Adhesive element and method for closing a continuous recess in a substrate with overpressure protection and overpressure-protected substrate

Abstract

Adhesive element (14) for closing a continuous recess (10) in a substrate (12), comprising i) a first carrier layer (26a) in the form of a film, a second carrier layer (17) in the form of a metallic layer, wherein the second carrier layer (17) has a thickness of 50 µm to 200 µm, and a third carrier layer (28) in the form of an air-permeable membrane having the following properties: • Thickness from 100 µm to 1500 µm • Air permeability from 10 to 150 l / h / cm 2 , measured according to ASTM D737-04 (2019) wherein the three carrier layers (26a, 17, 28) are preferably arranged in the specified order or alternatively the third carrier layer (28) is arranged between the first and the second carrier layer (26a, 17), ii) an adhesive layer (16) comprising an adhesive, preferably a pressure-sensitive adhesive, which is present on the surface of the second carrier layer (17) facing away from the first carrier layer (26a), wherein the adhesive element (14) comprises a pressure opening region (20) which is surrounded at least in sections by a weakened region (22) formed in the second carrier layer (17), wherein the average thickness of the second carrier layer (17) in the weakened region (22) is smaller than the average thickness of the second carrier layer (17) in the pressure opening region (20), wherein the third carrier layer (28) is designed such that the contour of the third carrier layer (28) is preferably located completely within the weakened region (22) formed in the second carrier layer (17a), wherein the adhesive element (14) is designed such that the action of a predetermined opening pressure on the pressure opening region (20) at least partially irreversibly destroys the adhesive element (15) in the weakened region (22) and forms a through hole (24) in the adhesive element (14), and wherein the first and second carrier layers (26a, 17) and the adhesive layer (16) are designed such that these carrier layers (26a, 17) and the adhesive layer (16) can allow air passing through the third carrier layer (28) to pass through, in that through holes (42) aligned in the z-direction are provided in the first and second carrier layers (26a, 17) and in the adhesive layer (16), which extend continuously through all layers (26a, 17, 28, 16) from the respective outermost surface of the adhesive element (14) to the third carrier layer (28), and / or the first and second carrier layers (26a, 17) have a recess (44) in the center, wherein the area of ​​the recess (44) is located within the area covered by the third carrier layer (28)

Description

[0001] The invention relates to a method for closing a continuous recess in a substrate, a corresponding overpressure-protected substrate, an adhesive element for permanently closing holes with overpressure protection, and a use of corresponding adhesive elements for permanently closing a hole in a substrate and for creating an overpressure protection.

[0002] When manufacturing complex products, it is often necessary to provide holes in the processed components and substrates for manufacturing reasons. These holes allow further processing steps to be carried out during the manufacturing process, for example, by providing access to an interior space where additional components are to be arranged. However, at the end of the manufacturing process, these holes are often no longer required and are even detrimental for numerous end applications, for example, because they allow the ingress of moisture or contaminants.For this purpose, it is known in the prior art to permanently close corresponding through-holes in substrates during production, wherein in particular the use of adhesive elements, for example so-called die cuts, represents an efficient possibility for permanently closing holes, as disclosed for example in EP 3 569 406 A1, EP 3 943 283 A1 or EP 3 992 259 A1.

[0003] In many cases, however, continuous recesses in the substrate serve more than just manufacturing purposes. Rather, it may be necessary to be able to influence the pressure inside substrates, such as battery casings. Suitable pressure regulation devices, such as valves, must be provided in the area of ​​the continuous recesses for the necessary pressure management.

[0004] So-called overpressure relief devices, sometimes also referred to as "burst systems," are particularly important in the area of ​​pressure management inside substrates. These overpressure relief devices, which are usually more complex in design, serve to protect the installed components in electronic devices, for example, and allow pressure equalization with the environment when a certain internal pressure is reached, by releasing the excess pressure through venting.

[0005] Corresponding overpressure protection devices are particularly relevant for battery housings, such as those currently used in electromobility, for example. These battery housings contain the components of the electrochemical cells, which serve to electrochemically store and generate energy and are available, for example, in the form of so-called pouch cells. Such electrochemical cells, such as lithium-ion batteries, represent complex and, in some cases, failure-prone systems, particularly since they often contain flammable substances, especially electrolytes, and high temperatures can occur during operation.

[0006] As a result, in the worst case, batteries can experience what is known as thermal runaway. In the course of such a thermal runaway, the released gases or the evaporation of liquid components often lead to a strong buildup of pressure inside the battery casing, which can lead to the uncontrolled destruction of the battery casing or the destruction of adjacent battery cells within the casing, resulting in an undesirable chain reaction in the worst case.

[0007] For this reason, high-performance pressure relief devices for battery enclosures are particularly important for safety. The increasing relevance of electromobility in the automotive industry and the growing use of electrochemical energy storage systems are leading to a constant interest in improving pressure relief devices that are particularly suitable for use with battery enclosures.

[0008] A prior art overpressure relief device is disclosed, for example, in CN 107178638 A. Prior art overpressure relief devices are often technically complex components that typically require significant manufacturing effort to fit into the continuous recesses of the substrates. They also exhibit a comparatively high weight and a certain volume. Furthermore, corresponding prior art bursting systems often have to be specifically designed for certain hole geometries and, in many cases, are not flexibly adaptable to different dimensions of the holes to be sealed.

[0009] From DE 102022 117 176 A1, a method for closing a continuous recess in a substrate is known, comprising the method steps: a) producing or providing an adhesive element, comprising: i) an adhesive layer comprising an adhesive composition, ii) a carrier layer arranged on the adhesive layer, comprising a first carrier layer, and b) adhering the adhesive element to the substrate by means of the adhesive layer, so that the adhesive element completely covers the continuous recess and the continuous recess is closed in a fluid-tight manner by the adhesive element, wherein the adhesive element comprises a pressure opening region which is at least partially surrounded by a weakened region formed in the carrier layer,

[0010] In addition, battery casings always contain air inside them in addition to the electrochemical cells due to the manufacturing process. During charging or when a lot of energy is drawn from the battery cells under load, the battery cells and thus the surrounding air heat up. This causes pressure to build up within the battery casing. To prevent this pressure, which arises during regular battery operation, from leading to (irreversible) expansion of the battery casing, an additional requirement is that a corresponding measure within the battery casing not only provides for bursting to immediately relieve pressure, but also allows the overpressure or underpressure in the battery casing caused by operation to be reduced in a controlled and continuous manner.

[0011] The primary object of the present invention was to eliminate or at least reduce the disadvantages of the prior art.

[0012] In particular, it was the object of the present invention to provide an adhesive element (and method) for closing a continuous recess in a substrate, which enables a reliable closure of the continuous recesses against the penetration of particles, objects and water, which enables a reliable pressure equalization, in particular pressure reduction by venting and which at the same time enables a reliable immediate pressure reduction as a result of an overpressure when the pressure exceeds a certain value.

[0013] It was an object of the present invention that the adhesive element should be producible using components that require the smallest possible installation space and have a low dead weight.

[0014] In addition, it was an object of the present invention that the closing of the through-holes with the adhesive element to be specified should be particularly easy, wherein easy automation should desirably be ensured.

[0015] It was a supplementary object of the present invention that the adhesive element to be specified should be particularly flexible for closing through-holes with different hole geometries due to the components to be used and ideally should not require any specific adaptation of the components used for different hole geometries.

[0016] A further object of the present invention was to provide a particularly reliable and durable hole closure with the adhesive element to be specified until the overpressure protection device is activated. The service life should be at least equal to the service life of the battery.

[0017] In light of the above, it was an object of the present invention to provide an overpressure-protected substrate produced with the adhesive element to be specified.

[0018] Furthermore, it was an object of the present invention to provide an adhesive element for permanently closing holes with overpressure protection, which can be used in the method to be specified and also to provide a use based thereon.

[0019] The objects described above can surprisingly be achieved if, instead of complex, constructive bursting systems for closing through-holes in substrates, specific adhesive elements are used with which the through-hole can be glued over, but which, due to a weakening in the carrier layer, comprise a pressure opening area which breaks open largely irreversibly as a result of a predetermined opening pressure, so that pressure equalization can take place through the resulting through-hole in the adhesive element, as defined in the claims.Furthermore, an air-permeable membrane is provided in the carrier layer, which allows the passage of air from the sealed substrate, such as a battery housing, when a certain pressure builds up in the battery housing due to heating, and which allows the passage of air into the battery housing when the battery housing cools down again after operation or the charging process.

