Moisture resistant adhesive tapes

Abstract

The present invention relates to removable adhesive tapes which comprise at least one layer of adhesive material and a backing which is characterized by an improved resistance to moisture.

Description

[0001] Moisture-resistant adhesive tapes

[0002] The present invention relates to removable adhesive tapes comprising at least one adhesive layer and a carrier characterized by improved resistance to moisture.

[0003] Adhesive bonding is a modern joining method that has become established in many applications and has replaced traditional methods such as screwing or welding. For example, in the automotive industry, in the manufacture of consumer goods, and in many other areas, materials that previously required laborious screwing or welding are now bonded. The demands placed on adhesive tape are as diverse as the applications for adhesive bonding. In addition to the materials to be joined, the type of stress is also of great importance. Depending on the environment and the type of stress, the adhesive tape must withstand different loads and, for example, be particularly moisture-resistant, heat-resistant, or mechanically resilient.

[0004] Adhesive tapes with 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 increased humidity.

[0005] Adhesive tapes used in electronic components such as mobile phones and the like must also have a high level of moisture resistance.

[0006] As the spread of such electronic devices increases, so do their areas of application. This also results in growing demands on the components installed. With the development of electronic devices worn on the body (so-called wearables) such as smart watches, it is becoming increasingly important that the adhesives used in them are highly resistant to various chemicals and do not lose their adhesive strength even after extended storage in various media. Similar demands are increasingly being placed on other electronic devices such as smartphones (mobile phones), tablets, notebooks, cameras, video cameras, keyboards, touchpads and the like. Technical development is increasingly focused on such devices, which are becoming smaller and lighter so that their owners can carry them with them at all times and usually carry them regularly.This is typically achieved by achieving low weight and / or appropriate size for such devices. Current development trends increasingly involve the incorporation of electronic components into precision mechanical and optical devices, increasing the potential for minimization. Because mobile devices are carried around, they are exposed to increased stress—particularly mechanical and chemical stress—such as bumping into edges, dropping them, contact with other hard objects in a pocket, or simply due to the constant movement of the device itself. However, mobile devices are also subject to greater stress due to exposure to moisture, temperature, and the like than "immobile" devices, which are typically installed indoors and are rarely or never moved.

[0007] The requirements profile for corresponding adhesive tapes used in the manufacture of such electronic devices is being further tightened in that the adhesive tapes must not only establish a strong bond between the materials to be bonded, but must also be removable in such a way that they can be removed again without leaving any residue and without damaging the bonded substrates.

[0008] Adhesive tapes that can be removed by stretching are generally known.

[0009] US 4,024,312 A proposes multilayer adhesive strips for medical applications, which combine an extensible carrier layer and a pressure-sensitive adhesive layer based on ABA block copolymers. The extensibility of the carrier layer should be at least 200% and the 50% modulus less than approximately 14 MPa. ABA block copolymers can be those with B blocks of butadiene, isoprene, ethylene, or butylene. SBS and SIS are explicitly mentioned for carrier layers, while only SIS is mentioned for pressure-sensitive adhesive layers.

[0010] US Pat. No. 6,372,341 B1 lists a number of possible elastomers for stretchable carrier layers, specifically mentioning LLDPE, LDPE, SIS, and SEBS. Many of the adhesives explicitly mentioned are based on polyacrylates, and carrier layers are based on LLDPE or LDPE. A stretchable adhesive strip containing a SEBS carrier and an adhesive made of resin-modified SIS are also mentioned.

[0011] DE 10 2012 223 670 A1 claims adhesive strips in a multilayer design that can be removed by stretching, comprising 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 with unsaturated polydiene elastomer blocks are preferred and explicitly mentioned.

[0012] DE 10 2021 210 261 A1 discloses adhesive tapes containing a carrier layer based on crosslinked polyurethane. The carrier layer can consist of extruded polyurethane or be obtained from an aqueous polyurethane dispersion.

