EP3748613B1 - Adhesive label - Google Patents

Description

The present invention relates to an activatable adhesive label comprising a web-shaped visible material, wherein at least one adhesive layer made of a moisture-activated adhesive which is non-tacky in the dry state is applied to one side of the flexible visible material.

Such adhesive laminates (adhesive labels) are used, for example, as labels, but also as adhesive tapes, especially for logistics applications, but also for common Label applications used for decoration, marking and sealing.

Labels usually consist of a visible material with a print and an adhesive layer.

Many of these labels also feature a removable layer (e.g., a siliconized liner) that covers the adhesive layer on the side facing away from the visible material. This additional layer serves to prevent the labels, for example, in roll form, from sticking to the nearest layer of the visible material. The disadvantage here is that the additional layer requires an additional layer of material, and this layer must be disposed of after being removed from the adhesive layer. This additional layer poses additional problems and demands on production, particularly when automated labeling is planned.

Furthermore, there are labels in the prior art that have a release coating on the side of the visible material facing away from the adhesive layer, which prevents the adhesive layer from bonding to the visible material. This increases costs and, moreover, prevents such materials from being freely printed.

Furthermore, these systems, which provide a release coating on the side of the visible material opposite the adhesive layer, are more difficult to process due to the permanent stickiness of the adhesive layer.

For this reason, there has long been a desire for activatable adhesive labels for labeling applications or as adhesive tapes that operate as so-called "linerless systems," i.e., they do not require a release layer on the adhesive layer or a release coating on the side of the visible material opposite the adhesive layer. Such systems are known, for example, from postage stamps, etc., and feature an adhesive layer that can be activated. Possible activation agents include moisture, but also radiation or heat.

For example, the EP 2 924 088 A1 a so-called "liner-free" or "linerless" label and an adhesive composition for use therewith, wherein two different hydrophilic polymer materials are present in the adhesive composition, one of which provides rapid initial adhesion upon activation with a fluid when it comes into contact with the activation fluid, and the second, more hydrophobic polymer component then provides the final adhesion.

Furthermore, for example, from the DE 92 18 531 U1 water-soluble layers known in adhesive structures. A label is from the DE 10 2017 109 074 A1 which describes a pressure-sensitive adhesive middle layer. Other relevant prior art documents are DE 697 22 043 T2 and EP 3 444 796 A1 .

The adjustment of desired adhesive forces, in particular rapid initial adhesion, but also permanent adhesion, therefore remains a goal.

It is therefore an object of the invention to provide an alternative activatable adhesive label which is non-adhesive in the dry state, but can be converted into an adhesive state by the action of a fluid, in which good adhesion between the visible material and the adhesive layer is ensured even in the wet state and in which rapid initial adhesion/tack adhesion can be provided.

The invention solves this problem by means of an activatable adhesive label having the features of claim 1, in which at least one middle layer is provided between the visible material and the adhesive layer, which middle layer is non-pressure-adhesive and not water-soluble or swellable. Further preferred embodiments are set forth in the subclaims.

• Trennung der haftklebenden von der aktivierbaren Schicht, wobei hierdurch u.a. eine Migration zwischen den Schichten verhindert odervermindert wird;
  • gegebenenfalls Erhöhung der Steifigkeit des Materials;
  • Verminderung der Wasserempfindlichkeit v.a. im aufgeklebten Zustand;
• weitere Funktionalitäten können vorgesehen sein, wie z.B. magnetische Eigenschaften, Farbe, etc;
• zur Kostenreduktion, indem eine Schicht mit geringeren Material- oder Produktionskosten eingesetzt wird.

This first middle class fulfils, among other things, the following functions:

• Separation of the pressure-sensitive adhesive layer from the activatable layer, thereby preventing or reducing migration between the layers;
  • if necessary, increase the stiffness of the material;
  • Reduction of water sensitivity, especially when glued on;
• further functionalities can be provided, such as magnetic properties, color, etc.;
• to reduce costs by using a layer with lower material or production costs.

Furthermore, a second middle layer is provided, which is pressure-sensitively adhesive, preferably at room temperature. This layer serves to improve the initial adhesion, i.e., the initial bond between a substrate and the adhesive label, while simultaneously improving the final adhesion through a dissipative component.

In addition, the first and/or second middle layer reduce the risk of separation between the adhesive layer and the visible material, especially when glued or applied.

Preferably, the visible material is provided directly adjacent to the second middle layer, if such a layer is provided, without any additional non-pressure-sensitive adhesive or pressure-sensitive adhesive layers being provided in between. The first middle layer is preferably directly adjacent to the adhesive layer. In particular, it is a three-layer adhesive structure and a visible material is preferably connected thereto.

