Moisture-resistant adhesive tapes

Abstract

The present invention relates to removable adhesive tapes comprising at least one adhesive layer and a carrier characterized by improved resistance to moisture.

Description

The present invention relates to removable adhesive tapes comprising at least one adhesive layer and a backing which is distinguished by improved resistance to moisture.Bonding as a modern connecting method is established in many fields of application and has displaced classical methods such as screwing or welding in many fields. For example, in the automobile industry, in the production of consumer goods and in many other areas, materials which had previously to be screwed or welded in a complicated manner are glued together. The scope of application of adhesive bonding is thus manifold, and the requirements placed on the adhesive tape are also manifold. Besides the materials to be joined, the type of stress is also of great importance. Depending on the environment and the stress, the adhesive tape must withstand other stresses and, for example, be particularly moisture-resistant, heat-resistant or mechanically loadable.Adhesive tapes having a high moisture resistance can be used, for example, in kitchen and electrical appliance construction, in container and apparatus construction, in ventilation and air conditioning technology, in the sanitary sector and other applications in environments with elevated atmospheric humidity.The adhesive tapes used in electronic components, such as mobile telephones or the like, must also have a high moisture resistance.As such electronic devices are becoming more widely used, their applications are increasing. This also results in increasing requirements for the installed components. Thus, the development of electronic devices (so-called wearables) worn on the body, such as smart watches, makes it increasingly important that the bonds used there have high resistance to various chemicals and do not lose any adhesive force even after prolonged storage in various media. Similar requirements are also being placed increasingly on other electronic devices such as smartphones (mobile telephones), tablets, notebooks, cameras, video cameras, touch devices, touchpads and the like.The technical development is increasingly directed to such devices which are made smaller and lighter so that they can be carried along by their owner at any time and are also usually carried along regularly. This is usually done by realization of low weights and / or suitable size of such devices. Within the framework of the current development trends, precision-mechanical and optical devices are increasingly (also) provided with electronic components, which increases the options for minimization. Due to the entrainment of the mobile devices, these are exposed to increased-in particular mechanical and chemical-loads, for example by abutting edges, by dropping, by contact with other hard objects in the pocket, but also already by the permanent movement due to entrainment per se. Mobile devices are also exposed to more severe loads due to moisture effects, temperature influences and the like than such "immobile" devices, which are usually installed in interior spaces and are not moved or are hardly moved.The profile of requirements for corresponding adhesive tapes which are used for producing such electronic devices is further exacerbated in that the adhesive tapes should not only build up a firm bond between the materials to be bonded, but should also be removable again, specifically in such a way that they can be removed again without leaving any residue without damage to the bonded substrates occurring.Adhesive tapes which can be redetached by stretching are generally known.U.S. Pat. No. 4,024,312 A proposes multilayer adhesive strips for medical applications in which an extensible carrier layer and a pressure-sensitive adhesive layer based on ABA block copolymers are used. The extensibility of the carrier should be at least 200% and the 50% modulus should be less than about 14 MPa. As ABA block copolymers, those having B blocks of butadiene, isoprene, ethylene or butylene can be used. Explicitly mentioned for carrier layers are SBS and SIS, and only SIS for pressure-sensitive adhesive layers.U.S. Pat. No. 6,372,341 B1 mentions a series of possible elastomers for extensible carrier layers and mentions in particular LLDPE, LDPE, SIS and SEBS. In many examples, explicitly mentioned adhesives are based on polyacrylates and carrier layers are based on LLDPE or LDPE. An extensible adhesive strip is also mentioned which comprises a backing of SEBS and an adhesive of resin-modified SIS.DE 10 2012 223 670 A1 claims adhesive strips which can be redetachated by extensive stretching in a multilayer design, having a polyurethane-based carrier layer and at least one pressure-sensitive adhesive layer made of a formulation based on a vinylaromatic block copolymer. Vinylaromatic block copolymers having unsaturated polydiene elastomer blocks are preferred and mentioned explicitly.DE 10 2021 210 261 A1 discloses adhesive tapes which comprise a carrier layer based on crosslinked polyurethane. The backing layer may be of extruded polyurethane or may be obtained from an aqueous polyurethane dispersion.The proposed products generally comprise an extensible carrier. Advantageous materials for extensible substrates have proven to be those based on polyurethane, produced from extrusion or aqueous dispersion. Polyurethanes, thermoplastic or elastomeric in