[0020] Surprisingly, the inventive design of adhesive elements and their use in corresponding processes not only enables a reliable and air-permeable closure of through-holes in substrates, but also allows for reliable and precisely adjustable opening behavior due to overpressure, depending on the extent of the carrier's weakening. The comparatively simple design of the adhesive element and its simple application result in a particularly advantageous process.

[0021] The corresponding adhesive elements are not only particularly easy to automate and cost-effective to produce, but also have a particularly low weight and volume. Advantageously, the corresponding adhesive elements and thus the corresponding process have a high tolerance for deviations in the hole geometry, allowing for more generous manufacturing tolerances and the adhesive elements used to seal continuous recesses of different dimensions.

[0022] The above-mentioned objects are thus achieved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention emerge from the subclaims and the following statements.

[0023] Such embodiments, which are designated as preferred below, are combined in particularly preferred embodiments with features of other embodiments designated as preferred. Combinations of two or more of the embodiments designated as particularly preferred below are thus very particularly preferred. Likewise preferred are embodiments in which a feature of one embodiment designated as preferred to any extent is combined with one or more further features of other embodiments designated as preferred to any extent. Features of preferred adhesive elements, overpressure-protected substrates, and uses emerge from the features of preferred methods.

[0024] The invention relates to an adhesive element for closing a continuous recess in a substrate, comprising i) a first carrier layer in the form of a film, a second carrier layer in the form of a metallic layer, wherein the second carrier layer has a thickness of 50 µm to 200 µm, and a third carrier layer in the form of an air-permeable membrane, in particular made of polytetrafluoroethylene (PTFE), which has the following properties: • Thickness from 100 µm to 1500 µm • Air permeability from 10 to 150 l / h / cm 2 , measured according to ASTM D737-04 (2019) wherein the three carrier layers are preferably arranged in the specified order or alternatively the third carrier layer is arranged between the first and the second carrier layer, ii) an adhesive layer comprising an adhesive mass which is present on the surface of the second carrier layer facing away from the first carrier layer, wherein the adhesive element comprises a pressure opening region which is at least partially surrounded by a weakened region formed in the second carrier layer, wherein the average thickness of the second carrier layer in the weakened region is smaller than the average thickness of the second carrier layer in the pressure opening region, wherein the third carrier layer is designed such that the contour of the third carrier layer is preferably completely within the weakened area formed in the second carrier layer, wherein the adhesive element is designed so that the action of a predetermined opening pressure on the pressure opening area at least partially irreversibly destroys the adhesive element in the weakened area and forms a through hole in the adhesive element, and wherein the first and second carrier layers and the adhesive layer are designed such that these carrier layers and the adhesive layer can allow air to pass through the third carrier layer by providing through holes aligned in the z-direction in the first and second carrier layers and in the adhesive layer, which extend continuously through all layers from the respective outermost surface of the adhesive element to the third carrier layer, and / or the first and second carrier layers have a recess in the middle, wherein the area of ​​the recess is located within the area covered by the third carrier layer.

[0025] Advantageously, the adhesive element according to the invention is essentially not limited with regard to the type of substrate. However, the adhesive element according to the invention is particularly suitable for use in the closure of battery housings, since in many cases, due to the high number of individual elements, these benefit particularly strongly from the low weight and low manufacturing costs of the solution found within the scope of the present invention. Therefore, the adhesive element is preferably used on a substrate that is a housing, preferably a housing of an electronic device or a battery, particularly preferably a battery.

[0026] A person skilled in the art will understand that a corresponding substrate may also comprise more than one continuous recess, but that in this case, it is preferred if all of the recesses are sealed with the adhesive element according to the invention. Alternatively, the continuous recesses present in the substrate could also be sealed partially with the adhesive element and partially by other means, for example, with conventional adhesive elements without overpressure protection.

[0027] In accordance with the expert understanding, the adhesive element is a flat adhesive element, i.e. it has a significantly greater extent in the two spatial directions of a plane than in the direction orthogonal to the plane. Such adhesive elements can be produced, for example, using methods that are well known to those skilled in the art and that are also used, for example, in the production of other adhesive elements. Typically, such flat adhesive elements are separated from a larger, previously produced adhesive composite using a suitable cutting process, so that the adhesive elements are available in large quantities. Separating can be achieved, for example, by punching out the adhesive elements, in which cases they are usually referred to as a diecut.It is therefore preferred that the adhesive element be produced by punching the adhesive element out of an adhesive composite. In this respect, an adhesive element according to the invention that is a punched product is particularly preferred.

[0028] As an alternative to the production of the adhesive elements in the process, for example by coating carriers with adhesive, these can also simply be provided, for example by purchasing them from a supplier.

[0029] The adhesive elements used comprise an adhesive layer located on the second carrier layer and a carrier with at least three carrier layers. The adhesive layer serves to adhere the adhesive element to the substrate and ensures the necessary adhesion of the adhesive element to the substrate to prevent unwanted, premature detachment under relatively low pressure differences between the two sides of the substrate or under other mechanical stress.

[0030] With a view to achieving the most efficient process possible, which in particular enables particularly easy application of the adhesive elements, but also allows for easy correction of imperfect application if necessary, it is proposed to implement the adhesive as a pressure-sensitive adhesive. Accordingly, an adhesive element according to the invention is preferred, wherein the adhesive is a pressure-sensitive adhesive.

[0031] According to expert understanding, a pressure-sensitive adhesive is an adhesive that possesses pressure-sensitive adhesive properties, i.e., the ability to form a permanent bond to a substrate even under relatively light pressure. Such pressure-sensitive adhesive tapes are generally permanently tacky even at room temperature, meaning they exhibit a certain viscosity and tackiness, allowing them to wet the surface of a substrate even under light pressure. Without wishing to be bound by this theory, it is often assumed that a pressure-sensitive adhesive can be considered an extremely viscous liquid with an elastic component, which consequently possesses characteristic viscoelastic properties that lead to the permanent tackiness and pressure-sensitive adhesive capacity described above.It is assumed that, with corresponding pressure-sensitive adhesives, mechanical deformation results in both viscous flow processes and the buildup of elastic restoring forces. The partial viscous flow serves to achieve adhesion, while the partial elastic restoring forces are particularly necessary to achieve cohesion. The relationships between rheology and pressure-sensitive tack are known in the art and described, for example, in "Satas, Handbook of Pressure Sensitive Adhesives Technology", Third Edition, (1999), pages 153 to 203. To characterize the degree of elastic and viscous components, the storage modulus (G') and the loss modulus (G'') are usually used. These can be determined by means of dynamic mechanical analysis (DMA), for example using a rheometer, as disclosed, for example, in WO 2015 / 189 323 A1.In the context of the present invention, an adhesive is preferably understood as pressure-sensitive adhesive and thus as a pressure-sensitive adhesive if, at a temperature of 23 °C in the deformation frequency range from 10° to 10. 1 rad / sec G' and G'' each at least partly in the range of 10 3 up to 10 7 Pa lie.

[0032] As a possible alternative to the preferred embodiment as a pressure-sensitive adhesive described above, it is conceivable to implement the adhesive as a reactive adhesive, i.e., as an adhesive that only cures following a curing step. The resulting curing of the adhesive and its effect as a structural adhesive make this embodiment particularly interesting for applications in which comparatively high predetermined opening pressures are to be established. Thus, a method according to the invention is preferred for certain applications, wherein the adhesive is a curable adhesive, preferably a radiation-curing and / or thermally curing adhesive, wherein the method preferably additionally comprises the following method step after method step b): c) At least partial curing of the curable adhesive.

