Tear strip for packaging, method for producing a tear strip and packaging

Description

[0001] The present invention relates to a tear strip for packaging, a method for producing such a tear strip, and packaging with such a tear strip.

[0002] Tear strips for packaging are a known technology and serve to facilitate the opening of sealed packages. However, tear strips are currently predominantly made of plastic, which is problematic from an environmental and recycling perspective. Therefore, initial attempts have already been made to produce compostable or biodegradable paper-based tear strips.

[0003] The prior art is disclosed in US 1 943 538 A, which describes a paper-based tear strip.

[0004] However, a disadvantage of these paper-based tear strips is that they exhibit significantly worse tearing behavior than the previous plastic-based tear strips, as the paper-based tear strips often tear off when being pulled and do not open the packaging or only open it partially.

[0005] It is therefore an object of the present invention to create a paper-based tear strip with improved tearing properties. A further object is to provide a method for producing such a tear strip. Finally, a further object is to create packaging with such a tear strip.

[0006] The problems are solved according to the invention by a tear strip with the features of claim 1, a method for producing such a tear strip with the features of claim 9, and by packaging according to claim 15. Advantageous embodiments with expedient further developments are described in the dependent claims, wherein advantageous embodiments of each aspect of the invention are to be regarded as advantageous embodiments of the other aspects of the invention.

[0007] A first aspect of the invention relates to a tear strip for packaging, comprising a layer system with a paper substrate and an adhesive layer arranged on a first side of the paper substrate. According to the invention, improved tearing behavior is achieved by the adhesive layer having, at least in certain areas, an uneven surface structure with relative elevations and depressions. In other words, according to the invention, a paper-based tear strip is provided whose adhesive layer has, in certain areas or completely, an uneven surface structure with relative elevations ("peaks") and relative depressions (valleys, depressions).Without wishing to be bound to this theory, the inventors assume that the improved tear-off behavior is achieved through this uneven surface structure, as it allows the tear strip to adhere to the packaging with varying degrees of strength in different areas. The depressions or valleys lead to a local weakening of the adhesive, while the raised areas or peaks result in a more intimate, material-bonded connection and thus a stronger bond. When the packaging is torn, the local weakening of the adhesive bond prevents the paper-based tear strip from adhering too strongly and tearing off. At the same time, the raised areas reliably prevent an overall insufficient bond with the packaging. Preferably, the adhesive layer has between 20 and 100 raised areas per square centimeter of paper substrate.Between 40 and 60, and especially around 50, raised areas per square centimeter are particularly preferred. The adhesive layer can consist of one or more suitable adhesives and may optionally contain additives. For example, an adhesive based on poly(meth)acrylate, natural or synthetic rubber, and / or a sealing wax may be used. Generally, "a / an" within this disclosure is to be read as an indefinite article, i.e., unless explicitly stated otherwise, always also as "at least one / at least one". Conversely, "a / an" can also be understood as "only one / only one".

[0008] In an advantageous embodiment of the invention, the paper substrate is compostable and / or biodegradable. This results in an improved environmental footprint. Alternatively or additionally, the paper substrate has a basis weight between 80 g / m² and 200 g / m², particularly between 100 g / m² and 140 g / m², and especially approximately 120 g / m². This ensures sufficient stability of the paper substrate for most applications and embodiments, and thus advantageous sealing and tearing properties of the tear strip. The amount of adhesive applied per unit area of ​​the paper substrate is particularly preferably selected as a function of the basis weight of the paper substrate, with higher application amounts per unit area generally being chosen for higher basis weights.This ensures both reliable sealing of the packaging and reliable tearing behavior without premature tearing or delamination of the tear strip. Alternatively or additionally, advantageous sealing and tearing behavior of the tear strip is guaranteed if the paper substrate has a strength of at least 75 N / 15 mm, preferably at least 110 N / 15 mm, in a principal direction and / or a thickness between 100 µm and 250 µm, particularly between 150 µm and 200 µm. A principal direction is understood to be the direction of the longest extension of the tear strip, that is, generally the extension along which the tearing of the associated packaging occurs.

