Metallized paper multilayer packaging material

Abstract

The present invention provides a metallized paper-based multilayer packaging material 1, which is made of a material having a thickness of 30 to 120 g / m 2 in order from the outside to the inside. 2 and at least one organic barrier layer 3 having a basis weight in the range of 0.5 to 20 g / m 2 at least one inorganic barrier layer 4 having a thickness of 1 to 100 nm and selected from the list of metals, metalloids, or combinations thereof; and at least one organic heat seal layer 5 made from an acrylic or methacrylic acid polymer grafted with at least one ionomer and having a thickness of 2 to 20 g / m. 2 and an organic heat seal layer 5 applied in an amount of

Description

Detailed Description of the Invention

[0001] [Technical field] The present invention relates to a paper-based multi-layer packaging material comprising a paper layer and an ultra-thin metal or metalloid layer for a water vapor barrier sandwiched between ultra-thin coating layers that provide an oxygen barrier and hermeticity to the structure.

[0002] [Background technology] Plastic packaging is frequently used in economic activities and people's daily lives. Plastic packaging has several advantages, such as flexibility and light weight. Lightweighting contributes to fuel savings and CO2 reduction, for example during transportation. The barrier properties of plastic packaging have a positive effect on extending shelf life and therefore help reduce food waste. Barrier properties also help ensure food safety.

[0003] However, due to increasing environmental awareness and to ensure a reduction in plastic waste, multi-layer packaging materials have been developed that comprise one paper or cardboard layer and one or more plastic or metal film layers to provide robustness and barrier properties, particularly oxygen and moisture barrier properties.

[0004] Recently, there has been an increased environmental awareness, especially with regard to waste materials, such as used packaging, that are not recycled or properly treated. This problem is considered very serious by the industry, which is devoting a great deal of effort to developing new packaging materials that are quickly and easily recyclable.

[0005] Currently, when producing multi-layer packaging structures, if layers of plastic are applied by known techniques, in particular by extrusion (extrusion lamination) or also by adhesive lamination processes, the thickness of the plastic film obtained on the paper is necessarily large.

[0006] Even when the extruded or laminated polymers in such multilayer structures are relatively thin, the cohesive strength of the polymer film is very high, as is the level of adhesion of the polymer to the paper or cardboard (i.e., cellulosic) substrate, which prevents the polymer from being removed from the substrate during recycling and prevents recycling and repulping of the cellulose fiber portion in the paper-stream recycling process.

[0007] Thus, multi-layer structures comprising a combination of paper and extruded or adhesively laminated (by conventional techniques such as extrusion lamination or extrusion coating) plastic (polymer) films have limited recyclability in standard paper recycling processes because the plastic layers are too thick to be dispersed during the subsequent recycling process and have too high a cohesive strength and adhesion level to adjacent layers of the structure to separate them from other layers of material, especially from the paper fibers. The extruded plastic film remains intact in the paper pulp bath, thus making it difficult to recycle the paper pulp through a repulping process.

[0008] Furthermore, the above-mentioned known recycling processes for laminated materials are expensive, energy consuming, and characterized by a relatively low yield of recycled paper fibers (less than 80% of the total amount of packaging material in the entire structure), and therefore are not sufficiently environmentally friendly in terms of disposal and recycling. There is also room for improving the recyclability of the remaining parts of the packaging material (i.e., the plastic polymer part and the metal part, e.g., the aluminum part) in the paper recycling process.

[0009] Furthermore, in packaging for food products, good barrier properties are essential to maintain the safety and quality of the packaged food, typically including gas barrier (e.g., to oxygen and water vapor (moisture)) and, if possible, liquid-tightness.

[0010] One way to provide a good moisture barrier to paper-based packaging materials is the introduction of a metal or metalloid layer into a so-called "metallized" layer. As used herein, the term "metallization" (e.g., in the expression "metallized barrier paper layer") is meant to encompass the deposition of metal or metalloid atoms on the surface of paper or paperboard. One can even consider embodiments that include the deposition of alloys of metals and metalloids. Metalloids have some of their properties close to metals. Aluminum oxide and silicon oxide are examples of metalloids.

[0011] Problems associated with the introduction of metal layers into paper-based packaging materials include the sensitivity of the metal layer to mechanical stress, as well as poor adhesion of the metal to the paper surface, poor smoothness, and high porosity of the paper material. Mechanical stress can easily result, for example, in the loss of the necessary barrier properties that the metallized packaging material is intended to provide. Mechanical stress can result, for example, from the processing of multilayer materials in the manufacture of packages using form-fill-seal packaging machines. During manufacturing, materials are stretched, bent, rolled, compressed, and / or heated during the formation and sealing of packages by conventional package formation methods. These packaging manufacturing processes impose high mechanical and / or chemical stresses on the materials, particularly on ultra-thin metallized coating layers of metal or metalloid, resulting in the development of largely irreversible damage, cracks, and tears in these layers.

