High-barrier multipack containing individual low-barrier packs

Abstract

The invention relates to a thermally sterilizable packaging system (10) comprising an outer multipack (12) that surrounds an outer packaging area (14) in which at least two inner individual packs (16) are received. The multipack (12) is made of a first packaging layer material (18) which comprises at least one polymer layer (44, 48, 52, 54, 56). The individual packs (16) are made of a second packaging material (60) which differs from the first packaging material. One packaging material (18, 60) of the first and second packaging materials, as a high-barrier packaging material, has an oxygen permeability of less than 0.5 cm³ / (m²·d·bar) and a water vapor permeability of less than 0.5 g / (m²·d), and the other packaging material (18, 60), as a low-barrier packaging material, has an oxygen permeability of more than 3 cm³ / (m²·d·bar) and a water vapor permeability of more than 2 g / (m²·d). According to the invention, the first packaging material (18) has at least two polymer layers (44, 48, 52, 54, 56) and is the high-barrier packaging material, and the second packaging material (60) is a packaging layer material (60) with at least one polymer layer (62, 64, 66, 68) and is the low-barrier packaging material.

Description

[0001] COLLECTIVE PACKAGING WITH HIGH BARRIER, CONTAINING INDIVIDUAL PACKAGING WITH LOW BARRIER

[0002] Description

[0003] Thermally sterilizable packaging system, comprising an outer collective packaging which surrounds an outer packaging space in which at least two inner individual packages are accommodated, wherein each individual package surrounds an inner packaging space and is designed to package a product, wherein the collective packaging is formed from a first packaging material which comprises at least one polymer layer as packaging layer material, and wherein the individual packages are formed from a second packaging material different from the first, wherein a packaging material comprising first and second packaging material as high-barrier packaging material has an oxygen permeability of less than 0.5 cm 3 / (m 2d bar), determined according to DIN 53380-3 at 23°C and 85% relative humidity, and a water vapor permeability of less than 0.5 g / (m 2 d), determined according to ISO 15106-2 at 23°C and 85% relative humidity, and wherein the other packaging material of the first and second packaging material, as a low-barrier packaging material, has an oxygen permeability of more than 3, preferably more than 5 cm 3 / (m 2 d bar), determined according to DIN 53380-3 at 23°C and 85% relative humidity, and a water vapor permeability of more than 2 g / (m 2 d), determined according to ISO 15106-2 at 23°C and 85% relative humidity.

[0004] The present invention is based on a shrink-wrapped film packaging as a collective packaging, which combines several metal cans, such as tinplate cans, into a single package as individual packaging. Such prior art metal cans are the aforementioned high-barrier packaging material and exhibit high-barrier properties against the passage of water vapor and oxygen. They are therefore suitable for packaging food, especially canned food, with a long shelf life.

[0005] Since the metal cans as the second packaging material already have high-barrier properties, the first packaging material does not require any special barrier properties and can be designed as the low-barrier packaging material as a cost-effective thermoplastic shrink-wrap polymer film.

[0006] The packaging system of the present invention, like the film-sealed canned multiple packs, is preferably also intended to relate to foodstuffs and in particular canned foodstuffs as products packaged in the individual packaging, although other products packaged in the individual packaging as canned foodstuffs or as foodstuffs in general are not to be excluded in principle.

[0007] A further advantage of these metal cans, in addition to their excellent barrier properties in terms of low oxygen and water vapor transfer rates, is their excellent thermal sterilizability. Metal cans easily withstand high temperatures of more than 120 °C, such as those reached during the sterilization of food packaging, for example, during retort sterilization with superheated steam, which is common in this field.

[0008] One disadvantage of metal cans, however, is their relatively high weight. As packaged portion sizes become smaller, this weight takes up an increasingly large proportion of the total weight of the packaged goods. Since packaged goods always have to be transported at least from the producer to the point of sale, the high tare weight worsens the CO2 transport footprint of the packaged product. Since transport capacities are generally weight-limited, exhausting the transport capacity with a high proportion of packaging weight results in a disadvantageously low utilization rate of the transport capacity with respect to the transported product.

[0009] Furthermore, it is relatively complex to permanently affix consumer information about origin, contents, weight, shelf life and the like to the outside of metal cans.

[0010] The object of the present invention is therefore to further develop the thermally sterilizable packaging system of the type mentioned above, while maintaining good barrier properties against the migration of oxygen and water vapor (moisture), in such a way that, for the same total weight of packaging weight and packaged goods, the proportion of packaging weight to the total weight is lower. This allows a larger proportion of products to be transported for a given transport weight. The product's CO2 footprint relative to the weight of the packaged product is thus reduced.

[0011] The prior art also includes film packaging systems with a packaging bag as the collective packaging and with individual packaging contained therein, for example, for sweets in a reduced size compared to their usual retail presentation form, such as so-called "minis." The individual sweet itself is usually packaged in a flowpack made of a packaging film as the second packaging layer material. Many packaged sweets are then repackaged in a packaging bag or in another flowpack made of packaging film. While the packaging of the individual sweets is usually opaque, the collective packaging as the outer packaging is at least partially transparent. However, such packaging systems do not have any special barrier properties with regard to the migration of oxygen and water vapor through the packaging material.If at all, the individual packaging that can be removed from the collective packaging has, for example, metallization, which, in addition to aesthetic effects, also offers a barrier effect.

[0012] However, the packaging films used for the aforementioned individual packaging are not suitable for thermal sterilization. Thermal sterilization, such as the aforementioned retort sterilization, is carried out using superheated steam. The packaging and its packaged product must withstand temperatures of over 120°C for extended periods without altering their structure, shape, or function. If an individual package of the aforementioned film packaging system possesses any special barrier properties due to a packaging material layer made of known barrier materials, these are greatly reduced or even eliminated by thermal sterilization.For example, if the barrier properties are based on the metallization of a polymer layer, this will be damaged by the temperature increase because the usually axially oriented carrier layer of the metallization shrinks during the strong heating and imposes its shrinkage deformation on the metallization it supports. If a barrier property is based on vinyl alcohol polymers such as EVOH or PVOH, the integrity of these moisture-sensitive materials is threatened by the moisture introduced by the superheated steam.