[0013] The proposed products generally contain an expandable carrier. Polyurethane-based materials, produced by extrusion or aqueous dispersion, have proven advantageous for expandable carriers. Thermoplastic or elastomeric polyurethanes with a wide range of mechanical properties are commercially available from various suppliers. While the moisture resistance of such carriers, which are obtained from extrusion and are typically thermoplastic, is often sufficient, particularly in thinner layer thickness ranges, the mechanical properties of not all carrier layers in this category are suitable for ensuring tear-free removal. In many cases, the modulus at 100% is too high and / or the carrier's extensibility is insufficient to allow the adhesive tape to be pulled out of the bonded component without premature tearing.

[0014] Backings with a lower modulus at 100% and simultaneously high extensibility can be obtained by selecting appropriate polyurethanes, which are available primarily as dispersions. Suitable polyurethanes for these softer backings are now known from DE 10 2021 210 261 A1. However, they have the disadvantage of insufficient moisture resistance, thus limiting their application possibilities.

[0015] In order to expand the application areas for adhesive tapes, there is a need for removable adhesive tapes that can also be used in humid or warm-humid environments. Against this background, the object of the present invention is to provide adhesive tapes for use in humid or warm-humid environments that can be removed by stretching.

[0016] This object is achieved by an adhesive tape as defined in claim 1. Preferred embodiments of the present invention are set forth in the independent and subordinate claims.

[0017] It has surprisingly been shown that the use of carriers made of certain polyurethanes produced by means of dispersion, so-called PUD, allows the production of adhesive tapes that have a high tensile strength and, at the same time, allow non-destructive removal with little effort and, at the same time, have a high resistance to humid heat, so that application in appropriate environments is possible.

[0018] A first subject matter of the present invention is accordingly a removable adhesive tape comprising at least one adhesive layer and a carrier which comprises at least one layer based on a polyurethane produced 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 WGL-WGI, of not more than 1%, where WGL is the water content after storage for 4 days at 40 °C and a relative humidity of 80% and WGi is the initial water content of the carrier, and where the water content is determined coulometrically according to the Karl Fischer method.

[0019] A detailed description of the measurement methods used to determine the specified parameters can be found in the "Test Methods" section of this document.

[0020] It is known that adhesive tapes, and in particular the backings used in the adhesive tapes, absorb moisture during storage, which can negatively affect the mechanical properties of the backing. For example, a backing originally suitable for removable adhesive tapes may lose this suitability after a certain period of time, particularly in humid environments. In contrast, it has been shown that the adhesive tape according to the invention does not have these disadvantages but is instead characterized by 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 backing and the water content of the backing after storage for 4 days at 40°C and 80% relative humidity. The water content can be determined coulometrically using the Karl Fischer method.In a preferred embodiment, this difference is less than 0.8%, preferably less than 0.7% and particularly preferably less than 0.6%.

[0021] Removable adhesive tapes can most advantageously be removed by pulling on the adhesive tape. This eliminates the need for chemical solvents or other methods that could damage the adhesive substrate. However, removal by pulling on the tape poses the problem that the adhesive tape, particularly the backing, tears, leaving residues of the adhesive tape on the adhesive substrate. Accordingly, the backing must have sufficient tensile strength as well as appropriate stretchability. While there are backings with a corresponding property profile, this usually comes at the expense of other properties such as moisture resistance. In the context of the present invention, it has surprisingly been shown that both property profiles can be advantageously combined.In a preferred embodiment, the carrier used in the adhesive tape according to the invention therefore has an elongation at break of at least 500%. The tear strength of the carrier is determined by its tensile strength; if this is too low, the adhesive tape will tear upon removal. Therefore, an embodiment in which the carrier has a tensile strength of at least 10 MPa, preferably at least 15 MPa, is preferred. In the context of the present invention, it has surprisingly been found that these properties could be retained even after storage thanks to the advantageous moisture resistance of the carrier. Thus, the carrier used in the adhesive tape according to the invention is further distinguished by the fact that it has a tensile strength of at least 10 MPa after storage for 4 days at 40°C and 80% relative humidity. Furthermore, the carrier displays an elongation at break of at least 500% after storage for 4 days at 40°C and 80% relative humidity.