[0012] In view of the above, there is a need for a metallized paper-based multi-layer packaging material that simultaneously exhibits the following properties: Sufficient barrier properties, especially against oxygen and moisture, High resilience to mechanical stress, so that the barrier remains at the same level even when subjected to deformation processes such as those used to manufacture the package; a significantly reduced amount of plastic polymer content compared to the content of cellulosic material; and preferably recyclability in paper recycling processes and / or biodegradability in a variety of environmental conditions, particularly (but not exclusively) in the marine environment.

[0013] [Summary of the Invention] The object of the present invention is to provide a metallized paper-based multi-layer packaging material, which comprises, in order from the outside to the inside, 30~120g / m 2 a paper layer having a basis weight falling within the range 0.5~20g / m 2 Amount of, preferably 1 to 10 g / m 2 More preferably, the amount is 2 to 8 g / m 2 at least one organic barrier layer of a polymer selected from the list of polyvinyl alcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol copolymer (BVOH), or combinations thereof, in an amount of at least one inorganic barrier layer selected from the list of metals, metalloids, or combinations thereof, said inorganic layer having a thickness of 1 to 100 nm; At least one organic heat-seal layer made from an acrylic or methacrylic polymer grafted with at least one ionomer, the heat-seal layer having a density of 2 to 20 g / m 2 Amount of 4 to 9 g / m 2 an organic heat seal layer applied in an amount of This is achieved by a metallized paper-based multi-layer packaging material comprising:

[0014] The total thickness of the polymer coating layers in the structure is greatly reduced compared to the thickness of the paper material, and as a result, the inventors have achieved overcoming the technical limitations of known multilayer barrier structures and have realized a packaging multilayer structure that has excellent barrier properties against oxygen and moisture transmission, and resistance to liquid contact from its inner or outer surface, while at the same time achieving a total cellulosic fiber content of preferably up to 85%, or even 95%, by weight of the total material.

[0015] Furthermore, the water-soluble pre-coating polymer layer enhances recyclability. The inventors have succeeded in forming a multilayer structure entirely free of polymer layers formed by extrusion lamination and / or adhesive lamination, providing a multilayer structure with a cellulosic fiber to non-cellulosic material ratio and an extremely high fiber content. In this structure, the polymer layer inhibits fragmentation of the metal layer during repulping due to the water solubility of the pre-coating layer and the relatively high adhesion of the post-metallization (or post-metalloidization) polymer to the metallization layer, resulting in high fiber purity from the repulping process. The resulting structure therefore exhibits excellent repulping performance, produces a high yield of high-quality fiber, and is acceptable for standard recycled paper mills in most countries. Due to the very low content of non-cellulosic polymer and vacuum-deposited metallic material, the entire material of the present invention is easily degraded, dissolved, and separated in recycling processes designed for cellulosic materials, such as paper or cardboard, unlike existing multilayer barrier structures known in the art.

[0016] A particular improvement provided by the present invention over existing barrier paper materials is the incorporation into the multi-layer barrier wrapping paper of a heat seal layer comprising an ionomer-grafted acrylic or methacrylic polymer.

[0017] The present inventors have surprisingly found that grafting an ionomer onto an acrylic or methacrylic acid polymer improves the heat seal innermost coating in at least two different ways.

[0018] First, heat seal layers made from such acrylic or methacrylic acid-ionomer materials achieve excellent resistance to mechanical stresses, particularly the bending, stretching, and shear forces applied to the material during the manufacture of packaging from the material. This mechanical resistance protects the entire structure, and in particular the adjacent inorganic layers, from damage, more particularly from irreversible cracking.

[0019] Second, it was found that grafting an ionomer onto an acrylic or methacrylic acid polymer changes the molecular structure of the material: the acrylic or methacrylic acid-ionomer molecules form a molecular matrix on the surface of the coating made from said material, resulting in a heat seal layer that exhibits high hot tack properties that result in excellent seal integrity of the formed and filled package and ultimately allows for barrier retention in the final package.

[0020] Advantageously, the organic heat seal material is a methacrylic acid polymer that is chemically modified (ie, grafted) with an ionomer.

