Metallized paper multi-layer packaging material

Abstract

A metallized paper-based multi-layer packaging material (1), comprising: 2 and a paper layer (2) having a basis weight in the range of 0.5 to 15 g / m 2 Preferably, the amount is 1 to 10 g / m 2 at least one first organic layer (3) of a biodegradable polymer selected from the list of polyvinyl alcohol (PVOH), butenediol vinyl alcohol copolymer (BVOH) or a combination thereof in an amount of 0.5 to 30 g / m; an inorganic layer (4) which is a vacuum deposited inorganic layer comprising a metal, a metalloid or a combination thereof, having a thickness of 1 to 100 nm; and at least one second organic layer (5) made of a biodegradable polymer having a tensile strength of more than 30 MPa and an elongation at break of more than 850%, the thickness being between 0.5 and 30 g / m. 2 Preferably, the amount is 1 to 10 g / m 2 and a second organic 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 water vapor barrier sandwiched between thin biodegradable polymer layers that provide oxygen barrier and hermeticity to the structure. The resulting packaging material has a very high cellulose content, providing recyclability and preferably biodegradability in a variety of environmental conditions.

[0002] [Background technology] Plastic packaging is often used in economic activities and people's daily lives. Plastic packaging has several advantages, such as flexibility and light weight. Light weight contributes, for example, to fuel savings and CO2 reduction 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 waste plastics, multi-layer packaging materials have been developed that comprise a paper or cardboard layer and one or more plastic or metal film layers to provide robustness and barrier properties, particularly to oxygen and moisture.

[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 and pollute the oceans. This problem is considered very serious by the industry, which is devoting a lot of effort to develop new packaging materials that are quickly and easily biodegradable when accidentally introduced into the natural, and especially the marine, environment.

[0005] Currently, when producing multi-layer packaging structures, when 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 high.

[0006] Even when the extruded polymer thickness of such multi-layer structures is relatively low, 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 standard techniques such as extrusion lamination or extrusion coating) plastic (polymer) films cannot be recycled in a paper stream recycling process 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 be separated from other adjacent material layers in the structure, especially from the paper fibers. The extruded plastic film remains intact in the paper pulp tank, thus making it difficult to recycle the paper pulp through a repulping process.

[0008] Furthermore, the recycling processes of the known laminated materials mentioned above are costly, energy consuming, and characterized by a relatively low yield of recycled paper fibers (about 60% of the total amount of packaging material in the entire structure), and therefore are not environmentally friendly enough in terms of disposal and recycling. There is also room to improve the recyclability of the remaining parts of the packaging material (i.e. the plastic polymer parts and the metal parts, e.g. the aluminum parts) in the paper recycling system.

[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. against oxygen and water vapor (moisture)) and possibly also 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 the paper or paperboard. One can even envisage embodiments that include the deposition of alloys of metals and metalloids. Metalloids are close in some of their properties 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 are the sensitivity of the metal layers to mechanical stresses, as well as poor adhesion of the metal to the paper surface, poor smoothness and high porosity of the paper material. Mechanical stresses can easily result in the loss of the necessary barrier properties that the metallized packaging material should provide, for example. This can result from the processing of multi-layer materials in the manufacture of packages using form-fill-seal packaging machines. During manufacture, the materials are stretched, bent, rolled, compressed, and / or heated during the formation and sealing of the packages by conventional package formation methods. These package manufacturing processes result in high mechanical and / or chemical stresses on the materials, especially the very thin metallized coating layers of metal or metalloid, resulting in the occurrence of damage, cracks and ruptures of 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, such that the barrier remains at the same level even when subjected to deforming processes, such as those used to manufacture the package; a plastic polymer content that is significantly reduced compared to the content of cellulosic materials; and preferably recyclability in the paper stream 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, from the outside to the inside, 40~120g / m 2 A paper layer having a basis weight falling within the range 0.5~15g / m 2 Preferably, the amount is 1 to 10 g / m 2 at least one first organic layer (3) of a biodegradable polymer or copolymer selected from the list of polyvinyl alcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol copolymer (BVOH), or combinations thereof, in an amount of a vacuum deposited or transferred metallized inorganic layer comprising a metal, metalloid, or a combination thereof, the inorganic layer having a thickness of 1 to 100 nm; At least one second organic layer made from a biodegradable polymer having a tensile strength of more than 30 MPa and an elongation at break of more than 850%, and a weight ratio of 0.5 to 30 g / m 2 Preferably, the amount is 1 to 10 g / m 2 a second organic layer, applied in an amount of This is achieved with a material having