nature, having a wide range of mechanical properties, are commercially available from various suppliers. Although the moisture resistance for such substrates which have been obtained from extrusion and are typically of thermoplastic nature is frequently sufficient here, the mechanical properties of not all representatives of this category are particularly suitable for the substrate layer in thinner layer thickness ranges in order to ensure tear-free detachment. In many cases, the modulus is too high at 100% and / or the extensibility of the carrier is not sufficient to be able to pull the adhesive tape out of the bonded component without premature tearing.Supports having a lower modulus at 100% and at the same time high extensibility can be obtained by selecting corresponding polyurethanes which are obtainable in particular as a dispersion. Suitable polyurethanes for these softer supports are now known from DE 10 2021 210 261 A1. However, they have the disadvantage of insufficient moisture resistance, so that their applications are limited.In order to expand the application fields for adhesive tapes, there is a need in this respect for removable adhesive tapes which can also be used in moist or damp-warm environments. Against this background, it is an object of the present invention to provide adhesive tapes for use in a moist or warm moist environment, which tapes can be redetached by extensive stretching.This object is achieved by an adhesive tape as defined in claim 1. Preferred embodiments of the present invention are set forth in the dependent and subordinate claims.It has surprisingly been found that the use of supports made of certain polyurethane produced by means of dispersion, known as PUD, allows the production of adhesive tapes which have a high tensile strength and at the same time allow destruction-free removal with a low expenditure of force and at the same time have a high moist heat resistance, so that an application in the corresponding environment is provided.A first subject of the present invention is accordingly a removable adhesive tape comprising at least one adhesive layer and a carrier comprising at least one layer based on a polyurethane prepared by means of dispersion, characterized in that the carrier has a maximum elongation at break of at least 300%, determined according to DIN 53504, and a moisture resistance, expressed as WG L- WG i, of not more than 1%, where WG L is the water content after storage for 4 days at 40° C. and a relative atmospheric humidity of 80%, and WG i is the initial water content of the carrier, and where the water content is determined coulometrically by the method of Karl Fischer.A detailed description of the measurement methods for determining the specified parameters can be found in the section "Test methods" of the present specification.It is known that adhesive tapes, and in particular the backings used in the adhesive tapes, absorb moisture on storage, which can have a negative effect on the mechanical properties of the backing. Thus, a backing originally suitable for removable adhesive tapes may lose this suitability after a certain time, especially in a moist environment. In contrast, it has been found that the adhesive tape of the invention does not have these disadvantages, but rather is distinguished by a remarkable moisture resistance. This moisture resistance is expressed in the context of the present invention as the difference between the initial water content of the support and the water content of the support after storage for 4 days at 40° C. and 80% relative humidity. The water content can be determined coulometrically in each case by the method of Karl-Fischer. In a preferred embodiment, this difference is less than 0.8%, preferably less than 0.7% and particularly preferably less than 0.6%.Most advantageously, removable adhesive tapes can be removed again by pulling on the adhesive tape. In this way, the use of chemical solvents or other methods which could lead to damage to the bonding substrate can be dispensed with. However, the detachment by pulling gives rise to the problem that the adhesive tape, in particular the backing, tears and residues of the adhesive tape thus remain on the bonding substrate. Accordingly, the support must have sufficient tear strength in addition to a corresponding elongation. Although there are supports with a corresponding profile of properties, this generally takes place at the expense of other properties such as moisture resistance. Within the scope of the present invention, it has surprisingly been found that both property profiles can be advantageously combined with one another. In a preferred embodiment, the backing used in the adhesive tape of the invention therefore has an elongation at break of at least 500%. The tear strength of the backing is determined by its tensile strength, if this is too low, the adhesive tape tears on redetachment. Therefore, an embodiment is preferred in which the carrier has a tensile strength of at least 10 MPa, preferably at least 15 MPa. In the context of the present invention, it has surprisingly been found that these properties could be obtained by virtue of the advantageous moisture resistance of the support even after storage. For example, the backing used in the adhesive tape of the invention is further characterized in that, after storage for 4 days at 40° C. and 80% relative atmospheric humidity, it has a tensile strength of at least 10 MPa. Furthermore, the support exhibits an elongation at break after