[0033] A major advantage of the adhesive element according to the invention is that it is very flexible with regard to the chemical nature of the adhesive used in the adhesive element. The fundamental functionality of the adhesive element according to the invention arises primarily from the interaction of a specifically weakened carrier layer with a generic adhesive and is therefore not limited to chemically specific adhesives. This advantageously enables the selection of suitable adhesives in light of the other application requirements, in particular with regard to adhesion to the respective substrate and / or temperature resistance for the intended application areas. However, it has been possible to identify adhesives with which particularly high-performance adhesive elements can be obtained.Preferred is an adhesive element according to the invention, wherein the adhesive comprises one or more polymers selected from the group consisting of polyurethanes, poly(meth)acrylates and synthetic rubbers, preferably poly(meth)acrylates and synthetic rubbers, particularly preferably poly(meth)acrylates.

[0034] In the context of the present invention, the term "poly(meth)acrylates" encompasses, in accordance with the expert understanding, polyacrylates and polymethacrylates as well as copolymers of these polymers. Poly(meth)acrylates may contain minor amounts of monomer units that are not derived from (meth)acrylates. In the context of the present invention, a "poly(meth)acrylate" is understood to mean a (co)polymer whose monomer base consists of a mass fraction of 70% or more, preferably 90% or more, particularly preferably 98% or more, of monomers selected from the group consisting of acrylic acid, methacrylic acid, acrylic esters, and methacrylic esters, based on the mass of the monomer base. The mass fraction of acrylic ester and / or methacrylic ester is preferably 50% or more, particularly preferably 70% or more.Poly(meth)acrylates are generally accessible by radical polymerization of acrylic and / or methacrylic-based monomers and, if appropriate, other copolymerizable monomers.

[0035] For certain applications, it is advantageous to implement the adhesive as a foamed adhesive, for example, as a syntactically foamed adhesive, which uses expanded microballoons, as are generally known from the prior art, or as a physically foamed adhesive, which can be produced, for example, using a propellant gas. Such foamed adhesives often have advantages, particularly with regard to shock resistance. In this respect, it can be considered an advantage of the adhesive element according to the invention that foaming of the adhesive does not impede the basic functionality of the adhesive elements according to the invention.Accordingly, an adhesive element according to the invention is preferred for certain applications, wherein the adhesive is a foamed adhesive, wherein the adhesive is preferably a physically foamed adhesive and / or comprises one or more components selected from the group consisting of hollow spheres and at least partially expanded microballoons.

[0036] According to a preferred embodiment, the adhesive layer has a basis weight of 10 to 200g / m 2 preferably a basis weight of 50 to 100 g / m 2 .

[0037] According to the invention, the carrier comprises a first carrier layer in the form of a film, a second carrier layer in the form of a metallic layer, and a third carrier layer in the form of an air-permeable membrane. In practice, according to a preferred embodiment, the carrier essentially consists of these three carrier layers. However, embodiments are also conceivable in which additional carrier layers are present, for example, one or more, preferably one or two, or, for example, three or more, additional carrier layers, wherein the carrier layers are preferably bonded to one another by intermediate adhesive layers.

[0038] Particularly for more demanding applications, for example when the adhesive closure is expected to be subjected to strong thermal and / or chemical and / or mechanical stress during use, it is possible for the carrier to comprise these additional carrier layers, which serve, for example, to optimize the physico-chemical properties, in particular the surface properties.

[0039] The first carrier layer can shield the underlying carrier layers, in particular the second carrier layer, from environmental influences and is particularly advantageous because the second carrier layer is made of metal, as this can prevent unwanted corrosion and any resulting damage to the second carrier layer in the long term.

[0040] The adhesive element according to the invention is fundamentally very flexible with regard to the material selection of the first carrier layer. Those skilled in the art can use typical materials that are already known as carrier materials in the field of adhesive technology. An adhesive element according to the invention is preferred in which the first carrier layer comprises a film selected from the group consisting of plastic films, for example, polyester films, polyethylene naphthalate (PEN) films, PUR films, PEEK films, PAEK films, polyimide films, or polyamide films, in particular polyester films such as polyethylene terephthalate or polybutylene terephthalate.

[0041] The first carrier layer provided according to the invention is advantageously used in thicknesses of 50 µm to 300 µm, more preferably in thicknesses of 100 µm to 200 µm.

[0042] Further preferably, the first carrier layer is provided on its underside with an intermediate adhesive layer, with which the first carrier layer is fixed to the second carrier layer. A pressure-sensitive adhesive, as described in detail above, is preferably used as the intermediate adhesive layer. The intermediate adhesive layer is preferably applied over the entire surface of the first carrier layer.

[0043] According to a preferred embodiment, this intermediate adhesive layer has a basis weight of 10 to 200 g / m 2 preferably a basis weight of 50 to 100 g / m 2 .

[0044] According to the invention, the second carrier layer is a metallic layer, also referred to as a metal layer. Within the scope of the invention, the term "metal" encompasses metals, but also alloys or metal oxides. The metal layer can be a metal foil. The metal layer can also be realized by vapor deposition, sputtering, electrostatic coating, or other application of the material in small-particle, atomic, ionic, or molecular form, in particular of metals, metal oxides, or the like. The metal layer provided according to the invention is advantageously used in thicknesses of 50 µm to 150 µm, more preferably in thicknesses of 70 µm to 100 µm.

[0045] A layer made of Al, Cu, Ag, Au, Pt, Pd, Zn, Cr, Ti, and the like is particularly suitable as a metal layer, although common impurities in the metals are not excluded. Aluminum has proven to be a particularly suitable metal. A layer made of an alloy is also within the scope of the invention. An alloy is a macroscopically homogeneous metallic material made of at least two elements (components), at least one of which is a metal and which together exhibit the typical metal characteristic of metallic bonding. In a further advantageous manner, layers made of copper or titanium or of metal oxide (MeOx layers) can be used according to the invention. Advantageous metal oxide layers consist, for example, of silicon dioxide (SiO2), titanium dioxide (TiO2), or zinc tin oxide (ZnSnO), or they comprise one or more of these metal oxides.The metal oxides more preferably comprise boron oxides, aluminum oxides, molybdates, vanadates and include their hydroxides and oxide hydrates or mixtures thereof.

[0046] According to an advantageous embodiment of the invention, the metallic layer consists of aluminum, more preferably in a thickness of 70 µm to 100 µm.

[0047] The second carrier layer provided according to the invention is used in thicknesses of 50 µm to 200 µm, more preferably in thicknesses of 70 µm to 100 µm

[0048] According to the invention, the third carrier layer forms an air-permeable membrane, particularly made of polytetrafluoroethylene (PTFE). Due to the material's very high hydrophobicity, air is allowed to pass through, but water or water vapor is largely prevented from passing through such membranes.

[0049] PTFE membranes are manufactured using a sintering process followed by a skiving process. The sintering process uses a combination of heat and pressure to bond the materials together. Skiving involves cutting the sintered form into thinner membranes.

[0050] The membrane provided according to the invention, preferably a PTFE membrane, is used in thicknesses ranging from 100 µm to 1500 µm, more preferably in thicknesses ranging from 130 µm to 1000 µm. PTFE membranes are preferred because they have a hydrophobic character. This means they allow air to pass through but prevent water from passing through.

[0051] Furthermore, the (PTFE) membrane has an air permeability of 10 to 150 l / h / cm 2 measured according to ASTM D 737 (2018) with a differential pressure of dp=70mbar.

[0052] The air permeability that can pass through the membrane, preferably made of PFTE, is determined using the measurement method described below.

[0053] The air permeability through the (polytetrafluoroethylene) membrane is measured using a device called a permeability tester or gas permeameter. This device measures the rate at which gas molecules flow through a specific area of ​​the membrane under certain conditions.

[0054] Typically, the membrane is mounted between two chambers, with a pressure difference across the membrane. The gas flow rate is then measured, and the permeability of the membrane can be calculated based on the pressure difference and the membrane area.

[0055] The standard method is described in ASTM D 737 (2018) “Standard Test Method for Air Permeability of Textile Fabrics”.

[0056] During testing, the (PTFE) membrane is stretched between two circular metal plates with an exposed diameter of 6.35 cm (2.5 inches). The membrane is then mounted in a test cell separating two chambers. The upstream chamber is filled with a gas, in this case air, at a specific pressure, while the downstream chamber is at a lower pressure.

[0057] The air flow through the membrane is determined by the pressure drop across the membrane using a differential pressure gauge. The air flow is then calculated based on the pressure difference decrease per unit time and the membrane area.

