EP3748612A1 - Adhesive label - Google Patents

Abstract

The invention relates to an adhesive label comprising a flexible sheet-like visible material, with at least one adhesive layer made of a water-soluble adhesive being applied to one side of the flexible visible material, in which at least one first middle layer is provided, which is not pressure-sensitive, is not water-soluble or water-swellable and is between the visible material and the water-soluble adhesive layer is arranged as well as a second middle layer, which is provided between the first middle layer and the visible material, which is designed to be pressure-sensitive.

Description

The present invention relates to an adhesive label comprising a sheet-like visible material, with at least one adhesive layer made of a water-soluble adhesive being applied to one side of the flexible visible material.

Adhesive laminates (adhesive labels) are used, for example, as labels, but also as adhesive tapes, in particular for logistics applications, but also for common label applications for decorating, identifying and closing.

Labels usually consist of a visible material that is provided with a print and an adhesive layer (adhesive layer).

A large number of designs for labels are known in the prior art. In the food sector in particular, there is also interest in removable labels, provided that the containers and receptacles on which the labels are applied are designed to be reusable. This applies e.g. B. for reusable glass containers such as bottles and glasses, but also for plastic containers that are to be temporarily provided with an adhesive label, which should then be peeled off again without leaving any residue, in order to enable the container to be reused hygienically.

Something similar is, for example, from EP 2 094 799 B1 known, wherein a pressure-sensitive adhesive composition based on acrylic emulsion is described and wherein the composition is removable after adding an aqueous basic solution at a temperature of at least 50 °. The EP 2 094 799 also describes multi-layer designs that make it easier to remove by designing the visible material accordingly.

It also describes the EP 1 242 555 B1 a water-soluble adhesive and appropriate labels.

It is therefore the object of the invention to provide an alternative adhesive label with a water-soluble adhesive layer which has good adhesive properties and good, residue-free detachment properties.

The invention solves this problem by an adhesive label with the features of claim 1. Further preferred embodiments are set out in the subclaims.

In this case, at least one first middle layer, which is not designed to be pressure-sensitive adhesive, is provided between the visible material and the adhesive layer.

• Trennung der Schichten zur Verminderung/Verhinderung der Migration zwischen den Schichten
• Einstellung der Wasserempfindlichkeit. So muss eine Eiswasserbeständigkeit des Etiketts gegeben sein, um üblichen Verwendungen Stand zu halten und auf der anderen Seite muss der Abwaschprozess zum Ablösen der Etiketten möglichst gut erfolgen können.
• Nach einem evtl. Entfernen der fühlbaren Schicht ist das Etikett dann klebefrei

This first middle class fulfills the following functions

• Separation of layers to reduce / prevent migration between layers
• Adjustment of water sensitivity. The label must be resistant to ice water in order to withstand normal uses and, on the other hand, it must be possible for the label to be washed off as effectively as possible.
• After removing the tactile layer, the label is then tack-free

The first middle layer is not water-soluble or swellable.

It is also provided that a second middle layer is provided, which is designed to be pressure-sensitive and is provided between the visible material and the first middle layer is. This is preferably pressure-sensitive adhesive at room temperature. This layer serves to improve the grip adhesion, that is to say the first adhesion between a substrate and the adhesive label, and at the same time the final adhesion is also improved by a dissipative component.

In addition, the first and / or second middle layer reduce the risk of the adhesive layer and the visible material separating, in particular in the affixed or applied state and especially in the "state" of being washed off.

The visible material is preferably provided directly adjacent to the second middle layer without further 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 preferably connected to it.

Such removable label structures enable the thickness of the water-soluble pressure-sensitive adhesive layer to be reduced. When the labels are peeled off, less dissolved adhesive is transferred into the washing solution so that it can be used better. In addition, the residual tack after detachment can be positively influenced, i.e. reduced, so that air separation processes can be better used for separation. The separation takes place after the washing process, whereby the packaging or the products on which the labels are applied are crushed into so-called flakes for processing. Light parts (e.g. label residue) are separated from the heavier flakes via an air stream.

