Device and method for UV radiation activation of web-shaped adhesive tapes

Abstract

Device (10) for use in the UV radiation activation of web-shaped adhesive tapes (12), comprising: x) a guide arrangement for guiding a web-shaped adhesive tape (12) along a guide track, wherein the guide arrangement comprises three or more guide elements (14) spaced apart from one another along the longitudinal direction L of the device (10), wherein at least one of the guide elements (14) is a rotatable guide element (14) which is arranged in the device (10) such that its axis of rotation points at least partially in the transverse direction Q orthogonal to the longitudinal direction L, and y) one or more UV radiation sources (16), wherein the UV radiation sources (16) have the intensity maximum of the emission at a wavelength λ in the range of 100 to 400 nm, wherein the guide elements (14) of the guide arrangement are at least partially arranged at different heights with respect to the height direction H which is orthogonal to the longitudinal direction L and transverse direction Q, and wherein the UV radiation sources (16) are each arranged in the device (10) such that a first part of the guide elements (14) is located above the UV radiation source (16) with respect to the vertical direction H and a second part of the guide elements (14) is located below the UV radiation sources (16) with respect to the vertical direction H, wherein the device comprises a housing in which the components of the device are arranged and into which the adhesive tape is inserted through a feed opening and removed through a dispensing opening, wherein the inner wall of the housing is at least partially, preferably substantially completely, mirrored.

Description

[0001] The invention relates to a device for use in the UV radiation activation of web-shaped adhesive tapes and a corresponding method for UV radiation activation of web-shaped adhesive tapes using such a device. The use of a corresponding device for curing web-shaped UV-curable adhesive tapes is also disclosed.

[0002] Adhesives and adhesive elements, such as adhesive tapes, are used in numerous modern manufacturing processes. The use of these adhesive technologies is not limited to simply joining separate elements by creating material-bonded connections. Rather, adhesives and adhesive elements are also used for numerous other purposes, with surface modification of substrates, i.e., bonding them, playing a particularly important role, in addition to sealing openings in substrates.

[0003] In addition to the pressure-sensitive adhesive tapes commonly used in everyday life, so-called reactive adhesive tapes are also used in industrial contexts. These tapes contain a reactive adhesive compound that can be cured under certain conditions. In their intended state, these curable adhesives have not yet reached their maximum degree of cross-linking and can be cured by external influences. This process initiates polymerization within the adhesive compound, thereby increasing the degree of cross-linking. As a result, the mechanical properties of the now-cured adhesive change, with viscosity, surface hardness, and strength increasing in particular.

[0004] Curable adhesives are known in the art and can have very different chemical compositions. These curable adhesives have in common that the crosslinking reaction can be triggered by external factors, for example, by energy input, in particular by temperature, plasma, or radiation curing, and / or contact with a polymerization-promoting substance, as is the case, for example, with moisture-curing adhesives. Exemplary adhesives are disclosed in DE 102015222028 A1, EP 3091059 A1, EP 3126402 B1, EP 2768919 B1, DE 102018203894 A1, WO 2017174303 A1, and US 4661542 A.

[0005] Through curing, the adhesives used become solid and mechanically resilient materials. This makes it advantageously possible to shape an adhesive element, which is malleable in its uncured state and in many cases tacky, onto the surface of a substrate and position it as desired. Subsequent curing then creates a structural material. The use of appropriate reactive adhesive tapes is therefore particularly suitable for joining separate elements in a durable, long-term manner through the resulting structural bond, or for creating a targeted coating of the cured adhesive tape on the surface of substrates to which it is bonded. This coating covers the underlying substrate and determines the surface properties of the substrate in the covered areas.

[0006] Of particular industrial importance are radiation-curing reactive adhesive tapes, especially UV-curable tapes, in which the curing reaction can be initiated by irradiation with ultraviolet light. In practice, the initiation step of the curing reaction, also known as activation, often represents a process step that incurs additional time and / or costs in a manufacturing process or requires complex process control.

[0007] For example, it is conceivable to apply UV-curable adhesive tapes to the substrate to be bonded before activation, such as in cable wrapping or protective coating for battery cells. In these cases, UV-induced curing is initiated only subsequently. This downstream UV radiation activation, particularly with complex substrates such as wrapped cable harnesses, often requires specialized curing equipment for the controlled application of the necessary UV radiation and / or well-trained personnel to ensure reliable curing.

[0008] Especially when large quantities of UV-curable adhesive tapes are to be applied per unit of time in an industrial manufacturing process, an alternative to downstream UV curing is to perform the UV activation immediately before application. This has the advantage that the UV-curable adhesive tape, as a continuous tape usually supplied from a roll, can be handled more efficiently before application to a substrate. This process takes advantage of the fact that UV-induced curing, and thus the transition into a structural material, does not occur instantaneously, but rather requires a certain amount of time until the UV-curable adhesive mass has completely transformed into the desired final state.During this period after activation, a UV-activated reactive adhesive tape can still be applied to the substrate to be bonded, after which the desired structural bond is achieved as a result of the progressive curing.

[0009] In current technology, UV activation prior to application is usually achieved by irradiating the UV-curable adhesive tapes on one side only, for example, using manually operated UV lamps. This often results in a time-consuming process and a large space requirement for storing the potentially long length of UV-curable tape during manual UV activation, as this necessitates ensuring that all areas of the tape are exposed to the required minimum radiation dose as uniformly as possible.

[0010] German patent DE 201 20 718 U1 describes a UV irradiation device with a CO2 atmosphere for the efficient curing and drying of materials. The design minimizes oxygen ingress and increases quality at a lower cost.

[0011] US patent 2013 / 0064987A1 discloses a process for manufacturing adhesive strips by UV polymerization in a serpentine transport path. The method increases efficiency and product quality while reducing energy consumption.

[0012] US patent 2014 / 0087087A1 deals with the production of photoreactive adhesive films using UV irradiation in two chambers and serpentine transport. The process improves the degree of polymerization and minimizes contamination.

[0013] US patent 2014 / 0147599A1 describes a production process for adhesive films with multiple deflections over three rollers to prevent creases. UV polymerization is efficient and enables high product quality with compact technology.