[0058] The test conditions specified in ASTM D737 (2018) are as follows: • Test temperature: 21 ± 1°C • Relative humidity: 65 ± 2% • Test gas: air • Test duration: 60 seconds • Differential pressure of Δp = 70 mbar

[0059] Further preferably, the (PTFE) membrane has a water inlet pressure greater than 100 mbar, preferably 120 to 400 mbar, measured according to the water column test according to ISO 20653 (2006). The membrane preferably has the IPX7 classification (ISO 20653, 2006-08). The first digit represents the degree of protection against direct contact and the ingress of foreign bodies (not tested here). The second digit refers to the protection against moisture and water penetration. The higher the number, the greater the protection. Class 7 means water tightness during temporary immersion in water (30 minutes, 1 m water column above the adhesive element).

[0060] The water column test takes place under the following conditions (see also Fig. 5): Test conditions according to ISO 20653 Test climate 23 ± 1 °C and 50 ± 5 % relative humidity Length of time 30 minutes Bore Ø 41 mm Punching Ø 90 mm Test substrate Steel Residence timeI Immediate testing after application Height of the water column 1.0 m Evaluation Visual inspection for water leakage

[0061] Suitable membranes include Virtek PTFE membranes from Porex Technologies Ltd, such as POREX® Virtek™ PTFE Materials PMV10, PMV15, or BM10. These membranes have pore sizes from <1 to 60 µm and a pore volume of 25 to 60%.

[0062] According to the invention, a continuous recess is completely covered and thereby closed by the adhesive element. The person skilled in the art will understand that this type of overpressure protection, which will be explained in more detail below, means that this closure can be broken open as a result of an acting pressure. For this purpose, according to the invention, a pressure opening region is provided in the adhesive element, which is at least partially surrounded by a weakened region formed in the second carrier layer, wherein the average thickness of the second carrier layer in the weakened region is smaller than the average thickness of the second carrier layer. The second carrier layer has a reduced mechanical load-bearing capacity in the weakened region. This results in a type of predetermined breaking point in the second carrier layer.Advantageously, the predetermined opening pressure, i.e., the pressure at which the overpressure protection device is to be activated, can be adjusted by the extent of the weakening of the weakened region. It is preferred if the second carrier layer in the weakened region has an average thickness in the range of 5 to 150 µm, preferably in the range of 10 to 100 µm, particularly preferably in the range of 15 to 60 µm, and / or if the average thickness of the second carrier layer in the weakened region is 5 to 95%, preferably 10 to 80%, particularly preferably 20 to 60%, smaller than the average thickness of the second carrier layer in the pressure opening region.

[0063] According to a particularly preferred embodiment of the adhesive element, the second carrier layer is formed from an aluminum foil with a thickness of 80 µm, wherein the aluminum foil has a closed groove-shaped weakened area in which the thickness of the aluminum foil is reduced to 30 µm. Furthermore, it is preferred if 90% of the theoretically possible groove length is weakened, so that when the adhesive element bursts, the resulting section only opens up instead of being completely severed. If the weakened area is circular, for example, 320° of 360° are weakened.

[0064] According to a preferred variant of the adhesive element according to the invention, the first carrier layer (and optionally all further carrier layers beyond the first, second and third carrier layers) also has a weakened region which has a reduced mechanical load-bearing capacity. For this weakened region too, it is preferable that the first or the respective carrier layer in the weakened region has an average thickness in the range from 5 to 150 µm, preferably in the range from 10 to 100 µm, particularly preferably in the range from 15 to 60 µm, and / or the average thickness of the first or the respective carrier layer in the weakened region is 5 to 95%, preferably 10 to 80%, particularly preferably 20 to 60% smaller than the average thickness of the first or the respective carrier layer in the print opening region.The weakened area in the first layer can also have a residual thickness of 0 µm, meaning that the first layer is completely pierced / punched through in the weakened area. Furthermore, these weakened areas in the second and first, or respectively the respective carrier layer, are preferably essentially congruent with one another—ideally, the weakened areas overlap one another—so that a pressure opening channel that is as continuous as possible is created through the carrier layers.

[0065] Those skilled in the art will therefore understand that the adhesive element is designed to form a through-hole as a result of the action of a predetermined opening pressure on the pressure opening area. In accordance with the expert's understanding, this action of a predetermined opening pressure refers to a pressure difference between the two sides of the adhesive element, as occurs, for example, when the adhesive element covers a recess in an otherwise closed vessel and an increase in pressure occurs inside the vessel. Those skilled in the art will understand that the predetermined opening pressure does not refer to the ambient pressure, which is experienced equally by all sides and areas of the adhesive element, so that there is no force acting on the pressure opening area relative to the rest of the adhesive element. In other words, the predetermined opening pressure thus refers to an opening pressure difference.

[0066] The term "at least partially irreversibly destroyed" used in the context of the present invention means, in accordance with the expert understanding, that complete destruction of the weakened area (or areas of weakness) is not necessary, as long as the destruction is sufficient to form a through-hole in the adhesive element. For example, a circular weakened area that completely surrounds a pressure opening area could be destroyed only over part of its circumference as a result of the predetermined opening pressure, so that the pressure opening area is only partially released from the adhesive element. Likewise, the destruction does not have to be completely irreversible.Due to the physico-chemical properties of typical adhesives, in particular their flow behavior, it would be at least theoretically conceivable that a pressure opening area pressed back into the adhesive element could be at least provisionally closed via the interaction of the adhesive, despite the irreversibly destroyed second carrier layer, in such a way that the raised pressure opening area is held in position by the adhesive layer.

[0067] Even though it is theoretically conceivable to provide larger, flatter areas of reduced thickness, and such more complex weakened areas may be useful for specific applications, it is preferable, with a view to precisely opening the weakened area while simultaneously simplifying production, to form it essentially as a groove-shaped recess, i.e., as an elongated depression, in the second carrier layer. Accordingly, it is preferred that the weakened area be formed as a groove-shaped recess in the first and / or second, or the respective, carrier layers.

[0068] Those skilled in the art will understand that the resistance that the adhesive element can offer to an applied pressure difference after the hole has been closed is significantly influenced by the mechanical strength of the carrier layer or the first and / or second or the respective carrier layer, whereas the contribution of the adhesive layer is less, particularly since in many cases it will be fluid to a certain extent. Accordingly, unless the predetermined opening pressure is to be achieved even at very low pressures, it is expedient to design the first and / or second or the respective carrier layer without completely continuous perforations in order to prevent premature fluid penetration at low pressures.It is preferred that the weakened region in the first and / or in the second or in the respective carrier layer does not comprise a recess that completely penetrates the carrier layer, in particular not the second carrier layer.

[0069] Due to the above-described significant influence of the carrier layer on the predetermined opening pressure and the generally existing flow behavior of the adhesive, it is advantageously not necessary to provide a corresponding reduction in the average thickness in the adhesive layer that complements the weakened region, which can simplify production. Against this background, an adhesive element according to the invention is preferred, wherein the average thickness of the adhesive layer in the weakened region is 20% or less, preferably 10% or less, particularly preferably 5% or less, very particularly preferably 1% or less, especially preferably 0.1% or less, smaller than the average thickness of the adhesive layer in the pressure-opening region.

[0070] Those skilled in the art will understand that the dimensions of the pressure opening area depend on the shape of the weakened area. The pressure opening area, which is at least partially released from the adhesive element in the event of overpressure, is thus defined in its shape and dimensions by the predetermined breaking point that causes this, i.e., the weakened area. In this respect, a variety of basic shapes can be provided for the pressure opening area. With a view to simple application and a secure hold of the adhesive element on the substrate, it is often expedient to orient the shape of the pressure opening area to the shape of the recess to be covered and to arrange the pressure opening area relatively centrally in the adhesive element.Consequently, an adhesive element according to the invention is preferred, wherein the pressure opening region has a basic shape that generally has a rounded convex figure, in particular is selected from the group consisting of circles, partial circles, in particular semicircles, ovals or polygons, preferably selected from the group consisting of circles, semicircles and ovals. Additionally or alternatively, an adhesive element according to the invention is preferred in which the pressure opening region has a basic shape that essentially corresponds to the cross-section of the continuous recess. In all embodiments, an adhesive element according to the invention is particularly preferred, wherein the center point of the adhesive element lies in the pressure opening region.