[0013] According to the invention, the present invention solves the underlying problem by a packaging system of the type mentioned at the outset, in which the first packaging material has at least two polymer layers and is the high-barrier packaging material, and in which the second packaging material is a packaging layer material with at least one polymer layer and is the low-barrier packaging material.

[0014] The packaging system according to the invention uses packaging layer materials with one or more polymer layers for both the collective packaging and the individual packaging. The net weight of at least the individual packaging is significantly reduced compared to conventional metal cans, with the same packaged product weight per individual packaging. Thus, the proportion of the packaging to the total weight of the packaged product is also reduced as desired.

[0015] The first packaging layer material preferably comprises at least three polymer layers. One of these is preferably a sealable inner layer, another is a carrier polymer layer carrying a barrier layer preferably made of metal or a metallization or metal oxide, and one polymer layer forms an outwardly exposed outer layer. The barrier effect can be achieved by a vinyl alcohol polymer layer as an alternative to or in addition to the aforementioned metallization or metal oxide layer. The number of polymer layers can be further increased by adhesive layers for adhesive or extrusion lamination.

[0016] Likewise, the second packaging layer material can preferably comprise two or more polymer layers. Again, one of these preferably forms a sealable inner layer, and another an outer layer. A vinyl alcohol polymer layer can be arranged between them as an at least temporary oxygen barrier layer. Here, too, the number of polymer layers can be increased by adding adhesive layers for adhesive or extrusion lamination.

[0017] For reasons of weight saving, at least one polymer layer of the first and / or second packaging layer material may comprise foamed polymer.

[0018] This advantageously makes it possible to design the individual packaging made from the second packaging layer material not only cost-effectively but also thermally sterilizable, because the second packaging layer material can be designed as a low-barrier packaging material that is robust with regard to thermal stress during sterilization, particularly during retort sterilization. The second packaging layer material does not require increased barrier properties against the migration of oxygen and water vapor through the second packaging layer material, which can generally only be achieved by selecting stress-sensitive materials in generally stress-sensitive layer thicknesses. Therefore, any individual packaging can be thermally sterilized without any risk of loss of function, shape, or structure of the individual packaging or its packaging material.

[0019] The initially apparent disadvantage of the lack of an increased barrier against oxygen and water vapor migration in individual packaging can be compensated for by the collective packaging, which has precisely these barrier properties. For this purpose, the collective packaging is made from the first packaging layer material, which is the high-barrier packaging material.

[0020] Oxygen on perishable products enables their oxidation. Water vapor, i.e., moisture, on products promotes their sogginess. This occurs even more strongly when the product exposed to moisture contains salts and is thus somewhat hygrophilic. Thus, the multipack, which is particularly easily perceived by consumers as the external packaging of the packaging system discussed here, can be made of a high-barrier packaging material. This material's sensitivity to elevated temperatures is not compromised, as the multipack does not need to be exposed to any temperature increase. For this reason, it can also be provided with consumer information that is visible on the exterior presented at the point of sale.It is completely unproblematic to apply a printing ink to a packaging layer material, even if it is a high-barrier packaging material comprising layers with particularly low oxygen and / or water vapor permeability, whereby in this context “black” is also understood as a printing ink.

[0021] In summary, the collective packaging has the required barrier properties but is not thermally sterilized, while the individual packaging is thermally sterilizable but lacks barrier properties. However, the overall packaging system arranged around the products packaged in the individual packaging provides both the required barrier properties and the required thermal sterilizability.

[0022] The packaged product can be any product, but is preferably a food, particularly preferably a canned food, such as pre-cooked vegetables, pre-cooked meat, and the like. The product can be a pourable or pieced product. The term "individual packaging" merely indicates that a package so designated can be separated from the plurality of individual packages and removed from the collective packaging. The term does not imply that only a single product, such as a single piece, is packaged in individual packaging.

[0023] An individual package is considered to be thermally sterilizable within the meaning of the present application if it can withstand a temperature of at least 120 °C, but not more than 131 °C, for at least 10 minutes, preferably for 120 minutes, without changes to its size or its function or the structure of its packaging layer material.

[0024] The packaging system described here is used to package multiple portions, so that after the collective packaging is opened, not all of the individual packaging contained therein is generally used. In order to be able to return the remaining individual packaging to the barrier protection provided by the collective packaging after the collective packaging has been opened, the collective packaging can have a closure device for resealing a removal opening. The removal opening can be identifiable as the intended opening point on the collective packaging even when it is closed after it has been filled by the manufacturer, either by visually identifying a tear or cutting line, by providing weakenings in the packaging layer material to guide a tear once initiated, or by other measures.

[0025] As already mentioned at the beginning, the oxygen and water vapor permeability of a packaging layer material is expressed as transfer rates. In the technical world, the abbreviation "OTR" is used to denote the oxygen transfer rate, and the abbreviation "WVTR" is used to denote the water vapor transfer rate.

[0026] According to a first preferred embodiment of the present invention, the closure device can comprise a form-locking device, known in the art as a "zipper." This is a form-locking device that has a closure strip running along the removal opening on each side of the removal opening. For efficient reclosure of the removal opening, the closure strips preferably extend over the entire length of the removal opening.

[0027] One of the closure strips has a male form-fitting formation running in the longitudinal direction of one closure strip along the removal opening. The other of the closure strips has a female form-fitting formation running in the longitudinal direction of the other closure strip along the removal opening. The female form-fitting formation is designed to positively receive the male form-fitting formation. In order to at least partially compensate for a weakening of the barrier properties of the collective packaging caused by the removal opening, each of the closure strips is preferably formed at least partially from a vinyl alcohol polymer. Suitable vinyl alcohol polymers are ethylene-vinyl alcohol copolymer (EVOH) and polyvinyl alcohol (PVOH), both of which advantageously have low oxygen transfer rates.

[0028] In order to give at least one of the closure strips, preferably both closure strips, increased mechanical stability compared to their formation from exclusively a vinyl alcohol polymer and / or in order to give at least one of the two closure strips, preferably both closure strips, not only a low oxygen transfer rate but also the lowest possible water vapor transfer rate, at least one of the closure strips can have a core strip extending over at least 70% of its longitudinal dimension and made of a polymer material other than the vinyl alcohol polymer. Preferably, the core strip extends over 90% of the longitudinal dimension of the closure strip, particularly preferably over 100% of the longitudinal dimension of the closure strip. Particularly preferably, both closure strips are initially produced as quasi-endless extruded profiles and cut to the required length.The core strip can bear a bar reformation of the vinyl alcohol polymer over at least 90%, particularly preferably over 100%, of its longitudinal dimension. Other sections of the core strip can be free of the vinyl alcohol polymer. Preferably, both closure strips are formed in the manner mentioned.