[0022] Depending on the application, it may be desirable for the adhesive tape to have damping properties in addition to sufficient moisture resistance, so that, for example, protection of the component or part to be bonded can be achieved. These damping properties can be represented by the compressive strength, which describes the force required to cause a certain dimensional change or compression in %. For adhesive tapes, the damping properties in the z-direction are particularly important. Therefore, an embodiment is preferred in which the adhesive tape has a compressive strength or compression hardness in the z-direction of a maximum of 100 N / cm. 2 at a compression of 50%, determined according to compression hardness in accordance with ISO 3386.

[0023] Compressive hardness describes the strength of foamed materials and indicates how much force is required to compress the material by a certain percentage from its initial state. The higher the value, the harder the material.

[0024] The carrier used in the adhesive tape according to the invention has at least one layer based on a dispersion-produced polyurethane. In the context of the present invention, polyurethane dispersions that have a specific proportion of polyether-based polyurethane have surprisingly proven particularly suitable for achieving the desired combination of removability and moisture resistance. Accordingly, an embodiment is preferred in which the carrier comprises at least one layer based on a dispersion-produced polyurethane, the polyurethane dispersion having a proportion of polyether-based polyurethane of at least 50 wt. %, based on the total solids content of the dispersion.

[0025] In addition to a polyether-based polyurethane, the dispersion may contain other polyurethanes. These other polyurethanes are preferably those selected from the group consisting of polycarbonate-based polyurethanes and polyester-based polyurethanes, as well as mixtures thereof. These polyurethanes have proven particularly advantageous for combining the property of sufficient tear strength with advantageous resistance to moisture. From the group of polyether-based polyurethanes, those based on polytetrahydrofuran are particularly preferred according to the invention, while from the group of polycarbonate-based polyurethanes, those based on hexanediol polycarbonate are preferred. Also suitable are polyether polyurethanes that contain segments of polypropylene glycol.

[0026] Polyether-based PLIDs generally possess high extensibility and moderate to low tear strength. Within the scope of the present invention, it has surprisingly been shown that the tear strength of corresponding supports can be advantageously improved by using a dispersion that also contains polycarbonate-based polyurethanes. In this way, both high extensibility and high tear strength could be achieved with simultaneous improvement in moisture resistance. Particularly suitable mixtures can also achieve improved optical properties with regard to transmission, b-value, and refractive index after storage in humid conditions.Therefore, a preferred embodiment of the present invention relates to an adhesive tape comprising a carrier having at least one layer based on a polyurethane produced by means of dispersion, wherein the dispersion comprises polycarbonate-based polyurethanes in addition to polyether-based polyurethanes, wherein the proportion of polyether-based polyurethanes in the dispersion is at least 50% by weight, based on the total weight of the dispersion.

[0027] In order to achieve a further improvement, in particular of the mechanical properties, a crosslinked carrier can also be used in the adhesive tape according to the invention. For this purpose, crosslinking components, so-called crosslinkers, can be added to the dispersion used to produce the carrier. The use of polyether-based polyurethanes in crosslinked form has proven particularly advantageous. Therefore, an embodiment is preferred in which the carrier 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 crosslinker. Preferred crosslinkers are crosslinkers based on azeridine, carbodiimide, melamine or isocyanate, with particular preference being given to crosslinkers based on isocyanate.In particular, the addition of a crosslinker based on isocyanate made it possible to further improve the tensile strength and thus the tear resistance of the carrier.

[0028] To improve moisture resistance, it may also be advantageous to additionally use acid scavengers. In a preferred embodiment, the at least one polyurethane-based layer in the carrier according to the invention is therefore obtained from a dispersion that also contains acid scavengers, preferably selected from the group of carbodiimides. These are particularly preferably used in an amount of 2 to 4 wt. %, based on the total weight of the dispersion.

[0029] Depending on the application, the carrier can be foamed or unfoamed. In a preferred embodiment, the at least one layer is foamed based on polyurethane, with microballoons added to the dispersion preferably being used for foaming. Both heat-expandable microballoons and pre-expanded microballoons are suitable. Alternatively, chemical and / or physical blowing agents can also be used for foaming. Foamed carriers have the advantage of improved damping properties, while unfoamed carriers have better optical properties.