storage at 40° C. for 4 days and 80% relative atmospheric humidity of at least 500°.Depending on the application, it may be desirable for the adhesive tape to have not only sufficient moisture resistance but also damping properties, so that here, for example, protection of the component or component to be bonded can be achieved. These damping properties can be mapped by the compression capacity, which describes which force is necessary to cause a certain dimensional change or compression in %. In the case of adhesive tapes, the damping properties in the z direction are of particular importance. Therefore, an embodiment is preferred in which the adhesive tape has a compressibility or compressive hardness in the z direction of at most 100 N / cm 2 at a compressive strength of 50%, determined according to compressive hardness on the basis of ISO 3386.The compressive strength describes the strength of foamed materials and provides information on how much force is required to compress the material from its initial state by a certain percentage. The higher the value, the harder the material.The backing used in the adhesive tape of the invention comprises at least one layer based on a polyurethane prepared by means of dispersion. In the context of the present invention, surprisingly, polyurethane dispersions which have a certain proportion of polyether-based polyurethane have proven particularly suitable for achieving the desired combination of redetachability and resistance to moisture. Accordingly, an embodiment is preferred in which the carrier comprises at least one layer based on a polyurethane produced by means of dispersion, wherein the polyurethane dispersion has a proportion of polyether-based polyurethane of at least 50% by weight, based on the total solids content of the dispersion.In addition to a polyether-based polyurethane, the dispersion may comprise further polyurethanes. These further polyurethanes are preferably those selected from the group consisting of polycarbonate-based polyurethanes and polyester-based polyurethanes and mixtures thereof. These polyurethanes have proved to be particularly advantageous in order to combine the property of sufficient tear strength with advantageous resistance to moisture. From the group of polyether-based polyurethanes, preference is given according to the invention in particular to those based on polytetrahydrofuran, while from the group of polycarbonate-based those based on hexanediol polycarbonate are preferably used. Also suitable are those polyether-polyurethanes which contain segments of polypropylene glycol.Polyether-based PUDs generally have a high extensibility and a rather moderate to low tear strength. In the context of the present invention, it has surprisingly been found that the tear strength of corresponding supports can be advantageously improved by using a dispersion which additionally comprises polycarbonate-based polyurethanes. In this way, both a high extensibility and a high tear strength with simultaneously improved moisture resistance could be achieved. In the case of particularly suitable mixtures, it is also possible to set improved optical properties, with regard to transmission, b value and refractive index after moisture storage. Therefore, a preferred embodiment of the present invention relates to an adhesive tape comprising a backing which has at least one layer based on a polyurethane prepared by means of dispersion, where the dispersion comprises, in addition to polyether-based polyurethanes, polycarbonate-based polyurethanes, where the fraction of polyether-based polyurethanes in the dispersion is at least 50% by weight, based on the total weight of the dispersion.In order to achieve a further improvement, in particular of the mechanical properties, a crosslinked carrier can also be used in the adhesive tape of the invention. To this end, crosslinking components, so-called crosslinkers, can be added to the dispersion used for preparing the support. It has proven particularly advantageous to use polyether-based polyurethanes in crosslinked form. Therefore, an embodiment is preferred in which the support according to the invention comprises at least one layer based on a polyether-based polyurethane produced by means of dispersion, wherein the dispersion further comprises at least one crosslinking agent. Crosslinkers preferred are crosslinkers based on acridine, carbodiimide, melamine or isocyanate, particular preference being given to the crosslinkers based on isocyanate. Here, it was possible to achieve a further improvement in the tensile strength and thus the tear resistance of the carrier, in particular by the addition of a crosslinking agent based on isocyanate.To improve the moisture resistance, it may also be advantageous to additionally use acid scavengers. In a preferred embodiment, the at least one layer based on polyurethane in the support according to the invention is therefore obtained from a dispersion which further comprises acid scavengers, these preferably being selected from the group of carbodiimides. These are particularly preferably used in an amount of 2 to 4% by weight, based on the total weight of the dispersion.Depending on the application, the carrier can be foamed or non-foamed. In a preferred embodiment, the at least one layer based on polyurethane is foamed, with microballoons which are added to the dispersion preferably being used for the foaming. Both microballoons expandable by temperature supply and preexpanded microballoons are suitable