Adhesive foil

Abstract

The present invention relates to an adhesive foil, in particular made of plastic, which comprises a coating with a lacquer film, characterized in that the lacquer film contains pigments whose average diameter is greater than the layer thickness of the lacquer film.

Description

[Technical field]

[0001] The present invention relates to an adhesive foil, in particular made of plastic, which comprises a coating with a lacquer film. [Background technology]

[0002] Plastics are materials that have a relatively low free surface energy and therefore a correspondingly low interfacial adhesion during adhesive bonding, coating or printing. This can lead to adhesive bond failures or weak sealing with the adhesive. This adhesion problem can also lead to the fact that the printed ink rubs off or the ink does not adhere to the surface.

[0003] For example, in the case of adhesive tapes or labels such as those used in the electronics industry, it must be ensured that the adhesive is removed from the substrate together with the adhesive tape, i.e. that no product-damaging adhesive residues are left behind on the substrate.

[0004] In the case of removable adhesives used in food freshness packaging, wet wipes, etc., it is sometimes necessary for the adhesive to remain on the substrate because its functionality would otherwise be impaired.

[0005] Furthermore, double-sided adhesive tapes which are used for permanent adhesive bonds, such as for adhesive bonding of parts in the automotive industry, must have such good adhesion that peeling is no longer possible.

[0006] However, standard foils cannot be used for the above applications, since they do not prevent adhesive transfer. However, good surface wettability alone does not result in good adhesion. It is therefore necessary to modify the foil surface. In order to be able to provide adhesive tapes and packaging materials with the required properties, for example the free surface energy of the foil is often increased by pretreatment. Common methods for plastic foils are plasma, corona or flame treatment and the effect of ozone or oxidizing gases such as fluorine.

[0007] Another method used in the prior art to modify the surface energy of foils is chemical treatment with trichloroacetic acid (TCA), in which the foil is etched with TCA, resulting in a molecular modification of the surface that has a beneficial effect on the adhesive properties.

[0008] For example, WO 2018 / 011237 A1 discloses a method for producing a single-sided adhesive foil, in which a support layer in the form of a polyester film (polyester terephthalate: PET) is treated, for example with trichloroacetic acid, in order to increase the surface energy of the polyester film before it is bonded to an adhesive layer.

[0009] However, treatment with TCA has the disadvantage that the PET foils become milky or matte when etched, which greatly impairs their appearance, and only untreated foils, i.e. those that do not have a pre-existing coating, e.g. with a metal, can be treated.

[0010] However, the major problem with TCA reforming is trichloroacetic acid itself, which is difficult to handle due to its highly corrosive properties and poses safety risks to workers and the environment.

[0011] Another common method for enhancing the adhesive properties of foils is coating them with an adhesion promoter, a so-called primer.

[0012] To solve the problem of poor adhesion of the metal layer to the foil, for example EP 3733749 A1 teaches applying an adhesion promoter layer between the foil and the metal layer, which consists of a self-crosslinking polymer and / or a polymer that can be crosslinked by a hardener, for example a water-based lacquer system based on polyurethane.

[0013] JP 2000053930A describes a primer layer for an adhesive tape made of polyethylene terephthalate (PET) foil, in which a primer layer made of a polyester-based resin is formed between a layer of urethane, acrylic or silicone-based adhesive and the PET foil.

[0014] JP 52-69942 A describes an adhesive tape in which improved adhesion is provided between a polyester carrier and a light-shielding coating layer by a primer layer, the primer being formed from a mixture of a vinylidene chloride copolymer and a polyurethane precondensate containing isocyanate groups. Summary of the Invention

[0015] The object of the present invention is to improve the properties of adhesive foils, especially made of plastics, without the need to subject the foil surface to costly modification such as etching with TCA or potentially harmful and environmentally hazardous treatments, and without the need to apply an adhesion promoter layer, especially with a suitable primer composition. In particular, it is possible to provide adhesive foils that have improved adhesion properties and achieve higher adhesion values, especially in the case of adhesive coatings, and thus do not undergo adhesive transfer, for example when the adhesive foil is used as an adhesive tape.