[0014] The total thickness of the polymer coating layers in the structure is greatly reduced compared to the thickness of the paper material, as a result of which the inventors have achieved overcoming the technical limitations of known multi-layer barrier structures and realizing a packaging multi-layer structure having excellent barrier properties against oxygen and moisture transfer, as well as resistance to liquid contact from its inner or outer surfaces, while at the same time constituting a total content of cellulosic fibers, preferably up to 95% by weight of the total material.

[0015] Moreover, the pre-coating polymer layer, being water soluble, enhances recyclability. The inventors have succeeded in forming a multi-layer structure completely free of polymer layers formed by extrusion (lamination and / or adhesive lamination), thus providing a multi-layer structure with a ratio of cellulosic fibers to non-cellulosic materials and a very high fiber content. The polymer layer is easily degraded in the repulping process due to the solubility of the pre-coating layer in water and also due to the relatively poor adhesion of the post-metallization (or post-metalloidization) polymer to the remaining part of the metallization layer. Thus, the resulting structure shows good repulping ability and high fiber yield, and is acceptable for waste paper collection 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 multi-layer barrier structures known in the art.

[0016] In a highly preferred embodiment of the invention, the biodegradable polymer used for the second organic layer is selected within the list: polycaprolactone (PCL), thermoplastic starch (TPS) or polybutylene adipate terephthalate (PBAT).

[0017] Of the above three types, polycaprolactone (PCL) is preferred due to its mechanical properties, heat sealability and biodegradability.

[0018] Advantageously, but not necessarily, the first organic layer may further comprise a mineral filler selected from the list of kaolin, calcium carbonate, talc, silica, wollastonite, clay, calcium sulfate fiber (also known as Franklin fiber), mica, glass beads, alumina trihydrate, and combinations thereof.

[0019] The inorganic layer is preferably selected from the list of metals, in particular aluminium, or metalloids, in particular aluminium oxides (AlOx), silicon oxides (SiOx). The inorganic layer may also be an alloy of these.

[0020] In one embodiment of the present invention, the multilayer material structure further comprises a third organic layer coated inside the second organic layer, the third layer being composed of a biodegradable polymer selected from the list of polybutylene succinate-co-butylene adipate (PBSA) or polyhydroxyalkanoate (PHA) based polymers at a concentration of about 0.5-30 g / m. 2 in the range of 1 to 15 g / m 2 Contains in amounts ranging from.

[0021] The organic layer is preferably prepared as an aqueous solution or dispersion, or in a concentration of 30 g / m 2 Less than 15 g / m 2 It is applied by extrusion of a very thin layer having a thickness of less than 100 nm.

[0022] The packaging material according to the invention is recyclable as paper and / or carton and preferably achieves high barrier properties such as: a water vapor transmission rate (WVTR) of 1 g / m2 or less after the material is folded 180° under a compressive load of 2 kilograms with the coated side of the paper under compressive stress during folding. 2 / day (measured at 23°C and 85% relative humidity) and / or an oxygen transmission rate (OTR) of 3cm 3 / m 2 / day bar (measured at 23°C and 50% RH).

[0023] Furthermore, the packaging material of the present invention advantageously has a strain at break under in-plane tensile load of maximum 4% in the machine direction of the paper and maximum 10% in the cross-machine direction.

[0024] 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 molding and then filling with an edible product for human or animal consumption and then sealing said packaging material.

[0025] 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.

[0026] 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 food or an edible product for animal consumption.

[0027] Preferably, said edible product is a powder, gel or kibble and is selected within 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.

[0028] 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."

[0029] 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 take place in conjunction with the drawings. [Brief description of the drawings]

[0030] [Figure 1] 1 shows a first embodiment of a multi-layer structure according to the present invention. [Diagram 2] 2 shows a second embodiment of a multi-layer structure according to the invention.

