nm.

[0072] In a preferred embodiment, the primer layer additionally or alternatively has a layer thickness also in the range of at least several hundred nm, and in particular in the range between 250 nm and 400 nm.

[0073] In general, the SiO2 barrier layer is preferably thinner than the O2 barrier layer and / or the primer layer. In particular, it is at least 2, 5, or 10 times thinner than the O2 barrier layer and / or the primer layer.

[0074] In a preferred embodiment, the entire layer structure – without a support layer – has a layer thickness in the range of at least several hundred nm, in particular at least 500 nm, and further preferably a maximum layer thickness of, for example, 1200 nm and in particular 1000 nm. In particular, the layer thickness of the layer structure consisting of SiO2 barrier layer(s), O2 barrier layer, and optionally primer layer is in the range between 550 nm (or 555 nm) and 950 nm.

[0075] In a preferred embodiment, the packaging material and a packaging made from the packaging material have no further layers besides these layers (SiO2 barrier layer or SiO2 impregnation, O2 barrier layer and primer layer), apart from any printing, especially on the outside, such as logos, contents information, etc.

[0076] It should also be emphasized that the packaging material described here, and preferably any packaging made from it, is plastic-free; that is, no plastic materials are used for the packaging material and / or the packaging made from it. In particular, the packaging material described here therefore meets the requirements of the EU Single-Use Plastics Directive (EU 2019 / 904).

[0077] The packaging material described here is characterized by excellent recyclability and overall very good environmental compatibility. It can be recycled like conventional paper, and the fibers it contains can be reused. The recycling rate, for example, is over 98%. Specifically, this type of packaging material can be disposed of like conventional paper. The applied coatings contain no relevant pollutants.

[0078] The packaging material described here is preferably used for a leak-proof container such as a can, bottle, cup, bag, etc., and in particular for containing liquid foods such as sauces, beverages, oil, vinegar, etc., or for containing moisture-sensitive foods such as spices or dried foods, etc. The container preferably consists entirely of the packaging material and therefore has no additional layers or coatings. It may, at most, be additionally printed.

[0079] The packaging material described is particularly suitable for use with dairy products. Furthermore, it is also ideal for packaging pharmaceutical products, especially due to its liquid-tight properties and suitability for sensitive contents such as medications or medical solutions.

[0080] The container is designed in particular as a closed or at least lockable container.

[0081] According to its second aspect, the problem relating to the packaging material is solved according to the invention by a packaging material having the features of claim 11.

[0082] The previously described multiple-layer structure of this packaging material enables the formation of a barrier against water vapor (WVTR) and fats, thus expanding the material's application possibilities. Furthermore, the layered structure allows for the creation of antimicrobial properties through appropriate modifications, which is particularly advantageous for packaging sensitive foods or medical products.

[0083] The packaging material according to this second aspect has a transparent paper backing layer, wherein - in order to achieve a desired transparency for visible light of at least 20% - the backing layer has a SiO2 impregnation.

[0084] SiO2 impregnation refers to the SiO2 impregnation described above, which is either introduced as an internal impregnation into the matrix of the substrate layer, or is formed as a coating (SiO2 barrier layer) applied to the substrate layer.

[0085] Visible light transmission (VLT) refers to the percentage of visible light that passes through the substrate. The VLT is at least 20%, meaning that 20% of the visible light is transmitted.

[0086] Transparent paper (glassine paper) is generally well-known. Studies have now shown that applying a SiO2 impregnation can create or increase its transparency. SiO2 impregnation therefore offers a dual benefit, as it forms a moisture barrier while simultaneously ensuring transparency.

[0087] The advantages and preferred designs mentioned previously in connection with the first aspect can also be combined with this transparent support structure.

[0088] Preferably, an O2 barrier layer, as previously described, is applied to the transparent substrate. In a particularly advantageous embodiment, a (further) SiO2 barrier layer is applied to the O2 barrier layer, resulting in a layer structure comprising the transparent substrate with the SiO2 impregnation, an O2 barrier layer applied thereon, and a further SiO2 barrier layer applied thereon.

[0089] To create the desired transparent substrate, a suitable transparent paper is first used, generally an already transparent paper, in particular a so-called glassine paper. This transparent paper is additionally impregnated with SiO2 to increase its transparency. The SiO2 impregnation is therefore applied to an existing transparent paper as an SiO2 layer. Transparent paper is generally understood to be paper that already has a transparency of, for example, at least 20% for visible light.