[0029] The material of the core strip is preferably a thermoplastic polymer. The material is preferably a polyamide. However, it can also comprise or be a polyester, such as polyethylene terephthalate. For the same layer thickness of a test material sheet, polyamide offers a higher water vapor barrier, i.e., a lower water vapor transfer rate, than, for example, polyethylene or polypropylene. The combination of polyamide and the vinyl alcohol polymer can thus provide a closure strip with an overall good barrier effect against both oxygen and water vapor migration through the closure strip, while maintaining a small strip volume.

[0030] When each closure strip is designed as described above and has a core strip, in order to achieve a high barrier effect after reclosing the collective packaging once opened, it is preferably provided that in the closed state of the form-locking device, when the male and female form-locking formations are in form-locking engagement with one another, the barrier formations of the two closure strips are in contact with one another over at least 80%, preferably over at least 95%, of the engagement length of the form-locking formations.

[0031] In the circumferential direction around the closure strip, the barrier formation at least partially surrounds the core strip, so that the core strip can be exposed in sections. Preferably, an exposed section of the core strip forms the form-fitting formation. However, it should not be ruled out that the barrier formation completely surrounds the core strip in the circumferential direction. In this case, the form-fitting formation is also formed from the material of the barrier formation.

[0032] At least one form-locking formation is preferred; particularly preferably, both form-locking formations of the closure strips involved are formed from a polymer different from the vinyl alcohol polymer, i.e., in particular, from polyamide or polyethylene terephthalate, in order to impart increased stability and strength to the form-locking formations and thus to the form-locking engagement formed between them. The two form-locking formations, one of which, when viewed in a cross-sectional area orthogonal to the longitudinal extension direction of the closure strips, forms a projection that engages a recess in the respective other form-locking formation, can thus form a water vapor barrier that extends across the removal opening, with a labyrinth seal formed between the projection and the recess.In addition to the form-fitting formations, the barrier formations can be made of vinyl alcohol polymer with appropriate dimensions so that they touch each other when the closure device is closed and also form an oxygen barrier across the removal opening that is as little disturbed as possible.

[0033] In a conventional manner, a positive engagement between the positive locking devices of the closure strips can be manually established by the respective user by locally establishing a positive lock at one end of the removal opening, further manually exerting pressure on the positive locking devices towards each other and allowing his pressure-exerting fingers to slide along the closure strips to the other longitudinal end of the removal opening.

[0034] To facilitate the convenient establishment of the positive locking engagement, the positive locking device can comprise a sliding slider that can be moved along the closure strips as an actuation aid for actuating the positive locking device. Such a closure device, comprising a zipper with a sliding slider, is also referred to in the art as a "slider."

[0035] The slider preferably engages around the closure strips and, when moving in one direction along the longitudinal dimension of the closure strips, at least supports the establishment of a positive engagement between the male and female positive engagement formations or completely ensures the establishment of the positive engagement. When moving in the opposite direction, the slider at least supports the removal of a positive engagement between the male and female positive engagement formations or completely ensures this.

[0036] In addition to or alternatively to the above-mentioned designs as a "zipper" or "slider", the closure device can have an adhesive zone with a cold adhesive to achieve the most tight reclosure possible. The cold adhesive is preferably a pressure-sensitive adhesive known per se, which adheres with its free sticky surface to every surface section of the collective packaging. The cold adhesive is therefore preferably arranged on a surface of a packaging wall section of the collective packaging for bonding to another packaging wall section of the collective packaging. The adhesive zone preferably forms an adhesive strip which extends over at least 75%, preferably over at least 90%, particularly preferably over 100% or more of the longitudinal dimension of the removal opening in order to enable the most extensive, preferably complete, reclosability of the removal opening.

[0037] The collective packaging is preferably designed as a collective packaging bag, since bag packaging can generally have a large packaging volume relative to its own weight. As a collective packaging bag, the collective packaging has a front packaging wall and a rear packaging wall. This should not preclude the collective packaging from also having side walls, although side walls are not absolutely necessary. For example, the collective packaging bag can be designed as a three- or four-edge sealed bag or as a flowpack. In the latter case, a flowpack, the rear packaging wall will have a longitudinal seal.

[0038] Regardless of the specific structural design of the collective packaging bag, the outer packaging space is located between the front and rear packaging walls. According to preferred embodiments, the cold-adhesive zone can then be arranged on the collective packaging bag as follows: i.) on an inner side of a packaging wall consisting of the front and rear packaging walls facing the other packaging wall or the outer packaging space, for adhesive connection to the inner side of the other packaging wall, or / and ii.) on an outer side of a packaging wall consisting of the front and rear packaging walls facing away from the other packaging wall or the outer packaging space, for adhesive connection to the outer side of the other packaging wall.

[0039] Option i.) allows easy re-closing of the dispensing opening by

[0040] Joining the facing inner sides of the front and back packaging walls. The resulting reseal is peelable and can be opened and closed as often as required.

[0041] Option ii.), which can be provided in addition to or as an alternative to option i.), enables the collective packaging bag to be rolled up from the end region bearing the removal opening over the removal opening, so that the latter is shielded from the outside environment within the material roll, for example in the manner of a labyrinth seal. To secure the material roll against further unrolling or partial opening caused by the inevitable elasticity of the packaging materials, the cold adhesive zone creates an adhesive bond between an outer side of the front or rear packaging wall and an outer side of the other packaging wall, consisting of the front and rear packaging walls.

[0042] In order to be able to at least roughly remove unwanted oxygen components from the outer packaging space after individual packages have been removed from the collective packaging and after it has been resealed, a preferred development of the invention can provide a valve in a wall section of the collective packaging through which gas can flow from the outer packaging space into the outside environment of the collective packaging, but not in the opposite direction. Then, after the collective packaging has been resealed, any air that has entered the outer packaging space can be forced out through the valve, which only acts in one direction, namely out of the outer packaging space. As air escapes from the outer packaging space through the valve, any moisture contained in the air also escapes.