here. Alternatively, chemical and / or physical foaming agents can also be used for foaming. Foamed backings have the advantage of improved cushioning properties, while non-foamed backings have the better optical properties.The thickness of the supports may vary depending on the application, but is preferably 10 to 400 μm.The adhesive tape of the invention has at least one adhesive layer. In this context, particular preference is given to adhesives based on vinylaromatic block copolymers, in particular those based on styrene-butadiene block copolymers.The present invention further provides a process for producing the adhesive tape of the invention. For this purpose, a dispersion based on polyurethane having a fraction of polyether-based polyurethane of at least 50% by weight, based on the total weight of the dispersion, is applied to a temporary carrier or a functional layer and dried. The functional layer can be, for example, the adhesive layer. In cases where the dispersion is applied to a temporary carrier, the adhesive layer is applied after dryingFor the best possible air bubble-free quality of the dispersion, it is preferably degassed before application to the temporary carrier. This can be done, for example, with the aid of a vacuum breather such as a vacuum thin-film rotation principle. Thus, the addition of defoamers can be dispensed with at the same time.The application of the PU dispersion to the temporary carrier is preferably carried out under clean room conditions, wherein different application tools such as doctor blade, nozzle or distributor channels can be used. In this respect, dispensing by means of a nozzle is preferred, since in this way the highest quality of optical properties can be achieved.The drying of the applied PU dispersion is preferably effected by supplying heat, in particular in a drying channel having different heating zones.The PU dispersion can be applied either to a temporary carrier or directly to a functional layer, such as in particular a pressure-sensitive adhesive. After drying, a second functional layer can be laminated onto the opposite side, so that a multi-layer product is obtained in one step. This procedure has the advantage that a multilayer product can be produced particularly efficiently and the bond strength / anchoring between the carrier and the functional layer is improved.To optimize the tensile strength, it has proven advantageous if the carrier is subjected to a tempering. Therefore, the method according to the invention further comprises a step in which the support is tempered. The temperature control can be carried out, for example, at a temperature of 120° C. or more.In cases where the PU dispersion used to produce the support comprises, in addition to the polyurethane, further constituents such as thickeners and / or other additives, it has proven advantageous to predispersion these further constituents and then feed them in portions to the PU dispersion in order to obtain a homogeneous and bubble-free dispersion. In a preferred embodiment of the process according to the invention, this therefore comprises a step in which thickeners and / or other additives are predispersed and fed in portions to the PU dispersion.The adhesive tape of the invention is designed in particular for the bonding of displays, battery bonds and use in electronic components which are exposed to atmospheric moisture.The present invention therefore further provides an electronic component comprising the adhesive tape of the invention. Electronic, optical and precision-mechanical devices in the sense of this application are in particular devices as are to be classified in class 9 of the International Classification of Goods and Services for the Entry of Brands (Classification of Niza); 10th edition (NCL(10-2013)); provided that these are electronic, optical or precision-mechanical devices, furthermore clocks and time-measuring devices according to class 14 (NCL(10-2013)), such as in particular• Scientific, marine, surveying, photographic, film, optical, weighing, measuring, signalling, control, rescue and training apparatuses and instruments; • Apparatuses and instruments for conducting, switching, converting, storing, regulating and controlling electricity;• Image recording, processing, transmitting and reproducing apparatuses such as televisions and the like• Acoustic recording, processing, transmitting and reproducing apparatuses such as broadcasting apparatuses and the like• Computers, computing and data processing equipment, mathematical equipment and instruments, computer accessories, office equipment - such as printers, facsimiles, copiers, typewriters, data storage equipment• Remote communication and multifunction devices with remote communication function, such as telephones, answering machines• Chemical and physical measuring devices, control devices and instruments, such as accumulator charging devices, multimeter, lamps, tachometers• Nautian Instruments• Optical devices and instruments• Medical devices and instruments and sports utility tools• Watches and chronometers• Solar cell modules, such as electrochemical dye solar cells, organic solar cells• solar cells, thin-film cells,• Fire extinguishing devices.The present invention is illustrated in more detail by the following examples, these being by no means to be understood as limiting the concept of the invention.Examples:i) Support:The following raw materials were used to prepare the carriers. Table 1: Table 1:Alberdingk U4101Alberdingk BoleyPolyether PU of 66 wt.