[0009] Further advantages arise from the fact that the first and / or a second side of the paper substrate is embossed and / or bleached and / or dyed and / or printed. This allows the tear strip to be easily adapted, both visually and / or functionally, to different requirements. For example, an embossed paper substrate can provide better non-stick properties for the non-adhesive second side.

[0010] In a further advantageous embodiment of the invention, the adhesive layer is applied to the first side either over the entire surface or in sections. In other words, either the entire surface of the paper substrate is provided with the adhesive layer, or only one or more surface areas. This allows the adhesive and tearing behavior to be controlled. Alternatively or additionally, advantageous tearing behavior is achieved by applying the adhesive layer with a weight between 15 g / m² and 60 g / m², and in particular between 20 g / m² and 30 g / m².In a further embodiment, a particularly uniform tearing behavior is achieved by the adhesive layer having a regular surface structure, in particular a dot structure and / or a wave structure and / or a line structure and / or a pyramid structure and / or a truncated pyramid structure and / or a hexagonal structure and / or a line structure with cups and / or a spherical structure. The raised and recessed areas of the surface structure thus exhibit regularly arranged structural elements, whereby only a single structural element type or two or more structural element types may be provided. In the case of multiple structural element types, these can generally have the same or different volumes.

[0011] An additional improvement in tear-off behavior results from the fact that the surface structure of the adhesive layer has, at least in certain areas, a periodic structural element, wherein at least one extension vector of the structural element's periodicity is preferably arranged obliquely to the main extension direction of the paper substrate. In other words, the extension vector of the structural element's periodicity is not parallel or coaxial, but rather arranged at an angle other than 0° or 180° to the main extension direction of the paper substrate. When the tear strip is opened, the forces that occur are advantageously deflected and better distributed, thereby reliably preventing the tear strip from breaking off.

[0012] In a further advantageous embodiment of the invention, a release layer is arranged on the second side of the paper substrate, either over the entire surface or in sections. The coating weight of the release layer is preferably between 0.1 g / m² and 2.0 g / m², and in particular between 0.2 g / m² and 1.0 g / m². This reliably prevents the tear strip from blocking or sticking to itself, for example, during winding. The release layer can be silicone-based, although other release layers based on polyacrylate, carbamate, polyvinyl ether wax, or other suitable compounds, as well as mixtures thereof, are also possible.

[0013] Alternatively or additionally, it has proven advantageous to place a release strip on the side of the adhesive layer facing away from the paper substrate. This also provides a way to prevent the tear strip from becoming stuck or adhering to itself or to unwanted areas of the packaging. The release strip can be, for example, a release film or release paper, such as silicone-coated paper.

[0014] In a further embodiment, advantageous storage or transport of the tear strip is achieved by winding it onto a spool with a preferably traversing winding and / or by assembling it as a flat spool.

[0015] A second aspect of the invention relates to a method for producing a tear strip for packaging, in which a layered system is produced by applying an adhesive layer to a first side of a paper substrate. According to the invention, improved tearing behavior is achieved by producing the adhesive layer, at least in certain areas, with an uneven surface structure featuring relative elevations and depressions. The resulting advantages are described in the first aspect of the invention, with advantageous embodiments of the first aspect being considered advantageous embodiments of the second aspect. Conversely, advantageous embodiments of the second aspect are also considered advantageous embodiments of the first aspect.Once manufactured, the tear strip can be wound onto spools with a traversing winding, allowing for long lengths of up to 40,000 m or more, typically 10,000–20,000 m. Alternatively, the tear strip can also be supplied as a flat spool.

[0016] In an advantageous embodiment of the invention, the paper substrate is provided with an uneven surface structure before the adhesive layer is applied, and / or the uneven surface structure is created within the adhesive layer itself. Generally, the uneven surface structure of the adhesive layer can be achieved by applying the adhesive layer itself unevenly to a paper substrate with a surface that is at least partially uniform. Alternatively or additionally, the paper substrate can first be provided with an uneven surface, at least partially, after which the adhesive layer is applied to the paper substrate uniformly or unevenly. In principle, the first side and / or the second side of the paper substrate can have an uneven surface.A smooth paper substrate generally offers easier coating than a rough or textured one.