[0043] Additionally or alternatively, the collective packaging can comprise at least one absorber comprising an oxygen absorber and a moisture absorber in order to keep the oxygen and moisture content in the outer packaging space as low as possible. Oxygen absorbers and moisture absorbers are generally known in packaging technology. In a simple embodiment, the oxygen absorber and / or the moisture absorber can be inserted into the outer packaging space in separate absorber packs, as is known for silica gel pads as a desiccant. In order to sacrifice as little volume of the outer packaging space as possible to accommodate the absorber, according to a preferred embodiment, at least one absorber comprising the oxygen absorber and the moisture absorber can be pressure-activatedly incorporated into a polymer layer exposed to the outer packaging space. Preferably, both absorbers are pressure-activatedly incorporated in the manner mentioned.For example, the absorbers can be encapsulated in microcapsules that are fragile under a predetermined pressure load and contained in the exposed polymer layer. By passing over the microcapsule-doped area, for example, with the back of a knife or a fingernail, the generated pressure can locally exceed the bursting strength of the microcapsules, thus releasing and activating the originally encapsulated absorber.

[0044] If an adhesive zone as described above is formed on the collective packaging, to which pressure must also be exerted locally in order to adhesively connect two surface sections of different wall sections of the collective packaging bag, the pressure exerted for connecting and thus for reclosing the removal opening can advantageously also be used to activate the at least one absorber if an absorption zone of the collective packaging formed by incorporating at least one pressure-activatable absorber from the oxygen absorber and the moisture absorber into the polymer layer exposed to the outer packaging space overlaps with the adhesive zone.

[0045] Furthermore, the collective packaging can be designed to generate and / or maintain a gas composition in the outer packaging space that differs from the normal atmosphere, even after opening and resealing. For example, an activatable gas source containing a gas with at least a reduced oxygen content can be accommodated in the outer packaging space of the collective packaging. The activatable gas source can be a breakable container that either directly contains gas or a substance that enters the gas phase upon breaking the container, or optionally several substances that, originally separate, mix when the container is broken, with the mixture entering the gas phase.

[0046] The container can again be formed by a plurality of microcapsules, which, in addition to or alternatively to the absorber microcapsules, are accommodated in a polymer layer of the first packaging layer material of the collective packaging, which is exposed to the outer packaging space. Although the protective gas atmosphere achievable with microcapsules, for example with an atmosphere with a high N2 or CO2 content, is less pronounced than that achievable with a fragile container, less is still better than nothing. In this context, the quasi-inert gases nitrogen and carbon dioxide, cited as examples, are referred to as protective gases, which, under normal circumstances, do not form compounds with other chemical elements in the absence of external energy sources.

[0047] To provide the high-barrier properties mentioned above, the first packaging layer material can have a metallization layer and / or a metal oxide layer and / or a vinyl alcohol-containing polymer layer as a barrier layer to reduce the migration of oxygen and / or moisture through the first packaging layer material. The metallization layer can be deposited physically or chemically from the vapor phase onto a surface of a carrier polymer layer using a method known per se. The same applies to the metal oxide layer. The metallization can be formed from any desired metal. The metallization is preferably formed from aluminum or an aluminum alloy. Suitable materials for the metal oxide layer are, in particular, silicon oxide with the structural designation SiOx and aluminum oxide with the structural designation AluOv, where x, u and v are integers.The best known aluminum-based metal oxide barrier material is AI2O3.

[0048] Carrier polymer layers for vapor deposition or vapor deposition of metal or metal oxide layers are preferably made of oriented polymer, particularly preferably biaxially oriented polymer. Polypropylene is particularly suitable for biaxial orientation.

[0049] The vinyl alcohol polymers with barrier properties mentioned above, EVOH and PVOH, are suitable.

[0050] To facilitate recycling of the collective packaging after use, the first packaging layer material is preferably formed of at least 90 wt.%, preferably at least 95 wt.%, polymer of one and the same monomer. The first packaging layer material can then be recycled in a monomaterial recycling stream. This material is preferably a polyolefin, particularly preferably polypropylene. However, it should not be ruled out that the collective packaging is formed of a packaging layer material with different varieties of polyethylene and consists of at least 90 wt.%, preferably at least 95 wt.%, polyethylene.

[0051] For the same reason, the second packaging layer material can additionally or alternatively be formed from at least 90 wt.%, preferably at least 95 wt.%, of a polymer of one and the same monomer. Since at least the last individual packaging removed and the collective packaging that is no longer needed are often disposed of together, the first and second packaging layer materials are preferably formed from at least 90 wt.%, preferably at least 95 wt.%, of the same polymer.

[0052] The first packaging layer material can, for example, have the following structure from the outside to the inside, i.e. towards the outer packaging space: a.) a layer of biaxially oriented polypropylene with a thickness of between

[0053] 15 and 30 pm, preferably between 17 and 23 pm, particularly preferably 20 pm, b.) a layer of printing ink applied in reverse printing, protected from the outside by the layer a.), c.) an adhesive would be either made of laminating adhesive, for example based on polyurethane, with a basis weight of between 2 and 5 g / m 2 , preferably between 3 and 4 g / m 2 , particularly preferably 3.5 g / m 2 , or as an extrusion lamination layer made of polypropylene with a basis weight of between 12 and 20 g / m 2 , preferably between 13 and 17 g / m 2 , particularly preferably 15 g / m 2 , d.) an optional primer layer, if the layer c.) the extrusion lamination layer is made of

[0054] polypropylene, e.) a metallization layer made of aluminum or a metal oxide layer made of SiOx or AluOv, where x, u and v are integers, carried by f.) a carrier polymer layer made of biaxially oriented polypropylene with a thickness of between 15 and 25 pm, preferably between 16 and 20 pm, particularly preferably 18 pm, g.) an adhesive layer analogous to the adhesive layer c.) with identical material and

[0055] Basis weight ranges, but with the proviso that the particularly preferred basis weight in the case of the formation of a laminating adhesive layer is 3.0 g / m 2and h.) a polypropylene layer, preferably made of cast or blown polypropylene. Layer h.) is preferably provided with color pigments, particularly preferably with white color pigments. The thickness of layer h.) is preferably between 40 and 100 μm, particularly preferably between 50 and 70 μm, and even more preferably 60 μm. Layer h.) can be coextruded from several sublayers. In particular, layer h.) can be formed from sealable polypropylene on its exposed surface.