[0021] In a highly preferred embodiment of the present invention, the inorganic layer comprises a metal or metalloid selected from the list of aluminum, aluminum oxide (AlOx), or silicon oxide (SiOx), said metal and / or metalloid being deposited either by vacuum evaporation or transfer metallization. In a particularly preferred embodiment, the inorganic layer is a vacuum-deposited layer of aluminum.

[0022] Furthermore, in a preferred embodiment of the present invention, the ionomer grafted onto the acrylic or methacrylic acid polymer is a sodium ionomer.

[0023] Preferably, the acrylic or methacrylic acid-ionomer polymer has a molecular weight of 85 to 90 g / mol.

[0024] Each organic layer is preferably deposited relative to the adjacent layer by either aqueous dispersion or aqueous solution deposition.

[0025] Advantageously, the organic barrier layer is deposited by aqueous solution deposition and the organic heat seal layer is deposited by aqueous dispersion coating.

[0026] In one embodiment of the present invention, the paper layer is covered on its outer surface with an ink layer. The ink layer is preferably 0.5 to 5 g / m 2 Preferably, the ink layer is selected from the list of water-based inks, solvent-free inks, or combinations thereof.

[0027] More preferably, the paper layer or ink layer has its outer surface covered with an outermost layer of overprint varnish (OPV). The OPV layer preferably has a thickness of 0.5 to 10 g / m 2 The sheet has a basis weight of .

[0028] The optional OPV layer also contributes to improving the barrier paper's resistance to hygroexpansive strain, as it provides an improved barrier to moisture (water vapor transmission rate or "WVTR"), especially under high humidity conditions.

[0029] In an advantageous embodiment, the outermost layer of overprint varnish is a styrene acrylic varnish.

[0030] The metallized paper-based multilayer packaging material according to the present invention advantageously achieves oxygen and moisture barrier properties as follows: a water vapor transmission rate (WVTR) of less than 0.5 g / m2 / day (measured at 23°C and 85% relative humidity) and / or an oxygen transmission rate (OTR) of less than 0.1 cm3 / m2 / day bar (measured at 23°C and 50% RH), measured according to flexibility testing standard ASTM F392 or equivalent, after subjecting the sample to an in-plane tensile pre-strain of up to 2% and after subjecting the sample to three cycles in a Gelboflex testing apparatus.

[0031] The metallized paper-based multilayer packaging material according to the present invention preferably has a strain at break under in-plane tensile load of up to 5% in the machine direction of the paper and up to 15% in the cross-machine direction, with the overall paper structure having a strain at break of 2.5% in the machine direction and 9% in the cross-machine direction, providing high mechanical recovery.

[0032] The present invention further relates to a three-dimensional sealed packaging article made from the aforementioned metallized paper-based multi-layer packaging material, obtained by shaping and then filling with an edible product for human or animal consumption and then sealing said packaging material.

[0033] The present invention further relates to the use of the aforementioned metallized paper-based multi-layer packaging material for packaging edible products for human or animal consumption.

[0034] The present invention further relates to a packaged edible product comprising a metallized paper-based multi-layer packaging material according to the present invention, the edible product being filled with a food or edible product for animal consumption.

[0035] Preferably, the edible product is a powder, gel or kibble and is selected from the following list: soluble coffee, nutritional compositions for consumption by infants, adults or the elderly, soups, confectionery or candy, chocolate-based products, dry animal food, dairy products.

[0036] As used herein, the words "comprises," "comprising," and similar words should not be construed in an exclusive or exhaustive sense. In other words, they are intended to mean "including, but not limited to."

[0037] Additional features and advantages of the present invention are described in, or will be apparent from, the following description of the presently preferred embodiments, which proceeds with reference to the drawings. [Brief explanation of the drawings]

[0038] [Figure 1]1 shows a first embodiment of a multilayer structure according to the invention. [Figure 2] 2 shows a second embodiment of a multilayer structure according to the invention.

[0039] [Mode for Carrying Out the Invention] Generally, as used herein, "extrusion coating" refers to a method of applying a layer of polymer by using an extruder to force a molten thermoplastic resin (e.g., polyethylene) through a horizontal slot die onto a moving web of substrate (e.g., paper). The product is a permanently coated web structure.

[0040] "Extrusion lamination" refers to a process akin to extrusion coating in which a polymer resin is extruded between two substrates (eg, a layer of paper and another layer of polymer film) to act as a binder.

[0041] "Adhesive lamination" refers to a process in which one paper material is coated with an adhesive and laminated to a second paper or paperboard material. In the lamination process, two thick layers of material are combined by either extrusion lamination or adhesive lamination, resulting in a thickness of each layer that is much greater than that achieved by dispersion coating.