[0017] In a further advantageous embodiment of the invention, the adhesive layer is applied to the paper substrate by means of an anilox roller, in particular a stencil roller. This allows the adhesive layer to be applied to the paper substrate with a defined local dosage of adhesive, thereby creating a defined surface structure with predetermined raised areas and depressions. In addition to the geometry of the structural element(s) that form the surface structure, the local application volume of the adhesive layer can also be precisely controlled by appropriately selecting the cells or raised areas of the anilox roller.

[0018] Further advantages arise from the fact that the paper substrate is coated on a second side with a printing layer and / or a release liner. The printing layer allows for customization of the tear strip's visual appearance. It also enables the addition of symbols or usage instructions. Printing can generally be done using gravure, flexographic, offset, laser, inkjet, or other suitable printing methods. The printing ink can be nitrocellulose (NC), polyurethane (PU), polyvinyl chloride (PVC), polyvinyl butyral (PVB), or other binders. The release liner prevents the tear strip from sticking to itself, for example.

[0019] Furthermore, it has proven advantageous to apply a layer of varnish between the printing layer and the release layer, as this makes it particularly easy to protect the printing layer from damage and, if necessary, to provide it with an additionally improved visual appearance.

[0020] By cutting the tear strip into several strips, preferably by shearing, the width of the tear strip can be adapted to different applications. The tear strip can initially be produced with a multiple of this width, which facilitates the coating process(s) for forming the layer system. Preferably, the tear strip has a width between 2 mm and 15 mm after cutting, particularly between 4 mm and 8 mm.

[0021] A third aspect of the invention relates to packaging comprising at least one tear strip, which is designed according to the first aspect of the invention and / or produced by a method according to the second aspect of the invention. The advantages resulting from this are described in the first and second aspects of the invention, with advantageous embodiments of the first and second aspects being considered advantageous embodiments of the third aspect of the invention. Conversely, advantageous embodiments of the third aspect of the invention are also considered advantageous embodiments of the first and second aspects of the invention. The packaging can preferably be fully compostable or biodegradable. Furthermore, the packaging can comprise two or more tear strips.

[0022] This shows: Fig. 1 a schematic cross-section through a tear strip according to the invention; Fig. 2 a schematic and partial top view of the tear strip according to the invention during the application of an adhesive layer; Fig. 3 a schematic perspective view of a tear strip spool; Fig. 4 a top view of a package on which the tear strip is arranged; and Fig. 5 an enlarged view of the in Fig. 4 details shown V.

[0023] Fig. 1Figure 1 shows a schematic cross-section through a tear strip 10 according to the invention. The tear strip 10 comprises a layer system 12, which in this case has a paper substrate 14, an adhesive layer 16 arranged on a first side of the paper substrate 14, and a release layer 18, which is generally optional, arranged on the second side of the paper substrate 14. The cross-section shows that the adhesive layer 16 has an uneven surface structure with a wave-like structure consisting of relative protrusions 20 and relative depressions 22.

[0024] The tear strip 10 shown is compostable and / or biodegradable. Generally, the paper substrate 14 is cellulose-based. However, other paper types, such as paper based on PET fibers, can also be used. The basis weight of the paper substrate 14 is between 90 and 200 g / m², for example, 120 g / m². The paper substrate 14 can be white or bleached, or unbleached or colored. It can also be printed on one or both sides. The paper substrate 14 exhibits high mechanical stability in the main extension direction H (see figure). Fig. 2 ) or direction of travel of at least 75 N / 15 mm, in particular at least 110 N / 15 mm or more. As can be seen in Fig. 1As can be seen, the paper substrate 14 is smooth to allow for good coating properties. However, it is also possible for the paper substrate 14 to have a structured surface on its first and / or second side, onto which the adhesive layer 16 and / or the release layer 18 is applied. Embossing the paper substrate 14 often results in improved non-stick properties on the non-adhesive second side.