[0056] The second packaging layer material can, for example, have the following structure from the outside to the inside, i.e. towards the outer packaging space: a.) a layer of polypropylene, preferably cast or blown polypropylene, with a thickness of between 25 and 40 pm, preferably between 27 and 33 pm, particularly preferably 30 pm, b.) an adhesive layer consisting either of laminating adhesive, for example based on polyurethane, with a basis weight of between 2 and 5 g / m2 , preferably between 3 and 4 g / m 2 , particularly preferably 3.5 g / m 2 , or as an extrusion lamination layer made of polypropylene with a basis weight of between 12 and 20 g / m 2 , preferably between 13 and 17 g / m 2 , particularly preferably 15 g / m 2 c.) a polypropylene layer, preferably made of cast or blown polypropylene. Layer c.) is preferably provided with color pigments, particularly preferably with white color pigments. The thickness of layer c.) is preferably between 40 and 100 μm, particularly preferably between 50 and 70 μm, and even more preferably 60 μm. Layer c.) can be coextruded from several sublayers. In particular, layer c.) can be formed from sealable polypropylene on its exposed surface.

[0057] Layer a.) of the second packaging layer material can carry an EVOH layer on its side facing the inner packaging volume, for example, through coextrusion, to also impart certain barrier effects to the second packaging layer material. If an EVOH layer is formed between the aforementioned polypropylene layer and the adhesive layer, this layer is between 20 and 50 μm thick.

[0058] It has been found that the bursting strength of the collective packaging is greater when at least one of the specified adhesive layers is formed by an extruded polypropylene layer for extrusion-laminating the outer BoPP layer to the metallization on the BoPP carrier polymer layer and / or for bonding the carrier polymer layer to the inner layer of cast or blown polypropylene, instead of an adhesion-laminated bond by interposing an adhesive layer, such as polyurethane. Current theory explains this by the fact that the extrusion-laminated polypropylene bond exhibits higher internal damping than the adhesion-laminated bond using adhesive application. The polypropylene layer for extrusion lamination is generally less inherently rigid or has a lower modulus of elasticity and is thicker than an adhesive application applied instead of extrusion lamination.The bursting strength is tested by dropping the packaging system from a height of 1 m and then from a height of 1.5 m onto a flat, hard surface, such as concrete, ceramic or stone. The collective packaging in its initially sealed state after filling contains gas and two or more individual packaging items. The gas can be conventional air or a protective gas atmosphere made up of an inert gas or a relatively inexpensive quasi-inert gas, such as nitrogen or carbon dioxide. Tests have shown that in order to achieve the best possible bursting strength it is advantageous if a larger proportion of the volume of the outer packaging space is taken up by individual packaging items and only a smaller proportion of the volume of the outer packaging space is taken up by gas. The volume in the outer packaging space taken up by the individual packaging items is preferably 2 to 5 times as large as the volume in the outer packaging space taken up by gas.A further improvement in bursting strength can be achieved by creating an overpressure in the outer packaging space relative to the external environment of the collective packaging, with the overpressure preferably being 1.1 to 1.3 times the pressure of the external environment outside the collective packaging. If in doubt, the overpressure situation should be tested at 20°C room temperature. Therefore, if the pressure in the external environment of the collective packaging, as a standard atmosphere, is 1013 hPa at 20°C room temperature, the pressure in the outer packaging space should preferably be between 1114 hPa and 1317 hPa.

[0059] The present invention is explained in more detail below with reference to the accompanying drawings. It shows:

[0060] Fig. 1 is a roughly schematic perspective view of an embodiment of a packaging system according to the invention of the present application,

[0061] Fig. 2 is a roughly schematic cross-sectional view through the closure strips of the collective packaging of Fig. 1,

[0062] Fig. 3 is a roughly schematic cross-sectional view through the first packaging layer material of the collective packaging of Fig. 1, and Fig. 4 is a roughly schematic cross-sectional view through the second packaging layer material of the individual packaging of Fig. 1.

[0063] Figure 1 shows a packaging system of the present invention in a purely schematic and exemplary manner and is generally designated 10. The packaging system 10 comprises an outer collective packaging 12 in the form of a sealed-edge bag with a folded-in bottom at its lower end region 12a, selected purely by way of example. Individual packages 16, indicated by dashed lines, in the form of four-edge sealed bags, selected purely by way of example, are accommodated in an outer packaging space 14 surrounded by the collective packaging 12. Pre-cooked vegetables such as carrots, peas, beans, potatoes, and the like are accommodated in the individual packages 16, for example. Therefore, before being repackaged in the collective packaging 12, the individual packages 16 were sterilized by a known retort sterilization process using superheated steam at a temperature of between 120°C and 135°C.The individual packaging 16 was exposed to the elevated temperatures for a period of time ranging from 10 minutes to 120 minutes.

[0064] The remaining volume of the outer packaging space 14 is filled with a quasi-inert gas, in this case for example dry nitrogen, in order to delay as long as possible the attack of oxygen and moisture (water vapor) on the vegetables packed in the individual packaging 16.

[0065] The collective packaging 12 is made from a single piece of first packaging layer material 18, which is folded back on itself in its lower end region 12a and is closed by a continuous sealing edge 20 to form the outer packaging space 14.

[0066] At its head region 12b, on the outer side 18a of the first packaging layer material 18, a target cutting line 22 for forming a removal opening is graphically depicted. By cutting along the target cutting line 22, the head region 12b with the transverse section of the sealing edge 20 is separated from the rest of the collective packaging 12. After this separation, the outer packaging space 14 is accessible for the removal of one or more individual packages 16.

[0067] Since, as a rule, only a portion of the total individual packaging 16 packed in the collective packaging 12 is removed during a first removal process, while a remaining portion of the individual packaging 16 remains in the outer packaging space 14 of the collective packaging 12, the collective packaging 12 has a closure device 24 which enables the removal opening formed along the desired cutting line 22 to be closed again.