[0090] Preferably, the transparent substrate has a transparency of at least 50%, and in particular at least 60% or at least 70%. The high values, especially those exceeding 70% VLT, are achieved particularly in combination with the transparency paper, which is preferably untreated, i.e., has no other coating before the application of the SiO2 barrier layer.

[0091] The combination with the O2 barrier layer, in particular, allows its use in packaging where both gas tightness, and thus protection from oxygen, and high light transmission are desired. Such packaging is therefore especially suitable, for example, for transparent packaging of oxygen-sensitive foods.

[0092] To achieve the desired transparency, the substrate (paper) typically has a suitable thickness or basis weight. The basis weight, for example, is a maximum of 120 g / m². 2 and especially below 100 g / m² 2 and preferably below 50 g / m² 2 and, for example, also below 30 g / m² 2 .

[0093] The transparent carrier layer is preferably used for packaging with a viewing window, the viewing window being formed by the transparent carrier layer. The packaging is therefore only partially formed by the transparent carrier layer. The remaining packaging is preferably formed by a non-transparent carrier layer, which is preferably also impregnated with at least one SiO2 layer and, for example, has a layer structure as previously described.

[0094] Alternatively, the entire packaging consists of the transparent carrier layer and is preferably used as a bag for containing foodstuffs, especially for individual food items such as baked goods, etc., or also fruit and vegetables.

[0095] In principle, the packaging material described here, both transparent and opaque, can also be used for other products that are not food. Examples include hygiene products (lotions, liquid soaps, creams), cleaning agents (liquid / powder), and other substances such as oils, etc.

[0096] The individual layers are applied using suitable methods, such as spraying, brushing, or printing. Typically, a liquid material is applied as a starting point for the various layers, which then forms the desired layer with the desired properties, primarily through subsequent drying.

[0097] The following steps are carried out to produce a particularly transparent support layer based on paper.

[0098] The carrier layer is used particularly for a packaging material, as previously described.

[0099] According to one method variant, a SiO2-generating substance is added in a suitable manner during a manufacturing step of the papermaking process. The papermaking process encompasses the steps from the preparation and provision of a fiber suspension to the pressing and drying of a fiber web produced from this suspension, which forms a paper layer. In papermaking, this paper layer is typically wound onto a roll at the end of the process.

[0100] The SiO2-generating substance then forms the carrier layer with the internal SiO2 impregnation integrated into the matrix of the carrier layer, as previously described.

[0101] The first process variant is used in particular for producing the transparent carrier layer (according to the second variant of the packaging material described above). This means that by introducing the SiO2-generating substance during the paper manufacturing process, a transparent paper layer is produced in a particularly simple manner. Alternatively, the first process variant can also be used as the basis for the carrier layer of the packaging material according to the first variant described above, which includes the O2 barrier layer.

[0102] It is worth emphasizing that the SiO2-generating substance is introduced directly during a manufacturing step of the papermaking process and is not applied to the finished paper only at the end of the manufacturing process.

[0103] In one of the previously described steps, the SiO2-generating substance is added in a suitable manner. In particular, the SiO2-generating substance is introduced into the pulp and thus into the fiber suspension.

[0104] During / after the dewatering step or the subsequent pressing and drying step, the SiO2-generating substance is added, for example as a liquid additive, and applied in particular to the fiber fleece, for example by spraying, brushing (e.g. with the help of a squeegee) or by printing.

[0105] According to a second process variant, which can be used as an alternative or supplement to the first process variant, the SiO2-generating substance is applied to an existing paper layer to form an SiO2 layer (SiO2 barrier layer). For this purpose, for example, the paper layer is unwound from a paper roll and then the SiO2-generating substance is applied.

[0106] This second process variant is used in particular for producing the carrier layer for the packaging material according to the first variant described above, which includes the O2 barrier layer. Alternatively, this second process variant is used to produce the transparent carrier layer for the packaging material according to the second variant of the packaging material described above.

[0107] The SiO2-generating substance is in particular the previously described sol-gel system, which in its initial state before gel formation has an alkoxysilane as its main component.

[0108] The SiO2 layer is the SiO2 layer / barrier layer described previously.

[0109] The (solid) content in the SiO2-generating substance is preferably in the range between 0.5 vol% and 28 vol%. The choice of content depends in particular on the desired application.