[0014] The inventors of the present invention aimed to make the UV radiation activation of web-shaped adhesive tapes prior to final bonding more time- and / or cost-efficient, while in particular ensuring the most consistent possible activation quality. To this end, the inventors initially considered a setup similar to a linear UV tunnel, such as those known from the food technology sector, where corresponding UV tunnels are used, for example, for the sterilization of food. Such a setup comprises a conveying device, for example, a conveyor belt, on which a UV-curable adhesive tape can be guided through a tunnel. Inside this tunnel, a multitude of UV radiation sources are arranged, which subject the adhesive tape passing through the UV tunnel to radiation.

[0015] This method was initially considered advantageous because the dwell time of each section of the UV-curable adhesive tape inside the tunnel, and thus the exposure time to UV radiation, could be precisely controlled by adjusting the conveying speed of the conveyor and the length of the UV tunnel. Furthermore, unlike manual UV activation methods, it is possible to maintain a predetermined distance between the UV-curable adhesive tape being cured and the UV radiation sources. It was also considered advantageous that the UV activation of UV-curable adhesive tapes prior to application could be advantageously automated using a suitable UV tunnel.

[0016] Despite these fundamentally advantageous properties, the inventors found that a corresponding device with a linear UV tunnel is, in most cases, unsuitable or at least insufficiently suitable for the specific application requirements in the field of adhesive technology. According to the inventors, this is because the UV radiation activation of UV-curable adhesive tapes regularly requires comparatively high radiation doses. To apply the necessary radiation dose to a section of the UV-curable adhesive tape, very long dwell times and / or very powerful UV radiation sources would be required in a linear UV tunnel.

[0017] However, the use of very powerful UV radiation sources can lead to problems with temperature management, especially cooling, of the corresponding equipment and is generally undesirable from the perspective of striving for maximum energy efficiency. Implementing long residence times has the disadvantage that this is difficult to achieve in practical applications by simply setting low feed rates, as the delivery rate of activated UV-curable adhesive tape is then insufficient to meet the industrial requirements of typical manufacturing processes.Furthermore, this can lead to a functional limitation in practice regarding the maximum length of UV-curable adhesive tapes that can be activated, as the sections of the tape that exit the UV tunnel first risk curing too extensively while the trailing sections are still slowly passing through. Therefore, especially when handling longer UV-curable tapes, the primary option is to design the UV tunnel to be very long in order to ensure sufficient dwell time in the device at high conveying speeds. However, this results in a UV activation device that requires a disproportionately large amount of space and cannot be easily integrated into existing production lines in many manufacturing facilities.

[0018] The inventors recognized an additional problem: the use of such a UV tunnel, like manual activation in most cases, results in only one-sided activation of the UV-curable adhesive tapes, since at least one side of the tape rests on the conveyor device. The chemical crosslinking reaction initiated by the UV radiation must therefore proceed from one side of the UV-curable tape through the adhesive mass. This can lead to an undesirable gradient in the curing state, particularly with thicker UV-curable tapes, which can negatively affect the processing properties.

[0019] The primary objective of the present invention was to eliminate or at least reduce the disadvantages of the prior art.

[0020] In particular, the object of the present invention was to provide a device for use in the UV radiation activation of web-shaped adhesive tapes and a method for UV radiation activation to be carried out therewith, with which UV radiation activation of web-shaped UV-curable adhesive tapes prior to bonding is possible in a particularly time- and / or cost-efficient manner.

[0021] It was an object of the present invention to enable the device to be specified for UV radiation activation to allow an advantageously high throughput of UV radiation-activated adhesive tape and to enable the processing of long web-shaped adhesive tapes.

[0022] It was an object of the present invention to make it possible to implement the device in a particularly compact design, and it was desirable that the device to be specified should enable advantageous temperature management.

[0023] A further object of the present invention was that the device and the corresponding method should enable a particularly reliable UV radiation activation of web-shaped adhesive tapes, which in particular should ensure a precisely set degree of UV radiation activation, and it was desirable that the corresponding method should place the lowest possible demands on the level of education and training of the workers used.

[0024] A further object of the present invention was to enable the most efficient and uniform activation of the UV-curable adhesive in the reactive adhesive tapes, particularly with reduced curing gradients, to be achieved with the specified device and the corresponding method, so that UV-radiation-activated adhesive tapes with excellent processing properties and resulting in excellent structural bonding in subsequent use could be produced with the specified device and the corresponding method.

[0025] Furthermore, it was an object of the present invention that the device to be specified and the corresponding method should be particularly automatable and should be advantageously operable in a process that is as continuous as possible.

[0026] It was a secondary objective of the present invention to also specify the use of a corresponding device in the curing of web-shaped UV-curable adhesive tapes.

[0027] The inventors of the present invention have now found that the problems described above can be solved by providing a device for use in the UV radiation activation of web-shaped adhesive tapes, comprising several rotatable guide elements spaced apart from one another along a direction and arranged at different heights transversely thereto, such that a web-shaped adhesive tape guided over the guide elements describes a meandering guide path and UV radiation sources are arranged between the guide elements to subject a web-shaped adhesive tape guided on the guide path to electromagnetic radiation, as defined in the claims.

[0028] Advantageously, this results in a device for use in the UV radiation activation of tape-shaped adhesive tapes, in which a long web of adhesive tape can be guided in a compact device with a small footprint, and the web guidance enables particularly efficient use of the UV radiation provided by the UV radiation sources. Despite a high web speed of the guided tape, the corresponding device can ensure a long dwell time of the tape in the device and intensive radiation exposure, even with a small footprint.

[0029] In particular, the device according to the invention makes it advantageously possible to largely automate the process for UV radiation activation of web-shaped adhesive tapes and to provide activated adhesive tape in consistent quality and precisely set activation states, without requiring comprehensive training of the workers used in the process.

[0030] In particular, the device according to the invention makes it possible to efficiently expose the guided web-shaped adhesive tape to UV radiation on both sides by placing two or more UV radiation sources, thereby advantageously counteracting the formation of pronounced curing gradients in the UV-curable adhesive mass.

[0031] By efficiently utilizing the UV irradiation power, the corresponding device can be operated more energy-efficiently and is advantageous in terms of its temperature management.

[0032] When using two or more UV radiation sources, the resulting bilateral UV radiation activation also synergistically reduces the required activation time, since UV activation from both sides requires less time overall than unilateral UV activation through the entire adhesive layer.