[0068] For example, the closure device 24 has a so-called "zipper" 26 with two opposing closure strips 26a and 26b. The zipper 26 is located between the front packaging wall 12c, facing the viewer in Figure 1, and the rear packaging wall 12d, facing away from the viewer in Figure 1, of the collective packaging 12 and is attached to their respective mutually facing inner sides (see also Figure 2). The zipper 26 forms a positive-locking device mentioned in the introduction to the description.

[0069] Furthermore, in the illustrated embodiment, the closure device 24 has, on the side of the zipper 26 facing the packaging space 14, an adhesive zone 28 on the inside of the front packaging wall 12c of the collective packaging 12, with a cold adhesive applied to the inside of the front packaging wall 12c. In the initially closed state, the adhesive zone 28 can initially be covered by a strip of release material to prevent its adhesive effect with respect to the opposite inside of the rear packaging wall 12d of the collective packaging 12. After the strip of release material is removed, the adhesive zone 28 is exposed to the opposite inside of the rear packaging wall 12d.Alternatively, the adhesive zone 28 can be peelably adhesively bonded to the inside of the rear packaging wall 12d, so that for the first opening of the collective packaging 12, in addition to separating the head region 12b, the front and rear packaging walls 12c and 12d must also be separated. The closure device 24 also has a further adhesive zone 30 made of cold adhesive on the outside, i.e., on the outside of the rear packaging wall 12d facing away from the outer packaging space 14. This further adhesive zone 30 makes it possible to roll the collective packaging 12 from the removal opening to the lower region 12b and to fix the roll thus formed "outside to outside" by the further adhesive zone 30. The further adhesive zone 30, which, like the adhesive zone 28, has a pressure-sensitive cold adhesive on one of the insides of the packaging walls 12c or 12d, is covered by release material until it is activated.The release material can, for example, be a strip of silicone-coated paper or similar. Covering the additional adhesive zone 30 prevents an area of ​​the exterior of the collective packaging 12 from being sticky and preventing a consumer from being undesirably caught by the additional adhesive zone 30 with parts of their clothing or hands.

[0070] After opening the collective packaging 12, the quasi-inert protective gas atmosphere originally contained therein escapes. In order to reduce the absolute oxygen and moisture content in the outer packaging space 14 after resealing, a valve 32 is arranged in the packaging wall—in the example shown, in the front packaging wall 12c of the collective packaging 12—through which valve, gas can be displaced from the outer packaging space 14 into the external environment U of the collective packaging 12, for example, by manually compressing the collective packaging 12, thereby reducing the volume of its outer packaging space 14.

[0071] In order to be able to reduce not only the absolute gas content but also the oxygen and moisture content of the gas atmosphere inside the outer packaging space 14, in the example shown, the inside of the front packaging wall 12c has an absorber zone 34 on or in its polymer layer 54 exposed to the outer packaging space 14 (see Fig. 3), in which microencapsulated oxygen and moisture absorbers are accommodated. By applying local pressure to the absorber zone 34, the microcapsules can be broken and the respective absorbers released, so that they exert their effect on the gas atmosphere in the outer packaging space 14 and absorb oxygen and moisture.

[0072] The absorber zone 34 overlaps with the adhesive zone 28, so that when the collective packaging 12 is reclosed, pressure is also exerted on the absorber zone 34 by the adhesive zone 28 and thus at least some of the absorbers arranged there are activated.

[0073] Additionally or alternatively, at least one gas-permeable bag 36 with an oxygen and / or moisture absorber can be accommodated in the outer packaging space 14 in order to permanently remove oxygen and moisture from the gas atmosphere in the outer packaging space 14.

[0074] Additionally or alternatively, a container 38 can be accommodated in the outer packaging space 14 as a source of a quasi-inert gas. After the collective packaging 12 is resealed, the container 38 can be broken, thus regenerating, at least within certain limits, an atmosphere rich in quasi-inert gas and thus relatively poor in oxygen and moisture in the outer packaging space 14.

[0075] Figure 2 shows a cross-sectional view of the zipper 26 of the form-locking device 24. The plane of the drawing in Figure 2 runs orthogonally to the direction of the closure strips 26a and 26b of the zipper 26, which are preferably formed by extrusion.

[0076] The closure strip 26a comprises a core strip 26a1, formed from polyamide in the example shown, which is connected to the inner side 12e of the front packaging wall 12c, for example by gluing. The core strip 26a1 has a male form-lock formation 40, which can be inserted into a female form-lock formation 42 of the core strip 26b1, preferably also made of polyamide, of the closure strip 26b of the zipper 26, which is connected to the inner side 12f of the rear packaging wall 12d, and can be locked thereto in a way that can be overcome. Along the entire length of the closure strips 26a and 26b, the core strips 26a1 and 26b1 each carry two barrier formations 26a2 and 26a3, or 26b2 and 26b3.These barrier formations are made of a vinyl alcohol polymer, in the example shown EVOH, and increase the barrier properties of the zipper 26 in the closed state against the migration of oxygen through the zipper 26 from the external environment U into the outer packaging space 14. The core strips 26a1 and 26b1 form a moisture barrier, so that the zipper 26 as a whole significantly inhibits both the migration of oxygen and the migration of moisture through the closed zipper 26. The barrier formations 26a2 and 26a3 on the one hand, and 26b2 and 26b3 on the other, are dimensioned such that when the zipper 26 is closed, the barrier formations 26a2 and 26b2 abut one another, as do the barrier formations 26a3 and 26b3.Thus, only a small gap remains as a barrier-free migration path through the closed zipper 26, which, however, is deflected several times by the design of the form-fitting formations 40 and 42 and thus forms a labyrinth seal, which also makes it difficult for oxygen and moisture to migrate through the closed zipper 26.

[0077] Figure 3 shows a rough schematic of an exemplary cross-section through a possible configuration of the first packaging layer material 18. The side 18a of the first packaging layer material 18 is the outer side facing the consumer. The opposite side 18b is the side facing the outer packaging space 14 on the finished collective packaging 12.