It is particularly preferred if the visible material consists of a paper material or a film material. The visible material can in particular also consist of multi-layer paper or film materials, in particular paper or film laminates. Polyethylene, polypropylene or PET films are particularly suitable as film materials. The thickness of the film can preferably be 5 to 250 µm, preferably 10 to 200 µm and more preferably 15 to 180 µm. The films are in particular films that can be printed using conventional printing processes. Paper can also be used as the visible material, whereby if paper is used, the thickness of the visible material layer is preferably 5 to 250 µm, preferably 15 to 200 µm and more preferably 40 to 100 µm. The papers are in particular papers that can be printed using conventional processes.

Particularly suitable as an adhesive layer are materials that contain an adhesive (adhesive system) or an adhesive that can be activated to an adhesive state by exposure to moisture or water, i.e., water in a liquid or vaporous state. This means that the adhesive layer is non-sticky when dry, in particular not pressure-sensitive, and can be activated by adding water or steam, or alternatively, another fluid in a liquid or vaporous state, so that the adhesive layer is converted to an adhesive state. After evaporation of the fluid, the adhesive layer is then non-sticky again. The layer is not water-soluble.

The fluid can optionally be tempered to achieve a faster reaction time and thus faster processing of the activatable adhesive label, i.e., adhesion to a substrate. The layer is preferably film-forming, but not pressure-sensitive.

The thickness of the adhesive layer can preferably be 1 to 50 µm, more preferably 3 to 20 µm, and even more preferably 5 to 15 µm. The non-adhesive properties in the dry state are preferably present at room temperature.

Room temperature should be understood as 23°C and, under room conditions, preferably a relative humidity of 50%.

The adhesive for the adhesive layer can preferably be selected from the group of polyvinyl acetates, ethylene vinyl acetates, glutin and starch derivatives (dextrin), polyvinyl alcohols and combinations thereof.

In addition, the adhesive layer may contain additives such as colloids or other additives such as surfactants, crosslinking agents or the like.

To determine the "pressure-sensitive adhesive" criterion for the first and/or second middle layer, the Dahlquist criterion shall be used. This means that layers are considered pressure-sensitive adhesive if the pressure is below 3 x 10 ⁵ Pa and above this value are considered non-adhesive. For the determination of the Dahlquist criterion, room temperature (23°C) and a deformation rate of 1 Hz should be used. The Dahlquist criterion is calculated as follows: " Dillard DA et al, Adhesion Science and Engineering: Surfaces, Chemistry and Applications, Elsevier Science BV, first edition 2002" (ISBN: 0444511407 ).

If reference is made to a pressure-sensitive adhesive middle layer made of an adhesive, this also includes designs in which the pressure-sensitive adhesive middle layer does not consist 100% of adhesive and also designs in which the pressure-sensitive adhesive middle layer comprises several adhesives, whereby the middle layer as such is intended to have adhesive, in particular pressure-sensitive adhesive, properties.

The second middle layer is pressure-sensitive adhesive according to the Dahlquist criterion, whereas the first middle layer is not pressure-sensitive adhesive according to this criterion.

The second middle layer can preferably be a layer with a thickness between 1 and 30 µm, preferably between 2 and 20 µm, and more preferably between 4 and 15 µm. The second middle layer also serves to improve the rheological properties of the activatable adhesive label and to provide a better bond between the adhesive layer and the substrate to be adhered.

The first middle layer is preferably between 1 - 30 µm, in particular 1 - 20 µm and in particular 4 - 8 µm thick.

It is therefore particularly preferred, particularly from an adhesive technology perspective, if the glass transition temperature Tg of the first and/or second middle layer is below the application temperature, in particular in the range < 0° C, preferably < -5° C and more preferably < -10° C, with the lower limit being -100° C, preferably -80° C and more preferably -65° C, so that a preferred application range of the glass transition temperature is between -10 and -65° C. The glass transition temperature of the polymers of the middle layer can be determined using conventional methods, such as differential thermal analysis or differential scanning calorimetry, e.g. according to ASTM 3418/82, so-called "midpoint temperature".

The glass transition temperature provides an indication of the deformability and thus of the ability and speed with which the contact surface between the layers can be formed and thus provides information about the tack (initial adhesion) and the final adhesion.

The measurable adhesion to the touch is >1 N, whereby the measurement was carried out with 15 g/m ² dry application on polyester film with a thickness of 30 µm according to FTM 9 (FINAT Technical Handbook 9th Edition).

As materials for the non-adhesive first middle layer, (poly)acrylates, Polyurethanes, ethylene vinyl acetates, polyvinyl acetates in "pure" form or materials crosslinked with suitable crosslinkers can be used.