[0030] The thickness of the supports can vary depending on the application, but is preferably 10 to 400 pm.

[0031] The adhesive tape according to the invention has at least one adhesive layer. Adhesives based on vinylaromatic block copolymers, especially those based on styrene-butadiene block copolymers, are particularly preferred.

[0032] The present invention further provides a process for producing the adhesive tape according to the invention. For this purpose, a polyurethane-based dispersion with a proportion of polyether-based polyurethane of at least 50 wt. %, 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 drying.

[0033] To ensure the best possible quality and bubble-free dispersion, it is preferably degassed before being applied to the temporary support. This can be achieved, for example, using a vacuum deaerator such as a vacuum thin-film rotation system. This also eliminates the need for defoamers.

[0034] The PU dispersion is preferably applied to the temporary substrate under clean-room conditions, using various application tools such as doctor blades, nozzles, or distribution channels. Application via a nozzle is preferred in this regard, as this method allows for the highest quality optical properties to be achieved.

[0035] The applied PU dispersion is preferably dried by applying heat, particularly in a drying tunnel with different heating zones. The PU dispersion can be applied either to a temporary carrier or directly to a functional layer, such as a pressure-sensitive adhesive. After drying, a second functional layer can be laminated to the opposite side, thus creating a multi-layer product in a single step. This process has the advantage of allowing a multi-layer product to be manufactured particularly efficiently and improving the bond strength / anchoring between the carrier and functional layer.

[0036] To optimize tensile strength, it has proven advantageous to subject the support to a tempering process. Therefore, the process according to the invention further comprises a step in which the support is tempered. The tempering can be carried out, for example, at a temperature of 120°C or more.

[0037] In cases where the PU dispersion used to produce the carrier contains additional components such as thickeners and / or other additives in addition to the polyurethane, it has proven advantageous to predisperse these additional components and then add them portionwise to the PU dispersion 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 added portionwise to the PU dispersion.

[0038] The adhesive tape according to the invention is designed in particular for the bonding of displays, battery bonding and application in electronic components exposed to atmospheric humidity.

[0039] Therefore, a further subject matter of the present invention is an electronic component comprising the adhesive tape according to the invention. Electronic, optical, and precision mechanical devices within the meaning of this application are, in particular, devices as classified in Class 9 of the International Classification of Goods and Services for the Purposes of the Registration of Marks (Nice Classification), 10th Edition (NCL(10-2013)), insofar as they are electronic, optical, or precision mechanical devices, as well as clocks and chronometric instruments according to Class 14 (NCL(10-2013)), such as, in particular,

[0040] • Scientific, nautical, surveying, photographic, cinematographic, optical, weighing, measuring, signaling, checking (supervision), life-saving, and teaching apparatus and instruments; • Apparatus and instruments for conducting, switching, transforming, accumulating, regulating, or controlling electricity; • Image recording, processing, transmission, and reproducing apparatus, such as televisions and the like

[0041] • Acoustic recording, processing, transmission and reproduction devices, such as radios and the like

[0042] • Computers, calculating and data processing equipment, mathematical equipment and instruments, computer accessories, office equipment - such as printers, fax machines, photocopiers, typewriters -, data storage devices

[0043] • Remote communication and multifunctional devices with remote communication function, such as telephones, answering machines

[0044] • Chemical and physical measuring devices, control devices and instruments, such as battery chargers, multimeters, lamps, speedometers

[0045] • Nautical equipment and instruments

[0046] • Optical devices and instruments

[0047] • Medical devices and instruments and those for athletes

[0048] • Clocks and chronometers

[0049] • Solar cell modules, such as electrochemical dye solar cells, organic

[0050] • Solar cells, thin-film cells,

[0051] • Fire extinguishers.

[0052] The present invention is explained in more detail with reference to the following examples, which are in no way to be understood as a limitation of the inventive concept.