[0071] The adhesive element according to the invention advantageously makes it possible, with comparatively minor changes in the manufacturing process of the adhesive element, to influence how far the adhesive element is opened when the overpressure protection device engages, and thus to influence the fluid flow. A through-hole that opens very widely is achieved in particular when the pressure opening area is surrounded as largely as possible by the weakened area. In one embodiment, it is particularly interesting to essentially completely surround the pressure opening area with the weakened area in the first and / or second or each carrier layer, so that it is particularly easy to completely remove from the adhesive element a pressure opening area that has been lifted out of the adhesive element as a result of an applied overpressure.Accordingly, an adhesive element according to the invention is preferred in which, in the first and / or in the second or in each carrier layer, the pressure opening area is surrounded by the weakened area to 50% or more, preferably to 70% or more, particularly preferably to 90% or more, very particularly preferably to 95% or more, particularly preferably to substantially 100%, of the circumference of the pressure opening area.

[0072] As an alternative embodiment, a weakened region can deliberately not be provided in a partial section of the circumference of the pressure opening region, so that an unweakened twist remains between the raised pressure opening region and the remaining adhesive element, which can advantageously prevent the raised pressure opening region from being torn off too easily as a result of mechanical stress and, for example, remaining as a foreign body in the housing. Thus, an adhesive element according to the invention is preferred in which, in the first and / or in the second or in each carrier layer, the pressure opening region is not surrounded by the weakened region to an extent of 0.1 to 10%, preferably 0.2 to 5%, particularly preferably 0.5 to 2%, of the circumference, based on the circumference of the pressure opening region.

[0073] The weakened areas in the adhesive element, i.e., the local reduction of the average thickness in the carrier layer, can advantageously be created using a wide range of possible processes. Punching is particularly suitable for producing adhesive elements in large quantities, whereas the use of laser structuring is particularly suitable for setting particularly precise weakened areas. In this respect, an adhesive element according to the invention is preferred, wherein the weakened area in the adhesive element is created using material-removing or cutting processing methods, preferably using laser structuring or punching.

[0074] Those skilled in the art will understand that the predetermined opening pressure is significantly influenced by the design of the adhesive element used, and in particular by the dimensions and configurations of the weakened areas, so that the structural design of the adhesive elements allows for precise adjustment of the desired opening behavior. In cases where the predetermined opening pressures are very low, an inherently reduced structural integrity of the entire adhesive element is often achieved, whereby manufacturing-related deviations in the weakened area and the resulting absolute fluctuations in the predetermined opening pressure can manifest themselves as relatively large relative uncertainties. Accordingly, the predetermined opening pressure is not selected to be too low.At the same time, particularly high predetermined opening pressures place, at least indirectly, higher demands on the adhesives used and their adhesive strength to the substrate, as the goal is to prevent adhesive failure of the entire adhesive element and thus premature venting before the pressure opening area opens. Therefore, in addition to targeted lower limits for the opening pressure, ranges and associated upper limits are selected that are suitable for numerous applications and can be easily adjusted using typical adhesives and carrier materials.An adhesive element according to the invention is preferred, wherein the predetermined opening pressure is 10 kPa or more, preferably 15 kPa or more, particularly preferably 20 kPa or more, very particularly preferably 25 kPa or more, and / or wherein the predetermined opening pressure is in the range from 5 to 200 kPa, preferably in the range from 10 to 150 kPa, particularly preferably in the range from 15 to 100 kPa, very particularly preferably in the range from 20 to 50 kPa.

[0075] An advantage of the adhesive element according to the invention can be seen in the fact that the necessary bonding of the adhesive elements is particularly simple, especially compared to bursting systems known from the prior art, and can therefore also be easily automated. Accordingly, a method according to the invention is also preferred, in which the bonding of the adhesive element is automated, preferably using a robot arm.

[0076] For optimal opening in the event of overpressure, the pressure opening area is arranged substantially concentrically over the continuous recess. An adhesive element according to the invention is preferred in which the pressure opening area is arranged concentrically over the continuous recess.

[0077] A particularly simple design, which offers great flexibility with regard to the hole geometry to be closed, is achieved when the pressure opening area is smaller than the through-hole to be closed, so that the through-hole lies completely above the pressure opening area in plan view. In these cases, an adhesive element according to the invention is preferred in which the pressure opening area has a smaller area than the cross-section of the through-hole, wherein the adhesive element is preferably bonded in such a way that the pressure opening area is arranged completely inside and above the through-hole.

[0078] However, in the above-described design, in which the pressure-opening region is completely surrounded by the edge of the continuous recess, it has proven disadvantageous that it makes it difficult to achieve an anisotropic opening behavior. In other words, such a design is more susceptible to opening due to overpressure acting on the carrier layer, i.e., in most applications, overpressure acting on the substrate from the outside, for example, into the interior of a sealed housing. Even if this may be desirable for certain designs, such an opening behavior is considered disadvantageous for most applications, particularly in the field of battery housings.To adjust the directional dependence of the opening behavior, the adhesive element should be bonded in such a way that the pressure opening area protrudes at least partially beyond the edge of the continuous recess, preferably completely and in all directions beyond the edge of the recess, for example, at least 3 mm, preferably 5 mm, more preferably 10 mm at any point along the edge of the recess. This advantageously ensures that the overlap between the edge of the continuous recess and the pressure opening area, together with the rigidity of the carrier layer, counteracts the unintentional opening of the pressure opening area toward the closed recess.Therefore, an adhesive element according to the invention is particularly preferred in which the adhesive element is bonded in such a way that the pressure opening area, based on the circumference of the continuous recess, projects beyond the edge of the continuous recess at least in sections, preferably by 50% or more, particularly preferably by 70% or more, very particularly preferably by 90% or more, extremely preferably by 95% or more, particularly preferably by substantially 100%, of the circumference, and / or wherein the pressure opening area has a larger area than the cross section of the continuous recess.

[0079] The degree of overlap also advantageously allows the load pressure to be adjusted up to which the pressure opening area is not detached from the adhesive element when pressure is applied from the outside, i.e. from the direction of the carrier layer, so that not only can an advantageous anisotropy of the opening behavior be achieved, but this can also be precisely adjusted in both directions. Accordingly, an adhesive element according to the invention is also particularly preferred in which the adhesive element is bonded by the pressure opening area projecting at least partially beyond the edge of the continuous recess in such a way that the bonded adhesive element withstands the action of a predetermined load pressure on the carrier in the pressure opening area, so that the adhesive element is not irreversibly destroyed in the weakened area and no through hole is formed in the adhesive element.Very particular preference is given to an adhesive element according to the invention in which the predetermined loading pressure is 100 kPa or more, preferably 200 kPa or more, particularly preferably 300 kPa or more, very particularly preferably 400 kPa or more.

[0080] In the advantageous embodiment described above, with an at least partial overlap of the pressure opening area with the edge of the recess, there is an effect that can limit the freest possible adjustment of the predetermined opening pressure while simultaneously setting a predetermined loading pressure. Particularly with high degrees of overlap, which may be necessary for setting high loading pressures, it can happen - at least with the preferred, quite extensive coating of the carrier layer with an adhesive layer - that the adhesive interaction of the adhesive layer in the overlap area makes a noticeable contribution to the necessary opening pressure, since in this case, the adhesion between the adhesive layer and the edge of the recess must also be overcome to raise the pressure opening area.In this case, the predetermined opening pressure is no longer essentially determined by the weakening of the carrier layer, but the pressure required for opening must also overcome the adhesive interaction between the adhesive layer and the substrate.

[0081] According to the invention, the adhesive element has a third carrier layer in the form of an air-permeable membrane, in particular made of polytetrafluoroethylene (PTFE). This third carrier layer is preferably provided below the second carrier layer, so that the carrier layers are arranged in the specified order. Alternatively, the third carrier layer is arranged between the first and second carrier layers.