[0042] "Dispersion coating" refers to a coating technique in which an aqueous dispersion of fine polymer particles or a polymer solution is applied directly to the surface of paper or paperboard to form a solid, nonporous film after drying. Dispersion coating can be performed by gravure, flexogravure, rod, blade, slot die, curtain air knife, roll coating, or any other known paper coating method. Because the polymer is mixed into an aqueous solution, dispersion coating can produce much thinner layers than extrusion lamination and / or adhesive lamination. This offers advantages in terms of polymer usage, its barrier performance, and the recyclability of the resulting paper structure. The goal of dispersion coating is to provide a barrier layer against water, water vapor, grease, oil, gas, etc., using an environmentally friendly coating. Another goal is to prepare the surface of the paper material for vacuum deposition processes.

[0043] "Fiber" refers to cellulose fibers, generally extracted from plants, seeds, or trees, which contain not only cellulose molecules but also hemicellulose and lignin.

[0044] The multi-layer structure according to the present invention is preferably designed to be suitable for recycling in standard recycled paper stream processes as well, in accordance with most local or national paper recycling regulations.

[0045] Recyclability in the paper recycling process is achieved by the multilayer structure according to the invention, wherein: The fiber content is significant compared to all the raw materials in the structure (the definition of recyclability in paper recycling processes varies depending on national legislation, but on average a material must contain at least 80% fiber to be accepted in paper-specific recycling processes), and The inorganic layer is ultrathin (i.e., a few nanometers, typically 1-100 nm) and consists of a few atoms in thickness. All organic polymer layers are deposited by aqueous dispersion or aqueous solution deposition coating, which means that the layers thus obtained are sufficiently thin relative to the thickness of the paper to achieve a very high paper content throughout the structure, making the entire structure compatible with the paper recycling processes mentioned above; The organic barrier layer preferably comprises a water-soluble polymer (i.e., PVOH, EVOH and / or BVOH), which makes it easier to separate the fibers from the rest of the material of the structure, especially from the cellulosic contents.

[0046] 1 illustrates a first embodiment of the present invention, in which a multi-layer structure 1 is configured, from its outer side (i.e., the side of the material facing the outside of a package made from the structure) to its inner side (i.e., the side that contacts a product packaged in a package made from the structure): Basis weight 62g / m 2 2. Very smooth paper layer Mainly provides gas (especially oxygen) barrier properties, 3g / m 2 a first organic polyvinyl alcohol-based (PVOH) coating layer 3 on the outer side of the metal coating, applied as an aqueous solution of an inorganic vacuum-deposited layer 4 of aluminum having a thickness of 40 nm, which primarily provides water vapor barrier properties; and It functions as a heat seal layer and is 5 g / m 2 a second organic coating layer 5 of a methacrylic acid ionomer based coating applied as an aqueous dispersion of , and is equipped with.

[0047] In this embodiment, the deposition techniques for the first and second organic layers as described above make it possible to improve the recyclability of said layers in the paper recycling process.

[0048] The structure 1 of this first embodiment has an oxygen transmission rate (OTR) value of 0.5 cm 2 measured at 23°C and 50% relative humidity (RH). 3 / m 2 / day and a water vapor transmission rate (WVTR) of 0.5 g / m2 measured at 23°C and 85% RH 2 / day or less, achieving high moisture barrier property and gas barrier property.

[0049] The overall strain at break of Structure 1 is measured at 2.5% in the machine direction and 9% in the cross-machine direction. These values ​​provide excellent recovery properties that allow the aluminum layer to be protected during processing of the structure in conventional package formation processes. When manufacturing packages from the material, the aluminum layer does not crack while bending, stretching, and / or sealing the material, resulting in comparable OTR and WVTR barrier levels being maintained before and after the package is formed from the multilayer structure material.

[0050] FIG. 2 shows a structure similar to that described above in connection with FIG.

[0051] However, in this second exemplary embodiment of the present invention, the paper layer 2 has an outer surface that is in the order from the outer surface of the packaging material to the inside: 1g / m 2 an outermost layer 7 of acrylic overprint varnish applied as an aqueous dispersion of 1g / m 2 water-based ink 6, applied as an aqueous dispersion of The water-based ink layer 6 is located between the outermost overprint varnish layer 7 and the paper layer 2.

[0052] The remaining layers of structure 1 remain similar to the structure described with reference to FIG. Mainly provides gas (especially oxygen) barrier properties, 3g / m 2 a first organic polyvinyl alcohol (PVOH) coating layer 3 applied as an aqueous solution of an inorganic vacuum-deposited layer 4 of aluminum having a thickness of 40 nm, which primarily provides water vapor barrier properties; and 5g / m 2and a second organic coating layer 5 of a methacrylic acid ionomer based coating applied as an aqueous dispersion of 1000 ppm by weight.