[0031] [Mode for carrying out the invention] Generally, as used herein, "extrusion coating" refers to a process for providing 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.

[0032] "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.

[0033] "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.

[0034] In the lamination process, two thick layers of material are combined by either extrusion lamination or adhesive lamination, resulting in a thickness for each layer that is much greater than that obtainable by dispersion coating.

[0035] "Dispersion coating" refers to a coating technique in which an aqueous dispersion of fine polymer particles or a polymer solution is applied neat to the surface of paper or paperboard to form a solid, non-porous film after drying. Dispersion coating can be performed by gravure, flexo-gravure, rod, blade, slot die, curtain air knife, or any other known paper coating method. In dispersion coating, much thinner layers can be created than extrusion lamination and / or adhesive lamination because the polymer is mixed into an aqueous solution. This provides advantages in terms of polymer usage, its barrier performance, and 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., by an environmentally friendly coating. Another goal is to prepare the surface of the paper material for the vacuum deposition process.

[0036] In all possible embodiments of the present invention, and particularly in the exemplary embodiments specifically described below, the multi-layer packaging structure is preferably biodegradable in soil or marine environments. Such preferred biodegradability can be achieved when the structure contains a cellulosic substrate, an extremely thin inorganic layer containing only a few metal or metalloid atoms per square meter, and when all polymeric components are biodegradable polymers.

[0037] The biodegradability of the final structure is defined and tested under the international standard ISO 22403 ("Assessment of the intrinsic biodegradability of materials exposed to marine inocula under mesophilic aerobic laboratory conditions").

[0038] In addition to, or instead of, the inherent biodegradability, the multi-layer structure according to the present invention is preferably designed to be recyclable in paper stream processes as well.

[0039] Recyclability in the paper stream is achieved by the multi-layer structure of the present invention, wherein: The cellulose content is predominant compared to all the raw materials contained in the structure (the definition of recyclability in the paper stream varies by national legislation, but on average a material is required to contain at least 80% cellulose to be accepted into paper-specific recycling processes); and The inorganic layer is extremely thin (i.e., a few nanometers, typically 1-50 nm) and consists of a few atoms in thickness. The organic polymer layers are all deposited by coating, which means that the layers thus obtained are sufficiently thin in relation to the thickness of the paper to achieve a very high paper content in the overall structure; the pre-metallization layer (or pre-metalloidization), i.e. the first organic layer, comprises a polymer that is water-soluble, which makes it easier to separate the fibers from the rest of the structure, in particular from the cellulose content; Finally, any subsequent organic layers (second organic layer, third organic layer, etc.) deposited inside the metal or metalloid layer will be characterized by low cohesion and adhesion with the rest of the structure components, making the entire structure compatible with paper recycling processes such as those described herein above.

[0040] FIG 1 illustrates a first embodiment of the present invention. In this embodiment, a multi-layer structure 1 is provided with, from its outer side to its inner side (i.e., the inner side in contact with the packaged product): Basis weight 62g / m 2 2. Very smooth paper layer of 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 mainly provides water vapor barrier properties; and 5g / m 2 a second organic coating layer 5 of polycaprolactone (PCL) applied as an aqueous dispersion of It is equipped with:

[0041] The innermost polycaprolactone layer 5 functions as the heat-sealable layer in this first embodiment.

[0042] The inorganic layer 4 of aluminum can be deposited by a direct metallization process or by a transfer metallization process.

[0043] In this embodiment, the first and second organic layers are applied by aqueous dispersion coating techniques, which can improve the recyclability of the layers in the paper stream process.

[0044] The structure 1 of the first embodiment has an oxygen transmission rate (OTR) value of 0.5 cm when measured at 23° C. and 50% relative humidity (RH). 3 / m 2 / day and has a water vapor transmission rate (WVTR) of 0.5 g / m2 measured at 38°C and 85% RH 2 / day or less, achieving high moisture barrier property and gas barrier property.