As pressure-sensitive adhesives for the second middle layer, preferably room-temperature pressure-sensitive adhesive systems, such as radically polymerized polymers, polyesters or polyadducts, are considered, particularly preferably polymers obtainable by emission polymerization. Typical polymer compositions for acrylate dispersions are, for example, from the DE 2 459 160 A1 , EP 0 625 557 B1 as well as EP 0 952 199 known, the disclosure of which is made the subject of the present invention.

Natural or synthetic rubber systems can also be used. Pressure-sensitive adhesive systems, whose properties can be adjusted through photochemical crosslinking, e.g., by irradiation with electron beams or UV light, are also possible. ^AcRESIN® from BASF AG, Ludwigshafen, Germany, or Loctite Durotak from Henkel KGaA, Düsseldorf, Germany, are particularly preferred. Other adhesives, particularly pressure-sensitive adhesives (PSAs), can also be used.

In addition, silicone-based or polyurethane-based pressure-sensitive adhesive systems can also be used.

The second middle layer can contain additional additives in addition to the pressure-sensitive adhesive polymer, whereby These include, in particular, tackifying resins (so-called tackifiers) and reactive components, such as external crosslinkers. However, the second middle layer particularly preferably consists exclusively of one or more pressure-sensitive adhesive polymers, although several pressure-sensitive adhesive polymers can also be used in combination.

In principle, it is also conceivable to configure the first and/or second middle layer in multiple layers. In this case, preferably all layers of the first middle layer are non-pressure-sensitive adhesive, while the second middle layer is pressure-sensitive adhesive. Furthermore, the remaining layers, such as in particular the moisture-activated adhesive layer, particularly for reasons of functionality or coatability, and/or also the visible material, can also be configured in multiple layers. The structure is preferably four-layered with visible material, first and second middle layers, and adhesive layer, whereby the individual layers can be single- or multi-layered. Preferably, no further layers are provided between the visible material and the adhesive layer, apart from the first or the two (first and second) middle layers.

According to the invention, it is further provided that the activatable adhesive label can be produced in roll form as a linerless laminate. It can then be used as a type of adhesive tape or as a label in smaller units (label blanks), with the production to the desired size preferably only immediately before application to a substrate. In addition to such roll-based packaging, stack-based packaging is also possible. This involves punching or cutting, for example, to the final size of the labels to be used, or cutting the roll-based web material. The activatable adhesive label can then be stored in a stack without additional intermediate layers for further processing.

Preferably, no adhesive-repellent treatment, e.g., with silicone, is planned or necessary for the visible material. This can expand the range of possible visible materials and, for example, improve printability.

Furthermore, it is particularly preferred that the adhesive layer be colored. This ensures that, upon application and activation, a portion of the dyes penetrates the substrate to be bonded and discolors it. In the event of a subsequent attempt at tampering by removing the adhesive label, either the substrate is destroyed or the discoloration of the bonded substrate becomes visible, revealing that a label or adhesive tape according to the invention was already applied at that location.

It is also possible to color one or both middle layers for optical reasons.

The activatable adhesive label is available through a coating process in which the first and/or the second middle layer and the adhesive layer are present and coated as an aqueous dispersion, solution, melt, or liquid 100% system. The coating of one or both middle layers and the adhesive layer is preferably carried out in a single operation.

A multiple cascade nozzle can be used for this purpose. A suitable coating process is described, for example, in US$3,508,947 previously known, which in this respect is incorporated into the subject matter of the present invention. The multilayer laminate (activatable adhesive label) is preferably produced by a process in which the at least two flowable compositions are continuously coated onto a web-shaped substrate, preferably the visible material. The coating is carried out using a multiple cascade nozzle. The coating speed is preferably 30 to 1500 m/min, more preferably 150 to 1200 m/min, and most preferably 300 to 1000 m/min.

The material layer for the first and/or second middle layer and the adhesive layer are fed separately as a liquid film into the coating device. A key feature of the multiple cascade nozzle is that a single film is formed from the individual films to be coated. In this single film, the individual films are arranged in the spatial arrangement required later in the multilayer laminate (adhesive label). The single film is then applied by the multiple cascade nozzle to the The film is applied to a moving web-like carrier. The process is preferably a slide-coating process. During slide-coating, the entire film slides over a surface, e.g., a metal surface, and is then deposited onto the substrate.

In contrast, in a slot coating process the entire film is applied directly from a slot or nozzle onto the substrate, i.e. without sliding.

Particularly preferred is a curtain coating process. In the curtain coating process, a freely falling film curtain is deposited on the substrate. To ensure that the film curtain can fall freely, the distance between the nozzle or other outlet opening and the moving substrate must be greater than the layer thickness to be coated. Particularly preferred is a slide coating process combined with a curtain coating process.