In comparison to a removable label, the pressure-sensitive adhesive layer of which is not water-soluble, water-soluble (removable) is to be understood as meaning that the adhesive force is greatly reduced or no longer present after removal, in particular the pressure-sensitive adhesive layer is no longer present or only partially or partially present. I.e. the label cannot be re-attached over the water-soluble adhesive layer. By contrast, non-water-soluble, detachable pressure-sensitive adhesive layers are understood to mean those which enable repeated gluing and can be removed without destruction. Labels that cannot be peeled off non-destructively are permanently adhesive.

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 multilayer paper or film materials, in particular paper or film laminates. In particular, polyethylene, polypropylene or PET films are suitable as film material. 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 foils are in particular foils that can be printed on using conventional printing processes. As visible material still comes Paper in question, the thickness of the visible material layer being preferably 5 to 250 μm, preferably 15 to 200 μm and more preferably 40 to 100 μm in the case of using paper. The papers are also, in particular, papers that can be printed using conventional methods.

Particularly suitable as the adhesive layer are materials which contain an adhesive (adhesive system) or an adhesive that is exposed to moisture or water, i.e. Water in the liquid or vapor state, is soluble. “Water-soluble” is to be understood here as meaning that the adhesive is dissolved or the adhesion is reduced, preferably when water or steam is ingress at a temperature greater than 50 ° C. This should result in a loss of liability of at least 25%, in particular at least 40%, in particular at least 50% and in particular at least 60% of the original liability.

According to a first exemplary embodiment, the water solubility should occur as described above and additionally an addition of more than 1% sodium hydroxide solution and a temperature of greater than 50 ° C. to the water or water vapor.

The following test is used to determine the adhesive forces: 180 ° peel test = FTM1 FINAT manual 9.

output

This solubility in water and the reduction in adhesion make the adhesive label particularly easy to detach easy to implement. Known pressure-sensitive adhesive systems come into consideration as possible pressure-sensitive adhesives. The following test should be used as a basis for the question of detachability:

Test method - adhesives / labels on PET trays

Ver. 1.4 - 2017.09.01.01

Sample size:

• 20 PET trays of small thickness;
• 20 thick PET trays

Method:

1. 1. All dishes must be washed in cold water to remove silicone residue.
2. 2. The labels to be tested must be affixed to a flat, flat surface of the tray, preferably on the underside.
3. 3. After 24 hours, at least 50 10x10mm samples must be taken from each marked area of the tray.
4. 4. 10x10 mm samples must be washed in a 1% sodium hydroxide solution at 70 ° C (**) and without additives with a 4 cm magnetic stirrer at 500 rpm for 6.5 minutes; Cup size 1000 ml with an inner diameter of 9.5 cm; The ratio between caustic soda and flakes should be 4: 1 (i.e. 200 ml: 50 flakes).
5. 5. Flake Priben must then be rinsed in cold water for 3 minutes.
6. 6. Flake samples must be dried at 80 ° C for 2 hours will.

Final calculation:

After the drying step, the samples are visually inspected to see how many samples have had the label removed and how many have not. The result is displayed in%.

• (*): Waschen, Spülen, Trocknen und Ofentests müssen separat für verschiedene Probendicken durchgeführt werden;
• (**): Das Temperaturniveau wird - im Vergleich zum Recycling von PET-Flaschen - gesenkt, um spröde Effekte zu vermeiden.

An oven test will be carried out to provide evidence of residues. Half of the washed and rinsed flakes are placed in an oven at 220 ° C for one hour; a high resolution image is then taken showing on the same frame the flakes that have just been washed and rinsed compared to those that have also been heated by the oven. The image is always displayed together with the above result in%.

• (*): Washing, rinsing, drying and oven tests must be carried out separately for different sample thicknesses;
• (**): The temperature level is lowered - compared to the recycling of PET bottles - in order to avoid brittle effects.

The thickness of the adhesive layer can preferably be 1 to 50 μm, more preferably 3 to 20 μm and more preferably 5 to 15 μm.