[0033] The aforementioned problems are thus solved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention are described in the dependent claims and the following descriptions.

[0034] Such embodiments, which are hereinafter referred to as preferred, are combined in particularly preferred embodiments with features of other embodiments also referred to as preferred. Combinations of two or more of the embodiments hereinafter referred to as particularly preferred are therefore especially preferred. Also preferred are embodiments in which a feature of one embodiment, referred to as preferred to any degree, is combined with one or more further features of other embodiments, which are referred to as preferred to any degree. Features of preferred methods and uses result from the features of preferred devices.

[0035] The invention relates in particular to a device for use in the UV radiation activation of web-shaped adhesive tapes, comprising: x) a guide arrangement for guiding a web-shaped adhesive tape along a guide track, wherein the guide arrangement comprises three or more guide elements spaced apart from one another along the longitudinal direction of the device, wherein at least one of the guide elements is a rotatable guide element which is arranged in the device such that its axis of rotation points at least partially in the transverse direction orthogonal to the longitudinal direction, and y) one or more UV radiation sources, wherein the UV radiation sources have the intensity maximum of the emission at a wavelength λ in the range of 100 to 400 nm, wherein the guide elements of the guide arrangement are at least partially arranged at different heights with respect to the height direction orthogonal to the longitudinal and transverse directions, and wherein the UV radiation sources are each arranged in the device such that a first part of the guide elements is located above the UV radiation source with respect to the vertical direction and a second part of the guide elements is located below the UV radiation sources with respect to the vertical direction.

[0036] The device according to the invention is intended for use in the UV radiation activation of web-shaped adhesive tapes; that is, it is designed to bring such web-shaped adhesive tapes, which comprise a UV-curable adhesive compound, into a state suitable for subsequent processing. For the purposes of understanding the present invention, it is advantageous to define the design of the device according to the invention partly with reference to the web-shaped adhesive tape, which is to be processed, i.e., UV-activated, in the device according to the invention in later use, particularly in the method according to the invention. However, it is readily understood by those skilled in the art that the web-shaped adhesive tape itself is not part of the device according to the invention.

[0037] The device according to the invention initially comprises a guide arrangement. This guide arrangement serves to guide the web-shaped adhesive tape, which is to be UV-activated, through the device during subsequent use. The specific design of the guide arrangement results in a guide path for the adhesive tape within the device, which is the path along which the web-shaped adhesive tape is guided during subsequent use.

[0038] According to the invention, the guide arrangement comprises at least three guide elements. These guide elements are spaced apart along the longitudinal direction of the device. In accordance with the skilled person's understanding, the longitudinal direction is typically the direction of the greatest length of the device and extends, for example, from the adhesive tape inlet to the adhesive tape outlet opening of the device. Within the scope of the present invention, the definition of the longitudinal direction, together with the other directions, serves to precisely define the structural design of the device according to the invention.

[0039] The guide elements provided according to the invention can, in principle, be formed by any elements used in adhesive technology for conveying and guiding adhesive tapes. For example, they can be rigid edges or curves around which the web-shaped adhesive tape can be deflected. However, within the scope of the above definition, at least one of the guide elements must be a rotatable guide element.

[0040] This rotatable guide element can advantageously also serve to drive the web-shaped adhesive tape in the device according to the invention and can, for example, be connected to an electric drive unit, such as an electric motor. Although it is conceivable to design some of the guide elements as rigid guide elements, it is preferred for essentially all embodiments if all guide elements are designed as rotatable guide elements, for example by being mounted to rotate accordingly, with the use of guide rollers or cylinders being particularly preferred. A device according to the invention is therefore preferred in which the guide elements are selected from the group consisting of guide rollers and guide cylinders.A device according to the invention is also preferred, wherein at least one of the rotatable guide elements, preferably the majority of the rotatable guide elements, and especially preferably all rotatable guide elements, are driven guide elements, preferably electrically driven guide elements.

[0041] A strip of adhesive tape guided over a rotatable guide element, such as a roller, extends along the axis of rotation of this rotatable guide element. Accordingly, it is advantageous to define the design of the device with reference to this axis of rotation. Even if it is at least theoretically conceivable to rotate the rotatable guide element relative to the longitudinal direction so that the axis of rotation is not exactly perpendicular to the longitudinal direction, the rotatable guide element will always point at least to a certain extent in the transverse direction, which is orthogonal to the longitudinal direction. In the inventors' estimation, the most relevant case in practice will be that the axis of rotation of the rotatable conveying element itself is essentially orthogonal to the longitudinal direction and thus runs parallel to the transverse direction.

[0042] The guide arrangement defined so far could be implemented in a non-inventive device, such as a UV tunnel, for example, by three guide rollers arranged in a line with their axes of rotation lying in the same plane. However, the device according to the invention deviates from this arrangement, as the guide elements are not all arranged in one plane, but rather are arranged relative to each other with a vertical offset. In accordance with the understanding of those skilled in the art, the vertical direction to which the vertical offset refers is the third axis of a Cartesian coordinate system, orthogonal to both the longitudinal and transverse directions. In a typical application scenario in a later production line, the vertical direction will, for example, usually run essentially vertically.

[0043] From the preceding definition of the arrangement of the guide elements, namely that they are spaced apart from one another longitudinally and partially offset along the vertical direction, it follows that a web-shaped adhesive tape guided over these guide elements describes a meandering path within the device. In other words, this is a device according to the invention, wherein the guide arrangement is configured to guide a web-shaped adhesive tape, guided by the guide elements, in loops. Again, in other words, this is a device according to the invention, wherein the guide elements of the guide arrangement are arranged such that the web length of a web-shaped adhesive tape guided by the guide elements within the guide arrangement is greater than the length of the guide arrangement along the longitudinal direction.

[0044] The more guide elements are used, the more loops can be created, and the greater the gain in path length inside the device for a given longitudinal dimension. A preferred device according to the invention comprises five or more, preferably seven or more, and particularly preferably nine or more, guide elements. A preferred additional or alternative device according to the invention is one in which the guide elements are equidistant from one another along the longitudinal direction.

[0045] For easier understanding of the device according to the invention, it is advantageous in the following explanations to assume the particularly practical embodiment in which the height direction corresponds to the vertical direction, so that the longitudinal and transverse directions lie in the horizontal plane. In this context, one can speak clearly of high and low or top and bottom.