[0016] This object is achieved according to the invention by means of an adhesive foil of the kind mentioned at the outset by means of the features of the independent claim 1. Advantageous further developments of the invention are the subject matter of the dependent claims.

[0017] The subject of the invention is an adhesive foil, especially made of plastic, which comprises a coating with a lacquer film, characterized in that the lacquer film contains pigments whose average diameter is greater than the layer thickness of the lacquer film.

[0018] Preferably, the particles have a diameter in the range of 2.0 to 12 μm, in particular an average diameter of 4 to 6 μm.

[0019] The fact that the lacquer film is provided with pigments whose average diameter is larger than the layer thickness of the lacquer film results in an increase in the surface area of ​​the layer or foil in question, which in turn results in higher adhesion values.

[0020] According to a preferred embodiment, the proportion by weight of pigment in the lacquer film is between 1 and 50%, preferably between 10 and 30%, relative to the non-volatile fraction (nfA) of the binder of the lacquer.

[0021] The pigments which can be used according to the invention are preferably selected from inorganic or organic pigments, and among the inorganic pigments, earth, mineral, metallic effect pigments, white pigments, iron oxide pigments, zirconium silicates and polymeric pigments are particularly preferred.

[0022] In a particularly preferred embodiment of the invention, the pigment is a polyamide pigment, preferably PA66 or PA12.

[0023] According to another embodiment, the lacquer film coated on the adhesive foil is an adhesion promoter layer.

[0024] Adhesion promoters, also called primers, are agents that improve the adhesive properties of a surface. Adhesion promoters are used to increase the adhesive strength of the material to which they are applied, whether for heavily loaded or difficult to adhere surfaces and coatings. Increasing adhesive strength often also increases water and chemical resistance as well as corrosion protection. Adhesion promoters are used especially in printing, coatings and adhesive tapes.

[0025] Thus, an adhesion promoter layer is advantageously used to further enhance adhesion between layers applied to the foil, such as between an adhesive layer and a paint layer.

[0026] Preferably, the adhesion promoter in the adhesion promoter layer is an ethylene acrylic acid (EAA) copolymer.

[0027] The present invention relates to a method for producing polyimide (PI), polypropylene (PP), uniaxially oriented polypropylene (MOPP), biaxially oriented polypropylene (BOPP), polyethylene (PE), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyetherketone (PEK), polyethyleneimide (PEI), polysulfone (PSU), polyaryletherketone (PAEK), polyethylene naphthalate (PEN), liquid crystal polymer (LCP), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyamide (PA), polycarbonate (PC), cycloolefin copolymer (COC), polyoxymethylene (POM), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), ethylene tetrafluoroethylene (ETFE), polytetrafluoroethylene (P TFE), tetrafluoroethylene-perfluoropropyl vinyl ether fluorocopolymer (PFA), tetrafluoromethylene-perfluoropropyl vinyl ether fluorocopolymer (MFA), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene-hexafluoropropylene fluoropolymer (EFEP), polymethyl methacrylate (PMMA), cellulose or lignin based plastics, polyhydroxyalkanoates (PHAs), thermoplastic starch (TPS), polylactic acid (PLA), polycaprolactone (PCL), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT) and / or mixtures and / or copolymers of these materials and / or foils selected from paper or metal and composites of these materials.

[0028] The plastic material of the foil may be recyclable or even made from recycled materials, in particular it may be made from renewable raw materials and may be biodegradable and / or marine biodegradable.

[0029] Preferably, the invention is applied to PET foils, this type of plastic foil being a particular advantage of the invention, since adhesion improvements have hitherto generally been achieved by the undesirable TCA treatment of polyester foils.

[0030] However, it is understood that improved adhesion properties can be obtained according to the invention with any other kind of (plastic) foil, in particular with the materials mentioned above.