[0053] Examples:

[0054] I) Carrier:

[0055] The following raw materials were used to produce the supports.

[0056] Table 1 :

[0057] The recipes for the production of the carriers are summarized in Table 2.

[0058] Table 2: ii) Adhesives:

[0059] For the following tests, the substrates were coated with adhesives based on styrene-butadiene block copolymers. The raw materials and formulations of the adhesives are shown in the following tables:

[0060] Table 3:

[0061] Adhesive KM 1:

[0062] Adhesive KM 2:

[0063] 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, as well as the photoinitiator Irgacure 651 at a concentration of 0.01 wt.%. Subsequently, the polymer was irradiated with a (UV) LED lamp with an intensity of 3000 [mJ / cm 2 ] polymerized for 10 min.

[0064] The prepolymer was then blended with photoinitiator Irgacure 184 (0.2 wt.%) and crosslinker (0.1 wt.% HDDA), and a vacuum pump was used to remove any bubbles from the mixture. The blend was then coated with a thickness of 100 μm between two siliconized PET films (each 50 μm thick). Further reaction was achieved by irradiation with a Heraeus UV-LED lamp (wavelength 365 nm) with a UV dose of 3000 mJ / cm³. 2 initiated.

[0065] Production of supports based on PUD

[0066] The appropriate polyurethane dispersion is mixed with the crosslinker and thickener using a conventional vertical stirring apparatus equipped with a ViscoJet stirrer. The polyurethane dispersion is placed in a sufficiently large container and stirred gently. The formation of whirlpools or any incorporation of air should be avoided throughout the mixing process. The crosslinker Imprafix 2794 is added in portions while stirring continuously. The thickener Ortegol PV301 (25 wt.% solids content) or the thickener BorchiGel 0625 (33 wt.% solids content) is then pre-diluted with water in a ratio of 1:1 and added in portions while stirring continuously. To achieve a homogeneous mixture, the stirring time is at least 30 minutes. The resulting thickened polyurethane dispersion is ideally prepared one day before coating. This allows any air bubbles that may have been stirred in to escape.The mixed polyurethane dispersions can then be spread onto a PET carrier with a release function using a spreader with a comma spreader at the desired basis weight and dried in a commercially available circulating air dryer at 60 °C. The resulting PUD core layers (i.e., PUD cores 1 to 3) are free of processing aids.

[0067] The adhesive layers are then laminated on both sides. The entire composite of carrier and adhesive layers is subjected to further tempering for better anchoring.

[0068] Production of adhesive tapes with PUD-based carrier (according to the invention)

[0069] All substrates were coated on both sides with 50 μm of adhesive KM 1 or KM 2. The composite was then heat-treated. Both the substrate and the composite consisting of the substrate and the adhesive applied to both sides were examined and evaluated for suitability.

[0070] Measurement results

[0071] The adhesive tapes produced were analyzed and measured as follows: a) Water content according to Karl Fischer

[0072] The water content of the backings used in the adhesive tapes was determined using the Karl Fischer method, as described in the Test Methods section. In addition to the initial water content (WGi), the water content was also determined after storage for 4 days at 40 °C and 80% relative humidity (WGL).

[0073] As can be seen from the values ​​in the table, only a slight increase in water content is observed for the supports used according to the invention. b) Tensile elongation

[0074] The tensile elongation was determined according to the method described in the Test Methods section. In addition to the initial tensile elongation, the tensile elongation was also determined after storage of the beams for 4 days at 40 °C and 80% relative humidity. b) Ripper 90°

[0075] The tear strength of the adhesive tape was determined using the method described below. The initial tear strength was determined at room temperature (RT), the tear strength after 4 days of storage at room temperature, and the tear strength after 4 days of storage at 40°C and 80% relative humidity. The percentage of 100 tested adhesive tapes that tore upon removal is given.

[0076] As can be seen from the measurement data, the adhesive tapes according to the invention combine good moisture resistance with the corresponding mechanical properties required for re-removability. Although the adhesive tape with the carrier based on a polycarbonate ester-based polyurethane also demonstrated satisfactory moisture resistance, its low stretchability made it unsuitable for re-removable adhesive tapes. Furthermore, in contrast to the adhesive tapes according to the invention, the mechanical properties could not be maintained when stored in humid environments, as evidenced by a significant increase in the number of failures of the adhesive tapes in the tear test.

