ADHESIVE LABEL

Description

[0001] 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.

[0002] Such adhesive laminates (adhesive labels) are used, for example, as labels, but also as adhesive tapes, particularly for logistics applications, but also for common label applications for decoration, marking and sealing.

[0003] Labels usually consist of a visible material with a print and an adhesive layer.

[0004] 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 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.

[0005] 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.

[0006] 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.

[0007] For some time now, there has been a desire for activatable adhesive labels for labeling applications or as adhesive tapes that operate as so-called "linerless systems," meaning 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.

[0008] For example, EP 2 924 088 A1 describes 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.

[0009] Furthermore, water-soluble layers in adhesive structures are known, for example, from DE 92 18 531 U1. A label is known from 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.

[0010] The setting of desired adhesive forces, in particular rapid initial adhesion, but also permanent adhesion, therefore remains a goal.

[0011] 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.

[0012] 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.

[0013] 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; possibly increasing the rigidity of the material; reducing water sensitivity, especially when bonded; further functionalities can be provided, such as magnetic properties, color, etc.; for cost reduction by using a layer with lower material or production costs.

[0014] 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.

[0015] 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.

[0016] Preferably, the visible material is provided directly adjacent to the second middle layer, if such a layer is provided, without any additional non-pressure-adhesive or pressure-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.

[0017] 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.

[0018] 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 the liquid or vapor state. This means that the adhesive layer is non-sticky in the dry state, in particular, it is not pressure-sensitive, and can be activated by adding water or steam, or alternatively, another fluid in the liquid or vapor 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.

[0019] 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.

[0020] 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.

[0021] Room temperature should be understood as 23°C and, under room conditions, preferably a relative humidity of 50%.

[0022] 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.

[0023] In addition, the adhesive layer may contain additives such as colloids or other additives such as surfactants, cross-linking agents or the like.

[0024] To determine the "pressure-sensitive adhesive" criterion for the first and / or second middle layer, the Dahlquist criterion should be used. This means that layers are considered pressure-sensitive adhesive if the pressure is below 3 x 10 5 Pa and non-pressure-sensitive if the pressure is above this value. Room temperature (23°C) and a strain rate of 1 Hz should be used to determine the Dahlquist criterion. The Dahlquist criterion is derived from: "Dillard DA et al., Adhesion Science and Engineering: Surfaces, Chemistry and Applications, Elsevier Science BV, first edition 2002" (ISBN: 0444511407).

[0025] 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.

[0026] 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.

[0027] 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 provide a better bond between the adhesive layer and the substrate to be bonded.

[0028] The first middle layer is preferably between 1 - 30 µm, in particular 1 - 20 µm and in particular 4 - 8 µm thick.

[0029] It is therefore particularly preferred, particularly from an adhesive technology point of view, 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".

[0030] 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.

[0031] 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).

[0032] As materials for the non-adhesive first middle layer, (poly)acrylates, polyurethanes, ethylene vinyl acetates, polyvinyl acetates in "pure" form or materials post-crosslinked via suitable crosslinkers can preferably be used.

[0033] Suitable pressure-sensitive adhesives for the second middle layer are preferably room-temperature pressure-sensitive adhesive systems, such as radically polymerized polymers, polyesters, or polyadducts, particularly preferably polymers obtainable by emission polymerization. Typical polymer compositions for acrylate dispersions are known, for example, from DE 2 459 160 A1, EP 0 625 557 B1, and EP 0 952 199, the disclosures of which are incorporated into the present invention.

[0034] 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, especially pressure-sensitive adhesives (PSAs), can also be used.

[0035] In addition, silicone-based or polyurethane-based pressure-sensitive adhesive systems can also be used.

[0036] In addition to the pressure-sensitive adhesive polymer, the second middle layer may contain other additives, particularly 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.

[0037] 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.

[0038] According to the invention, it is further provided that the activatable adhesive label can be manufactured 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), wherein the cutting to the desired size preferably takes place immediately before application to a substrate. In addition to such roll-form manufacturing, stack-form manufacturing is also possible. This involves punching or cutting, for example, to the final size of the labels to be used, or cutting the roll-form web material, whereby the activatable adhesive label can then be stored in stacks without additional intermediate layers for further processing.

[0039] Preferably, no adhesive-repellent treatment, e.g., silicone, is planned or necessary for the visible material. This can expand the range of possible visible materials and, for example, improve printability.

[0040] 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.

[0041] It is also conceivable to color one or both middle layers for optical reasons.

[0042] The activatable adhesive label is obtainable through a coating process in which the first and / or second middle layer and the adhesive layer are present and coated as an aqueous dispersion, solution, melt, or 100% liquid system. The coating of one or both middle layers and the adhesive layer is preferably carried out in a single operation.

[0043] A multiple cascade die can be used for this purpose. A suitable coating process is previously known, for example, from US Pat. No. 3,508,947, which 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 die. 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.

[0044] 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 an overall film is formed from the individual films to be coated. In this overall film, the individual films are arranged spatially as desired later in the multilayer laminate (adhesive label). The overall film is applied from the multiple cascade nozzle to the moving web-like carrier. The process is preferably a slide coating process. During slide coating, the overall film slides over a surface, e.g., a metal surface (sliding), and is then deposited onto the substrate.

[0045] 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.

[0046] 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.

[0047] Alternatively, the coating consisting of the first and / or second middle layer and the adhesive layer can be applied in several steps, e.g., one after the other. However, application in a single step is preferred.

[0048] The multi-layer adhesive laminate (activatable adhesive label) is suitable as a label or label cut, adhesive film or adhesive tape.

[0049] The overall structure of the adhesive label preferably has a thickness of 20 □m to 350 □m, preferably of 30 □m to 170 □m.

[0050] An exemplary preferred structure is shown below.

[0051] Visible material: Standard Vellum paper 70g / m 2< First middle layer: 10 gsm Encor 3130 (Arkema) Adhesive layer: 7 gsm Eukalin 7427GG (Eukalin)

[0052] An alternative embodiment is shown below: Visible material: Standard Vellum paper 70g / m 2< Second middle layer: V215 (BASF SE) 6g / m 2< First middle layer: 10 gsm Encor 3130 (Arkema) Adhesive layer: 7gsm Eukalin 7427GG (Eukalin)

[0053] Such activatable adhesive labels are preferably 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

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.