[0025] In this case, the adhesive layer 16 is applied over the entire surface of the first side of the paper substrate 14, although in principle only partial application is also possible. As can be seen in Fig. 2As can be seen in the schematic and partial top view of the tear strip 10 according to the invention during the application of the adhesive layer 16, the structured surface of the adhesive layer 16 has a regular line or wave structure, which is formed by the lines or waves created by the protrusions 20 as structural elements. The wave or line structure shown can be produced, for example, by means of a corresponding engraving of a coating cylinder, for example by means of a coating roller. It can be seen in Fig. 2Furthermore, the line structure with the raised areas 20 and indentations 22 is regularly formed, as the lines repeat periodically on the surface of the paper substrate 14. Additionally, an extent vector V of the periodicity of the line structure element is arranged obliquely to the main extent direction H of the paper substrate 14. In other words, the lines or raised areas 20 do not run perpendicular or parallel to the main extent direction H, but rather diagonally. In principle, however, other regular or irregular surface structures (patterns) can also be generated instead of linear or wave-shaped surface structures.

[0026] For the adhesive layer 16, a polyacrylate-based adhesive, a natural or synthetic rubber, or a sealing wax can be used. The adhesive application is typically in the range of 15 to 60 g / m², particularly between 20 and 30 g / m².

[0027] The release layer 18 can be applied to the entire surface or only to specific surface areas of the paper substrate 14. The release layer 18 is typically silicone-based, but other release agents, such as those based on polyacrylate, carbamate, or polyvinyl ether wax, can also be used. The application weight of the release layer 18 is normally in the range of 0.1 to 2.0 g / m², and in particular between 0.2 and 1.0 g / m².

[0028] Alternatively, the separating layer 18 can be omitted and the adhesive layer 16 can instead be covered with a separating film (not shown) or a separating paper, for example silicone paper.

[0029] Optionally, the paper substrate 14 can be printed, particularly on the non-adhesive side. If a release layer 18 is provided, printing preferably takes place directly on the paper substrate 14 before coating with the release layer 18. Printing can be carried out using gravure, flexographic, offset, or another printing process. The printing ink can be NC, PU, ​​PVC, PVB, or other binders. Optionally, an additional varnish coating (not shown) can be applied between the printing layer and the release layer 18. In this case, the layer structure of the layer system 12 would be: adhesive layer 16 – paper substrate 14 – printing layer – varnish layer – release layer 18.

[0030] Fig. 3Figure 1 shows a schematic perspective view of a tear strip spool 26. The tear strip 10 is wound onto a core 24. Preferably, the tear strip 10 is wound with a traversing winding, which allows for a long running length of up to 40,000 m, typically 10,000 to 20,000 m. Alternatively, the tear strip 10 can also be supplied as a flat spool. The tear strip 10 can be cut into narrower strips. The typical strip width for the most common packaging 28 is about 2 to 15 mm, particularly 4 to 8 mm. Cutting is typically done by shearing, but other cutting or separating methods are also possible.

[0031] Fig. 4 shows a top view of an unfolded package 28, on which a further embodiment of the tear strip 10 according to the invention is arranged. Fig. 4 will be viewed in conjunction with Fig. 5explained, which shows an enlarged view of detail V. One can see in particular in Fig. 5 , that the adhesive layer 16 in the present case has a regular dot pattern consisting of dot-shaped elevations 20 and corresponding depressions 22.