[0077] In Example 4, the 50 μm PUD 4 carrier is coated with the 50 μm KM 2 adhesive. It simultaneously meets the highest optical properties requirements for clear adhesive tapes and can therefore be used in displays. The optical properties achieve the following values: transmission of 99.3%; haze of 0.39; b-value of 0.09; and refractive index of 1.472.

[0078] Test methods

[0079] Unless otherwise stated, all measurements are conducted at 23 °C and 50% relative humidity. The mechanical and adhesive data were determined as follows:

[0080] thickness

[0081] The thickness of an adhesive layer can be determined by determining the thickness of a section of such an adhesive layer applied to a liner, defined in terms of its length and width, minus the (known or separately determinable) thickness of a section of the same dimensions of the liner used. The thickness of the adhesive layer can be determined using commercially available thickness gauges (touch-type testers) with an accuracy of less than 1 pm. If thickness variations are detected, the average value of measurements taken at at least three representative locations is given, thus, in particular, not measured at creases, folds, spots, and the like.

[0082] Just as the thickness of an adhesive layer can be determined, the thickness of an adhesive tape (adhesive strip) or a carrier can be determined analogously using commercially available thickness gauges (touch gauges) with an accuracy of less than 1 m. If thickness fluctuations are detected, the average value of measurements taken at at least three representative locations is given, thus excluding creases, folds, spots, and the like.

[0083] Coulometric Karl Fischer titration (water content)

[0084] The measurement is performed according to DIN EN ISO 15512 Method B. Samples are weighed at approximately 0.3 g into glass vials and immediately sealed. A triplicate determination is performed. For each sample preparation, three empty vials are prepared to determine the blank value applicable to the corresponding climatic conditions. The blank values ​​are always measured before the samples are measured. The measurement is performed at 140 °C. The determined water content is expressed in [%].

[0085] Tensile test using a tensile testing machine, Zwick

[0086] From the sample to be tested (adhesive tape, i.e., preferably a backing coated with adhesive on both sides or just a raw backing), 15 mm wide strips with a length of approximately 150 mm are cut lengthwise using a strip cutter or razor blade knife. The sample, preconditioned for 24 hours in the test environment, is clamped vertically in the center of the clamping jaws with a clamping length of 10 mm and stretched at a speed of 800 mm / min until it tears. The tear should occur somewhat in the center of the strip. If the tear occurs near the jaws (closer than 1 cm), the value is discarded and a different strip is tested. Five measurements are performed for each sample variant. The test environment is 23 °C and 50% relative humidity. The measurements are carried out in accordance with EN ISO 527.

[0087] Indication of results:

[0088] F x % [N / cm], [N / mm 2 ] - Force at x % elongation

[0089] Feruch [N / cm], [N / mm 2 ] - Force at tear / break of the sample (ie tensile strength) RD [%] - Elongation at break, ie percentage elongation at tear / break of the sample

[0090] Modulus at x% elongation, elongation at break

[0091] The modulus at x% elongation or the elongation at break in [MPa] of a sample are determined according to DIN 53504.

[0092] Removability (display) using a tensile testing machine

[0093] In the removability test, the double-sided adhesive tape to be tested is bonded between two test panels made of polycarbonate and glass.

[0094] Test specimens 20 mm wide are cut from the adhesive tape to be tested. These test specimens are bonded to the first glass test plate after uncovering the first siliconized PET film over a length of 70 mm. After uncovering the second siliconized PET film, the free adhesive is covered on both sides with 36 μm PET. The second PC test plate is cleaned with isopropanol and preconditioned for 1 to a maximum of 10 minutes at 23 °C and 50% relative humidity, and then bonded to the opposite side of the bonded strip (i.e. test specimen) in such a way that the PC plate protrudes beyond the glass plate. The back of the composite is rolled over the steel plate 10 times using a 4 kg roller (five times back and forth).After at least 24 hours of application at 23 °C and 50% relative humidity, the strips are stripped from the adhesive joint at the grip tab using a tensile testing machine (Zwick) at a constant (feed) speed of 800 mm / min at an angle of 0°. The specimen is fixed with an angle-adjustable adapter, and the grip tab is clamped vertically in the center of the clamping jaws.