[0046] In principle, it is possible to design several guide elements adjacent to each other along the longitudinal direction in such a way that they interact to form a loop of the meandering guide path, for example, by arranging three adjacent guide elements at the same height, so that the web-shaped adhesive tape is guided over them to, for example, three further, lower guide elements, so that the loops of the guide path are each formed by three guide elements. The inventors consider such a design possible, but less preferred in view of the space requirements and complexity of the device according to the invention. Rather, in the inventors' opinion, it is advantageous for realizing a compact construction and a simple design to provide adjacent guide elements along the longitudinal direction with a height offset from each other, so that the guide elements are arranged in a quasi-alternating manner.A device according to the invention is therefore preferred, wherein the guide elements of the guide arrangement are arranged such that, along the longitudinal direction, adjacent guide elements are arranged at different heights with respect to the vertical direction.

[0047] According to the inventors, preferred embodiments of the invention can be particularly conveniently specified by referring to the theoretical center of gravity line, which results from the centers of the guide elements. With an even number of guide elements, where the upper and lower guide elements are all located at the same height level, this center of gravity line runs exactly midway between the two height levels. With an odd number of guide elements distributed across two height levels, the center of gravity line may be shifted towards the higher height level, i.e., upwards or downwards. This deviation, which can be caused by the odd number of guide elements, decreases with an increasing total number of guide elements if they are evenly distributed across the height levels.

[0048] With reference to this center of gravity line, the feature described above can alternatively be defined relative to the center of gravity line via the vertical offset. In other words, it is a device according to the invention, wherein the guide elements of the guide arrangement are arranged such that, with respect to the vertical direction, the guide elements lie partly above and partly below the center of gravity line referenced to the centers of the guide elements.

[0049] According to the inventors, it is particularly advantageous if the upper and lower guide elements are arranged at essentially the same height. A preferred device according to the invention is one in which the guide elements of the guide arrangement are arranged such that the center of gravity line, referenced to the centers of the guide elements, runs parallel to the longitudinal direction. A preferred additional or alternative device according to the invention is one in which the guide elements that lie on the same side of the center of gravity line referenced to the centers of the guide elements, with respect to the vertical direction, are arranged at least partially, preferably predominantly, and particularly preferably essentially completely, at the same distance from the center of gravity line.

[0050] To ensure functionality for use in the UV radiation activation of adhesive tapes, the device according to the invention comprises at least one, preferably several, UV radiation sources whose emission intensity maximum lies at a wavelength λ in the range of 100 to 400 nm, i.e. in the UV range.

[0051] The above definition of UV radiation sources based on the intensity maximum of the emission is convenient in accordance with the skilled person's understanding, since many radiation sources, such as conventional lamps, can also exhibit components in the UV range within their emission spectrum. In light of the above definition, the skilled person readily understands that the UV radiation sources are UV emitters whose emission spectrum includes electromagnetic radiation in the defined wavelength range not merely as a minor component, but rather exhibits the maximum emission intensity at that wavelength. Against this background, the skilled person also understands that the corresponding UV radiation sources are, in particular, dedicated UV lamps or UV LEDs, the latter being especially preferred.A preferred device according to the invention is one in which the UV radiation sources have the intensity maximum of the emission at a wavelength λ in the range of 200 to 390 nm, preferably in the range of 300 to 380 nm, and particularly preferably in the range of 350 to 370 nm. A particularly preferred device according to the invention is one in which the UV radiation sources are UV LEDs.

[0052] In the device according to the invention, the UV radiation sources are not placed arbitrarily. Rather, they are arranged, so to speak, between the offset guide elements with respect to their height. Figuratively speaking, this places the UV radiation sources inside the guide arrangement in such a way that the loop-shaped guide track, which is realized by the guide elements, passes by the radiation sources. Those skilled in the art understand that the UV radiation sources are advantageously oriented so that the radiation emitted by the UV radiation sources is directed towards the guide track, allowing an adhesive tape guided in the device to be exposed to UV radiation from the UV radiation sources.

[0053] The preferred arrangement of the UV radiation sources can advantageously be further described with reference to the center of gravity line of the guide elements defined above. According to the inventors, it is advantageous to arrange the radiation sources themselves as close as possible to the same plane and, additionally or alternatively, as close as possible to the center between the upper and lower guide elements. A preferred device according to the invention is one in which the UV radiation sources are arranged, with respect to the vertical direction, at least partially, preferably predominantly, and particularly preferably essentially completely, at the same distance from the center of gravity line referenced to the centers of the guide elements.A preferred or alternative device according to the invention is further preferred, wherein the mean absolute distance of the UV radiation sources to the center of gravity line referenced to the centers of the guide elements in the vertical direction is smaller than the mean absolute distance of the guide elements from the center of gravity line, preferably by 50% or more, particularly preferably by 75% or more. A further preferred or alternative device according to the invention is further preferred, wherein the UV radiation sources lie, with respect to the vertical direction, at least partially, preferably predominantly, particularly preferably substantially completely, on the center of gravity line referenced to the centers of the guide elements.

[0054] Particularly when using a fully mirrored housing, as further disclosed below, advantageous results can be achieved even with a single UV radiation source. However, in the inventors' opinion, it is particularly preferred for essentially all embodiments to use two or more UV radiation sources, which are preferably spaced apart from one another along the longitudinal direction or relative to the path direction in the guide track. Therefore, a device according to the invention is preferred, wherein the device comprises two or more, preferably three or more, and particularly preferably four or more, UV radiation sources spaced apart from one another along the longitudinal direction.

[0055] Particularly efficient utilization of the radiation output of the UV radiation sources is achieved when a UV radiation source is not positioned at the first or last turn of the meandering path of the adhesive tape, but rather is positioned such that the adhesive tape is guided around the UV radiation source by three guide elements. In this case, a UV radiation source can simultaneously expose both the portion of the adhesive tape before the turn and the portion of the adhesive tape after the turn to UV radiation. Against this background, a device according to the invention is preferred in which the UV radiation sources are each arranged in the device such that, with respect to the guide path of a web-shaped adhesive tape guided by the guide elements, they lie between two guide elements.