[0082] The third carrier layer preferably does not substantially protrude beyond the print opening region, and / or the dimensions of the third carrier layer preferably substantially correspond to the dimensions of the print opening region. Preferably, the continuous recess is at least partially, preferably completely, covered with the third carrier layer before the adhesive element is bonded on, wherein the dimensions of the third carrier layer are preferably selected such that the third carrier layer completely extend beyond the dimensions of the print opening region, wherein the adhesive element is bonded on such that the print opening region at least partially, preferably completely, covers the third carrier layer. The person skilled in the art will understand that an adhesive element according to the invention is expedient in which the third carrier layer does not comprise an adhesive. Furthermore, the third carrier layer usually and preferably does not have a weakened region.

[0083] With a view to achieving the greatest possible material-saving production and good handling properties, it is advantageous that the dimensions of the adhesive layer and the first and second carrier layers as well as the additional carrier layers should be as similar as possible. Even if it may be preferable for some applications to allow the second carrier layer to protrude beyond the adhesive layer, it is preferred, particularly with a view to manufacturing efficiency, if it is completely covered by the adhesive layer. Thus, an adhesive element according to the invention is preferred in which the second carrier layer is covered on one side by 50% or more, preferably by 70% or more, particularly preferably by 90% or more, very particularly preferably by 95% or more, especially preferably essentially completely, by the adhesive layer.

[0084] Further preferably, the first and second carrier layers have identical dimensions. However, the first carrier layer can also extend beyond the second carrier layer. In a circular embodiment of the adhesive element, the diameter of the first carrier layer can be 10 mm larger than the diameter of the second carrier layer.

[0085] Depending on the size of the continuous recess, for example in a battery housing, and the desired burst pressure and air permeability, the dimensions and shapes of all layers can be adapted. For a circular recess, circular layers and a circular pressure opening area are preferred.

[0086] Furthermore, the adhesive element according to the invention provides that the first and second carrier layers and the adhesive layer are designed such that these carrier layers and the adhesive layer can allow air that passes through the third carrier layer to pass through. As already described above, the main function of the third carrier layer is to allow a gaseous medium such as air to pass through when the adhesive element is used to seal a substrate such as a battery housing. This ensures that a slowly building up pressure within the battery housing, for example because the air therein heats up during charging or discharging processes, is released in a controlled manner by said heated air passing through the membrane. When the battery housing cools down again, cooled air from the outside flows back into the housing.In order to enable this flow of a medium such as air through the membrane, it must be ensured that the other layers present in the adhesive element, such as the first or second carrier layer and the adhesive layer, are also designed in such a way that they allow flow through.

[0087] Only when a rapid pressure increase occurs, for example because thermal runaway occurs in a battery cell within the battery housing, causing the liquid components in the cell to evaporate, is the adhesive element according to the invention no longer able to equalize the pressure via the third carrier layer in the form of the membrane, so that when the predetermined load pressure is exceeded, the pressure opening area opens.

[0088] In one variant, through-holes aligned essentially in the z-direction are provided in the first and second carrier layers and in the adhesive layer. These extend continuously through all layers from the outermost surface of the adhesive element to the third carrier layer. It is clear to those skilled in the art that, when there are several layers lying one above the other, these through-holes must be congruent in the individual layers in order to form a continuous channel. The diameter of the preferably cylindrical through-holes is preferably between 1 and 10 mm. The diameter of the through-holes in the adhesive layer and the composition of the adhesive layer are coordinated such that these holes in the adhesive layer do not flow closed.

[0089] In a second variant, the first and second carrier layers have a recess in the center. In a preferred embodiment of the adhesive element, the first and second carrier layers have the shape of a circular ring. This applies in particular if the adhesive element itself is circular. The area of ​​the recess is located within the area covered by the third carrier layer, so that the first and second carrier layers overlap the third carrier layer in the entire edge region. The third carrier layer is thus covered in the entire edge region. Further preferably, the recess essentially does not protrude beyond the print opening area, further preferably the recess lies completely within the print opening area.

[0090] In a third variant, one or more recesses are present in the first and second carrier layers and, in addition, the described through holes are present in the remaining areas of the first and second carrier layers.

[0091] According to a preferred embodiment of the adhesive element, the first and second carrier layers have a central round, preferably circular, recess that is of equal size and arranged congruently one above the other. Further preferably, the recess is shaped such that the first and second carrier layers have an overhang of 10 to 20 mm on all sides.

[0092] In one variant, the central recess is not circular (but, for example, oval or rectangular, with the corners preferably rounded). Alternatively, several smaller recesses form the recess, for example, six circular recesses with a diameter of 5 mm or 15 recesses with a diameter of 10 mm each. 2 Area.

[0093] According to a further embodiment of the adhesive element, a further, fourth carrier layer is present. The outer diameter of the fourth layer is larger than the diameter of the recess in the battery housing and protrudes partially or completely beyond the recess. At the same time, the diameter of the pressure opening area in carrier layers 1 and 2 is the same, larger, or smaller than the outer diameter of the fourth layer, preferably the same size and flush with the outer dimensions of the fourth carrier layer. The fourth layer has a certain rigidity and offers a certain resistance when pressure is applied to the adhesive element from the outside. This also delays unintentional opening of the predetermined breaking point in carrier layers 1 and 2 and achieves anisotropic opening behavior. The fourth layer can contain a plastic film similar to carrier layer 1, for example a PET film, for example with a thickness of between 25 µm and 200 µm.In a further embodiment, the fourth layer may contain a metal foil similar to carrier layer 2, for example an aluminum foil, for example in a thickness between 25 µm and 200 µm.

[0094] In the embodiment of the adhesive element in which the third carrier layer is arranged below the second carrier layer (i.e. not between the first and second carrier layers), a fourth carrier layer in the form of a film can be present between the second carrier layer and the third carrier layer. On the upper side, this fourth carrier layer is fixed to the second carrier layer by the adhesive layer. The dimensions of the fourth carrier layer are such that the fourth carrier layer completely projects beyond the third carrier layer and is in turn completely projected beyond by the second carrier layer. On the underside, a connection to the third carrier layer is made by applying a strip of adhesive extending over the entire length of the outer edge to the upper side of the third carrier layer in the region of the outer edge. The width of the adhesive strip is between 2 and 10 mm, preferably between 3 and 7 mm.The fourth carrier layer has a recess that is congruent with the recesses of the layers above it or has the through holes described above, so that continuous channels are created.

[0095] In one variant, the fourth carrier layer has a recess whose area exactly corresponds to the area of ​​the third carrier layer, so that the fourth carrier layer surrounds the third carrier layer on all sides, for example, in the form of a circular ring that encloses the inner circle forming the third carrier layer. The recess is then circular and has the same area as the third carrier layer. In this variant, the third carrier layer is not equipped with an adhesive strip.

[0096] In the embodiment of the adhesive element in which the third carrier layer is arranged between the first and second carrier layers (i.e. not beneath the second carrier layer), the third carrier layer is preferably fixed in place by the intermediate adhesive layer present on the underside of the first carrier layer. A connection to the second carrier layer is made on the underside by applying an adhesive strip extending over the entire length of the outer edge to the underside of the third carrier layer in the region of the outer edge. The width of the adhesive strip is between 2 and 10 mm, preferably between 3 and 7 mm. The fourth carrier layer has a recess that is congruent with the recesses in the layers above it or has the through-holes described above, thus creating continuous channels. A silicone-based adhesive is preferably selected for the adhesive strip.

[0097] Additionally or alternatively, an adhesive element according to the invention is also preferred, wherein the substrate comprises one or more materials selected from the group consisting of metals, composite materials, for example comprising glass or carbon fibers, and plastics, preferably plastics and metals, particularly preferably metals, in particular coated metals.

[0098] The person skilled in the art will understand that the invention also relates to a method for permanently closing holes with overpressure protection, with which the adhesive element according to the invention is bonded.

[0099] The method for closing a continuous recess in a substrate comprises the following process steps: a) producing or providing one of the adhesive elements and b) Bonding the adhesive element to the substrate by means of the adhesive layer so that the adhesive element completely covers the continuous recess and the continuous recess is sealed fluid-tight by the adhesive element.

[0100] The method according to the invention serves to close through-holes in substrates, in particular holes, and is particularly relevant in practice for closing holes through which an interior space in the substrate is connected to the environment. Accordingly, a method according to the invention is preferred, wherein the substrate comprises an interior space, which is closed by adhering the adhesive element to the through-hole.

[0101] A method according to the invention is also preferred, wherein the substrate comprises two or more continuous recesses, wherein preferably all continuous recesses are closed with the adhesive element.

