DE102021122296A9 - Layered composite containing paper layers with a separating layer containing dextrin - Google Patents

Abstract

The present invention relates to a flexible composite layer (10) containing paper layers, comprising a paper layer (12) containing fibers and a fiber-free additional layer (22) connected to the paper layer (12). According to the invention, between the paper layer (12) and the fiber-free additional layer Layer (22) a dextrin-containing intermediate layer (24) is arranged.

Description

The present invention relates quite fundamentally to a flexible composite layer containing paper layers, comprising a paper layer containing fibers and a further, fiber-free layer connected to the paper layer.

Such a layer composite, which has at least one paper layer and a non-fibrous further layer connected to the paper layer, is well known in the field of packaging technology.

Although paper has been known as a packaging material for a long time, with the recent focus on increasing sustainability of packaging material, paper is currently gaining popularity in the packaging industry due to its good recycling properties. However, the strength of paper is limited at a given basis weight. In addition, paper as a fibrous material can absorb and store liquid due to at least residual capillary effects, which makes it appear unsuitable for the packaging of moisture-containing products.

In order to eliminate or at least mitigate any disadvantages of paper as a packaging material, paper is used in composite layers together with other layers. The other layers are selected in terms of their properties depending on the application for which the packaging material is intended. A paper ply can be connected to a polymer ply to form a ply composite which, due to the polymer ply, is liquid-impermeable, tear-resistant and optionally equipped with further barrier properties. A paper layer in such a layered composite makes it possible to reduce the proportion of polymer in the packaging material and thus, for example, the amount of polymer produced after the packaging has been used.

For the recycling of packaging material, the greatest possible purity of the packaging material is advantageous in order to be able to reuse the packaging material by means of a recycling process that is as uniform as possible.

In the case of the laminated composite discussed here, containing paper layers, purity of type is certainly not given, since the further layer is free of fibrous material and is therefore no further paper layer.

In particular, when the material of the fibrous-free further layer of the laminated composite discussed here containing paper layers comes into contact with the paper layer in a flowable state, i.e. liquid or pasty, the material can flow around sections of fibers of the paper layer during application. As a result, a very strong bond can be achieved between the fibrous material of the paper layer and the material of the other layer that is free of fibrous matter. However, this efficient connection, which is advantageous for the formation of the layered composite, makes it more difficult to recycle the layered composite after it has been used.

Due to the fact that the material of the fibrous-free additional layer can partially surround fibers of the paper ply due to its flowable application in the hardened state, the paper ply often cannot be completely separated from the fibrous-free additional layer during recycling, in particular during a repulping process. As a result, the fibrous-free material of the further layer is also contaminated by the fibers of the original paper layer adhering to it. As a result, the fiber mass of the paper layer that can be used for recycling paper production is reduced and the material of the fibrous-free further layer is contaminated, so that the latter is only suitable for low-value applications, for example in cement production or as fuel for thermal recycling.

The object of the present invention is therefore to improve a layered composite containing paper layers of the type mentioned at the outset with regard to its recyclability.

This object is achieved by the present invention in a layered composite containing paper layers mentioned at the outset in that a dextrin-containing intermediate layer is arranged between the paper layer and the further, fiber-free layer.

As a starch degradation product, dextrin is water-soluble, so that the dextrin-containing intermediate layer between the paper layer and the fiber-free further layer can be dissolved by adding water. The paper layer can then be completely separated from the fiber-free further layer. The dextrin arranged between the paper layer and the adhesive layer prevents sections of fibers of the paper layer from flowing around the material of the fiber-free further layer, which is applied in liquid or paste form. As a result, almost all or ideally all fibers of the paper layer can be repulped. As a result, the material of the fibrous-free additional layer is not contaminated by fibers of the paper ply and is present after the separation of the paper ply from the fibrous-free additional layer in a substantially unmixed form. Thus, almost the entire paper layer or even the entire paper layer can be reused as recycled paper. Likewise can the non-contaminated, fibrous-free further layer can also be recycled.

