EP4377218A1

EP4377218A1 - Tear-open strip for a packaging and method for producing a tear-open strip

Info

Publication number: EP4377218A1
Application number: EP22760662.1A
Authority: EP
Inventors: Dirk Hullmann
Original assignee: Mayr Melnhof Karton AG
Current assignee: Mayr Melnhof Karton AG
Priority date: 2021-07-26
Filing date: 2022-07-26
Publication date: 2024-06-05
Also published as: CA3227170A1; WO2023006786A1; CN118055887A; DE102021119281A1; KR20240040763A

Abstract

The invention relates to a tear-open strip (10) for a packaging (28), comprising a layer system (12) which has a paper substrate (14) and an adhesive layer (16) arranged on a first side of the paper substrate (14), the adhesive layer (16) having at least in some regions an uneven surface structure with relative elevations (20) and relative depressions (22). The invention also relates to a method for producing such a tear-open strip (10).

Description

On tear strips for a package and method of making one

tear strip

DESCRIPTION:

The present invention relates to a tear strip for a package, a method for producing such a tear strip and a package with such a tear strip.

Package tear strips are well known in the art and are used to facilitate opening of sealed packages. However, tear strips are currently predominantly made of plastic, which is problematic for environmental and recycling reasons. Initial attempts have therefore already been made to produce compostable or biodegradable paper-based tear strips.

A disadvantage of these paper-based tear strips, however, is the fact that they show a significantly poorer tearing behavior than the previous plastic-based tear strips, since the paper-based tear strips often tear off when they are torn open and the packaging does not open or only opens partially.

It is therefore the object of the present invention to create a paper-based tear strip with improved tearing behavior. Another object is to provide a method of making such a tear strip. Finally, another object is to create a package with such a tear strip.

The objects are achieved according to the invention by a tear strip with the features of claim 1, a method for producing such Tear strip with the features of claim 9 and solved by a package according to claim 15. Advantageous configurations with expedient developments are described in the dependent claims, with advantageous configurations of each aspect of the invention being to be regarded as advantageous configurations of the respective other aspects of the invention.

A first aspect of the invention relates to a tear strip for packaging, comprising a layer system which has 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 in that the adhesive layer has an uneven surface structure with relative elevations and relative depressions, at least in regions. In other words, a paper-based tear strip is provided according to the invention, the adhesive layer of which has an uneven surface structure with relative elevations (“heights”) and relative depressions (valleys, cups) in some areas or completely. Without wishing to be bound by this theory, the inventors assume that the improved tear-off behavior is achieved by this uneven surface structure, since the tear strip can thus be bonded to an associated packaging to varying degrees locally, since the depressions or valleys lead to a local weakening of the bond, while the elevations or heights lead to a more intimate material connection and thus to a firmer bond. When the packaging is torn open, the local weakening of the adhesive bond prevents the paper-based tear strip from sticking too tightly and tearing off. At the same time, however, the elevations reliably prevent the adhesive bond with the associated packaging being too weak overall. Preferably, the adhesive layer has between 20 and 100 bumps per square centimeter of paper substrate. Between 40 and 60, in particular about 50, elevations per square centimeter are particularly preferred. In principle, the adhesive layer can consist of one or more suitable adhesives exist and may contain additives. For example, an adhesive based on poly(meth)acrylate, a natural or synthetic rubber and/or a sealing wax can be used. In general, “a/an” in the context of this disclosure should be read as an indefinite article, i.e. always as “at least one/at least one” unless expressly stated otherwise. Conversely, "a/an" can also be understood as "only one/only one".

In an advantageous embodiment of the invention, it is provided that the paper substrate is compostable and/or biodegradable. This achieves an improved environmental balance. Alternatively or additionally, it is provided that the paper substrate has a grammage between 80 g/m ² and 200 g/m ² , in particular between 100 g/m ² and 140 g/m ² , in particular about 120 g/m ² . This ensures sufficient stability of the paper substrate and thus advantageous sealing and tearing behavior of the tear strip for most applications and embodiments. The amount of adhesive applied per unit area of the paper substrate is particularly preferably selected as a function of or as a function of the grammage of the paper substrate, with higher amounts applied per unit area generally being selected for higher grammages. In this way, on the one hand, reliable sealing of a package and, on the other hand, reliable tearing behavior without premature tearing or tearing of the tear-off strip can be ensured. Alternatively or additionally, an advantageous sealing and tearing behavior of the tear strip is ensured in that the paper substrate has a stability of at least 75 N/15 mm, preferably at least 110 N/15 mm and/or a thickness of between 100 μm and 250 μm in a main extension direction. in particular between 150 pm and 200 pm. A main direction of extent is understood to mean the direction of the longest extent of the tear strip, that is to say generally the extent along which the associated packaging is torn open. Further advantages result from the fact that the first and/or a second side of the paper substrate is or are embossed and/or bleached and/or colored and/or printed. As a result, the tear strip can be optically and/or functionally adapted to different requirement profiles in a particularly simple manner. For example, an embossed paper substrate can provide better release of the non-stick second side.