[0102] Preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying figures. In the figures: Fig. 1a shows a cross-section through the structure of an adhesive element according to the invention before application to the substrate in a first preferred embodiment; Fig. 1b shows a cross section through the structure of an adhesive element according to the invention before application to the substrate in a second preferred embodiment; Fig. 1c shows a cross section through the structure of an adhesive element according to the invention before application to the substrate in a third preferred embodiment; Fig. 1d shows a cross section through the structure of an adhesive element according to the invention before application to the substrate in a fourth preferred embodiment; Fig.1e shows a cross section through the structure of an adhesive element according to the invention before application to the substrate in a fifth preferred embodiment; Fig. 1f shows a cross-section through the structure of an adhesive element according to the invention before application to the substrate in a fifth preferred embodiment; Fig. 2 a second schematic exploded view of the structure of an adhesive element according to the invention before application to the substrate in a preferred embodiment; Fig. 3 a schematic representation of an overpressure-protected substrate according to the invention with closed overpressure protection; and Fig. 4 a schematic representation of an overpressure protected substrate according to the invention with open overpressure protection.

[0103] Fig.1a shows a cross section through the structure of an adhesive element 14 according to the invention before application to the substrate 12 in a first preferred embodiment.

[0104] The adhesive element 14 according to the invention comprises an adhesive layer 16, via which the adhesive element 14 can be attached to the substrate 12 in such a way that the continuous recess 10 in the substrate 12 is closed. In the example shown, the Fig. In Figure 1, the substrate 12 is a metallic battery housing, with only one wall of the battery housing being shown, which defines its interior. The diameter of the circular, continuous recess 10 in the substrate 12 is, for example, 35 mm.

[0105] In the example shown, the adhesive layer 16 comprises a pressure-sensitive adhesive based on poly(meth)acrylates, which can also be syntactically foamed, for example, by using expanded microballoons.

[0106] The adhesive element 14 has a first carrier layer 26a, which together with the intermediate adhesive layer 26b forms a first adhesive part 26 and which is substantially completely covered by the intermediate adhesive layer 26b, a second carrier layer 17, which together with an adhesive layer 16 forms a second adhesive part 19 and which is substantially completely covered by the adhesive layer 16, and a third carrier layer 28 in the form of a membrane made of PTFE.

[0107] The diameter of the circular first carrier layer 26a in shape as well as the diameter of the second carrier layer 17 located underneath are, for example, 80 or 90 mm.

[0108] The first carrier layer 26a is, for example, a 190 µm thick PET film (polyethylene terephthalate) coated with 75 g / m 2 coated with an acrylate-based adhesive. The first adhesive part 26 can, for example, be the tesa® 50349 adhesive tape.

[0109] The second carrier layer, for example, is an 80 µm thick aluminum foil coated with 40 g / m 2 coated with an acrylate-based adhesive. The second adhesive part 19 can be, for example, the tesa® 50575 adhesive tape.

[0110] Below the adhesive layer 16 there is a third carrier layer 28 made of a PTFE membrane, the dimensions of which essentially correspond to the dimensions of the pressure opening area 20 and which essentially completely covers the adhesive layer 16 in the pressure opening area 20.

[0111] In the Fig.1a shows that the adhesive element 14 comprises a pressure opening region 20 formed by a weakened region 22 in the carrier layers 26a, 17, as well as in the intermediate adhesive layer 26b and in the adhesive layer 16. The pressure opening region 20 is located centrally in the adhesive element 14 and, in the example shown, is essentially circular, so that its basic shape essentially corresponds to the continuous recess 10 in the substrate 12 that is to be sealed in the method according to the invention. The diameter of the circular pressure opening region 20 is, for example, 60 mm.

[0112] Due to this construction, the adhesive element 14 according to the invention is designed such that the action of a predetermined opening pressure on the pressure opening region 20, for example as a result of an overpressure prevailing in the interior of the substrate 12, can cause at least partially irreversible destruction in the weakened region 22, by means of which a through hole 24 is formed in the adhesive element 14.

[0113] In the example shown, the weakened region 22 is formed as a groove-shaped recess in the first carrier layer 26a and the second carrier layer 17, which substantially completely surrounds the pressure opening region 20, wherein the average thickness of the first carrier layer 26a and the second carrier layer 17 in the region of the weakened region 22 is reduced by approximately 20 to 60% compared to the original thickness, depending on the desired opening pressure.

[0114] Furthermore, several through-holes 42, distributed over the entire surface of the print opening area 20 and aligned in the z-direction, are provided in the first and second carrier layers 26a, 17, in the intermediate adhesive layer 26b, and in the adhesive layer 16. These extend continuously through all layers 26a, 17, 26b, 16 from the outermost surface of the adhesive element 14 to the third carrier layer 28.

[0115] In the Fig.1a, the adhesive element 14 according to the invention is bonded, for example, automatically using a robot arm, with the pressure-opening region 20 and the continuous recess 10 being arranged concentrically in the example shown. To achieve advantageous anisotropy in the opening behavior, the bonding is carried out such that the pressure-opening region 20 protrudes beyond the edge of the continuous recess 10 over the entire circumference, so that the overlap can resist externally applied load pressure.

[0116] Fig. 1b shows a cross section through the structure of an adhesive element 14 according to the invention before application to the substrate 12 in a second preferred embodiment.

[0117] The structure of the adhesive element 14 according to Fig. 1b corresponds in the sequence of the individual layers to the adhesive element 14, as shown in the Fig.1a. Instead of through-holes 42 distributed over the entire surface of the print opening area 20 and aligned in the z-direction, a central recess 44 is provided in the second preferred embodiment of the adhesive element 14. The recess 44 extends continuously through all layers 26a, 17, 26b, 16 up to the third carrier layer 28. The diameter of the circular recess 44 is smaller than the diameter of the third carrier layer 28 and is preferably between 10 and 20 mm, here, for example, 20 mm.

[0118] Fig. 1c shows a cross section through the structure of an adhesive element 14 according to the invention before application to the substrate 12 in a third preferred embodiment.

[0119] The structure of the adhesive element 14 according to Fig. 1c corresponds in the sequence of the individual layers largely to the adhesive element 14, as shown in the Fig.1b. In the adhesive element 14 according to the third preferred embodiment, a fourth carrier layer 62 in the form of a film, for example a 190 µm thick polyethylene terephthalate film, is present between the adhesive layer 16 and the third carrier layer 28. The diameter of the fourth carrier layer corresponds to the diameter of the print opening area according to the adhesive element according to Fig. 1b, i.e., 60 mm. The third carrier layer 28 has a diameter of 40 mm. Furthermore, an adhesive strip 29 in the shape of a circular ring is applied to the upper side of the third carrier layer 28, with the width of the circular ring being 5 mm. The third carrier layer 28 and the adhesive strip 29 together form a third adhesive part 27.

[0120] Fig. 1d shows a cross section through the structure of an adhesive element 14 according to the invention before application to the substrate 12 in a fourth preferred embodiment.

[0121] The structure of the adhesive element 14 according to Fig. 1d corresponds in the sequence of the individual layers largely to the adhesive element 14, as shown in the Fig. 1b. The third carrier layer 28, which is circular and has a diameter of 40 mm, is enclosed in a circular ring by the fourth carrier layer 62, formed, for example, from a 130 µm thick polyethylene terephthalate film. The outer diameter of the fourth carrier layer 62 is 60 mm.

[0122] Fig. 1e shows a cross section through the structure of an adhesive element 14 according to the invention before application to the substrate 12 in a fifth preferred embodiment.

[0123] The structure of the adhesive element 14 according to Fig. 1e corresponds in the sequence of the individual layers largely to the adhesive element 14, as shown in the Fig.1c. In the adhesive element 14 according to the fifth preferred embodiment, the third carrier layer 28 is arranged between the intermediate adhesive layer 26b and the second carrier layer 17. The diameter of the third carrier layer is 30 mm. The third carrier layer 28 has a diameter of 40 mm. Furthermore, on the underside of the third carrier layer 28, there is an adhesive strip 29 in the shape of a circular ring, the width of the circular ring being 5 mm. The third carrier layer 28 and the adhesive strip 29 together form a third adhesive part 27.