[0110] When producing a transparent carrier layer, a proportion in the upper range, for example between 15 vol% and 28 vol%, is preferably used. For SiO2 impregnation, especially in combination with the O2 barrier layer, a proportion in the lower range, up to e.g. 15 vol%, is used.

[0111] According to the first process variant, the SiO2-generating substance is preferably introduced during the preparation and provision of a fiber suspension. This suspension is a fiber slurry mixture of water and fibers and is also referred to as pulp.

[0112] Alternatively or additionally, the SiO2-generating substance is added during or after a process step of dewatering the fiber suspension to produce a fiber web, for example, by being applied or introduced. In normal papermaking, the fiber suspension is regularly dewatered first to form a fiber web. This occurs, for example, in a papermaking plant in a wire section where the fiber suspension is applied to a wire screen, thus dewatering the fiber suspension, which typically consists of over 90% water.

[0113] Preferably, the SiO2-generating substance is added after the dewatering step and before pressing the fiber fleece. Adding it only after the dewatering step has the particular advantage that less of the SiO2-generating substance is required overall, since a large proportion of the SiO2-generating substance would also be washed out during dewatering. Therefore, it is also preferable to omit the addition of the SiO2-generating substance before the dewatering step.

[0114] Alternatively or additionally, the additive can also be added during a process step of pressing and / or drying the fiber web. In papermaking, after passing through the wire section, the dewatered fiber web is typically pressed using a press, usually with rollers, and additionally dried either simultaneously or in a downstream drying section. Drying is preferably combined with a pressing process, for example, by using heated rollers. The pressing, and optionally the combined pressing and drying, typically takes place in a calender, which is a system of several stacked and, in particular, heated rollers through which the fiber web is passed.

[0115] In a suitable design, the SiO2-generating substance achieves a transparency of the carrier layer for visible light of at least 20%, preferably at least 50%, and particularly at least 60% or even at least 70%. Thus, a transparent carrier layer is formed as packaging material, as already explained in connection with the second aspect of the packaging material.

[0116] To form the transparent carrier layer, the SiO2-generating substance is preferably applied to an already transparent paper layer. Studies have shown that this significantly increases transparency, for example by at least 5% or even at least 10%. Overall, this achieves transparencies of over 70% and even over 75%.

[0117] To form the SiO2 impregnation, drying is preferably carried out. This involves an active heat treatment of the SiO2-generating substance. The drying process is preferably applied only at the end of the paper manufacturing process, i.e., in particular after pressing and drying the fiber web.

[0118] In a particularly preferred embodiment, the drying process takes place at a temperature of no more than 100 °C. The SiO2-generating substance described above is therefore particularly characterized by the fact that only low temperatures are required to produce the SiO2 impregnation. Specifically, the temperature for the tempering process lies in the range between 60 °C and 100 °C. This also results in gentle treatment, and the low temperature also means that less energy is required.

[0119] In the second process variant, the SiO2-generating substance is applied using a printing process, specifically flexographic printing. This allows conventional printing presses used in papermaking to be used cost-effectively for applying the SiO2-generating substance. Therefore, no special additional measures or machinery are required.

[0120] Exemplary embodiments of the invention are explained in more detail below with reference to the figures. These show simplified and schematic representations of: Fig. 1. a layered structure of a carrier layer as packaging material, Fig. 2 a transparent support layer, Fig. 3. A representation illustrating a paper manufacturing process in which a SiO2-generating substance is added. Fig.4. A representation illustrating a process in which the SiO2-generating substance is applied to a sheet of paper by a printing process. Fig. 5 A representation illustrating a process in which the SiO2-generating substance is added to a calender, Fig. 6. A cup as an example of a container as packaging, Fig. 7. A transparent bag as an example of a container as packaging consisting of a transparent carrier layer as well as Fig. 8 a package with a viewing window made of a transparent carrier layer.

[0121] Fig. Figure 1 shows a packaging material 2 with a layer structure 4, which has a carrier layer 6 made of a paper material, onto which a sequence of several layers is applied, namely a SiO2 barrier layer 8, an O2 barrier layer 10 and a primer layer 12.

[0122] In the exemplary embodiment of the Fig. 1. The primer layer 12 is applied as the first layer to the carrier layer 6. Following this, a first SiO2 barrier layer 8 is applied, followed by an O2 barrier layer 10, onto which a (second) SiO2 barrier layer 8 is immediately applied.