In a further advantageous embodiment of the invention, it is provided that the adhesive layer is applied to the first side over the entire surface or in sections. In other words, it is provided that either the entire surface of the paper substrate is provided with the adhesive layer, or only one or more surface areas. This allows the sticking and tearing behavior to be controlled. Alternatively or additionally, advantageous tearing behavior is achieved by the adhesive layer having an application weight of between 15 g/m ² and 60 g/m ² , in particular between 20 g/m ² and 30 g/m ² . A particularly uniform tearing behavior is achieved in a further embodiment in that the adhesive layer has a regular surface structure, in particular a dot structure and/or a wavy 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 dome structure. The elevations and depressions of the surface structure thus have regularly arranged structure elements, it being possible for only a single type of structure element or two or more types of structure element to be provided. In the case of several structural element types, these can generally have the same or different volumes.

An additionally improved tearing behavior results from the fact that the surface structure of the adhesive layer has a periodic structural element at least in regions, with at least one Extension vector of the periodicity of the structural element is preferably arranged obliquely to the main direction of extension of the paper substrate. In other words, it is provided that the extension vector of the periodicity of the structural element is not arranged parallel or coaxial, but at an angular position other than 0° or 180° to the main extension direction of the paper substrate. When the tear strip is torn open, the forces that occur are advantageously deflected and better distributed, as a result of which the tear strip is prevented in a particularly reliable manner.

In a further advantageous embodiment of the invention, it is provided that a separating layer is arranged over the entire surface or in sections on the second side of the paper substrate, with an application weight of the separating layer preferably between 0.1 g/m ² and 2.0 g/m ² , in particular between 0.2 g/m ² and 1.0 g/m ² . This reliably prevents the tear strip from becoming blocked or sticking to itself, for example when it is being wound up. The separating layer can be silicone-based, although in principle other separating layers based on polyacrylate, carbamate, polyvinyl ether wax or other suitable compounds and mixtures thereof can also be provided.

As an alternative or in addition, it has proven to be advantageous for a separating strip to be arranged on a side of the adhesive layer which faces away from the paper substrate. This also represents a way of preventing the tear strip from blocking or sticking to itself or to undesired areas of an associated packaging. The separating strip can, for example, be a separating film or a separating paper, for example silicone paper.

An advantageous storage or an advantageous transport of the tear strip is achieved in a further embodiment that this rolled up on a spool with a preferably traversing winding and/or made up as a flat spool.

A second aspect of the invention relates to a method for producing a tear strip for packaging, in which a layer 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 in that the adhesive layer is produced at least in regions with an uneven surface structure with relative elevations and relative depressions. The resulting advantages can be found in the descriptions of the first aspect of the invention, with advantageous configurations of the first aspect of the invention being to be regarded as advantageous configurations of the second aspect of the invention. Conversely, advantageous refinements of the second aspect of the invention are also to be regarded as advantageous refinements of the first aspect of the invention. After its production, the tear strip can be wound on spools with traversing winding, which allow a long running length of up to 40,000 m or more, typically 10,000 - 20,000 m. Alternatively, the tear strip can also be made up as a flat coil.

In an advantageous embodiment of the invention, it is provided that the paper substrate is provided with an uneven surface structure before the application of the adhesive layer and/or that the uneven surface structure is produced in the adhesive layer. In general, therefore, the uneven surface structure of the adhesive layer can be achieved in that the adhesive layer itself is applied correspondingly unevenly to a paper substrate with an at least regionally uniform surface. Alternatively or additionally, it can also be provided that the paper substrate is initially provided with an uneven surface, at least in regions, after which the adhesive layer is applied evenly or unevenly to the paper substrate. Basically can the first side and/or the second side of the paper substrate having an uneven surface. A smooth paper substrate is usually easier to coat than a rough or structured one.

In a further advantageous embodiment of the invention, it is provided that the adhesive layer is applied to the paper substrate by means of an anilox roller, in particular a hatch roller. This makes it possible to apply the adhesive layer to the paper substrate with a defined local dosage of the adhesive and thus to produce a defined surface structure with predetermined elevations and depressions. In addition to the geometry of the structural element or elements that form the surface structure, the local application volume of the adhesive layer can also be precisely controlled by a suitable choice of the cells or elevations of the anilox roller.