The fiber-free further layer can have been introduced into the layered composite as an extruded layer. The fiber-free additional layer can then be a polymer layer which either forms a polymer layer of the composite layer, such as a sealing layer, or which, as an extrusion laminating layer, connects a further polymer layer, in particular a polymer film, to the paper layer. As an extrusion laminating layer, the material of the fiber-free further layer can comprise or be a polyolefin, preferably polyethylene, particularly preferably low-density polyethylene (LDPE).

As an alternative to the extrusion laminating agent layer, the fibrous-free further layer of the paper-layer-containing composite according to the invention discussed here can be an adhesive layer, the material of which is applied in liquid or pasty form, but not as a melt extrudate. The material of the fibrous-free additional layer can be applied in liquid or paste form as a solution with a solvent that evaporates after application or as a multi-component mixture with an initially liquid or paste-like structure-forming material and an agent mixed into it for crosslinking or curing the structure-forming material. One possible adhesive is polyurethane, which is preferably applied as a two-component adhesive to form the adhesive layer.

Through the use of the dextrin-containing intermediate layer, the material of the fibrous-free layer that has been processed to be flowable during the production of the layer composite no longer comes into contact with the paper layer in the flowable state, but only with the dextrin-containing layer.

In principle, it can be sufficient to achieve the separation effect of the paper layer from the fiber-free further layer if the layer containing dextrin consists of at least 50% by weight of dextrin. Then, by dissolving the dextrin in water, the dextrin-containing layer can be weakened to such an extent that the cohesion of the then formerly dextrin-containing layer is no longer sufficient to further bind the paper layer to the fibrous-free further layer. The greater the dextrin content of the dextrin-containing layer, the easier it is to weaken the remaining layer by dissolving the dextrin out of the dextrin-containing layer in such a way that the paper layer no longer remains connected to the fiber-free further layer. Therefore, according to an advantageous development of the present invention, the dextrin-containing layer can consist of at least 80% by weight or even at least 90% by weight of dextrin.

However, the dextrin-containing layer does not necessarily have to contain foreign matter, so that the dextrin-containing layer can consist only of dextrin except for unavoidable impurities. This makes it easier to remove the dextrin-containing layer by adding water to the paper-containing layer composite in a recycling process. The easier it is to remove the dextrin-containing layer, the easier and more complete the fiber material of the paper layer can be removed from the material of the fiber-free further layer.

A coated or precoated paper layer is also considered a paper layer in the sense of the present application. As a separating layer, the dextrin-containing layer preferably contacts the paper layer directly, so that after the dextrin-containing layer has dissolved, the fiber material of the paper layer and preferably only this material is detached from the composite layer. In principle, however, it should not be ruled out that a further layer is arranged between the paper layer and the layer containing dextrin, although this is not preferred.

The dextrin-containing layer preferably covers the paper layer and its fibrous material completely and preferably forms a closed surface, undisturbed by the fibrous material of the paper ply, on its side facing away from the paper ply.

In order to separate the fibrous-free additional layer directly from the composite layer by dissolving the dextrin-containing layer, the dextrin-containing layer preferably directly contacts the fibrous-free additional layer.

The dextrin-containing layer is therefore preferably applied to the paper layer, for example in a printing process, for example by using anilox rollers. After sufficient drying, the material of the fibrous-free further layer is applied to the dextrin-containing ply in liquid or pasty form, either to the dextrin-containing ply or to a layer to be connected to the paper ply by the fibrous-free further ply, usually a polymer ply, in particular a polymer film. The polymer layer to be connected, in particular polymer film, preferably has a weight per unit area of between 10 and 50 g/m ² . The layer to be joined is preferably not a paper layer and is preferably also free of fibrous material.

The fiber-free further layer is not a paper layer. The fiber-free additional layer can be a polymer layer which has the material properties of the paper layer in an advantageous manner for supplemented the packaging tasks. As a polymer layer, the fibrous-free further layer can preferably be a polyolefin layer, in particular a layer made of polypropylene or of polyethylene.