[0123] In an alternative variant, a SiO2 barrier layer 8 is first applied to the carrier layer 6, followed by the primer layer 12. On top of this, another SiO2 barrier layer 8 is applied, followed by the O2 barrier layer 10, and then by an outer SiO2 barrier layer 8.

[0124] In both variants described above, it is also possible that the carrier layer 6 itself is provided with an internal SiO2 impregnation 14, in which case an SiO2-based protective effect is formed within the carrier layer 6. For this purpose, a SiO2-generating substance S is introduced, particularly during papermaking, as will be discussed in more detail below in connection with Fig. 3 will be explained.

[0125] Preferably, in the layer structure 4, such an internal SiO2 impregnation 14 is omitted.

[0126] It should be emphasized that the outermost layer of the packaging material 2 is preferably formed by a SiO2 barrier layer 8. This protects the underlying layers from dampness and moisture.

[0127] The SiO2 barrier layer 8 is generally a very thin layer, with a layer thickness in the range of only 5 nm to 50 nm.

[0128] In contrast, the O2 barrier layer 10 and / or the primer layer 12 have a significantly greater thickness. For example, the thickness of the O2 barrier layer is in the range of 300 nm to 500 nm, and for the primer layer, it is in the range of 250 nm to 400 nm.

[0129] The entire layer structure, excluding the support layer 6, preferably has a layer thickness in the range between 550 nm and 950 nm.

[0130] This SiO2 barrier layer is therefore essential for the intended application of packaging liquid, moist, or moisture-sensitive products. The SiO2 barrier layer 8 comes into contact with the product being packaged.

[0131] The one to Fig.The layer structure 4 described in section 1 (with its described variants) constitutes, in particular, the final layer structure 4 for the packaging material 2, i.e., the packaging material 2 no longer has any additional layers. At most, a printing layer may be applied to the outside, i.e., in this case, to the underside of the carrier layer 6.

[0132] In Fig. Figure 2 is a simplified representation of a transparent support layer 16, which forms the final layer of the packaging material 2. In the exemplary embodiment of the Fig.2 formed by a transparent paper layer, i.e., a transparency paper 18, onto which a SiO2 barrier layer 8 is applied, which in the case of the transparent substrate 16 is simply referred to as the SiO2 layer. In its initial state, before the application of the SiO2 layer 8, the transparency paper already exhibits a certain transparency to visible light of, for example, 30-50%. The additional SiO2 layer 8 significantly increases the transparency. Overall, transparency values ​​(VLT) of over 60%, and in particular also over 70% and up to over 75%, can be achieved in this way.

[0133] Alternatively or additionally to applying the SiO2 layer 8, the transparency paper 18 can again be provided with an internal SiO2 impregnation 14. This can also create or increase transparency.

[0134] In the simplest case, a transparent support layer 16 is formed by a normal support layer 6 made of paper material with the internal SiO2 impregnation 14 introduced therein.

[0135] In principle, there is also the possibility of using the transparent support structure 16, as described in Fig. 2 is shown, to be provided with further layers, in particular for example with the O2 barrier layer 10. In this case, in addition to good moisture resistance, a high gas tightness is also achieved, so that moisture-sensitive and / or oxygen-sensitive products in particular can be packaged with such a transparent packaging material.

[0136] There are different variants for producing the SiO2 impregnation, i.e., optionally for producing the SiO2 barrier layer 8 or the inner SiO2 impregnation 14.

[0137] According to a first preferred method variant as described in Fig.As shown in Figure 3, the manufacturing process for paper involves the addition of the aforementioned SiO2-generating substance S, as previously described in detail in the general description section. In the Fig. Figure 3 shows different locations where this SiO2-generating substance S can be added.

[0138] In the paper manufacturing process, a fiber suspension F is first prepared and made available in a known manner. This suspension contains paper fibers and mostly water (typically over 90%). It is also referred to as pulp. This fiber suspension F is then applied to a screen 20, where a large portion of the water can already evaporate. A continuous fiber web V is formed from interconnected paper fibers. This web is then fed into a roller section with rollers 22, where it is pressed.

[0139] The SiO2-generating substance S is, for example, already added to the fiber suspension F.

[0140] Preferably, the SiO2-generating substance S is added subsequently, specifically after the sieve 20 and preferably before pressing. This has the advantage that the pressing process forces the SiO2-generating substance S at least partially into the matrix of the fiber fleece V, allowing the internal SiO2 impregnation 14 to form there.

