CA3227170A1

CA3227170A1 - Tear-open strip for a packaging and method for producing a tear-open strip

Info

Publication number: CA3227170A1
Application number: CA3227170A
Authority: CA
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: 2023-02-02
Also published as: EP4377218A1; KR20240040763A; DE102021119281A1; WO2023006786A1; CN118055887A

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

Tear-open strip for a packaging and method for producing a tear-open strip ________________________________________________________________ DESCRIPTION:
The present invention relates to a tear-open strip for a packaging, to a method for producing such a tear-open strip as well as to a packaging with such a tear-open strip.
Tear-open strips for packagings are known from the prior art and serve for facilitating opening of sealed packagings. However, tear-open strips are presently predominantly composed of plastic, which is problematic for environmental protection and recycling reasons. Therefore, there were already first attempts to produce compostable or biodegradable tear-open strips on paper basis.
However, the circumstance is to be regarded as disadvantageous in these paper-based tear-open strips that they exhibit a substantially inferior tear-open behavior than the previous plastic-based tear-open strips, since the paper-based tear-open strips often tear off upon tearing open and do not or only partially open the packaging.
Therefore, it is the object of the present invention to provide a paper-based tear-open strip with improved tear-open behavior. A further object is in providing a method for producing such a tear-open strip. Finally, a further object is in providing a packaging with such a tear-open strip.
According to the invention, the objects are solved by a tear-open strip with the features of claim 1, a method for producing such a tear-open strip with the features of claim 9 as well as by a packaging according to claim 15.
Advantageous configurations with convenient developments are described in the dependent claims, wherein advantageous configurations of each inventive aspect

2 are to be regarded as advantageous configurations of the respectively other inventive aspects.
A first aspect of the invention relates to a tear-open strip for a packaging, comprising a layer system, which comprises a paper substrate and an adhesive layer arranged on a first side of the paper substrate. According to the invention, an improved tear-open behavior is achieved in that the adhesive layer comprises an uneven surface structure with relative elevations and relative depressions at least in some regions. In other words, a paper-based tear-open strip is provided according to the invention, the adhesive layer of which comprises an uneven surface structure with relative elevations ("peaks") and relative depressions (valleys, wells) in some regions or in complete manner.
Without wishing to be bound by this theory, the inventors assume that the improved tear-open behavior is achieved by this uneven surface structure, since the tear-open strip can thereby be locally differently strongly adhered to an associated packaging, since the depressions or valleys result in a local weakening of the adherence, while the elevations or peaks result in a more intimate firmly-bonded connection and thereby in a firmer adherence. Upon tearing the packaging open, it is then prevented by the local weakenings of the adhesive connection that the paper-based tear-open strip too firmly adheres and tears off. However, by the elevations, it is reliably prevented at the same time that an overall too weak adherence to the associated packaging would occur. Preferably, the adhesive layer comprises between 20 and 100 elevations per square centimeter of paper substrate. Between 40 and 60, in particular about 50 elevations per square centimeter are particularly preferred.
Basically, the adhesive layer can be composed of one or more suitable adhesives and optionally contain additives. For example, an adhesive based on poly(meth)acrylate, a natural or synthetic rubber and/or a sealing wax can be employed. Generally "a/one" are to be read as indefinite articles within the scope of this disclosure, thus always also as "at least a/at least one"
without explicitly opposite indication. Conversely, "a/one" can also be understood as "only a/only one".

3 In an advantageous configuration of the invention, it is provided that the paper substrate is compostable and/or biodegradable. Hereby, an improved environmental balance is realized. Alternatively or additionally, it is provided that the paper substrate has a gramnnage between 80 g/m2 and 200 g/m2, in particular between 100 g/m2 and 140 g/m2, in particular about 120 g/m2.
Hereby, a sufficient stability of the paper substrate and thereby an advantageous sealing and tear-open behavior of the tear-open strip are ensured for most of the application cases and embodiments. Particularly preferably, the application amount of the adhesive per area unit of the paper substrate is selected depending on or as a function of the grammage of the paper substrate, wherein higher application amounts per area unit are generally selected for higher grammages. Hereby, a reliable closure of a packaging on the one hand and a reliable tear-open behavior without premature tear-off or tear-down of the tear-open strip on the other hand can be ensured.
Alternatively or additionally, an advantageous sealing and tear-open behavior of the tear-open strip is ensured in that the paper substrate has a stability of at least 75 N/15 mm, preferably of at least 110 N/15 mm in a main extension direction, and/or a thickness between 100 pm and 250 pm, in particular between 150 pm and 200 pm. By a main extension direction, the direction of the longest extension of the tear-open strip is understood, that is usually the extension, along which tearing open of the associated packaging is effected.
Further advantages arise in that the first and/or a second side of the paper substrate is embossed and/or bleached and/or dyed and/or printed. Hereby, the tear-open strip can be particularly simply optically and/or functionally adapted to different requirement profiles. For example, an embossed paper substrate can effect a better nonstick characteristic of the non-adhering second side.
In a further advantageous configuration of the invention, it is provided that the adhesive layer is applied to the first side all over or in sections. In other words, it is provided that either the entire surface of the paper substrate is provided with