[0032] The parameter values ​​specified in the documents for defining process and measurement conditions for characterizing specific properties of the subject matter of the invention are also to be considered as included in the scope of the invention in the event of deviations - for example due to measurement errors, system errors, weighing errors, DIN tolerances and the like. REFERENCE MARK LIST:

[0033] 10 Tear strip 12 Layer system 14 Paper substrate 16 Adhesive layer 18 Separation layer 20 Raised areas 22 Indentations 24 Core 26 Tear strip spool 28 Packaging H Main extension direction V Extension vector

Claims

1. A tear-open strip (10) for a packaging (28), comprising a layer system (12), which comprises a paper substrate (14) and an adhesive layer (16) arranged on a first side of the paper substrate (14), characterized in that the adhesive layer (16) comprises an uneven surface structure with relative elevations (20) and relative depressions (22) at least in some regions.

2. The tear-open strip (10) according to claim 1, characterized in that the paper substrate (14) is compostable and / or biodegradable and / or that the paper substrate (14) has a grammage between 80 g / m2 and 200 g / m2, in particular between 100 g / m2 and 140 g / m2, and / or that the paper substrate (14) has a stability of at least 75 N / 15 mm, preferably of at least 110 N / 15 mm in a main extension direction (H) and / or a thickness between 100 µm and 250 µm, in particular between 150 µm and 200 µm.

3. The tear-open strip (10) according to claim 1 or 2, characterized in that the first and / or a second side of the paper substrate (14) is embossed and / or bleached and / or dyed and / or printed.

4. The tear-open strip (10) according to any one of claims 1 to 3, characterized in that the adhesive layer (16) is applied to the first side all over or in sections and / or that the adhesive layer (16) has an application weight between 15 g / m2 and 60 g / m2, in particular between 20 g / m2 and 30 g / m2 and / or that the adhesive layer (16) comprises a regular surface structure, in particular a dot structure and / or a wave structure and / or a line structure and / or a pyramid structure and / or a truncated pyramid structure and / or a hexagonal structure and / or a line structure with wells and / or a calotte structure.

5. The tear-open strip (10) according to claim 4, characterized in that the surface structure of the adhesive layer (16) comprises a periodic structural element at least in some regions, wherein at least one extension vector (V) of the periodicity of the structural element is preferably arranged obliquely to the main extension direction (H) of the paper substrate (14).

6. The tear-open strip (10) according to any one of claims 1 to 5, characterized in that a separating layer (18) is arranged all over or in sections on the second side of the paper substrate (14), wherein an application weight of the separating layer (18) is preferably between 0.1 g / m2 and 2.0 g / m2, in particular between 0.2 g / m2 and 1.0 g / m2.

7. The tear-open strip (10) according to any one of claims 1 to 6, characterized in that a separating strip is arranged on a side of the adhesive layer (16) facing away from the paper substrate (14).

8. The tear-open strip (10) according to any one of claims 1 to 7, characterized in that it is rolled up on a reel (26) with preferably traversing winding and / or is packaged as a flat reel.

9. A method for producing a tear-open strip (10) for a packaging (28), in which a layer system (12) is produced in that an adhesive layer (16) is applied to a first side of a paper substrate (14), characterized in that the adhesive layer (16) is produced with an uneven surface structure with relative elevations (20) and relative depressions (22) at least in some regions.

10. The method according to claim 9, characterized in that the paper substrate (14) is provided with an uneven surface structure before applying the adhesive layer (16) and / or that the uneven surface structure is generated in the adhesive layer (16).

11. The method according to claim 9 or 10, characterized in that the adhesive layer (16) is applied to the paper substrate (14) by means of an anilox roll, in particular a hachure roll.

12. The method according to any one of claims 9 to 11, characterized in that the paper substrate (14) is provided with a printing layer and / or with a separating layer (18) on the second side.

13. The method according to claim 12, characterized in that a varnish layer is applied between the printing layer and the separating layer (18).

14. The method according to any one of claims 9 to 13, characterized in that the tear-open strip (10) is cut into multiple strips, preferably by means of scissors cut, wherein the strips preferably have a width between 2 mm and 15 mm, in particular between 4 mm and 8 mm.

15. A packaging (28) comprising at least one tear-open strip (10), which is formed according to any one of claims 1 to 8 and / or is produced by means of a method according to any one of claims 9 to 14.