[0056] A particularly preferred embodiment arises when a UV radiation source is placed inside each of two adjacent turns of the guide track. In this case, the portion of the adhesive tape guided between the respective UV radiation sources is exposed to UV radiation on both sides, since the top side is irradiated by the first and the bottom side by the second UV radiation source. This enables particularly energy-efficient use of the radiation power and advantageously allows for the activation of the UV-curable adhesive tape on both sides, thereby increasing the curing speed and reducing the occurrence of curing gradients.A device according to the invention is particularly preferred, wherein the device comprises two or more UV radiation sources and is configured to irradiate a web-shaped adhesive tape guided along the guide track by the guide elements with the UV radiation sources at least sectionally, preferably in the area between two guide elements adjacent along the guide track, on both sides.

[0057] According to the inventors, a particularly advantageous design is achieved by arranging a guide element and a UV radiation source at essentially the same height along the longitudinal direction, with the UV radiation source being positioned higher or lower relative to the vertical direction to meet the aforementioned arrangement criterion. This results in an advantageous device according to the invention, in which the web-shaped adhesive tape can be particularly efficiently exposed to UV radiation on both sides in the sections between two adjacent guide elements along the web direction, i.e., guide elements traversed successively by the adhesive tape.A device according to the invention is preferred for this purpose, wherein the number of UV radiation sources in the device corresponds to the number of guide elements, wherein preferably one UV radiation source and one guide element are arranged offset from each other by 0.05*Lv or less with respect to the longitudinal direction, particularly preferably by 0.02*Lv or less, most preferably by 0.01*Lv or less, and particularly preferably not at all, wherein Lv is the length of the device along the longitudinal direction, measured between the centers of the UV radiation source and the guide element.

[0058] To ensure a particularly high level of occupational safety and to avoid unnecessary radiation emissions into the environment, the device according to the invention comprises a housing in which the other components of the device are arranged and into which the adhesive tape is inserted through a feed opening and removed through a discharge opening. The use of such a housing can be advantageously employed to further improve the energy efficiency of the process and the uniformity of the UV radiation activation. For this purpose, the inventors propose equipping the interior of the housing with reflective surfaces so that a portion of the UV radiation emitted by the UV radiation sources is reflected back onto the adhesive tape to be activated by the mirrors.According to the invention, the device comprises a housing in which the guide arrangement and the UV radiation sources are arranged, wherein the inner wall of the housing is at least partially, and particularly preferably substantially completely, mirrored.

[0059] Particularly when the components of the device are housed in a casing, a significant temperature increase can occur inside the casing, especially when using multiple high-power UV radiation sources. For many types of radiation-activated curable adhesives, an increased temperature is not inherently detrimental; in many cases, it can even synergistically accelerate the curing reaction and / or improve the curing result. Therefore, the increased internal operating temperature of a casing can potentially even further reduce the required dwell time in the device, thus enabling, for example, higher web speeds of the adhesive tape. However, the inventors consider it particularly advantageous to ensure that unwanted overheating does not occur, especially when using very high-power UV radiation sources.For this purpose, the inventors propose that a cooling system should be provided. A device according to the invention is preferred, wherein the device comprises a temperature control device, preferably a cooling system.

[0060] To make the subsequent work steps in a production line following UV radiation activation even more efficient, the inventors propose that the device according to the invention can additionally be equipped with a separating device designed to cut the UV radiation-activated adhesive tape dispensed from the device. This separating device, which could be, for example, a cutting device, can be operated manually or automatically, with automatic singulation of the UV radiation-activated adhesive tapes being particularly preferred from the perspective of efficient process control.

[0061] Prior art has proposed special UV-curable adhesives comprising dyes or other indicator systems by which successful UV activation and / or the degree of curing achieved can be detected via a color change. Such UV-curable adhesives are also preferred for use with the device according to the invention. For optimal processing of such UV-curable adhesives, the inventors propose that the device according to the invention, particularly in the area located downstream of the last UV radiation source in the direction of travel, be equipped with an electronic image acquisition unit. This unit is configured to determine the color, i.e., the absorption behavior for electromagnetic radiation in the visible range, of the UV-activated adhesive tape and / or to detect changes in the color of the UV-activated adhesive tape.A corresponding embodiment advantageously makes it possible to determine, using the device according to the invention, by detecting the coloration of the activated adhesive tape, that the UV radiation activation has taken place to a sufficient or desired extent.

[0062] In an advantageous further development of the embodiment disclosed above, the device according to the invention can also be provided with an electronic control device which is configured to control the device according to the invention depending on the color information detected by the electronic image acquisition device, in order to ensure a predefined activation level at the output of the device according to the invention by changing the dwell time of the adhesive tape in the device.

[0063] The inventors consider it a further preferred embodiment of the device according to the invention if at least some of the guide elements are movable, in particular height-adjustable, so that they can be adjusted with respect to the vertical direction. The ability to move at least some of the guide elements along the vertical direction makes it possible to essentially spread the entire guide arrangement and to adjust the total travel distance of the adhesive tape, and thus the dwell time in the device, reversibly and non-destructively. This makes it particularly efficient to adjust the total travel distance of the adhesive tape without changing the radiation output of the UV radiation sources or the UV radiation source.without irreversible structural changes to the device according to the invention, to control the residence time so that the degree of curing of the UV-curable adhesive tapes at the output of the device according to the invention can be optimally adjusted, for example also automatically depending on color information detected by an electronic image acquisition unit.

[0064] The invention also relates to a method for UV radiation activation of web-shaped adhesive tapes with a device according to the invention, comprising the following method steps: a) Manufacture or supply of a web-shaped adhesive tape, comprising: i) a support layer, wherein the support layer is at least partially transparent to electromagnetic radiation of wavelength λ, and ii) an adhesive layer arranged on the substrate layer, comprising a UV-curable adhesive compound, b) Guiding the web-shaped adhesive tape with the guide elements of the guide arrangement along the guide track, wherein the guiding is carried out in such a way that the web length of the web-shaped adhesive tape guided by the guide elements in the device is greater than the length of the guide arrangement along the longitudinal direction, and c) Irradiation of the adhesive layer of the web-shaped adhesive tape guided along the guide track in the guide arrangement by the guide elements with electromagnetic radiation emitted from the UV radiation sources with a wavelength λ in the range of 100 to 400 nm to initiate the curing of the UV-curable adhesives.