4 the adhesive layer or only one or more surface regions. Hereby, the adhesive and tear-open behavior can be controlled. Alternatively or additionally, an advantageous tear-open behavior is achieved in that the adhesive layer has an application weight between 15 g/m2 and 60 g/m2, in particular between 20 g/m2 and 30 g/m2. In further configuration, a particularly uniform tear-open behavior is achieved in that the adhesive layer has 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. Thereby, the elevations and depressions of the surface structure comprise regularly arranged structural elements, wherein only a single structural element type or two or more structural element types can be provided. In case of multiple structural element types, they can generally have identical or different volumes.
An additionally improved tear-open behavior arises in that the surface structure of the adhesive layer comprises a periodic structural element at least in some regions, wherein at least one extension vector of the periodicity of the structural element is preferably arranged obliquely to the main extension direction of the paper substrate. In other words, it is provided that the extension vector of the periodicity of the structural element is not parallel or coaxially arranged, but in an angular position unequal to 00 and 180 , respectively, to the main extension direction of the paper substrate. Upon tearing the tear-open strip open, forces occurring therein are advantageously deflected and better distributed, whereby a tear-off of the tear-open strip is particularly reliably prevented.
In a further advantageous configuration of the invention, it is provided that a separating layer is arranged all over or in sections on the second side of the paper substrate, wherein an application weight of the separating layer is preferably between 0.1 g/m2 and 2.0 g/m2, in particular between 0.2 g/m2 and 1.0 g/m2. Hereby, blocking or sticking of the tear-open strip to itself, for example in winding, can be reliably prevented. The separating layer can be formed based on silicone, wherein other separating layers based on polyacrylate,

5 carbamate, polyvinyl ether wax or other suitable compounds as well as mixtures hereof can basically also be provided.
Alternatively or additionally, it has proven to be advantageous that a separating strip is arranged on a side of the adhesive layer facing away from the paper substrate. This too presents a possibility of preventing blocking or sticking of the tear-open strip to itself or undesired regions of an associated packaging. For example, the separating strip can be a separating foil or a separating paper, for example a silicone paper.
In further configuration, an advantageous storage or an advantageous transport of the tear-open strip is achieved in that it is rolled up on a reel with preferably traversing winding and/or is packaged as a flat reel.
A second aspect of the invention relates to a method for producing a tear-open strip for a packaging, in which a layer system is produced in that an adhesive layer is applied to a first side of a paper substrate. According to the invention, an improved tear-open behavior is achieved in that the adhesive layer is produced with an uneven surface structure with relative elevations and relative depressions at least in some regions. The advantages resulting from it can be taken from the descriptions of the first inventive aspect, wherein advantageous configurations of the first inventive aspect are to be regarded as advantageous configuration of the second inventive aspect. Conversely, advantageous configurations of the second inventive aspect are also to be regarded as advantageous configuration of the first inventive aspect. After its production, the tear-open strip can be reeled on reels with traversing winding, which allow a large running length of up to 40,000 m or more, typically 10,000 - 20,000 m.
Alternatively, the tear-open strip can also be packaged as a flat reel.
In an advantageous configuration of the invention, it is provided that the paper substrate is provided with an uneven surface structure before applying the adhesive layer and/or that the uneven surface structure is generated in the