A polymer layer connected to the paper layer by means of the fiber-free additional layer, in particular a polymer film, can have a monoaxial orientation, for example, to guide a tear introduced into the layer composite. Alternatively, the polymer layer can have a biaxial orientation to increase its strength and/or to increase its barrier properties.

The layered composite can have a barrier layer, such as a metallization or ceramic barrier layers, such as layers of aluminum oxide or silicon oxide, or polymeric barrier layers, such as ethylene-vinyl alcohol copolymer (EVOH) or polyvinyl alcohol (PVOH) to increase the barrier effect of the layered composite against a To increase the passage of water vapor and/or oxygen and/or fats and oils through the composite layer.

A metallization, which is usually vapour-deposited or physically or chemically deposited onto a substrate layer, is preferably provided on a polymer layer, in particular a polymer film, as the substrate layer. The fibrous-free further layer then preferably serves as an adhesive layer in order to connect the substrate layer to the paper layer. The metallization is preferably provided on the substrate layer on the side facing the paper or adhesive layer. Thus, the metallization in the composite layer is shielded by at least one additional layer on each side and is thus well protected from undesirable external mechanical influences.

With a suitable choice of barrier layer material, the dextrin-containing layer can contact the barrier layer directly.

For reasons of as uncomplicated recycling as possible of the layered composite containing paper layers, it is preferably free of a metal foil, in particular aluminum foil.

The paper layer preferably has a basis weight of between 30 and 100 g/m ² .

Depending on the application method, the dextrin-containing layer has a preferred application weight in the range from 1 to 4 g/m ² .

Of course, the above-mentioned layers of the composite layer containing paper layers do not have to be the only layers of the composite layer. This can include other functional layers, such as a print application layer or a sealing layer. Usually, a print application layer is located near one end of the laminate in the thickness direction, and the sealant layer is located at the other end of the laminate in the thickness direction. The print job can be printed straight onto the paper layer or can be applied as reverse printing to a transparent polymer film, which can be laminated to the paper layer by another layer of adhesive, preferably again with a layer containing dextrin in between.

The present application also relates to the use of a layer composite containing paper layers, which is designed according to the above description, for the production of a product packaging. The product packaging can be an overwrap which is folded around the product to be packaged and then fixed in the folded state. Alternatively, the packaging formed from the composite layer described above can be a packaging bag. The term "packaging bag" is to be understood generally as packaging preformed by sealing seams, which encloses a packaging space surrounded by the paper-containing layered composite. Such a packaging bag can be, for example, a 3- or 4-side sealed bag, a stand-up bag, a packaging bag with a sealed bottom part, in particular also made of the composite layer containing paper layers, a flow pack and the like.

• 1 eine grobschematische Querschnittsansicht einer ersten Ausführungsform eines erfindungsgemäßen papierlagenhaltigen Lagenverbunds,
• 2 eine grobschematische Querschnittsansicht einer zweiten Ausführungsform eines erfindungsgemäßen papierlagenhaltigen Lagenverbunds,
• 3 eine grobschematische perspektivische Ansicht einer Verpackung, welche aus einem beispielhaften Lagenverbund der 1 oder 2 gebildet ist.

Finally, the present application also relates to packaging, in particular for human or animal foodstuffs, comprising a layer composite containing paper layers as described above.

• 1 a rough schematic cross-sectional view of a first embodiment of a paper-ply-containing composite layer according to the invention,
• 2 a rough schematic cross-sectional view of a second embodiment of a paper-containing layered composite according to the invention,
• 3 a rough schematic perspective view of a package, which consists of an exemplary composite layer 1 or 2 is formed.

The figures are of a rough schematic nature and are not true to scale.

In 1 a paper-ply-containing ply composite according to the present application is generally denoted by 10 . The composite layer 10 includes a paper layer 12, for example with a basis weight of between 50 and 70 g/m ² . The layered composite 10 is used to produce product packaging (see 3 ).