Further advantages result from the fact that the paper substrate is provided with a printed layer and/or with a separating layer on a second side. The optical appearance of the tear strip can be adjusted with the help of the printed layer. Furthermore, the tear strip can be provided with symbols or instructions for use. Printing can generally take place using gravure printing, flexographic printing, offset printing, laser printing, inkjet printing or another suitable printing process. The ink can be based on nitrocellulose (NC), polyurethane (PU), polyvinyl chloride (PVC), polyvinyl butyral (PVB) or other binders. The separating layer prevents the tear strip from sticking to itself, for example.

It has also been shown to be advantageous if a layer of lacquer is applied between the printed layer and the separating layer, since the printed layer can be protected from damage particularly easily in this way and optionally provided with an additionally improved visual appearance. By cutting the tear strip into several strips, preferably by means of a scissors cut, the width of the tear strip can be adapted to different applications, whereby the tear strip can initially be produced with a multiple of this width, which facilitates the coating process or processes for forming the layer system. After cutting, the tear strip preferably has a width of between 2 mm and 15 mm, in particular between 4 mm and 8 mm.

A third aspect of the invention relates to packaging which comprises at least one tear strip which is designed according to the first aspect of the invention and/or is produced by means of a method according to the second aspect of the invention. The resulting advantages can be found in the descriptions of the first and second aspects of the invention, advantageous configurations of the first and second aspects of the invention being to be regarded as advantageous configurations of the third aspect of the invention. Conversely, advantageous configurations of the third aspect of the invention are also to be regarded as advantageous configurations of the first and second aspects of the invention. The packaging can preferably be designed to be completely compostable or biodegradable. Furthermore, the package may include two or more tear strips.

Further features of the invention result from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and/or shown alone in the figures, can be used not only in the combination specified in each case, but also in other combinations, without going beyond the scope of the invention leave. The invention is therefore also to be considered to include and disclose embodiments that are not explicitly shown and explained in the figures, but that result from the explained embodiments and can be generated by separate combinations of features. There are too Versions and combinations of features are to be regarded as disclosed, which therefore do not have all the features of an originally formulated independent claim. Furthermore, embodiments and combinations of features, in particular through the embodiments presented above, are to be regarded as disclosed which go beyond or deviate from the combinations of features presented in the back references of the claims. It shows:

1 shows a schematic cross section through a tear strip according to the invention;

2 shows a schematic and sectional view of the tear strip according to the invention during the application of an adhesive layer;

Figure 3 is a schematic perspective view of a tear tape spool;

Figure 4 is a plan view of a package on which the tear strip is placed; and

Fig. 5 shows an enlarged representation of detail V shown in Fig. 4.

Fig. 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 the present case comprises a paper substrate 14, an adhesive layer 16 arranged on a first side of the paper substrate 14 and a fundamentally optional layer on the second side of the Paper substrate 14 arranged release layer 18 has. It can be seen in the cross section that the adhesive layer 16 has an uneven surface structure with a wavy structure made up of relative elevations 20 and relative depressions 22 . The tear strip 10 shown is compostable and/or biodegradable. In general, the paper substrate 14 is based on cellulose. However, other types of paper, for example paper based on PET fibers, can also be provided. The grammage of the paper substrate 14 is between 90 and 200 g/m ² , for example 120 g/m ² . The paper substrate 14 can be white or bleached or unbleached or colored. Provision can also be made for the paper substrate 14 to be printed on one or both sides. The paper substrate 14 has a high mechanical stability in the main extension direction H (see FIG. 2) or running direction of at least 75 N/15 mm, in particular at least 110 N/15 mm or more. As seen in Figure 1, the paper substrate 14 is smooth to allow for good coatability. In principle, however, provision can also be made for the paper substrate 14 to have a structured surface on its first and/or second side, to which the adhesive layer 16 and/or the separating layer 18 is applied. By embossing the paper substrate 14, a better anti-adhesion property of the non-adhesive, second side can often be achieved.

In the present case, the adhesive layer 16 is applied to the entire surface of the first side of the paper substrate 14, it also being possible, in principle, to only apply it to certain areas. As can be seen in Fig. 2, which shows a schematic and sectional 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 contains lines or waves formed by the elevations 20 Waves are formed 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 hatching roller. It can also be seen in FIG. 2 that the line structure with the elevations 20 and depressions 22 is formed regularly since the lines are repeated periodically on the surface of the paper substrate 14 . Additionally is a Extension vector V of the periodicity of the line structure element is arranged obliquely to the main extension direction H of the paper substrate 14 . In other words, the lines or elevations 20 do not run perpendicularly or parallel to the main extension direction H, but rather run diagonally. Basically, instead of linear or wavy surface structures, other regular or irregular surface structures (patterns) can also be produced.