6 adhesive layer. Thus, the uneven surface structure of the adhesive layer can generally be achieved in that the adhesive layer itself is correspondingly nonuniformly applied to a paper substrate with a surface uniform at least in some regions. Alternatively or additionally, however, it can also be provided that the paper substrate is first provided with a nonuniform surface at least in some regions, whereafter the adhesive layer is uniformly or nonuniformly applied to the paper substrate. Therein, the first side and/or the second side of the paper substrate can generally have a nonuniform surface. Therein, a smooth paper substrate usually offers a simpler capability of coating than a rough or structured one.
In a further advantageous configuration of the invention, it is provided that the adhesive layer is applied to the paper substrate by means of an anilox roll, in particular a hachure roll. This allows applying the adhesive layer to the paper substrate with a defined local dosage of the adhesive and thereby generating a defined surface structure with predetermined elevations and depressions.
Besides the geometry of the structural element or elements, which form the surface structure, the local application volume of the adhesive layer can also be precisely controlled by suitable choice of the wells and elevations, respectively, of the anilox roll.
Further advantages arise in that the paper substrate is provided with a printing layer and/or with a separating layer on a second side. With the aid of the printing layer, the optical impression of the tear-open strip can be adapted.
Furthermore, the tear-open strip can hereby be provided with symbols or use indications. The print can generally be effected in gravure printing, flexographic printing, offset printing, laser printing, inkjet printing or another suitable printing method. The printing ink can be based on nitrocellulose (NC), polyurethane (PU), polyvinylchloride (PVC), polyvinyl butyral (PVB) or other binders. The separating layer prevents undesired sticking of the tear-open strip for example to itself.

7 Therein, it has further proven to be advantageous if a varnish layer is applied between the printing layer and the separating layer since the printing layer is particularly simply protected from damage in this manner and can optionally be provided with an additionally improved optical impression.
In that the tear-open strip is cut into multiple strips, preferably by means of scissors cut, the width of the tear-open strip can be adapted to different application purposes, wherein the production of the tear-open strip can first be effected with a multiple of this width, which facilitates the coating process or processes for forming the layer system. Preferably, the tear-open strip has a width between 2 mm and 15 mm, in particular between 4 mm and 8 mm, after cutting.
A third aspect of the invention relates to a packaging, which includes at least one tear-open strip, which is formed according to the first inventive aspect and/or is produced by means of a method according to the second inventive aspect. The advantages resulting from it can be taken from the descriptions of the first and second inventive aspects, wherein advantageous configurations of the first and second inventive aspects are to be regarded as advantageous configuration of the third inventive aspect. Conversely, advantageous configurations of the third inventive aspect are also to be regarded as advantageous configuration of the first and second inventive aspects.
Preferably, the packaging can be formed completely compostable or biodegradable. Furthermore, the packaging can include two or more tear-open strips.
Further features of the invention are apparent from the claims, the figures and the description of figures. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of figures and/or shown in the figures alone are usable not only in the respectively specified combination, but also in other combinations without departing from the scope of the invention. Thus, implementations are also to be considered as encompassed and disclosed by

8 the invention, which are not explicitly shown in the figures and explained, but arise from and can be generated by separated feature combinations from the explained implementations. Implementations and feature combinations are also to be considered as disclosed, which thus do not comprise all of the features of an originally formulated independent claim. Moreover, implementations and feature combinations are to be considered as disclosed, in particular by the implementations set out above, which extend beyond or deviate from the feature combinations set out in the relations of the claims. There shows:
Fig. 1 a schematic cross-section through a tear-open strip according to the invention;
Fig. 2 a schematic and partial top view to the tear-open strip according to the invention during the application of an adhesive layer;
Fig. 3 a schematic perspective view of a tear-open strip reel;
Fig. 4 a top view of a packaging, on which the tear-open strip is arranged;
and Fig. 5 an enlarged representation of the detail V shown in Fig. 4.
Fig. 1 shows a schematic cross-section through a tear-open strip 10 according to the invention. The tear-open strip 10 includes 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 as well as a basically optional separating layer 18 arranged on the second side of the paper substrate 14. One recognizes in the cross-section that the adhesive layer 16 comprises an uneven surface structure with a wave-like structure of relative elevations 20 and relative depressions 22.
The shown tear-open strip 10 is compostable and/or biodegradable. Generally, the paper substrate 14 is formed based on cellulose. However, other paper