% polytetrahydrofuran and 34 wt.% meta-tetramethylxylylene diisocyanateImpranil DL 1116CovestroPolyester polyurethane dispersion of about 51% by weight of adipic acid, 29% by weight of 1,6-hexanediol, 15% by weight of neopentyl glycol and 5% by weight of hexamethylene diisocyanate (HDI)Impranil DL 1068CovestroPolytetrahydrofuran (PolyTHF) based polyether polyurethane, 4% by weight of HDIImpranil DLC-FCovestroPolycarbonate ester polyurethane dispersion based on hexanediol carbonateImprafix 2794CovestroWater-based blocked aliphatic polyisocyanateOrtegol PV 301EvonikNonionic thickener for water-based coating systemsBorchi Gel 0625Borchers GmbHNonionic thickener for water-based coating systemsThe formulations for the preparation of the carriers are summarized in Table 2. Table 2: Table 2:Core layer PUD 1PU DispersionImpranil DL 111697,40ThickenerOrtegol PV 3010,60Cross-linking agentsImprafix 27942,00Core layer PUD 2PU DispersionAlberdingk U410197,65ThickenerBorchigel 06250,35Cross-linking agentsImprafix 27942,00Core layer PUD 3PU DispersionImpranil DL106897,65ThickenerOrtegol PV 3010,35Cross-linking agentsImprafix 27942,00Core layer PUD 4PU DispersionImpranil DL106887,50PU DispersionImpranil DLC-F10,00ThickenerOrtegol PV 3010,50Cross-linking agentsImprafix 27942,00Core layer PUD 5PU DispersionImpranil DLC-F97,58ThickenerOrtegol PV 3010,42Cross-linking agentsImprafix 27942,00ii) Adhesives:For the following tests, the supports were each coated with adhesives based on styrene-butadiene block copolymers. The raw materials and formulations of the adhesives are shown in the following tables: Table 3: Table 3: Table 3:Kraton D 1152Kraton Performance Polymers, Inc.Styrene-butadiene-styrene triblock copolymerDecolyte A115DRTSolid α-pinene tackifier resin, ring and ball softening temperature: 115° CWingtack 10Cray Valley USA, LLCLiquid hydrocarbon resin (soft resin)Expancel 920 DU 20NouryonExpandable MicrospheresIrganox 1010BASF SE, LudwigshafenAnti-ageing agents are anti-ageing agentsAdhesive KM 1:Adhesive KM 1:Synthetic RubberKraton 115248,6Resin PartDecolyte A11545,7Wingtack 103,0Anti-ageing agents are anti-ageing agentsIrganox 10101,2MicroballoonsExpancel 920 DU201,5Adhesive KM 2:A reactor conventional for radical polymerizations was charged with 160 g of 2-ethylhexyl acrylate, 120 g of 4-hydroxybutyl acrylate and 120 g of tert-butyl acrylate, and the photoinitiator Irgacure 651 in a proportion of 0.01 wt %. Polymerization was then carried out using a (UV) LED lamp with an intensity of 3000 [mJ / cm 2] for 10 min.Subsequently, the prepolymer was mixed with photoinitiator Irgacure 184 (0.2% by weight) and crosslinker (0.1% by weight HDDA) and a reduced pressure was applied by means of a vacuum pump in order to free the mixture of bubbles. Subsequently, the coating of the blend took place in a thickness of 100 μm between two siliconized PET films (50 μm each). The further reaction was initiated by irradiation with a Heraeus UV LED lamp (wavelength 365 nm) at a UV dose of 3000 mJ / cm 2.Preparation of the Carriers Based on PUDThe mixing of the corresponding polyurethane dispersion with the crosslinking agent and thickener is effected in each case via a conventional vertical stirring apparatus with a Visco Jet stirrer. The polyurethane dispersion is placed in a sufficiently large container and stirred carefully. Formation of drumbs or any stirring in of air should be avoided in the entire mixing process. The crosslinker Imprafix 2794 is fed in portions with continuous stirring. Subsequently, the thickener Ortegol PV301 (25% by weight solids content) or the thickener BorchiGel 0625 (33% by weight solids content) is pre-diluted with water in a ratio of 1:1 and fed in portions with continuous stirring. To obtain a homogeneous mixture, a stirring time of at least 30 minutes is maintained. The thickened polyurethane dispersion prepared in this way is optimally prepared one day before the coating. Stirred-in air bubbles can thus still escape. The blended polyurethane dispersions can now be spread onto a PET carrier having a release function using a comma doctor coater with a desired weight per unit area and dried at 60° C. in a commercial air circulating dryer. The PUD core layers produced (i.e. PUD cores 1 to 3) are free from process aids.The adhesive layers are then laminated on both sides. The overall composite of carrier and adhesive layers is subjected to a further tempering for better anchoring.Production of the Adhesive Tapes with Carrier Based on PUD (According to the Invention)All supports were each equipped on both sides with 50 μm adhesive KM 1 or KM 2. The composite was then heat-treated. Both the backing and the overall composite of backing and double-sidedly applied adhesive were investigated and assessed for suitability.Measurement results: Measurement resultsThe adhesive tapes produced were analyzed and measured as follows.a) Water content according to Karl-FischerThe water content of the backings used in the adhesive tapes was determined according to the Karl Fischer method as described in the Test Methods section. In addition to the initial water content (WG i) the water content was determined after storage at 40° C. and 80% relative humidity (WG L) for 4 days.See, for example. 1PUD 10,912,241,33See, for example. 