[0031] In a preferred embodiment of the invention, the adhesive foil has a coating with a lacquer film on both sides.

[0032] A further preferred embodiment of the invention is characterized in that the adhesive foil has a metallized layer, onto which a coating with a lacquer film is applied.

[0033] Until now it has been difficult to provide a coated foil with good adhesion for further material layers such as paint layers, adhesive layers, etc., because surface modifications such as TCA treatments cannot be applied to foils that already have a layer (e.g. a metal coating). The present invention can now provide an already coated foil with improved adhesion properties.

[0034] According to a particularly advantageous embodiment of the invention, the tensile strength of the self-adhesive coating applied to the lacquer film (composite adhesion) is >6 N / 15 mm.

[0035] In the following, the invention will be explained in more detail with reference to examples and drawings. [Brief description of the drawings]

[0036] [Figure 1] 1 shows a schematic structure of an adhesive tape material comprising an adhesive foil according to one embodiment of the present invention. [Diagram 2] 1 shows a schematic structure of a metallized label or freshness seal comprising an adhesive foil according to one embodiment of the present invention. [Diagram 3]1 shows a schematic structure of a double-sided adhesive tape including an adhesive foil according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] The layer structure in Figure 1 shows a carrier foil 1, e.g. a PET foil, provided on one side with a siliconized or carbamate coating 2. The coating 2, also known as a "release coating", prevents the layers from sticking to each other when the foil is wound into a roll.

[0038] On the other side, the carrier foil 1 is coated with a lacquer film 3, which in a preferred embodiment may be an adhesion promoter or primer layer, preferably an ethylene-acrylic acid copolymer modified in particular with polyurethane. The application of the lacquer to the carrier foil 1 can be carried out for example by means of an anilox cylinder, which ensures a good flow of the lacquer layer. According to the invention, the application thickness or weight is, for example, 0.2 g / m 2 This lacquer film 3, which is a lacquer film having a mean diameter greater than the layer thickness of the lacquer film 3, i.e. in the range from 2.0 to 12 μm, in order to increase the surface area of ​​the lacquer film layer. Preferred pigments are earth, mineral, metallic effect pigments, white pigments, iron oxide pigments, zirconium silicates and polymeric pigments. Particularly preferred pigments are, for example, polyamide pigments PA66 or PA12. The weight proportion of pigments in the lacquer film is 1 to 50% relative to the non-volatile fraction of the binder of the lacquer.

[0039] The self-adhesive coating 4 is applied to a lacquer film 3, for example based on conventional acrylic or hot melt adhesives, and is suitable for use in the electronics industry.

[0040] The layered structure of the label or freshness seal shown in Figure 2 comprises in addition to a carrier foil 1, which, in contrast to Figure 1, does not have a silicone or carbamate coating on one side of the foil, but a metallized layer 6, for example a layer of Al, onto which is applied a paint layer 5 printed over or partially over the entire surface, a pigment-containing lacquer film 3. The metallized layer 6 can be deposited, for example by PVD or CVD methods, by sputtering or by electron beam evaporation, and may be about 5 to 100 nm thick depending on the concrete application of the foil.

[0041] Similar to the adhesive tape structure shown in FIG. 1, there is a self-adhesive coating 4 on a lacquer film 3, but in this case it comprises an adhesive suitable for repeated peeling and application of labels or freshness seals.

[0042] FIG. 3 shows, in contrast to the adhesive foil embodiment of FIG. 1, a carrier foil 1 which has a coating on both sides with a lacquer film or adhesion promoter layer 3 to which an adhesive layer 4 is applied on each side.

[0043] Such double-sided adhesive tapes can be used to permanently bond objects together (e.g. parts in the automotive industry) since due to the foil according to the invention they have better adhesive properties than conventional double-sided adhesive tapes. EXAMPLES

[0044] The adhesion value of the adhesive foil according to the invention was investigated using a tensile tester (Zwick measuring method). The adhesive foil investigated was a PET foil with the following lacquer film: Coating: Polyurethane modified ethylene-acrylic acid copolymer (EAA) ·Layer thickness: 0.2g / m 2 Pigment: Polyamide 66

[0045] The following test procedure was performed to measure the adhesive properties of the adhesive foil.