The adhesive for the adhesive layer can preferably be selected from the group consisting of acrylates, ethylene vinyl acetates, polyurethanes, Polyvinyl alcohols and combinations thereof can be selected.

In addition, the adhesive layer can contain additives such as colloids or other additives such as e.g. contain surface-active substances, as well as crosslinking agents, rheological additives, hydrophilicizing or water repellent agents or the like.

The Dahlquist criterion should be used to determine the “pressure-sensitive adhesive” criterion for the first and / or second middle layer. In other words, layers are regarded as pressure-sensitive adhesive at a value below 3 × 10 ⁵ Pa and non-pressure-sensitive adhesive above this value. To determine the Dahlquist criterion, room temperature (23 ° C) and a deformation rate of 1 Hz should be used. The Dahlquist criterion results from): " Dillard DA et al, Adhesion Science and Engineering: Surfaces, Chemistry and Applications, Elsevier Science BV, first edition 2002 "(ISBN: 0444511407 ).

In the context of the invention, room temperature should be understood to mean 23 ° C. and, under room conditions, preferably a relative humidity of 50%.

If one speaks of 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 of 100% adhesive and also designs in which the pressure-sensitive adhesive middle layer comprises several adhesives, the middle layer as such should have adhesive properties.

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

A layer which is between 1 and 30 μm, preferably between 2 and 20 μm and more preferably between 4 and 15 μm thick can preferably be used as the second middle layer. The second middle layer also serves to improve the rheological properties of the activatable adhesive label and to provide a better connection between the adhesive layer and a substrate to be glued.

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

It is therefore particularly preferred 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, 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 between -10 and -65 ° C results. The glass transition temperature of the polymers of the middle layer can be determined by the usual methods, such as Differential thermal analysis or differential scanning calometry, for example according to ASTM 3418/82, so-called “midpoint temperature”, can be determined.

The glass transition temperature gives an indication of the deformability and thus of the extent and speed of enlarging the contact area and thus makes a statement about the tack (grip) and the final adhesion.

Polyurethanes, acrylates, in particular non-crosslinked acrylates or EVA can be preferred materials of the non-pressure-sensitive adhesive first middle layer.

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

In addition, natural or synthetic rubber systems can also be used. Furthermore, pressure-sensitive adhesive systems whose properties can be adjusted by photochemical crosslinking, for example by irradiation with electron beams or UV light. In particular, acRESIN® from BASF, Ludwigshafen, Germany, or Loctite Durotak from Henkel KGaA, Düsseldorf, Germany, should be mentioned as preferred. In addition, other adhesives, in particular Pressure Sensitive Adhesives (PSA), can also be used.

In addition, silicone-based or polyurethane-based pressure-sensitive adhesive systems can also be used for the second middle layer.

In addition to the pressure-sensitive adhesive polymer, the second middle layer can contain further additives, particularly tackifying resins (so-called tackifiers) and reactive components, such as external crosslinkers. Particularly preferably, however, the second middle layer consists exclusively of one or more pressure-sensitive adhesive polymers, it also being possible to use a number of pressure-sensitive adhesive polymers in combination.

For optical reasons, coloring one or both middle layers is also conceivable.

The adhesive label can be obtained by 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 liquid 100% system. One or both middle layers and the adhesive layer are preferably coated in one operation.

A multiple cascade nozzle can be used for this. A coating method suitable for this is, for example, from U.S. 3,508,947 previously known, which in this respect is made the subject of the present invention. The multi-layer laminate (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 a transfer layer, eg a liner, but also alternatively the visible material. The so-called transfer process is preferred. The coating is carried out using a multiple cascade nozzle. The coating speed is preferably 30 to 1500 m / min, particularly preferably 150 to 1200 m / min and very particularly 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. An essential 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 in the spatial arrangement as they are later desired in the multilayer laminate (adhesive label). The entire film is fed from the multiple cascade nozzle onto the moving web-shaped carrier. The method is preferably a slide coating method. With slide coating, the entire film slides over a surface, e.g. a metal surface (sliding) and is then placed on the substrate.