[0095] The measurement is taken at an angle of 0°, and the force required to continuously remove / strip the sample is recorded by the tensile testing machine—the so-called stripping force F. The measurement is completed as soon as the sample has been completely stripped from between the two test plates or the sample breaks during the measurement. At least two measurements are taken per sample. The test environment is 23°C and 50% relative humidity.

[0096] Indication of results:

[0097] Fstripp [N / cm] - force required to strip the test specimen from the adhesive joint at an angle of 0° (stripping force) tear test (battery) using a tensile testing machine

[0098] In the tear test, a first test panel made of polyethylene and a second test panel made of steel are used. The first test panel made of polyethylene is wrapped with a double-sided tesa® 67215 adhesive tape, to which a "battery film" is then applied. The tesa® 67215 adhesive tape is 150 μm thick and contains a 30 μm thick polyurethane carrier, on which a 60 μm thick foamed pressure-sensitive adhesive layer based on vinyl aromatic block copolymer is applied on both sides. The "battery film" is an aluminum-laminated polymer film with a thickness of 88 μm from the manufacturer DNP – the film is typically used in the production of lithium polymer batteries.

[0099] Test specimens 8 mm wide and 60 mm long are punched or lasered from the adhesive tape to be tested. These test specimens are glued over a length of 50 mm to the first polyethylene test plate wrapped with battery foil as described above, so that a 10 mm long tab protrudes. The tab is covered on both sides with 36 μm PET. The second steel test plate is cleaned with acetone and pre-conditioned for 1 to a maximum of 10 minutes at 23 °C and 50% relative humidity, and then glued to the opposite side of the glued strip (i.e. test specimen) in such a way that the two test plates lie flush, i.e. congruent, on top of each other. The back of the composite is rolled over the steel plate 10 times using a 4 kg roller (five times back and forth).After a minimum of 4 hours of application at 23 °C and 50% relative humidity, the strips on the grip tab are stripped from the adhesive joint using a tensile testing machine (made by Zwick) at a constant speed of 800 mm / min at a 90° angle over the edge of the first polyethylene test panel wrapped with battery foil. The specimen is secured with an angle-adjustable adapter, and the grip tab is clamped vertically in the center of the clamping jaws.

[0100] The measurement is taken at an angle of 90°, and the force required to continuously remove / strip the sample is recorded by the tensile testing machine—the so-called stripping force F. The measurement is completed as soon as the sample has been completely stripped from between the two test plates or the sample breaks during the measurement. At least six measurements are taken per sample. The test environment is 23°C and 50% relative humidity.

[0101] Indication of results:

[0102] Tear at 90° - the test is considered passed if less than 20% of the test specimens tear during the stripping process. Fstripp 90° [N / cm] - force required to strip the test specimen from the adhesive joint at an angle of 90° (stripping force)

[0103] Figure 1 shows the tensile test using a tensile testing machine. The reference symbols have the following meaning:

[0104] 21 : Handle, reinforced on both sides with 36 pm PET

[0105] 22: adhesive tape to be tested

[0106] 23: Test plates bonded together (test substrates)

[0107] 25: Angle-adjustable adapter for fixing the specimen

[0108] 26: Device for adjusting the measuring angle, 0 to 90°

[0109] transmission

[0110] The transmittance of the adhesive tape is determined according to ASTM D1003-13 (Procedure A (BYK Gardner Haze Gard Plus), standard illuminant D65). A correction for interfacial reflection losses is made. The transmittance of other layers is determined analogously and refers to the actual thickness of the layer.