2PUD 50,871,120,251PUD 20,731,210,482PUD 30,831,360,533PUD 40,811,240,434PUD 40,811,240,43As can be seen from the values in the table, only a slight increase in the water content is observed in the supports used according to the invention.b) Tensile elongationThe tensile elongation was determined according to the method described in the Test Methods section. In addition to the initial tensile elongation, the tensile elongation after storage of the supports for 4 days at 40° C. and 80% relative atmospheric humidity was also determined.See, for example. 1PUD 1KM 11,476534,0See, for example. 2PUD 5KM 17,228023,51PUD 2KM 11,387527,22PUD 3KM 11,881613,93PUD 4KM 12,480535,14PUD 4KM 22,480535,1See, for example. 1PUD 1KM 11,16229,5See, for example. 2PUD 5KM 13,927020,31PUD 2KM 11,279019,52PUD 3KM 11,37455,93PUD 4KM 12,169023,24PUD 4KM 22,169023,2b) Tearer 90°The tear strength of the adhesive tape was determined by the method described below. The initial tear strength at room temperature (RT), the tear strength after storage for 4 days at room temperature and the tear strength after storage for 4 days at 40° C. and 80% relative humidity were determined. The proportion of 100 adhesive tapes tested which have torn when redetached is given.See, for example. 1PUD 1KM 100100See, for example. 2PUD 5KM 13050801PUD 2KM 10002PUD 3KM 1010603PUD 4KM 1010204PUD 4KM 20010As can be seen from the measurement data, the adhesive tapes of the invention combine good moisture resistance with corresponding mechanical properties, as are required for redetachability of the adhesive tapes. Although the adhesive tape with the carrier based on a polycarbonate ester-based polyurethane also exhibited satisfactory moisture resistance, it was not suitable for removable adhesive tapes because of its low extensibility. In contrast to the adhesive tapes of the invention, it was also not possible to retain the mechanical properties when stored in a moist environment, as evidenced by a marked increase in the failures of the adhesive tapes in the tear test.In Ex. In FIG. 4, the carrier PUD 4 is provided in 50 μm with the adhesive composition KM 2 in 50 μm and at the same time meets the highest demands on the optical properties of clear adhesive tapes and can thus be used for application in a display. The optical properties reach the following values, such as a transmission of 99.3%; haze 0.39; b value 0.09; refractive index 1.472.Test MethodsAll measurements are carried out at 23° C. and 50% relative humidity, unless otherwise stated. The mechanical and adhesive data were determined as follows:Thickness: ThicknessThe thickness of an adhesive layer can be determined by determining the thickness of a portion, defined with respect to its length and its width, of such an adhesive layer applied to a liner, minus the (known or separately determinable) thickness of a portion of the same dimensions of the liner used. The thickness of the adhesive layer can be determined with precisions of less than 1 μm deviation using commercially available thickness measurement devices (probe testing devices). If thickness variations are detected, the mean value of measurements is given at at least three representative points, i.e. in particular not measured at creases, folds, specks and the like.As already the thickness of an adhesive layer, the thickness of an adhesive tape (adhesive strip) or of a carrier can also be determined analogously by means of commercially available thickness measurement devices (probe testing devices) with precisions of less than 1 μm deviation. If thickness variations are detected, the mean value of measurements is given at at least three representative points, i.e. in particular not measured at creases, folds, specks and the like.Coulometric Karl-Fischer titration (water content)The measurement is carried out on the basis of DIN EN ISO 15512 method B. The samples are weighed out using about 0.3 g in glass vials and sealed directly. A triple determination is made. For each sample preparation, 3 empty vials are prepared for determining the blank value applicable to the corresponding climate condition. The measurement of the blank values is always carried out before the measurement of the samples. The measurement is carried out at 140° C. The water content determined is stated in [%].Tensile Test by Tensile Testing Machine, ZwickFrom the sample to be examined (adhesive tape, i.e. preferably backing provided with adhesive on both sides or only blank backing), strips 15 mm wide and having a length of about 150 mm are cut in the longitudinal direction by means of a strip cutter or razor blade knife. The sample preconditioned in the test climate for 24 hours is clamped vertically into the middle of the clamping jaws with a clamping length of 10 mm and stretched at a speed of 800 mm / min until it breaks. The tear should occur somewhat in the middle of the strip. If the crack occurs near the jaw (closer than 1 cm), the value must be discarded and a further strip tested for this purpose. 