[0124] Fig. 1f shows a cross section through the structure of an adhesive element 14 according to the invention before application to the substrate 12 in a sixth preferred embodiment.

[0125] The structure of the adhesive element 14 according to Fig. 1f corresponds in the sequence of the individual layers largely to the adhesive element 14, as it is in the Fig.1e. In the adhesive element 14 according to the sixth preferred embodiment, the residual material thickness in the weakened region 22 of the first carrier layer 26 is 0 µm, i.e., the carrier layer 26 is completely severed / pierced / punched in the weakened region 22.

[0126] Fig. Figure 2 shows a schematic exploded view of the structure of an adhesive element 14 according to the invention prior to application to the substrate 12 in the first preferred embodiment. The first adhesive part 26 and the second carrier layer 19 form a carrier 18 coated with the adhesive layer 16. A third carrier layer 26 is located beneath this adhesive layer 16.

[0127] Fig. 3 now shows an overpressure-protected substrate 12 according to the invention, the continuous recess 10 of which is closed by the adhesive element 14, as it is, for example, starting from the Fig.1a can be obtained. Due to the previously described structure of the adhesive element 14 and its arrangement over the continuous recess 10, the overpressure-protected substrate 12 can be designed such that it can withstand a load pressure of 400 kPa or more acting from the direction of the carrier 18 without causing destruction of the adhesive element 14 in the weakened region 22.

[0128] In fact, a corresponding structure was even able to withstand the irradiation of the overpressure-protected substrate 12 with a high-pressure water jet cleaner (IPX9K, ISO 20653:2013) without any failure of the closure.

[0129] At the same time, it is possible to specifically set a predetermined opening pressure, for example in the range from 5 to 200 kPa, when this pressure acts in the desired opening direction, that is to say, for example, from the inside of the battery housing to the outside, the pressure opening region 20 is lifted out of the adhesive element 14 as a result of at least partial destruction of the weakened region 22 and thereby forms a through hole 24 through which the excess pressure can be relieved.

[0130] The final state resulting from the intervention of the overpressure protection is in Fig. 4 is schematically visualized, wherein in advantageous embodiments the complete detachment of the pressure opening area 20 from the adhesive element 14 is additionally avoided by the fact that the weakened area 22 is not guided over the entire circumference, so that an unweakened connection remains between the pressure opening area 20 and the legal adhesive element 14. List of reference symbols 10 Continuous recess 12 Substrat 14 Adhesive element 16 adhesive layer 17 Second support layer 18 carriers 19 Second adhesive part 20 Pressure opening area 22 weakening area 24 through holes 26 First adhesive part 26a First support layer 26b Intermediate adhesive layer 27 Third adhesive part 28 Third support layer 29 adhesive strips 42 through holes 44 recess 62 Fourth support layer

Claims

[1] Adhesive element (14) for closing a continuous recess (10) in a substrate (12), comprising i) a first carrier layer (26a) in the form of a film, a second carrier layer (17) in the form of a metallic layer, wherein the second carrier layer (17) has a thickness of 50 µm to 200 µm, and a third carrier layer (28) in the form of an air-permeable membrane having the following properties: • Thickness from 100 µm to 1500 µm • Air permeability from 10 to 150 l / h / cm 2 , measured according to ASTM D737-04 (2019) wherein the three carrier layers (26a, 17, 28) are preferably arranged in the specified order or alternatively the third carrier layer (28) is arranged between the first and the second carrier layer (26a, 17), ii) an adhesive layer (16) comprising an adhesive, preferably a pressure-sensitive adhesive, which is present on the surface of the second carrier layer (17) facing away from the first carrier layer (26a), wherein the adhesive element (14) comprises a pressure opening region (20) which is surrounded at least in sections by a weakened region (22) formed in the second carrier layer (17), wherein the average thickness of the second carrier layer (17) in the weakened region (22) is smaller than the average thickness of the second carrier layer (17) in the pressure opening region (20), wherein the third carrier layer (28) is designed such that the contour of the third carrier layer (28) is preferably located completely within the weakened region (22) formed in the second carrier layer (17a), wherein the adhesive element (14) is designed such that the action of a predetermined opening pressure on the pressure opening region (20) at least partially irreversibly destroys the adhesive element (15) in the weakened region (22) and forms a through hole (24) in the adhesive element (14), and wherein the first and second carrier layers (26a, 17) and the adhesive layer (16) are designed such that these carrier layers (26a, 17) and the adhesive layer (16) can allow air passing through the third carrier layer (28) to pass through, in that through holes (42) aligned in the z-direction are provided in the first and second carrier layers (26a, 17) and in the adhesive layer (16), which extend continuously through all layers (26a, 17, 28, 16) from the respective outermost surface of the adhesive element (14) to the third carrier layer (28), and / or the first and second carrier layers (26a, 17) have a recess (44) in the center, wherein the area of ​​the recess (44) is located within the area covered by the third carrier layer (28) [2] Adhesive element (14) according to claim 1, characterized by , that the first carrier layer (26a) comprises a film selected from the group consisting of plastic films, in particular polyester films such as polyethylene terephthalate or polybutylene terephthalate and / or the first carrier layer (26a) has a thickness of 50 µm to 300 µm, preferably 100 µm to 200 µm. [3] Adhesive element (14) according to claim 1 or 2, characterized by that the first carrier layer (26a) is provided on the underside with an intermediate adhesive layer (26b), preferably made of a pressure-sensitive adhesive. [4] Adhesive element (14) according to at least one of claims 1 to 3, characterized by , that the second carrier layer (17) comprises a metal foil made of aluminum, preferably in a thickness of 70 µm to 100 µm, and / or the second carrier layer (17) has a thickness of 70 µm to 100 µm. [5] Adhesive element (14) according to at least one of the preceding claims, characterized by that the third carrier layer (28) comprises an air-permeable membrane made of polytetrafluoroethylene (PTFE), which preferably has the following properties: • Thickness from 130 µm to 1000 µm • Water inlet pressure greater than 100 mbar, preferably 120 to 400 mbar, measured according to the water column test according to ISO 20653 (2006) [6] Adhesive element (14) according to at least one of the preceding claims, characterized by that the weakened area (22) is formed as a groove-shaped recess in the second carrier layer (17). [7] Adhesive element (14) according to claim 6, characterized by in that the first carrier layer (26a) has a weakened region (22) which is designed as a groove-shaped recess in the first carrier layer (26a), wherein the weakened regions (22) in the second carrier layer (17) and the first carrier layer (26a) are preferably arranged congruently one above the other. [8] Adhesive element (14) according to at least one of the preceding claims, characterized by that the predetermined opening pressure is 10 kPa or more. [9] Method for closing a continuous recess (10) in a substrate (12), comprising the method steps: a) producing or providing an adhesive element (14) according to at least one of the preceding claims and b) Adhering the adhesive element (14) to the substrate (12) by means of the adhesive layer (16) such that the adhesive element (14) completely covers the continuous recess (10) and the continuous recess (10) is closed by the adhesive element (14), wherein the adhering of the adhesive element (14) is carried out such that the pressure opening area at least partially covers the continuous recess in the substrate. [10] Method according to claim 9, characterized by that the substrate (12) is a housing, preferably a housing of an electronic device or a battery, particularly preferably a battery. [11] Method according to one of claims 9 or 10, characterized bythat the adhesive element (14) is stuck on by the pressure opening area (20) projecting at least partially beyond the edge of the continuous recess (10) in such a way that the glued-on adhesive element (14) withstands the action of a predetermined load pressure on the carrier layer (18) in the pressure opening area (20), so that the adhesive element (14) is not irreversibly destroyed in the weakened area (22) and no through hole (24) is formed in the adhesive element (14). [12] Overpressure-protected substrate (12), comprising a closed interior space with at least one closed opening, wherein the closed opening is closed with an adhesive element (14) according to at least one of claims 1 to 8, wherein the pressure opening region (20) of the adhesive element (14) at least partially covers the closed opening, wherein the overpressure-protected substrate (12) is designed such that the adhesive element (14) is at least partially irreversibly destroyed in the weakened region (22) as a result of a predetermined overpressure in the interior, so that a pressure reduction in the interior can take place through the through-hole (24) formed in the adhesive element (14).

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