[0046] On the test foil, a sheet of a given adhesive film is adhered to the test specimen transversely to the running direction and firmly pressed in place with a roller. The adhesive film is then pulled uniformly from the test foil at a 90° pulling angle.

[0047] The measurements carried out showed that the adhesion of the lacquer system of the adhesive foil was >6 N / 15 mm. The adhesive of the adhesive film remained attached to the lacquer film of the adhesive foil, which shows that the adhesive properties of the adhesive foil according to the invention are significantly improved compared to prior art adhesive foils and that the adhesive foil can be advantageously used, for example, in adhesive tapes for the electronics industry.

Claims

1. 1. An adhesive foil, in particular made of plastic, which comprises a coating with a lacquer film, characterized in that the lacquer film contains pigments whose average diameter is greater than the layer thickness of the lacquer film.

2. 2. Adhesive foil according to claim 1, characterized in that the diameter of its particles is in the range of 2.0 to 12 μm, preferably said average diameter is 4 to 6 μm.

3. 3. Adhesive foil according to claim 1 or 2, characterized in that the weight proportion of the pigment in the lacquer film is 1 to 50%, preferably 10 to 30%, relative to the non-volatile fraction (nfA) of the binder of the lacquer.

4. 2. Adhesive foil according to claim 1, characterized in that the pigment is selected from inorganic pigments or organic pigments.

5. 2. Adhesive foil according to claim 1, characterized in that the inorganic pigments are selected from earth, mineral, metallic effect pigments, white pigments, iron oxide pigments, zirconium silicates and polymeric pigments.

6. 6. Adhesive foil according to claim 5, characterized in that the pigment is a polyamide pigment, preferably PA66 or PA12.

7. 2. Adhesive foil according to claim 1, characterized in that the lacquer film is an adhesion promoter layer.

8. The adhesive foil according to claim 7, characterized in that the adhesion promoter of the adhesion promoter layer is an ethylene-acrylic acid copolymer.

9. The foil may be made of polyimide (PI), polypropylene (PP), uniaxially oriented polypropylene (MOPP), biaxially oriented polypropylene (BOPP), polyethylene (PE), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyetherketone (PEK), polyethyleneimide (PEI), polysulfone (PSU), polyaryletherketone (PAEK), polyethylene naphthalate (PEN), liquid crystal polymer (LCP), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyamide (PA), polycarbonate (PC), cycloolefin copolymer (COC), polyoxymethylene (POM), acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), ethylene tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE), 2. The adhesive foil according to claim 1, characterized in that it is selected from the group consisting of tetrafluoroethylene-perfluoropropyl vinyl ether fluorocopolymer (PFA), tetrafluoromethylene-perfluoropropyl vinyl ether fluorocopolymer (MFA), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene-hexafluoropropylene fluoropolymer (EFEP), polymethyl methacrylate (PMMA), cellulose or lignin-based plastics, polyhydroxyalkanoates (PHA), thermoplastic starch (TPS), polylactic acid (PLA), polycaprolactone (PCL), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBAT) and / or mixtures and / or copolymers of these materials and / or paper or metal and composites of these materials.

10. 10. The adhesive foil according to claim 9, characterized in that it is a PET foil.

11. 2. The adhesive foil according to claim 1, characterized in that the adhesive foil is coated with the lacquer film on both sides.

12. 2. The adhesive foil according to claim 1, characterized in that the adhesive foil has a metal coating layer, and the coating with the lacquer film is applied to the metal coating layer.

13. 2. Adhesive foil according to claim 1, characterized in that when a self-adhesive coating is applied to the lacquer film, the tensile strength (composite adhesion) is >6 N / 15 mm.

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