[0141] During this pressing process with rollers 22, a certain amount of dewatering often still occurs; therefore, this area is also referred to as the wet area.

[0142] Often, a further pressing stage is formed by a so-called calender, in which the fiber fleece is fed to calender rollers 24 in a drying area.

[0143] In principle, it is also possible that such a calender is implemented as a separate process step, as is the case, for example, with the Fig. 5 will be explained in more detail below.

[0144] In this embodiment, a paper layer 25 produced during the manufacturing process forms a carrier layer 6 impregnated with the SiO2-generating substance S. An additional drying process may be provided, for example, to form the internal SiO2 impregnation 14; this is particularly relevant to the Fig. 4 is explained in more detail. Alternatively, drying and heat treatment are carried out using the heated calender rolls 24.

[0145] Finally, the paper layer 24 is rolled up into a roll 26.

[0146] In connection with Fig.Section 4 describes a process in which the SiO2-generating substance S is applied as a coating to an existing paper layer 24, thus forming the SiO2 barrier layer 8. The paper layer 24 is, for example, a conventionally manufactured paper layer 24 or one produced using the process described above. Fig. 5. A paper layer 24, which already has an internal SiO2 impregnation 14, is produced. The paper layer 24 is unwound, for example, from a roll 26. Alternatively, the components are part of a papermaking plant and are connected, for example, to the rollers 22 or 24.

[0147] In this process, the SiO2-generating substance S is preferably introduced by a printing process using a printing device 28. The SiO2-generating substance S is therefore fed to the printing device 28 and printed onto the paper layer 24, covering the entire surface. Downstream of the printing device 28, the paper layer 24 thus has an applied layer of the SiO2-generating substance S. The paper layer 24 thus formed is then fed, in a particularly continuous process, to a heat treatment device, in particular an oven 30, in which the SiO2-generating substance S is dried and tempered. This is carried out, in particular, at a temperature below 100 °C and especially within a temperature range between 60 °C and 100 °C. During this process, the SiO2 barrier layer 8 is formed. The drying is therefore carried out in a continuous process.

[0148] For the formation of the layer structure 4, for example, according to Fig. 1. In a suitable configuration, several coating stages are arranged within a process line so that, particularly within a continuous manufacturing process, the various layers are applied successively. For example, each individual layer is applied by a printing process followed by drying. Alternatively, the various layers can also be applied by spraying, brushing, etc.

[0149] As an alternative to the several inline coating stages connected in series, these can also each be applied in a separate (offline) coating process, in which, for example, the respective carrier layer 6 provided with one or more coatings is unrolled from a roll 26, coated with one or more layers and rolled up again.

[0150] In connection with Fig.Figure 5 describes a variant embodiment in which a paper layer 25, which is produced in particular by conventional means (and has no SiO2 barrier layer 8 and / or internal SiO2 impregnation 14), is fed into a calender which has heated calender rolls 24 and optionally also further unheated rolls 22, wherein the SiO2-generating substance S is supplied before and / or between the calender rolls 22, 25. The heating of the calender rolls 25 results in a temperature treatment of the SiO2-generating substance S, so that the SiO2 barrier layer 8 is formed.

[0151] In the Fig. Figures 6 to 8 are simplified illustrations of different application examples for the manufactured packaging material 2 and for different types of packaging: Thus, the packaging material 2, as it is used especially for the Fig. 1 was described, for example a container 32 ( Fig.6) especially for liquids, in particular for liquid foods such as beverages, sauces, etc. For example, container 32 is a drinking cup. Specifically, it is a sealed container 32, so that the products stored in it are completely sealed off from the environment, in particular also gas-tight.

[0152] In the embodiment according to Fig. 7 the transparent packaging material 2 will be, for example, according to Fig. 2 is used to provide transparent packaging, such as a bag 34. This is used in particular for storing moisture-sensitive products, especially food.

[0153] Alternatively, packaging material 2 with layer structure 4 and, in particular, the O2 barrier layer 10 can also be used for such a closed package. The closed packaging ensures that the contained products are gas-tight.