[0078] The outer side 18a is formed from a layer of biaxially oriented polypropylene (BoPP) 44, which, on its side opposite the outer side 18a, is provided with a layer 46 of printing inks in reverse printing in order to provide consumer information on the collective packaging 12 that is perceptible to the consumer, protected from the influences of the external environment U by the layer 44. The layer 44 has a preferred thickness of 20 μm. The layer 46 of printing inks is considerably thinner than the layer 44 and its thickness depends on the number of printing inks that are reverse printed on the layer 44. The first packaging layer material 18 also has a biaxially oriented polypropylene layer 48 as a carrier polymer layer, which has a metallization layer 50 deposited from a vapor phase on its side facing away from the outer packaging space 14.This metallized BoPP layer 48, or more precisely, the metallization layer 50 it supports, is adhesively laminated to the printing ink layer 46 by means of an intermediate polyurethane adhesive 52. The polyurethane adhesive layer 52 preferably has a basis weight of 3.5 g / m². 2 The carrier polymer layer 48 has a preferred thickness of 18 pm. The deposited metallization layer 50 typically has a thickness of less than 1 pm.

[0079] The inner side 18b of the first packaging layer material 18 is formed by a non-stretched layer 54 of polypropylene. The layer 54 can be formed from cast or blown polypropylene. It has no molecular orientation of its polypropylene beyond the conventional production of a cast or blown polypropylene film, for example, by calendering, and is sealable, so that the sealing edge 20 of the multipack 12 is formed by zone-by-zone heat-sealing of adjacent layers 54 of the folded first packaging layer material 18. The layer 54 has a preferred thickness of 60 μm.

[0080] Layer 54 is extrusion-laminated to the carrier polymer layer 48 of biaxially oriented polypropylene through an intermediate extruded polypropylene layer 56. The extrusion lamination of layer 54 to layer 48 through the further polypropylene layer 56 with a basis weight of approximately 15 g / m 2significantly increases the bursting strength of the collective packaging 12 or the packaging system 10 when dropped from a height of 1 m or 1.50 m onto a hard surface. This is presumably due to the internal friction and damping of the extrusion lamination layer 56 made of polypropylene, which is approximately 5 to 8 times thicker than a similarly effective adhesive layer made of polyurethane, which, however, can be used instead of the extrusion lamination layer 56. The metallization layer 50 imparts to the first packaging layer material 18 very good barrier properties with respect to the migration of oxygen and moisture through the first packaging layer material 18 with an oxygen transfer rate of less than 0.5 cm 3 / (m 2 d bar) and with a water vapor transfer rate of less than 0.5 g / (m 2 d).

[0081] Figure 4 shows a roughly schematic cross section through a second packaging layer material 60 from which the individual packaging 16 is formed in the illustrated embodiment.

[0082] The outer side 60a of the second packaging layer material 60, facing away from the inner packaging space 70, is formed by a layer 62 of polypropylene, preferably blown polypropylene. Layer 62 does not exhibit any molecular orientation of its polypropylene beyond the orientation achieved by conventional production of a blown polypropylene film, for example, by calendering. Layer 62 has a preferred thickness of 30 μm.

[0083] The inner side 60b facing the inner packaging space 70 is formed by a layer 64 of cast or blown polypropylene. This layer 64 also has no molecular orientation of its polypropylene beyond that achieved by conventional production of a cast or blown polypropylene film, for example, by calendering. The layer 64 is preferably 60 μm thick and colored white. It is sealable, so that the individual packages 16 can be formed by heat-sealing adjacent inner sides 60b of the second packaging layer material 60.

[0084] In order to produce an individual packaging 16 that is as burst-resistant as possible, the two outer layers 62 and 64 are preferably connected to one another by an extrusion lamination layer 66 made of polypropylene. The extrusion lamination layer 66 preferably has an application weight of 15 g / m 2The layer thicknesses mentioned are preferred. The thicknesses of the individual layers of first and second packaging layer material can be within the thickness ranges specified for the individual layers in the introduction to the description.

[0085] Both the first packaging layer material 18 and the second packaging layer material 60 each have a weight fraction of polypropylene of more than 90%, preferably even more than 95%, which is why each of the packages 12 and 16 formed from them can be recycled in a monomaterial recycling stream.

[0086] Alternatively, an oxygen barrier layer 68 made of EVOH with a thickness of between 20 and 50 μm can be arranged between layer 62 and the extrusion lamination layer 66. The EVOH layer 68 can be produced by coextrusion with the polypropylene layer 62.

[0087] Although the EVOH layer 68 does not survive a retort sterilization process, which is particularly used for food packaging, unscathed, the optional additional EVOH layer 68 can nevertheless increase the performance of the packaging system 10. The EVOH layer 68 can suffer a so-called "retort shock" during retort sterilization, which reduces its oxygen barrier properties, thus increasing the overall oxygen transfer rate achievable with the second packaging layer material 60. On the one hand, the oxygen transfer rate is reduced by the second packaging layer material until the retort shock. On the other hand, a second packaging layer material 60 with EVOH layer 68, but with retort shock, still exhibits lower oxygen transfer rates than the same packaging layer material without EVOH layer 68.Thus, individual packaging 16 formed from the second packaging layer material 60 with EVOH layer 68 protects the products packaged therein from oxygen access until the individual packaging 16 is packaged in the collective packaging 12.

[0088] As the term "retort shock" suggests, the oxygen barrier effect, initially significantly reduced by retort sterilization, is not permanent. Part of the oxygen barrier effect lost during retort sterilization is regained over time, possibly through plastic flow of EVOH within the EVOH layer. The theory behind the regression of the oxygen barrier effect after retort sterilization and retort shock is not fully understood, but can be phenomenologically demonstrated.

[0089] Nevertheless, the oxygen transfer rate of the second packaging layer material 60, even with EVOH layer 68, is at least six times higher than the oxygen transfer rate of the first packaging layer material 18.