On the visible side of the composite layer 10 that can be viewed by the consumer, ie that side which is on the outside of a packaging formed from the composite layer 10, a print order 14 is applied to the paper layer 12 as a straight print, for example in four-color printing. The print job 14 is protected from external mechanical influences by a protective lacquer 16 . The print job 14 can provide the consumer with information about the content, quantity, use and/or origin of packaging formed from the composite layer 10 .

The layered composite 10 also includes a polymer film 18 made of biaxially oriented polypropylene. The polymer film 18 located on the product side of the paper layer 12 that is closer to the later packaged product is metallized and has a metallization layer 20 deposited thereon. The metallization layer 20 is located on the side of the polymer film 18 that is closer to the paper layer 12. The polymer film 18 with its metallization layer 20 gives the laminar structure 10 strength and barrier properties against migration of both water vapor and oxygen through the laminar structure 10.

in the in 1 The first exemplary embodiment shown is the metallized polymer film 18 connected to the paper layer 12 by means of an adhesive layer 22 applied between the metallization layer 20 and the paper layer 12 . The adhesive layer 22 can have a two-component adhesive based on polyurethane, for example, in a manner known per se.

However, the adhesive applied in liquid or paste form to form the adhesive layer 22 does not come into direct contact with the paper layer 12 but with a layer 24 containing dextrin. After the dextrin-containing layer 24 has dried sufficiently, the adhesive is applied to it as a laminating adhesive to form the adhesive layer 22 .

The layer 24 containing dextrin has, for example, an application weight in the range from 1 to 4 g/m ² . The dextrin-containing layer 24 serves as a separator for shielding fibers of the paper ply 12 from the adhesive of the adhesive layer 22. By forming the dextrin-containing layer 24, the adhesive of the adhesive layer 22 does not wet the paper ply 12 and thus fibers contained in the paper ply 12.

After the composite layer 10 has been used, the water-soluble layer 24 containing dextrin can be dissolved by adding water and the paper layer 12 can thus be separated from the adhesive layer 22 . By arranging the dextrin-containing layer 24 as a separating layer, the complete paper layer 12 can be detached from the composite layer 10 . Because the fibrous material of the paper ply 12 is not wetted by the adhesive of the adhesive ply 22, the adhesive ply 22 is not contaminated by fibers of the paper ply. Thus, by using the dextrin-containing layer 24 as a separating layer, both the paper layer 12 and the polymer portion of the layer composite 10 arranged on the product side of the paper layer 12 can be successfully recycled in a recycling process. The paper sheet 12 can be repulped (repulped) into a pulp. High-quality recycling paper can be produced from the pulp produced in this way.

The dextrin-containing layer 24 is at least 50% by weight dextrin, but most preferably is formed as entirely of dextrin as possible.

On the product side of the polymer film 18 that faces the product that will be packaged later, a sealing layer 26 for thermally sealing the composite layer 10 can be formed as a layer that is exposed on the product side of the composite layer 10 .

In 2 an exemplary second embodiment of a layer composite containing paper layers is shown in cross section. Identical or functionally identical components or component sections as in 1 are in 2 provided with the same reference numbers, but increased by the number 100.

The in 2 illustrated second embodiment described only insofar as it differs from the first embodiment of the 1 differs, whose description otherwise also the explanation of the second embodiment of 2 serves.

A first difference between the first and second embodiments is that the metallized biaxially oriented polypropylene polymer film 118 is bonded not by a two-part adhesive but by an extrusion liner 128 of low density polyethylene (LDPE) to the rest on the product side of the polymer film 118 or its metallization layer 120 located layers of the composite layer 110 is connected. The LDPE of the extrusion liner layer 128 was applied to the dextrin-containing layer 124 from a melt by extrusion. The polymer film 118 with its metallization The sealing layer 120 was then laminated to the dextrin-containing ply 124 and to the paper ply 112 supporting it by means of the extrusion liner ply 128 .

Instead of the extrusion laminating layer 128, an adhesive layer 122 with a multi-component adhesive or with a solvent-based adhesive can of course also be used in the second embodiment. Likewise, in the first embodiment, instead of the adhesive layer 22 , an extrusion laminating agent layer 28 could create the connection between the metallized polymer film 18 and the dextrin-containing layer 24 .