[0045] The tensile strength of the polycaprolactone polymer used for the PCL layer 5 is measured at 33 MPa under standard test conditions (DIN EN ISO 527-1) and its elongation at break is measured at 910%. These values ​​provide good recovery properties that allow the aluminum layer to be protected during processing of the structure in conventional packaging formation processes. When producing a package from the material, no cracks of the aluminum layer occur during bending, stretching and / or sealing of the material, so that the OTR and WVTR barrier levels are maintained equally before and after the package is formed from the multi-layer structure material.

[0046] As an alternative in this first embodiment, the innermost PCL dispersion coated heat seal layer can be replaced by a thermoplastic starch (TPS) or polybutylene adipate terephthalate (PBAT) heat seal layer having a thickness of 9 gsm applied by aqueous dispersion coating.

[0047] The tensile strength of the TPS polymer used instead of PCL is determined under standard test conditions (DIN EN ISO 527-1) to be 29 MPa and its elongation at break is determined to be 1000%.

[0048] If PBAT is used as a replacement polymer for PCL, the polymer used in this case has a tensile strength measured at 40 MPa and an elongation at break of 1120%.

[0049] In figure 2 a second embodiment of a paper-based barrier multi-layer packaging structure 1 according to the invention is shown.

[0050] In this second embodiment, the multi-layer structure is, in order from its exterior to its interior (i.e., the interior in contact with the packaged product): Basis weight 62g / m 2 Very smooth paper layer 2 3g / m 2 a first organic coating layer 3 of PVOH, applied as an aqueous solution in an amount of a 40 nm thick vacuum-deposited inorganic (aluminum) layer 4; It is equipped with:

[0051] A second organic layer 5 of polycaprolactone (PCL) polymer is then applied to the inside of the inorganic layer 4 as the first layer inward of the metal coating at a thickness of 5 g / m 2 The coating is applied as an aqueous dispersion in an amount of 1000g / g.

[0052] A third organic layer 6 of polybutylene succinate-co-butylene adipate (PBSA) polymer is then applied inside the second organic layer 5, which acts as the second layer inside the metal coating. The layer has a thickness of 8 g / m 2 is applied as an extrusion coating in an amount of

[0053] A second organic layer 5 of PCL serves as a tie layer between the inorganic layer 4 and a third organic layer 6 of PBSA. The innermost PBSA-based coating layer 6 serves as the heat-sealable layer in this second embodiment of the invention.

[0054] As in the first embodiment, alternative polymers to PCL can be envisaged, provided that the recovery properties (tensile strength, elongation at break) correspond to the requirements set for implementing the invention. For example, PCL can be replaced by TPS or PBAT polymers, characterized by tensile strength values ​​of more than 30 MPa and elongations at break of more than 850%.

[0055] As an alternative third embodiment, in the third organic heat seal layer 6, the PBSA can be replaced with a polyhydroxyalkanoate (PHA), also having a thickness of 8 gsm.

[0056] A structure corresponding to the above embodiment meets the requirements for biodegradability of the material or packaging made from it under standard conditions.

[0057] In all of the above embodiments of the present invention, the multi-layer structure may include other additional layers and optional layers therein that are 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 that is deposited on the outside of the printing layer and thus constitutes the outermost layer of the entire structure. The printing layer and the optional protective layer are techniques known to those skilled in the art, and therefore will not be described in more detail.

[0058] In all embodiments of the present invention, technical parameters such as, for example, basis weight, tensile strength, elongation at break and strain at break can be determined by the skilled person according to standard methods that are widely used and known in the art. Therefore, it is not necessary to provide further details on these standard measurement methods or the equipment required to perform such methods. Examples of such standard methods are as follows: for the measurement of "basis weight", the standard method is based on the ISO 536:2019 standard, for the measurement of "elongation at break", the standard method is based on the ISO 1924-2:2008 standard, for the measurement of "tensile strength", the standard method is based on the ISO 1924-2:2008 standard, and for the measurement of "strain at break", the method of measurement is based on the same standard (i.e. ISO 1924-2:2008) as that used for the measurement of elongation at break.