[0053] Structures corresponding to the above embodiments meet the requirements for recyclability of such materials or packaging made from such materials in standard paper recycling mill conditions.

[0054] In all of the above-described embodiments of the present invention, the multilayer structure may include other additional layers and optional layers not described in full detail. Such layers may include, for example, a printing layer on the outer surface of the paper layer, and optionally, a protective layer disposed on the outside of the printing layer, thus constituting the outermost layer of the entire structure. The printing layer and the optional protective layer are well known to those skilled in the art, and therefore will not be described in further detail.

Claims

1. A metallized paper-based multilayer packaging material (1) comprising, in order from the outside to the inside, 30 to 120 g / m ２ a paper layer (2) having a basis weight in the range of 0.5 to 20 g / m ２ , preferably 1 to 10 g / m ２ and more preferably 2 to 8 g / m ２ at least one organic barrier layer (3) of a polymer selected from the list of polyvinyl alcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol copolymer (BVOH), or combinations thereof, in an amount of at least one inorganic barrier layer (4) selected from the list of metals, metalloids, or combinations thereof, said inorganic layer having a thickness of 1 to 100 nm; At least one organic heat-seal layer (5) made from an acrylic or methacrylic polymer grafted with at least one ionomer, said heat-seal layer (5) having a coating weight of 2 to 20 g / m ２ , preferably 4 to 9 g / m ２ an organic heat seal layer (5) applied in an amount of A metallized paper-based multilayer packaging material (1).

2. 2. The metallized paper-based multilayer packaging material (1) of claim 1, wherein the inorganic layer comprises a metal or metalloid selected from the list of aluminum, aluminum oxide (AlOx), or silicon oxide (SiOx), and wherein the metal and / or metalloid is deposited by either vacuum deposition or transfer metallization.

3. 3. The metallized paper-based multi-layer packaging material (1) according to claim 1 or 2, wherein the ionomer grafted onto the acrylic or methacrylic polymer is a sodium ionomer.

4. The metallized paper-based multilayer packaging material (1) according to any one of claims 1 to 3, wherein the ionomer-grafted acrylic or methacrylic polymer has a molecular weight of 85 to 90 g / mol.

5. The metallized paper-based multi-layer packaging material (1) according to any one of claims 1 to 4, wherein each of the organic layers is deposited on the adjacent layer by either aqueous dispersion or aqueous solution deposition.

6. 6. The metallized paper-based multilayer packaging material (1) according to claim 5, wherein the organic barrier layer (3) is deposited by aqueous solution deposition and the organic heat-seal layer (5) is deposited by aqueous dispersion coating.

7. The metallized paper-based multi-layer packaging material (1) according to any one of claims 1 to 6, wherein the paper layer (2) is covered on its outer surface with an ink layer (6).

8. 8. The metallized paper-based multilayer packaging material (1) according to claim 7, wherein the ink layer is preferably selected from the list of water-based inks, solvent-free inks, or a combination thereof.

9. 9. The metallized paper-based multilayer packaging material (1) according to claim 7 or 8, wherein the paper layer or the ink layer is covered on its outer surface by an outermost layer (7) of overprint varnish (OPV).

10. 10. The metallized paper-based multilayer packaging material (1) according to claim 9, wherein the outermost overprint varnish layer (7) is a styrene acrylic varnish.

11. The packaging material has a density of 0.5 g / m ２ / day (measured at 23°C and 85% relative humidity), and / or ３ / m ２ The metallized paper-based multilayer packaging material (1) according to any one of claims 1 to 10, having an oxygen transmission rate (OTR) of less than 1 / day bar (measured at 23°C and 50% RH).

12. 12. The metallized paper-based multilayer packaging material of any one of claims 1 to 11, wherein the packaging material has a strain at break under in-plane tensile load of up to 5% in the machine direction and up to 15% in the cross-machine direction of the paper.

13. 13. A three-dimensional sealed packaging article made of the metallized paper-based multilayer packaging material (1) according to any one of claims 1 to 12, obtained by shaping said packaging material, filling it with an edible product for human or animal consumption and then sealing it.

14. Use of the metallized paper-based multilayer packaging material (1) according to any one of claims 1 to 12 for packaging edible products for human or animal consumption.

15. A packaged edible product comprising the metallized paper-based multilayer packaging material (1) according to any one of claims 1 to 12 filled with a food or edible product for animal consumption.

Images