[0154] Finally, it illustrates Fig. 8 a packaging, for example, in the form of a box or case 36, which has a viewing window 38. The viewing window 38 consists of the transparent support layer 16 as previously described. The rest of the box 36 consists of another material, in particular cardboard and, for example, of the packaging material 2 with the layer structure 4 as described in connection with Fig. 1 was described. Reference symbol list 2 Packaging material 4-layer structure 6 Support position 8 SiO2 barrier layer 10 O2 barrier layer 12 Primer layer 14 internal SiO2 impregnation 16 transparent carrier layers 18 Transparency paper 20 sieves 22 rollers 24 calender rollers 25 layers of paper 26 rolls 28 Printing device 30 Heat treatment device 32 containers 34 bags 36 Box 38 viewing windows S SiO2-generating substance F Fiber suspension V Fiber fleece QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 12 005 672 B2 [0004, 0026] EP 2 234 494 B1 [0005, 0038, 0045] EP 2019 / 904

[0037] EP 2019 / 904

[0076]

Claims

[1] Packaging material (2) especially for liquid or moisture-sensitive foodstuffs, having a layered structure (4) which has - a support layer (6) consisting of a paper material, - a SiO2 impregnation (8, 14) wherein the SiO2 impregnation is designed as an internal impregnation (14) and is introduced into the carrier layer (6) and / or is applied as a SiO2 barrier layer (8), - an O2 barrier layer (10). [2] Packaging material (2) according to the preceding claim, wherein the SiO2 impregnation is formed at least as a SiO2 barrier layer (8) which is applied to the O2 barrier layer (10) and / or forms an outermost layer of the layer structure (4). [3] Packaging material (2) according to one of the preceding claims, wherein the layer structure (4) additionally comprises a primer layer (12), wherein a SiO2 barrier layer (8) is applied between the primer layer (12) and the O2 barrier layer (10). [4] Packaging material (2) according to one of the preceding claims, wherein the layer structure has and in particular is formed by the layer sequence carrier layer (6) - primer layer (12) - SiO2 barrier layer (8) - O2 barrier layer (10) - SiO2 barrier layer (8). [5] Packaging material (2) according to one of the preceding claims, wherein the SiO2 impregnation (8, 14) is a silicon-based protective impregnation formed using a sol-gel process. [6] Packaging material (2) according to one of the preceding claims, wherein the O2 barrier layer (10) is a silicate layer which is formed in particular by a crosslinking reaction. [7] Packaging material (2) according to one of the preceding claims and according to claim 3, wherein a primer layer (12) is applied which has bio-based polymers and in particular consists largely of such, wherein the proportion of bio-based polymers in the primer layer (12) is preferably over 95 vol%. [8] Packaging material (2) according to one of the preceding claims, wherein optionally and in particular in combination - each SiO2 barrier layer (8) has a layer thickness in the range between 5 nm and 50 nm, - the O2 barrier layer (10) has a layer thickness in the range between 300nm and 500nm - the primer layer (12) has a layer thickness in the range between 250 nm and 400 nm, - the layer structure (4) without support layer (6) has a total layer thickness in the range between 555 nm and 950 nm. [9] Packaging material (2) according to any of the preceding claims, which is plastic-free and in particular has no further layers other than the layers mentioned (8, 10, 12), apart from any printing etc. [10] Packaging material (2) according to one of the preceding claims, wherein the packaging material (2) is used for a liquid-tight container (32, 34, 36) such as a can, bottle, cup (32), bag (34), etc. for holding liquid or moisture-sensitive foodstuffs, wherein the container (32, 34, 36) preferably consists of the packaging material (2). [11] Packaging material (2), in particular according to one of the preceding claims, which has a transparent carrier layer (16) made of paper, wherein, in order to achieve a desired transparency for visible light of at least 20% (VLT), the transparent carrier layer (16) has a SiO2 impregnation. [12] Packaging material (2) according to the preceding claim, wherein an O2 barrier layer (10) and preferably additionally an SIO2 barrier layer (8) is applied to the transparent carrier layer (16). [13] Packaging material (2) according to one of the two preceding claims, wherein a transparent paper (18) is used for the carrier layer (6) which is provided with the SiO2 impregnation (8, 14) to increase transparency. [14] Packaging material (2) according to any one of claims 11 to 13, wherein a transparency of at least 50% and specifically of at least 60% or 70% is achieved. [15] Packaging material (2) according to any one of claims 11 to 14, wherein the transparent carrier layer (16) is used for one or more of the following products: - Packaging (36) with viewing window (38), wherein the viewing window (38) is formed by the transparent carrier layer (16), - Bag (34), in particular for holding foodstuffs, wherein the bag is formed by the transparent carrier layer (16).

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