An adhesive based on polyacrylate, a natural or synthetic rubber or a sealing wax can be used for the adhesive layer 16 . The application of adhesive is typically in the range between 15 and 60 g/m ² , in particular 20 to 30 g/m ² .

The separating layer 18 can likewise be applied to the entire surface or only to specific surface areas of the paper substrate 14 . The separating layer 18 is typically silicone-based, but in general other separating agents, for example based on polyacrylate, carbamate or polyvinyl ether wax, can also be used. The coating weight of the separating layer 18 is normally in the range between 0.1 and 2.0 g/m ² , in particular between 0.2 and 1.0 g/m ² .

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

Optionally, the paper substrate 14 can be printed, in particular on the non-adhesive side. If a release liner 18 is provided, printing is preferably done directly on the paper substrate 14 prior to coating with the release liner 18. Printing may be by rotogravure, flexographic, offset, or other printing methods. The ink can be based on NC, PU, PVC, PVB or other binders. Optionally between the Printing layer and the separating layer 18 an additional lacquer coating (not shown) are applied. In this case, the layer structure of the layer system 12 would be adhesive layer 16-paper substrate 14-printing layer-varnish layer-separating layer 18.

3 shows a schematic perspective view of a tear-off strip spool 26. The tear-off strip 10 is wound onto a core 24 for this purpose. The tear-off strip 10 is preferably wound with traversing winding, as a result of which a long running length of up to 40,000 m, typically 10,000 to 20,000 m, is made possible. Alternatively, the tear strip 10 can also be made up as a flat coil. The tear strip 10 can be cut into narrower strips. The typical stripe width for the most common packages 28 is about 2 to 15 mm, in particular 4 to 8 mm. Cutting is typically done with scissors, but other types of cutting or separating are also possible.

FIG. 4 shows a plan view of an unfolded package 28 on which another exemplary embodiment of the tear strip 10 according to the invention is arranged. FIG. 4 is explained in conjunction with FIG. 5, which shows an enlarged representation of detail V. FIG. It can be seen in particular in FIG. 5 that the adhesive layer 16 in the present case has a regular dot pattern of punctiform elevations 20 and corresponding depressions 22 .

The parameter values specified in the documents for the definition of process and measurement conditions for the characterization of specific properties of the subject matter of the invention are also to be regarded as included within the scope of the invention within the scope of deviations - for example due to measurement errors, system errors, weighing errors, DIN tolerances and the like . REFERENCE LIST:

10 tear strips 12 layer system

14 paper substrate

16 adhesive layer

18 release layer

20 elevations 22 depressions

24 core

26 tear strip reel 28 packaging H main direction of extension V vector of extension

Claims

EXPECTATIONS:

1. Tear strip (10) for a package (28) comprising a layer system (12) which has 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) has an uneven surface structure with relative elevations (20) and relative depressions (22), at least in regions.

2. Tear 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/m ² and 200 g/m ² , in particular between 100 g/m ² and 140 g/m ² 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 and/or in a main extension direction (H) or has a thickness between 100 μm and 250 μm, in particular between 150 μm and 200 μm.

3. Tear 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 colored and/or printed.

4. tear strip (10) according to any one of claims 1 to 3, characterized in that the adhesive layer (16) is applied over the entire surface or in sections on the first side and / or that the adhesive layer (16). Coating weight between 15 g/m ² and 60 g/m ² , in particular between 20 g/m ² and 30 g/m ² and/or that the adhesive layer (16) has a regular surface structure, in particular a dot structure and/or a wavy 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 dome structure.

5. Tear-open strip (10) according to Claim 4, characterized in that the surface structure of the adhesive layer (16) has a periodic structural element at least in regions, with at least one extension vector (V) of the periodicity of the structural element preferably being inclined at an angle to the main extension direction (H) of the paper substrate (14 ) is arranged.

6. Tear-off strip (10) according to one of Claims 1 to 5, characterized in that a separating layer (18) is arranged over the entire surface or in sections on the second side of the paper substrate (14), with an application weight of the separating layer (18) preferably between 0, 1 g/m ² and 2.0 g/m ² , in particular between 0.2 g/m ² and 1.0 g/m ² .

7. Tear-off strip (10) according to 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. tear strip (10) according to one of claims 1 to 7, characterized in that it is rolled up on a spool (26) with a preferably traversing winding and/or is made up as a flat spool.

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

10. The method according to claim 9, characterized in that the paper substrate (14) is provided with an uneven surface structure before the application of the adhesive layer (16) and/or that the uneven surface structure is produced 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 a screen roller, in particular a hatched roller.

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

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

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

15. Packaging (28) comprising at least one tear strip (10) which is designed according to any one of claims 1 to 8 and/or produced by means of a method according to any one of claims 1 to 14.