Alternatively, the coating consisting of the first and/or second middle layer and the adhesive layer can also be applied in several steps, e.g., one after the other. However, application in a single step is preferred.

The multi-layer adhesive laminate (activatable adhesive label) is suitable as a label or label cut, adhesive film or adhesive tape.

The overall structure of the adhesive label preferably has a thickness of 20 □m to 350 □m, preferably of 30 □m to 170 □m.

An exemplary preferred structure is shown below.

Visible material: Standard Vellum paper 70g/m ² First middle layer: 10 gsm Encor 3130 (Arkema) Adhesive layer: 7gsm Eukalin 7427GG (Eukalin)

• Sichtmaterial: Standard Vellum Papier 70g/m²
• Zweite Mittelschicht: V215 (BASF SE) 6g/m²
• Erste Mittelschicht: 10 gsm Encor 3130 (Firma Arkema)
• Haftschicht: 7gsm Eukalin 7427GG (Firma Eukalin)

An alternative embodiment is shown below:

• Visual material: Standard Vellum paper 70g/ ^m2
• Second middle layer: V215 (BASF SE) 6g/m ²
• First middle class: 10 gsm Encor 3130 (Arkema)
• Adhesive layer: 7gsm Eukalin 7427GG (Eukalin company)

Such activatable adhesive labels are primarily used as logistics labels or adhesive tapes, as well as for typical label or adhesive tape applications for decoration, marking, or sealing. In particular, they can serve as a replacement for pre-assembled wet-glue applications, e.g., for bottles, cans, or other containers where the labels are pre-assembled into a label stack.

Claims (17)

1. An activatable adhesive label comprising a flexible sheet-like visible material, wherein at least one adhesive layer made of a moisture-activatable adhesive which is not sticky when dry is applied to one side of the flexible visible material, wherein at least a first middle layer is provided, which comprises adhesives which are not adhesive at room temperature and is not adhesive and not water-soluble or water-swellable and is arranged between the visible material and the moisture-activatable adhesive layer, and that a second middle layer is provided, which is adhesive, in particular is adhesive at room temperature.
2. The activatable adhesive label according to claim 1, characterized in that the second middle layer is arranged between the visible material and the first middle layer.
3. The activatable adhesive label according to either of the preceding claims, characterized in that the visible material comprises a film or paper and is in particular designed to be printable.
4. The activatable adhesive label according to any of the preceding claims, characterized in that the visible material has a thickness of 5 - 250 µm, preferably 15 - 200 µm, preferably 40 - 100 µm, for paper and 5 - 250 µm, preferably 10 - 200 µm, and preferably 15 - 180 µm, for film.
5. The activatable adhesive label according to any of the preceding claims, characterized in that the first middle layer is not adhesive at room temperature.
6. The activatable adhesive label according to any of the preceding claims, characterized in that the first middle layer has a thickness of 1 - 15 µm, preferably 2 - 10 µm, preferably 4 - 8 µm.
7. The activatable adhesive label according to any of the preceding claims, characterized in that the second middle layer has a thickness of 1 - 30 µm, preferably 2 - 20 µm, and in particular 4 - 15 µm.
8. The activatable adhesive label according to any of the preceding claims, characterized in that the adhesive layer has a thickness of 1 - 50 µm, preferably 3 - 20 µm, preferably 5 - 15 µm.
9. The activatable adhesive label according to any of the preceding claims, characterized in that the adhesive of the adhesive layer is activatable by means of water or steam.
10. The activatable adhesive label according to any of the preceding claims, characterized in that the adhesive of the adhesive layer is not water-soluble but film-forming.
11. The activatable adhesive label according to any of the preceding claims, characterized in that the side of the visible material opposite the middle layer is not equipped to be adhesive-repellent.
12. The activatable adhesive label according to any of the preceding claims, characterized in that the activatable adhesive label can be manufactured as a linerless adhesive label, in particular in roll form or as a stack of label cutouts or label blanks.
13. The activatable adhesive label according to any of the preceding claims, characterized in that the adhesive layer and/or the first and/or second middle layer is colored.
14. The activatable adhesive label according to any of the preceding claims, characterized in that the activatable adhesive label can be produced by coating the first and/or second middle layer and the adhesive layer onto the visible material in one method step using a multiple cascade nozzle.
15. The activatable adhesive label according to any of the preceding claims, characterized in that the activatable adhesive label can be applied to the visible material by coating the first and/or second middle layer and the adhesive layer in a curtain coating method.
16. A label blank made from an activatable adhesive label according to any of the preceding claims.
17. A use of an activatable adhesive label according to any of claims 1-15 as a label blank, adhesive tape or adhesive film.