[0065] The method according to the invention serves for the UV radiation activation of web-shaped adhesive tapes or their UV-curable adhesives and utilizes a device according to the invention for this purpose. In a first process step, the web-shaped adhesive tape is produced or provided, whereby in practice, for typical production lines, for example in the automotive industry, the provision of a suitable curable adhesive tape is of greater practical relevance. A method according to the invention in which the web-shaped adhesive tape is provided, preferably from an adhesive tape roll, is particularly relevant for the subsequent application.

[0066] The web-shaped adhesive tape comprises the UV-curable adhesive compound, which is precisely the part that is to be cured during the subsequent UV activation. A preferred method according to the invention is one in which the adhesive layer consists of the curable adhesive compound.

[0067] A person skilled in the art understands that the UV-curable adhesive used in the inventive method is an adhesive that can be cured by the radiation emitted by the UV radiation sources. It is therefore an inventive method wherein the UV-curable adhesive can be cured by irradiation with electromagnetic radiation with a wavelength in the range of 100 to 400 nm, preferably in the range of 200 to 390 nm, particularly preferably in the range of 300 to 380 nm, and especially preferably in the range of 350 to 370 nm.

[0068] With regard to handling characteristics when bonding to the substrate, it is preferred for essentially all embodiments if the UV-curable adhesive is designed as a pressure-sensitive adhesive, since this allows for easy positioning and fixation of the corresponding UV-activated adhesive tape on the substrate, and also enables repositioning of the adhesive elements to correct positioning errors if necessary. A method according to the invention is particularly preferred in which the UV-curable adhesive is a pressure-sensitive adhesive.

[0069] In accordance with professional understanding, and regardless of whether it can be cured, a pressure-sensitive adhesive is an adhesive that possesses tacky properties, meaning it forms a permanent bond to a substrate even under relatively light pressure. Such adhesive tapes are typically removable from the substrate after use with virtually no residue and are generally permanently tacky even at room temperature. This means they exhibit a certain viscosity and tackiness, allowing them to wet the surface of a substrate even with minimal pressure. The tackiness of a pressure-sensitive adhesive tape results from the fact that a pressure-sensitive adhesive is used as the adhesive.Without being bound to this theory, it is often assumed that an adhesive compound can be considered an extremely highly viscous liquid with an elastic component, which consequently exhibits characteristic viscoelastic properties that lead to the permanent inherent tackiness and pressure-sensitive adhesion described above. It is assumed that, in such adhesive compounds, mechanical deformation results in both viscous flow processes and the generation of elastic restoring forces. The viscous flow component serves to achieve adhesion, while the elastic restoring forces component is particularly necessary for achieving cohesion. The relationships between rheology and pressure sensitivity are known in the prior art and are 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, which can be determined by means of dynamic mechanical analysis (DMA), for example using a rheometer, as disclosed, for example, in WO 2015 / 189323. Within the scope of the present invention, an adhesive compound is preferably considered to be tacky and thus a pressure-sensitive adhesive if, at a temperature of 23 °C in the deformation frequency range of 10 °C to 10 °C, the following properties are observed: 1 rad / sec G' and G'' each at least partially in the range of 10 3 up to 10 7 Pa lie.

[0070] Particularly due to the mechanical stress on the adhesive tape in the guide arrangement expected in the device according to the invention, which would likely be too high in many cases for UV-curable adhesives that have not yet fully cured, the adhesive tape to be used comprises a carrier layer. In light of the foregoing, those skilled in the art will understand that a major advantage of the device according to the invention lies in the fact that it enables the simultaneous UV activation of the adhesive tape from two sides. However, since one side of the adhesive tape is formed by the carrier layer, this advantage would not materialize, or would be significantly reduced, if the carrier layer prevented the UV radiation from reaching the UV-curable adhesive.Thus, it is defined above that the support layer should be at least partially transparent to the corresponding electromagnetic radiation of wavelength λ, with predominant or even substantially complete transparency being preferred. Support layers are preferably designed with regard to their material, structure, and thickness such that the intensity of the incident radiation of wavelength λ is reduced by less than 50%, preferably less than 30%, and most preferably less than 10% when passing through the support layer. Such support layers can be realized, for example, with suitable transparent plastic films, but can also be realized by using porous materials, such as nonwovens.A preferred method according to the invention is wherein the carrier layer comprises one or more carrier materials selected from the group consisting of woven fabrics, non-woven fabrics and plastic films, for example PET films and polyolefin films.

[0071] The loop-shaped path of the adhesive tape in the device according to the invention means that in two successive turns, the carrier layer and the adhesive layer will be on the inside, respectively, and will thus come into contact with the guide elements. At least theoretically, it is conceivable to design the guide elements with surfaces with reduced adhesion, so that unwanted adhesion of the adhesive layer to the guide elements can be prevented. This could be a viable design, at least with relatively highly cross-linked adhesives and rotating guide elements. However, in the inventors' opinion, it is preferable for essentially all embodiments if a suitable separating layer, for example a liner, is arranged on the adhesive to prevent unwanted adhesion of the UV-curable adhesive to the guide elements of the device according to the invention.This effectively places the UV-curable adhesive within the device according to the invention between the carrier layer and the release layer. Those skilled in the art understand that, in this case, the statements made above regarding the carrier layer apply accordingly to the release layer with respect to its permeability to the electromagnetic radiation of wavelength λ used to initiate curing. A preferred method according to the invention is therefore one in which the web-shaped adhesive tape comprises a release layer arranged on the adhesive layer, wherein the release layer is at least partially, preferably predominantly, and particularly preferably substantially completely transparent to electromagnetic radiation of wavelength λ, and wherein the release layer is preferably coated with a silicone release layer.

[0072] Particularly preferred methods according to the invention are carried out with preferred devices according to the invention.

[0073] A method according to the invention is particularly preferred, wherein the initiation of the curing of the UV-curable adhesive mass is carried out with electromagnetic radiation of a wavelength λ in the range of 200 to 390 nm, preferably in the range of 300 to 380 nm, particularly preferably in the range of 350 to 370 nm.

[0074] A preferred method is additionally or alternatively a method according to the invention in which the initiation of the curing of the UV-curable adhesive mass is carried out with electromagnetic radiation whose intensity maximum lies at the wavelength λ.