9 types, for example paper based on PET fibers, can also be provided. The grammage of the paper substrates 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 dyed. Similarly, it can be provided that the paper substrate 14 is printed on one side or on 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 N/15 mm, in particular of at least 110 N/15 mm or more. As one sees in Fig. 1, the paper substrate 14 is smooth to allow a good capability of coating. However, it can basically also be provided that the paper substrate 14 comprises a structured surface on its first and/or second side, to which the adhesive layer 16 and/or the separating layer 18 are applied. By embossing the paper substrate 14, a better nonstick characteristic of the non-adhering, second side can often be achieved.
In the present case, the adhesive layer 16 is applied to the first side of the paper substrate 14 all over, wherein only an application in some regions can basically also be provided. As one recognizes in Fig. 2, which shows a schematic and partial top view to the tear-open strip 10 according to the invention during the application of the adhesive layer 16, the structured surface of the adhesive layer 16 comprises a regular line or wave structure, which is formed by lines or waves formed by the elevations 20 as the structural elements. The shown wave or line structure can for example be generated by means of a corresponding gravure of a coating cylinder, for example by means of a hachure roll. Furthermore, one sees in Fig. 2 that the line structure with the elevations 20 and depressions 22 is regularly formed, since the lines periodically repeat themselves on the surface of the paper substrate 14. In addition, an extension vector V of the periodicity of the line structural 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 extend perpendicularly or parallel to the main extension direction H, but extend in diagonal manner. However, other regular or irregular surface structures (patterns) can basically also be generated instead of line- or wave-shaped surface structures.

10 For the adhesive layer 16, an adhesive based on polyacrylate, a natural or synthetic rubber or a sealing wax can be employed. The adhesive application is typically in the range between 15 and 60 g/m2, in particular at 20 to 30 g/m2.
The separating layer 18 can also be applied all over or only to certain surface regions of the paper substrate 14. The separating layer 18 is typically based on silicone, however, other separating agents, for example based on polyacrylate, carbamate or polyvinyl ether wax, can generally also be used. The application weight of the separating layer 18 is normally in the range between 0.1 and 2.0 g/m2, in particular between 0.2 and 1.0 g/m2.
Alternatively, the separating layer 18 can be omitted and the adhesive layer can instead be covered with a separating foil (not shown) or a separating paper, for example a silicone paper.
Optionally, the paper substrate 14 can be printed, in particular on the non-adhering side. If a separating layer 18 is provided, the print is preferably directly effected on the paper substrate 14 before coating with the separating layer 18.
The print can be effected in gravure printing, flexographic printing, offset printing or another printing method, The printing ink can be based on NC, PU, PVC, PVB
or other binders. Optionally, an additional varnish coating (not shown) can be applied between the printing layer and the separating layer 18. In this case, the layer construction of the layer system 12 would be adhesive layer 16 - paper substrate 14 - printing layer - varnish layer - separating layer 18.
Fig. 3 shows a schematic perspective view of a tear-open strip reel 26.
Hereto, the tear-open strip 10 is wound to a core 24. Therein, the tear-open strip 10 is preferably reeled with traversing winding, whereby a large running length of up to 40,000 m, typically 10,000 to 20,000 m, is allowed. Alternatively, the tear-open strip 10 can also be packaged as a flat reel. The tear-open strip 10 can be cut into narrower strips. The typical strip width for the most usual packagings 28 is about 2

11 to 15 mm, in particular 4 to 8 mm. Cutting is typically effected in scissors cut, however, other cutting or separating types are also possible.
Fig. 4 shows a top view of an unfolded packaging 28, on which a further embodiment of the tear-open strip 10 according to the invention is arranged.
Fig. 4 is explained in synopsis with Fig. 5, which shows an enlarged representation of the detail V. One recognizes in particular in Fig. 5 that the adhesive layer 16 has a regular dot pattern of dot-shaped elevations 20 and corresponding depressions in the present case.
The parameter values specified in the documents for definition of process and measurement conditions for characterizing specific characteristics of the inventive subject matter are to be regarded as encompassed by the scope of the invention also within the scope of deviations - for example due to measurement errors, system errors, weighing errors, DIN tolerances and the like.

12 LIST OF REFERENCE CHARACTERS:
Tear-open strip 5 12 layer system 14 paper substrate 16 adhesive layer 18 separating layer elevations 10 22 depressions 24 core 26 tear-open strip reel 28 packaging H main extension direction 15 V extension vector

Claims

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 pm and 250 pm, in particular between 150 pm and 200 pm.

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 pyrarnid 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 rnethod 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 mrn 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.