[0111] Haze

[0112] The haze of the entire assembly 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 forward at a large angle by the sample being irradiated. Thus, the haze value quantifies material defects in the surface or structure that impair clear visibility. The standard requires the measurement of four transmission measurements. For each transmission measurement, the light transmittance is calculated. The four transmittances are added together to determine the percentage haze value. The haze of other layers is determined analogously and refers to the actual thickness of the layer. b-value

[0113] The b-value is a measure of discoloration on a yellow-blue color scale and, together with the L-value (brightness) and the a-value (red-green color scale), provides an objective determination of color perception. The so-called Lab values ​​are determined using the Spectro-Guide-Sphere-Gloss device from BYK Gardner in accordance with ASTM D2244-096 and DIN 6174. First, a triple background measurement is performed on a known reference substrate. The adhesive tape is then measured on this reference substrate, also at three different locations. To determine the b-value, the average of the three individual values ​​is calculated and the average of the reference value is subtracted.

[0114] refractive index

[0115] An Abbemat 350 refractometer (Anton Parr) is used to determine the refractive index. First, a test measurement is performed against air or water to verify functionality. The adhesive tape or individual components are then applied to the measurement window, and the measurement is started. The measurement is performed at 20 °C.

[0116] Compressive hardness according to ISO 3386

[0117] The measurement method is used for the characterization and quality control of foams.

[0118] The compression hardness is the compressive stress in N / cm determined at a specified deformation of the foam during the loading process 2 .

[0119] Test specimens measuring 30 x 30 mm are cut from the material to be tested and stacked to a height of 15 mm. The cut specimens must then be conditioned in the test atmosphere for 24 hours. A sample of the foam to be tested is compressed five times using a compression testing machine under specified conditions. During the final compression test, the deformation diagram is recorded, and the compressive stress at the specified deformation is determined. If required, the force during the first compression test is also determined. Five specimens are tested per sample or product.

Claims

Patent claims 1. Removable adhesive tape comprising at least one adhesive layer and a carrier which comprises at least one layer based on a polyurethane produced 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 WGL-WGI, of not more than 1%, where WGL is the water content after storage for 4 days at 40 °C and a relative humidity of 80% and WGi is the initial water content of the carrier, and where the water content is determined coulometrically according to the Karl Fischer method.

2. Adhesive tape according to claim 1, characterized in that the carrier has a maximum elongation at break of at least 500%, determined according to DIN 53504.

3. Adhesive tape according to at least one of the preceding claims, characterized in that the carrier has a tear strength of at least 10 MPa, determined according to DIN 53504.

4. Adhesive tape according to at least one of the preceding claims, characterized in that 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 weight of the dispersion.

5. 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, wherein the dispersion comprises polycarbonate-based polyurethanes in addition to polyether-based polyurethanes, wherein the proportion of polyether-based polyurethanes in the dispersion is at least 50% by weight, based on the total weight of the dispersion.

6. Adhesive tape according to at least one of the preceding claims, characterized in that the carrier is foamed.

7. 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 crosslinker.

8. Adhesive tape according to at least one of the preceding claims, characterized in that the adhesive is an adhesive based on vinyl aromatic block copolymers.

9. A 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 proportion of polyether-based polyurethanes of at least 50% by weight, based on the solids content of the dispersion, (i) is applied to a temporary support and dried or (ii) is applied to a functional layer and dried.

10. The method according to claim 9, characterized in that the polyurethane dispersion is degassed before application.

11. A method according to at least one of claims 9 to 10, characterized in that the dispersion is applied by means of a nozzle.

12. A method according to at least one of claims 9 to 11, characterized in that the drying is carried out by means of heat supply.

13. The method according to at least one of claims 8 to 12, characterized in that the method further comprises a step in which the carrier is tempered.

14. An electronic component comprising an adhesive tape according to at least one of claims 1 to 8.

15. An electronic component according to claim 14, characterized in that the component is one of those classified in Class 9 of the International Classification of Goods and Services for the Purposes of the Registration of Marks (Nice Classification), 10th Edition (NCL(10-2013)), provided that it comprises electronic, optical or precision mechanical devices, and furthermore clocks and chronometric instruments according to Class 14 (NCL(10-2013)).

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