[0075] The inventors have succeeded in identifying particularly advantageous curing conditions with which, in the inventive method, particularly advantageous UV-activated adhesive tapes can be obtained that are well suited for subsequent application to a substrate. A preferred method according to the invention involves irradiation with a radiation dose in the range of 1 to 12 J / cm². 2 , preferably in the range of 2 to 11 J / cm² 2 , especially preferred in the range of 3 to 10 J / cm² 2 . Preferably, or alternatively, a method according to the invention is used, wherein the UV-curable adhesive mass is irradiated for a time in the range of 0.5 to 60 s, preferably 1 to 30 s, particularly preferably 2 to 15 s, and / or wherein the residence time of a point of the web-shaped adhesive tape in the device is in the range of 0.5 to 60 s, preferably 1 to 30 s, particularly preferably 2 to 15 s.

[0076] After the initiation of curing, the curing process takes place over a longer period, for example, over a period of approximately 24 hours, the length of which depends on the design of the adhesive tape. A preferred method according to the invention is one in which the UV-curable adhesive is cured after process step c), wherein the UV-curable adhesive is preferably cured to more than 50%, particularly preferably to more than 70%, and most preferably to more than 90%, particularly preferably to more than 95%, based on the maximum possible degree of curing.

[0077] Furthermore, the inventors have succeeded in identifying preferred embodiments for the UV-curable adhesives to be used, with which excellent results can be obtained in the inventive method using the inventive devices. A preferred method according to the invention comprises the following: x1) one or more (co-)polymers, x2) one or more polymerizable epoxy compounds, and x3) ​​one or more cationic initiators,

[0078] A preferred or alternative method according to the invention is wherein the combined mass fraction of the (co-)polymers in the curable adhesive mass is 25% or more, preferably 30% or more, particularly preferably 35% or more, based on the mass of the UV-curable adhesive mass.

[0079] A preferred or alternative method according to the invention is also a method wherein one or more (co-)polymers are selected from the group consisting of poly(meth)acrylates, polyurethanes, polyvinyl acetals, such as polyvinyl butyral, polysiloxanes, synthetic rubbers, polyesters, phenoxypolymers, polyvinyl alcohols, polyvinyl alcohol copolymers, and alkene-vinyl acetate copolymers, preferably selected from the group consisting of poly(meth)acrylates, phenoxypolymers, polyvinyl alcohols, polyvinyl alcohol copolymers, polyvinyl acetals, such as polyvinyl butyral, and ethylene-vinyl acetate copolymers (EVA or EVAC, poly(ethylene-co-vinyl acetate)), in particular selected from the group consisting of poly(meth)acrylates, phenoxypolymers, and ethylene-vinyl acetate copolymers.

[0080] A preferred or alternative method according to the invention is furthermore or alternatively a process wherein the one or more polymerizable epoxide compounds are selected from the group consisting of epoxide compounds with at least one cycloaliphatic group, in particular a cyclohexyl group or dicyclopentadienyl group, and / or wherein the one or more polymerizable epoxide compounds are selected from the group consisting of bisphenol-A diglycidyl ethers and bisphenol-F diglycidyl ethers, preferably bisphenol-A diglycidyl ethers.

[0081] A preferred or alternative method according to the invention is also a method wherein the combined mass fraction of the polymerizable epoxy compounds in the curable adhesive mass is in the range of 35 to 95%, preferably in the range of 40 to 90%, particularly preferably in the range of 45 to 85%, and most preferably in the range of 50 to 80%, based on the mass of the UV-curable adhesive mass.

[0082] For essentially all applications, a method according to the invention is preferred in which one or more cationic initiators are selected from the group consisting of radiation-activated initiators. A method according to the invention is particularly preferred in which the combined mass fraction of the cationic initiators in the curable adhesive is in the range of 0.1 to 7%, preferably in the range of 0.3 to 5%, and most preferably in the range of 0.5 to 4%, based on the mass of the UV-curable adhesive.

[0083] As explained above, particularly preferred devices according to the invention comprise an optical detection unit with which the degree of curing at the outlet of the device according to the invention can be determined for UV-curable adhesives where the color properties depend on the degree of curing achieved. This enables particularly efficient process control and integrated quality control, especially with automated and sensor-controlled process control. Accordingly, it is also particularly preferred to use a suitable UV-curable adhesive. A method according to the invention is particularly preferred, wherein the UV-curable adhesive additionally comprises: x4) one or more pH color indicators with at least one pH-dependent color change.

[0084] A preferred method according to the invention is one in which the curable adhesive is composed in such a way that a pH-dependent color change of one or more pH color indicators occurs during the cationic curing of the UV-curable adhesive.

[0085] Finally, the use of a device according to the invention for curing web-shaped UV-curable adhesive tapes by curing the UV-curable adhesive masses, in order to reduce curing gradients in the UV-curable adhesive mass, is also disclosed.

[0086] The invention and preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying figures. These figures show: Fig. 1. A schematic cross-sectional representation of a non-inventive device; and Fig. 2 a schematic cross-sectional representation of a device according to the invention during the execution of the method according to the invention in a preferred embodiment.

[0087] Fig. Figure 1 shows a schematic cross-sectional view through a device 10 (not according to the invention) for use in UV radiation activation of web-shaped adhesive tapes 12, which is designed in the manner of a UV tunnel, with the housing not shown. In the schematic view, three guide elements 14, which are designed as rotatable, driven rollers, are arranged in one plane. These guide elements 14 guide the web-shaped adhesive tape 12 along a substantially straight guide path, which is indicated by the broad arrows, under three UV radiation sources 16 along the longitudinal direction L. The vertical direction H is orthogonal to this longitudinal direction L and to the transverse direction Q running along the axis of rotation of the guide elements 14, so that in the device 10 (not according to the invention), the UV radiation sources 16 are all located above the guide elements 14 with respect to the vertical direction H.The device 10 according to . Fig. 1. The required installation space in the longitudinal direction L is entered as length a.

[0088] In contrast to the non-inventive device 10 of the Fig. 1 shows the Fig. 2 a device 10 according to the invention in a preferred embodiment. In the embodiment according to Fig. 2 The guide arrangement also includes three electrically driven guide elements 14 spaced apart from each other along the longitudinal direction L, which, however, are arranged at different heights with respect to the vertical direction H and are accordingly located partly above and partly below the UV radiation sources 16.