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

It is also particularly preferably a curtain coating process. In the curtain coating process, a free falling film curtain is placed on the substrate. In order for the film curtain to 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. It is particularly preferably a slide coating process in combination with a curtain coating process. A transfer layer or, alternatively, the visible material can again be used as the substrate.

Alternatively, the coating can consist of the first and / or second middle layer and adhesive layer, but also in several operations, e.g. so one after the other. However, application in one operation is preferred.

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

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

An exemplary preferred structure is shown below. Visible material: Standard vellum paper 70g / m ² Second middle class: Pressure sensitive adhesive e.g. V215 (BASF SE) 6g / m ² First middle class: Non-adhesive middle layer, for example Tubicoat E4 (CHT Germany GmbH) 6g / m ² Adhesive layer: Washable pressure sensitive adhesive e.g. Fulltak SE8301 (HB Fuller) 6g / ²

Such activatable adhesive labels are preferably used in the food industry and as typical labels or adhesive tape applications for decorating, identifying or closing. In particular, they are used in reusable or recyclable containers.

Claims (15)

Adhesive label comprising a flexible sheet-like visible material, with at least one adhesive layer of a water-soluble adhesive being applied to one side of the flexible visible material, characterized in that at least one first middle layer is provided, which is not pressure-sensitive, is not water-soluble or water-swellable and is formed between the visible material and the water-soluble adhesive layer is arranged, as well as a second middle layer which is provided between the first middle layer and the visible material, which is designed to be pressure-sensitive. Adhesive label according to claim 1, characterized in that the adhesive of the second middle layer is not water-soluble and in particular not water-swellable or its adhesion is reduced by a maximum of 25%, in particular by a maximum of 10% due to the ingress of water. Adhesive label according to Claim 1 or 2, characterized in that the visible material comprises a film or a paper and is in particular designed to be printable. Adhesive label according to claim 3, characterized in that the visible material in the case of paper has a thickness of 5 - 250 µm, preferably 15 - 200 µm, preferably 40 - 100 µm and, in the case of a film, 5-250 µm, preferably 10-200 µm and preferably 15-180 µm. Adhesive label according to one of the preceding claims, characterized in that the first middle layer comprises non-pressure-sensitive adhesives at room temperature, in particular is not pressure-sensitive adhesive at room temperature. Adhesive label according to one of the preceding claims, characterized in that the adhesive layer and the second middle layer are pressure-sensitive adhesive at room temperature. Adhesive label according to one 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. Adhesive label according to one of the preceding claims, characterized in that the second middle layer has a thickness of 1 to 30 µm, in particular 2 to 20 µm and in particular 4 to 15 µm. Adhesive label according to one of the preceding claims, characterized in that the adhesive layer has a thickness of 1 to 50 µm, preferably 3 to 20 µm, preferably 4 to 15 µm. Adhesive label according to one of the preceding claims, characterized in that the adhesive is the Adhesive layer by means of water or steam at a temperature> 50 ° C or at least by means of water or steam at a temperature> 50 ° C and addition of more than 1% NaOH based on the amount of water is soluble or at least its adhesion by at least 25%, in particular at least 40%, in particular at least 50% and in particular at least 60% is reduced. Adhesive label according to one of the preceding claims, characterized in that the adhesive layer and / or the first and / or second middle layer is colored. Adhesive label according to one of the preceding claims, characterized in that the adhesive label can be produced by coating the first and / or second middle layer and the adhesive layer on a web-shaped carrier, in particular on a transfer layer, in particular a liner, in one process step with a multiple cascade nozzle and subsequent connection with the visible material. Adhesive label according to one of the preceding claims, characterized in that the adhesive label can be applied by coating the first and / or second middle layer and the adhesive layer in a curtain coating process on a web-shaped carrier, in particular on a transfer layer, in particular a liner. Label blank from an adhesive label according to one of the preceding claims. Use of an adhesive label according to one of Claims 1-14 as a label blank, label sheet, adhesive tape or adhesive film.