5 measurements are carried out per sample variant. The test climate is 23° C. and 50% rel. Humidity. The measurements are carried out on the basis of EN ISO 527.Data on the results:Modulus at x% Elongation, Elongation at breakThe modulus at x% elongation or the elongation at break in [MPa] of a sample are determined in accordance with DIN 53504.Redetachability (display) by means of a tensile testing machineIn the re-releasability test, the double-sided adhesive tape to be tested was adhered between two test plates. Test plates made of polycarbonate and glass are used.Samples having a width of 20 mm are cut from the adhesive tape to be tested. These specimens, after the first siliconized PET film has been uncovered, are bonded to the first glass test plate over a length of 70 mm. After the second siliconized PET film has been uncovered, the free adhesive is covered on both sides with 36 μm of PET. The second test plate made of PC, after cleaning with isopropanol and preconditioning for 1 to at most 10 min at 23° C. and 50% relative humidity, is bonded to the opposite side of the bonded strip (i.e. test piece) in such a way that the PC plate protrudes beyond the glass plate. The composite is rolled over 10 times over the rear side of the steel plate with a 4 kg roll (five times back and forth). After at least 24 h of pull-on time at 23° C. and 50% relative atmospheric humidity, the strips are stripped from the adhesive joint at an angle of 0° on the tab by means of a tensile testing machine (from Zwick), at a constant (feed) speed of 800 mm / min. The specimen is fixed with an angularly adjustable adapter and the handle is clamped vertically into the middle of the clamping jaws.It is measured at an angle of 0° and during this time the force required continuously for dissolving / stripping the sample is taken up by the tensile testing machine-the so-called stripping force F Stripp. The measurement is complete as soon as the sample has been completely stripped out between the two test plates or the sample has torn during the measurement. At least 2 measurements per sample are performed. The test climate is 23° C. and 50% rel. Humidity.Data on the results:Tear test (battery) by means of tensile testing machineIn the tear test, a first test plate made of polyethylene and a second test plate made of steel are used. The first test plate made of polyethylene has been wound around with a double-sided adhesive tape tesa® 67215, to which a "battery foil" has subsequently been applied. The adhesive tape tesa® 67215 is a total of 150 μm thick and comprises a polyurethane backing 30 μm thick, on each of which is arranged on both sides a foamed PSA layer based on vinylaromatic block copolymer 60 μm thick. The "battery foil" is an aluminum-laminated polymer foil having a thickness of 88 μm from the manufacturer DNP-the foil is typically used for producing lithium polymer batteries.Samples 8 mm wide and 60 mm long are punched or lasered from the adhesive tape to be tested. These test specimens are bonded over a length of 50 mm to the first test plate made of polyethylene, which is wound around with battery foil as described above, so that a 10 mm long grip tab protrudes. The grip tab is covered on both sides with 36 μm PET. After cleaning with acetone and preconditioning for 1 to at most 10 min at 23° C. and 50% relative humidity, the second test plate made of steel is bonded to the opposite side of the bonded strip (i.e. test piece) in such a way that the two test plates lie flush, i.e. congruently, one above the other. The composite is rolled over 10 times over the rear side of the steel plate with a 4 kg roll (five times back and forth). After at least 4 h of pull-on time at 23° C. and 50% relative humidity, the strips are stripped from the adhesive joint at an angle of 90° over the edge of the first test plate made of polyethylene, which has been wound around with battery foil, by means of a tensile testing machine (from Zwick) at a constant speed of 800 mm / min. The specimen is fixed with an angularly adjustable adapter and the handle is clamped vertically into the middle of the clamping jaws.It is measured at an angle of 90° and during this time the force continuously required for dissolving / stripping the sample is taken up by the tensile testing machine-the so-called stripping force F Stripp. The measurement is complete as soon as the sample has been completely stripped out between the two test plates or the sample has torn during the measurement. At least 6 measurements per sample are performed. The test climate is 23° C. and 50% rel. Humidity.Data on the results:Tearer 90° - The test is considered passed if less than 20% of the specimens tear during the stripping operation.FIG. 1 shows the tear test by means of a tensile testing machine. In this, the reference symbols have the following meaning: 21 Grip tab, adhesive tape 23 to be tested, reinforced 22 on both sides with 36 μm PET, test plates (test substrates) bonded to one another, 25 Angle-adjustable adapters for fixing the specimen 26, Device for adjusting the measurement angle, 0 to 90°TransmissionThe transmission of the adhesive tape is determined in accordance with ASTM D1003-13 (Procedure A (BYK Gardner Haze Gard Plus), Standard Illuminant D65). A correction for interfacial reflection losses is made. The transmission of other layers is determined analogously and refers to the actual thickness of the layer.HazeeThe haze of the overall construction is determined as described in ASTM D1003-13 using a BYK Gardner Haze Gard Plus. The haze value describes the proportion of transmitted light that is scattered from the irradiated sample to the front at a large angle. Thus, the haze value quantitates defects in the surface or structure that interfere with clear see-through. The standard requires the measurement of four transmission measurements. For each transmission measurement, the light transmittance is calculated. The four transmittances are calculated as the percent haze value. The haze of other layers is determined analogously and refers to the actual thickness of the layer.b valueThe b value is a measure of discoloration on a yellow-blue color scale and, together with the L value (lightness) and the α value (red-green color scale), gives an objective