Claims

Claims Thermally sterilizable packaging system (10), comprising an outer collective packaging (12) which surrounds an outer packaging space (14) in which at least two inner individual packages (16) are accommodated, wherein each individual package (16) surrounds an inner packaging space (70) and is designed to package a product, wherein the collective packaging (12) is formed from a first packaging material (18) which, as packaging layer material (18), comprises at least one polymer layer (44, 48, 52, 54, 56), and wherein the individual packages (16) are formed from a second packaging material (60) different from the first, wherein a packaging material (18, 60) made of first and second packaging material as a high-barrier packaging material has an oxygen permeability of less than 0.5 cm 3 / (m 2d bar), determined according to DIN 53380-3 at 23°C and 85% relative humidity, and a water vapor permeability of less than 0.5 g / (m 2 d), determined according to ISO 15106-2 at 23°C and 85% relative humidity, and wherein the other packaging material (18, 60) of the first and second packaging material, as a low-barrier packaging material, has an oxygen permeability of more than 3 cm 3 / (m 2 d bar), determined according to DIN 53380-3 at 23°C and 85% relative humidity, and a water vapor permeability of more than 2 g / (m 2d), determined according to ISO 15106-2 at 23°C and 85% relative humidity, characterized in that the first packaging material (18) has at least two polymer layers (44, 48, 52, 54, 56) and is the high-barrier packaging material, and in that the second packaging material (60) is a packaging layer material (60) with at least one polymer layer (62, 64, 66, 68) and is the low-barrier packaging material. Thermally sterilizable packaging system (10) according to claim 1, characterized in that the collective packaging (12) has a closure device (24) for reclosing a removal opening. Thermally sterilizable packaging system (10) according to claim 2, characterized in that the closure device (24) comprises a form-locking device, wherein the form-locking device has a closure strip (26a, 26b) running along the removal opening on each side of the removal opening, wherein one of the closure strips (26a) has a male form-locking formation (40) running in the longitudinal direction of one closure strip (26a) along the removal opening and wherein the respective other of the closure strips (26a, 26b) has a female form-locking formation (42) running in the longitudinal direction of the respective other closure strip (26b) along the removal opening for the form-locking reception of the male form-locking formation (40), wherein each of the closure strips (26a, 26b) is formed at least partially from a vinyl alcohol polymer.Thermally sterilizable packaging system (10) according to claim 3, characterized in that at least one of the closure strips (26a, 26b) has a core strip (26a1, 26b1) extending over at least 70% of its longitudinal dimension and made of a polymer material other than the vinyl alcohol polymer, wherein the core strip (26a1, 26b1) carries a barrier formation (26a2, 26a3, 26b2, 26b3) made of the vinyl alcohol polymer at least in one section over at least 90% of its longitudinal dimension.Thermally sterilizable packaging system (10) according to claim 4, characterized in that each of the two closure strips (26a, 26b) has a core strip (26a1, 26b1) extending over at least 70% of its longitudinal dimension and made of a polymer material other than the vinyl alcohol polymer, wherein each core strip (26a1, 26b1) carries a barrier formation (26a2, 26a3, 26b2, 26b3) made of the vinyl alcohol polymer at least in one section over at least 90% of its longitudinal dimension, wherein in the closed state of the form-locking device, when the male and the female form-locking formation (40, 42) are in form-locking engagement with one another, the barrier formations (26a2, 26a3, 26b2, 26b3) of the. both closure strips (26a, 26b) are in contact with each other over at least 80% of the engagement length of the form-locking formations (40, 42).

6. Thermally sterilizable packaging system (10) according to one of claims 3 to 5, characterized in that the form-locking device comprises a sliding slide which can be displaced along the closure strips (26a, 26b) as an actuating aid for actuating the form-locking device, wherein the sliding slide engages around the closure strips (26a, 26b) and, when moved in one direction along the longitudinal dimension of the closure strips (26a, 26b), at least supports the production of a form-locking engagement between the male and the female form-locking formation (40, 42) and, when moved in the opposite direction, at least supports the removal of a form-locking engagement between the male and the female form-locking formation (40, 42).

7. Thermally sterilizable packaging system (10) according to one of claims 2 to 6, characterized in that the closure device (24) has an adhesive zone (28, 30) with a cold adhesive, wherein the cold adhesive is arranged on a surface of a packaging wall section (12c) of the collective packaging (12) for adhesive bonding to another packaging wall section (12d) of the collective packaging (12).

8. Thermally sterilizable packaging system (10) according to claim 7, characterized in that the collective packaging (12) as a collective packaging bag has a front packaging wall (12c) and a rear packaging wall (12d), between which the outer packaging space (14) is located, wherein the cold adhesive zone (28, 30) is arranged: i.) on an inner side (12e, 12f) of a packaging wall (12c, 12d) made up of front and rear packaging walls (12c, 12d) facing the other packaging wall (12d, 12c) for adhesive connection with the inner side (12f, 12e) of the respective other packaging wall (12d, 12c) and / or ii.) on an outer side (18a) of a packaging wall (12c, 12d) comprising the front and rear packaging walls (12c, 12d), facing away from the respective other packaging wall (12d, 12c), for adhesive connection to the outer side (18a) of the respective other packaging wall (12d, 12c). Thermally sterilizable packaging system (10) according to one of the preceding claims, characterized in that a valve (32) is arranged in a wall section of the collective packaging (12), through which valve gas can flow from the outer packaging space (14) into the external environment (U) of the collective packaging (12), but not in the opposite direction. Thermally sterilizable packaging system (10) according to one of the preceding claims, characterized in that the collective packaging (12) has at least one absorber consisting of an oxygen absorber and a moisture absorber.Thermally sterilizable packaging system (10) according to claim 10, characterized in that at least one absorber from the oxygen absorber and the moisture absorber is pressure-activatedly incorporated into a polymer layer exposed toward the outer packaging space. Thermally sterilizable packaging system (10) according to claim 11, including claim 7, characterized in that an absorption zone (34) of the collective packaging (12) formed by incorporating at least one pressure-activated absorber from the oxygen absorber and the moisture absorber into the polymer layer (54) exposed toward the outer packaging space (14) overlaps with the adhesive zone (28, 30). Thermally sterilizable packaging system (10) according to one of the preceding claims, characterized in that an activatable gas source (38) with a gas with at least a reduced oxygen content is accommodated in the outer packaging space (14) of the collective packaging (12). Thermally sterilizable packaging system (10) according to one of the preceding claims, characterized in that the first packaging layer material (18) has a metallization layer (50) and / or a metal oxide layer and / or a vinyl alcohol-containing polymer layer as a barrier layer for reducing the migration of oxygen and / or moisture through the first packaging layer material (18). Thermally sterilizable packaging system (10) according to one of the preceding claims, characterized in that the first packaging layer material (18) is formed from at least 90 wt. % polymer of one and the same monomer and / or that the second packaging layer material (60) is formed from at least 90 wt.-% polymer of one and the same monomer.

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