Further deviating from the embodiment of FIG 1 the layered composite 110 of the second embodiment has a print application 114 which is applied to a transparent polymer film 130 in reverse printing. The polymer film 130, for example a film made from biaxially oriented polypropylene, effectively protects the print job 114 from external influences.

The reverse-printed polymer film 130 can advantageously be attached again by an adhesive layer 132 . Instead of an adhesive layer 132, another layer of extrusion laminating material could also connect the polymer film 130 to the paper layer 112.

Again, to facilitate recycling of the layered composite 110, the adhesive layer 132 is separated from the paper layer 112 by a further layer 134 containing dextrin. The statements made above regarding the dextrin-containing layer 24 of the first embodiment apply to the dextrin-containing layer 134 .

Thus, in contrast to the first embodiment, the paper layer 112 is covered by a dextrin-containing layer not only on one side but on both opposite sides in the direction of thickness.

In none of the illustrated embodiments is there a further paper ply adjoining a dextrin-containing ply 24, 124 or 134 on the side facing away from the paper ply 12 or 112, respectively.

Merely for the sake of completeness, it should be pointed out that the second embodiment can also have a print job 114 applied to the paper layer 112 in recto printing instead of the reverse printing described, and vice versa.

In 3 an exemplary packaging 90 is shown, which is formed from the paper-containing layered composite 10 or 110 in a manner known per se.

Claims (14)

Flexible layer composite (10; 110) containing paper layers, comprising a fibrous paper ply (12; 112) and a fibrous-free further ply (22; 128, 132) connected to the paper ply (12; 112), characterized in that between the paper ply (12; 112) and the fiber-free further layer (22; 128, 132) an intermediate layer (24; 124, 134) containing dextrin is arranged. Layer composite containing paper layers (10; 110) according to claim 1 , characterized in that the dextrin-containing layer (24; 124, 134) consists of at least 50% by weight, preferably at least 80% by weight, more preferably at least 90% by weight dextrin, more preferably with the exception of unavoidable Impurities consists only of dextrin. Layer composite containing paper layers (10; 110) according to claim 1 or 2 , characterized in that the fiber-free further layer is a polymer layer (22; 128, 132). Layer composite (10; 110) containing paper layers according to one of the preceding claims, characterized in that the fibrous-free further layer (22; 128, 132) is an adhesive layer which connects the paper layer (12; 112) with a polymer layer (18; 118, 130 ), In particular with a polymer film (18; 118, 130) connects. Layer composite containing paper layers (10; 110) according to claim 4 , characterized in that the adhesive layer has an adhesive, in particular a multi-component adhesive. Layer composite containing paper layers (10; 110) according to claim 4 or 5 , characterized in that the adhesive layer is an extrusion liner (128). Laminate (10; 110) containing paper plies according to one of the preceding claims, characterized in that the dextrin-containing ply (24; 124, 134) directly contacts the paper ply (12; 112). Layered composite (10; 110) containing paper layers according to one of the preceding claims, characterized in that the dextrin-containing layer (24; 124, 134) directly contacts the fibrous-free further layer (22; 128, 132). Paper layer-containing layer composite (10; 110) according to any one of the preceding claims, including the claim 4 , characterized in that the polymer layer (18; 118, 130) has a monoaxial or biaxial orientation. Laminate (10; 110) containing paper plies according to one of the preceding claims, characterized in that the laminate (10; 110) containing paper plies has a barrier layer (20; 120) against the passage of water vapor and/or oxygen. Layer composite containing paper layers (10; 110) according to claim 10 , characterized in that the layer containing dextrin directly contacts the barrier layer. Use of a layered composite (10; 110) containing paper layers according to one of Claims 1 until 11 for producing a product packaging (90). use after claim 12 , characterized in that the product packaging (90) is a wrap-around packaging or a packaging bag. Packaging (90) comprising a layered composite (10; 110) containing paper layers according to one of Claims 1 until 11 .

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