determination of color perception. The so-called Lab values are determined with the Spectro Guide Sphere Gloss instrument from BYK Gardner according to ASTM D2244-096 and DIN 6174. First, a 3-fold background measurement is performed on a known reference background. Subsequently, the adhesive tape is likewise measured at three different locations on this reference background. To determine the b value, the mean value is then formed from the three individual values and the mean value of the reference is subtracted.Refractive index:An Abbemat 350 refractometer (Anton Parr) is used to determine the refractive index. First, a test measurement is carried out against air or water in order to check the functionality. The adhesive tape or the individual components are then applied to the measurement window and the measurement is started. The measurement is carried out at 20° C.Compressive Hardness Based on ISO 3386The measurement method is used for characterizing and quality controlling foams. The compressive strength is the compressive stress in N / cm 2. determined in the case of a fixed deformation of the foam during the loading process.Test specimens are cut to size 30 x 30 mm from the material to be tested and are stacked to a height of 15 mm. The cut samples must then be conditioned under the test climate for 24 hours. A sample of the foam to be tested is compressed by means of a pressure testing machine under specified conditions of 5X. During the last upsetting process, both the deformation diagram is recorded and the compressive stress at the predetermined deformation is determined. In addition, if required, the force is also determined during the first upsetting process. 5 samples per sample or product are tested.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedU.S. Pat. No. 4,024,312 A

[0009] U.S. Pat. No. 6,372,341 B1

[0010] DE 10 2012 223 670 A1

[0011] DE 10 2021 210 261 A1 [0012, 0014]Cited Non-Patent LiteratureDIN EN ISO 15512

[0060]

Claims

Removable adhesive tape comprising at least one adhesive layer and a backing comprising at least one layer based on a polyurethane prepared by means of dispersion, characterized in that the backing has a maximum elongation at break of at least 300%, determined according to DIN 53504, and a moisture resistance, expressed as WG L- WG i, of not more than 1%, where WG L is the water content after storage for 4 days at 40°C and a relative atmospheric humidity of 80%, and WG i is the initial water content of the backing, and where the water content is determined coulometrically by the method of Karl Fischer.Adhesive tape according to Claim 1, characterized in that the backing has a maximum elongation at break of at least 500%, determined in accordance with DIN 53504.Adhesive tape according to at least one of the preceding claims, characterized in that the backing has a tear strength of at least 10 MPa, determined in accordance with DIN 53504.Adhesive tape according to at least one of the preceding claims, characterized in that the backing comprises at least one layer based on a polyurethane prepared by means of dispersion, the polyurethane dispersion having a fraction of polyether-based polyurethane of at least 50% by weight, based on the total weight of the dispersion.Adhesive tape according to at least one of the preceding claims, characterized in that the carrier has at least one layer based on a polyurethane produced by means of dispersion, the dispersion comprising, in addition to polyether-based polyurethanes, polycarbonate-based polyurethanes, the fraction of polyether-based polyurethanes in the dispersion being at least 50% by weight, based on the total weight of the dispersion.Adhesive tape according to at least one of the preceding claims, characterized in that the backing is foamed.Adhesive tape according to at least one of the preceding claims, characterized in that the polyurethane is crosslinked, preferably by means of an isocyanate-based crosslinking agent.Adhesive tape according to at least one of the preceding claims, characterized in that the adhesive is an adhesive based on vinylaromatic block copolymers.Process for producing an adhesive tape according to at least one of Claims 1 to 8, in which a dispersion based on polyurethane comprising a fraction of polyether-based polyurethanes of at least 50% by weight, based on the solids content of the dispersion, is (i) applied to a temporary carrier and dried, or (ii) applied to a functional layer and dried.Process according to Claim 9, characterized in that the polyurethane dispersion is degassed before application.Process according to at least one of Claims 9 to 10, characterized in that the dispersion is applied by means of a nozzle.Method according to at least one of Claims 9 to 11, characterized in that the drying is effected by means of heat input.The method according to at least one of claims 8 to 12, characterized in that the method further comprises a step of tempering the support.Electronic component comprising an adhesive tape according to at least one of Claims 1 to 8.Electronic component according to Claim 14, characterized in that the component is one of the types to be classified in class 9 of the International Classification of Goods and Services for the Entry of Brands (Classification of Niza); 10th edition (NCL(10-2013)). if these are electronic, optical or precision-mechanical devices, furthermore clocks and time-measuring devices according to class 14 (NCL(10-2013)).

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