Claims

1. Metallized paper-based multilayer packaging material (1), wherein the layers are arranged in order from the outside to the inside: 40-120 g / m ２ A paper layer (2) having a basis weight that falls within the range, 0.5–15 g / m ２ Amount, preferably 1 to 10 g / m ２ A first organic layer (3) of at least one layer of a biodegradable polymer or copolymer selected from the list of polyvinyl alcohol (PVOH), ethylene vinyl alcohol (EVOH), butenediol vinyl alcohol copolymer (BVOH), or combinations thereof, An inorganic layer (4) having a thickness of 1 to 100 nm, comprising a metal, a metalloid, or a combination thereof, which is vacuum deposited or transferred and metallized. A second organic layer (5) of at least one layer made from a biodegradable polymer having a tensile strength of over 30 MPa and an elongation at break of over 850%, wherein the concentration is 0.5 to 30 g / m². ２ Amount, preferably 1 to 10 g / m ２ A second organic layer (5) is applied in the amount of, A metallized paper-based multilayer packaging material that possesses the following features.

2. The metallized paper-based multilayer packaging material (1) according to claim 1, wherein the biodegradable polymer used in the second organic layer (5) is selected from the list of polycaprolactone (PCL), thermoplastic starch (TPS), or polybutylene adipate terephthalate (PBAT).

3. The metallized paper-based multilayer packaging material (1) according to claim 1 or 2, wherein the first organic layer (3) further comprises a mineral filler selected from the list of kaolin, calcium carbonate, talc, silica, wollastonite, clay, calcium sulfate fibers (also known as Franklin fibers), mica, glass beads, alumina trihydrate, and combinations thereof.

4. The metallized paper-based multilayer packaging material (1) according to claim 1 or 2, wherein the metal or metalloid inorganic layer (4) is selected from the list of aluminum, aluminum oxide (AlOx), silicon oxide (SiOx), or alloys thereof.

5. The material further comprises a third organic layer (6) coated on the inside of the second organic layer (5), wherein the third layer contains a biodegradable polymer selected from the list of polybutylene succinate-co-butylene adipate (PBSA) or polyhydroxyalkanoate (PHA) polymers in a concentration of 0.5 to 30 g / m². ２ A range of preferably 1 to 15 g / m ２ A metallized paper-based multilayer packaging material (1) according to claim 1 or 2, comprising in an amount within the range of the specified range.

6. The organic layer (3, 5, 6) is applied either as an aqueous solution or an aqueous dispersion, or by extrusion of an ultrathin layer having a thickness of less than 30 g / m ２ 2, preferably less than 15 g / m ２ 2, of the metallized paper-based multilayer packaging material (1) according to claim 1 or 2.

7. The metallized paper-based multilayer packaging material (1) according to claim 1 or 2, wherein the packaging material is recyclable as paper and / or carton.

8. The packaging material is folded 180° under a compressive load of 2 kilograms, such that the coated side of the paper is under compressive stress while the material is folded, and then 1 g / m ２ Water vapor transmission rate (WVTR) less than / day (measured at 23°C and 85% relative humidity), and / or 3 cm ３ / m ２ A metallized paper-based multilayer packaging material (1) according to claim 1 or 2, having an oxygen permeability (OTR) of less than / day bar (measured at 23°C and 50% RH).

9. The metallized paper-based multilayer packaging material according to claim 1 or 2, wherein the fracture point strain of the packaging material under in-plane tensile load is a maximum of 4% in the machine direction and a maximum of 10% in the machine transverse direction of the paper.

10. A three-dimensional sealed packaging article made of the metallized paper-based multilayer packaging material (1) described in claim 1 or 2, the three-dimensional sealed packaging article obtained by molding the packaging material, filling it with an edible product for human or animal consumption, and then sealing it.

11. Use of the metallized paper-based multilayer packaging material (1) according to claim 1 or 2 for packaging food products intended for consumption by humans or animals.

12. A packaged food product comprising the metallized paper-based multilayer packaging material (1) according to claim 1 or 2, which is filled with a food product for consumption by humans or animals.

13. The packaged edible product according to claim 12, wherein the edible product is a powder, gel, or kibble, selected from the list of soluble coffee, nutritional compositions for consumption by infants, adults, or the elderly, soups, confectionery or candy, chocolate-based products, and dried animal foods.

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