[0089] The exemplary device 10 comprises three UV radiation sources 16 arranged in a line, the radiation sources 16 being located below the center of gravity line S, which is referenced to the centers of the guide elements, with respect to the vertical direction H, but centrally located within the device 10. This arrangement guides the web-shaped adhesive tape 12 in meandering loops within the device 10, with the guide rail passing between two UV radiation sources 16 in such a way that the portion of the web-shaped adhesive tape 12 running between two guide rollers 14 is exposed to UV radiation on both sides.

[0090] The UV radiation sources 16 can, for example, be designed as UV LEDs and exhibit the emission intensity maximum at a wavelength λ of approximately 365 nm. The installation space required for the corresponding device 10 is illustrated by the delineated section b. In the device 10 according to the invention, Fig. 2 results in a significantly greater length of the guide path of the web-shaped adhesive tape 12 in the device 10, although the required installation space is smaller compared to the device 10 of the Fig. 1 was reduced in an advantageous way (a > b).

[0091] In the schematic exemplary device 10 of the Fig. 2. The components of the device 10 shown are arranged in a mirrored housing (not shown). To enable advantageous temperature control despite the housing arrangement, the device 10 includes a temperature control device 18, which can be used to cool the interior of the device 10. A separating device is also provided at the outlet of the housing of the device 10, which serves to separate UV-activated web-shaped adhesive tapes 12 after they have passed through the device 10 (not shown). Furthermore, the device 10 includes an electronic image acquisition unit with which the color of the UV-curable adhesive in the web-shaped adhesive element 12 can be determined (not shown). In conjunction with a suitable UV-curable adhesive in which the degree of curing can be indicated by a dye, this enables particularly efficient process control of the device 10.

[0092] In the example shown, the Fig. 2 the middle guide element 14 is designed as a movable guide element which can be moved upwards or downwards along the height direction H in order to change the length of the guide track and thus the dwell time of the web-shaped adhesive tape 12 in the device 10.

[0093] The device 10 according to the invention can, for example, be operated in the method according to the invention such that an observed section of the web-shaped adhesive tape 12 inside the device 10 has a residence time of about 15 s and consequently, for example, a total UV dose of 6500 mJ / cm² applied to both sides. 2 learns. Reference symbol list 10 Device 12 strips of adhesive tape 14 Guide element 16 UV radiation sources 18 Temperature control device L Longitudinal direction Q transverse direction H Altitude S center of gravity line

Claims

[1] Device (10) for use in the UV radiation activation of web-shaped adhesive tapes (12), comprising: x) a guide arrangement for guiding a web-shaped adhesive tape (12) along a guide track, wherein the guide arrangement comprises three or more guide elements (14) spaced apart from one another along the longitudinal direction L of the device (10), wherein at least one of the guide elements (14) is a rotatable guide element (14) which is arranged in the device (10) such that its axis of rotation points at least partially in the transverse direction Q orthogonal to the longitudinal direction L, and y) one or more UV radiation sources (16), wherein the UV radiation sources (16) have the intensity maximum of the emission at a wavelength λ in the range of 100 to 400 nm, wherein the guide elements (14) of the guide arrangement are at least partially arranged at different heights with respect to the height direction H which is orthogonal to the longitudinal direction L and transverse direction Q, and wherein the UV radiation sources (16) are each arranged in the device (10) such that a first part of the guide elements (14) is located above the UV radiation source (16) with respect to the vertical direction H and a second part of the guide elements (14) is located below the UV radiation sources (16) with respect to the vertical direction H, wherein the device comprises a housing in which the components of the device are arranged and into which the adhesive tape is inserted through a feed opening and removed through a dispensing opening, wherein the inner wall of the housing is at least partially, preferably substantially completely, mirrored. [2] Device (10) according to claim 1, wherein the device (10) comprises two or more UV radiation sources (16) spaced apart from each other along the longitudinal direction. [3] Device (10) according to one of claims 1 or 2, wherein the guide arrangement comprises five or more guide elements (14). [4] Device (10) according to one of claims 1 to 3, wherein the UV radiation sources (16) have the intensity maximum of the emission at a wavelength λ in the range of 200 to 390 nm. [5] Device (10) according to any one of claims 1 to 4, wherein the device (10) comprises a temperature control device (18) for controlling the temperature. [6] Device (10) according to one of claims 1 to 5, wherein the guide elements (14) of the guide arrangement are arranged such that along the longitudinal direction L adjacent guide elements (14) are arranged at different heights with respect to the vertical direction H. [7] Device (10) according to any one of claims 1 to 6, wherein the guide elements (14) of the guide arrangement are at least partially arranged at the same distance from the center of gravity line S related to the centers of the guide elements (14). [8] Device (10) according to one of claims 2 to 7, wherein the device (10) is configured to irradiate a web-shaped adhesive tape (12) guided along the guide track by the guide elements (14) at least sectionally on both sides with the UV radiation sources (16). [9] Device (10) according to one of claims 2 to 8, wherein the UV radiation sources (14) lie at least partially on the center of gravity line S with respect to the vertical direction H and the center of the guide elements. [10] Method for UV radiation activation of web-shaped adhesive tapes (12) with a device (10) according to any one of claims 1 to 9, comprising the method steps: a) Manufacturing or supplying a web-shaped adhesive tape (12), comprising: i) a support layer, wherein the support layer is at least partially transparent to electromagnetic radiation of wavelength λ, and ii) an adhesive layer arranged on the substrate layer, comprising a UV-curable adhesive compound, b) Guiding the web-shaped adhesive tape (12) with the guide elements (14) of the guide arrangement along the guide path, wherein the guiding is carried out such that the web length of the web-shaped adhesive tape guided by the guide elements in the device (10) is greater than the length of the guide arrangement along the longitudinal direction L, and c) Irradiation of the adhesive layer of the web-shaped adhesive tape (12) guided along the guide path by the guide elements (14) in the guide arrangement with electromagnetic radiation emitted by the UV radiation sources (14) of a wavelength λ in the range of 100 to 400 nm to initiate the curing of the UV-curable adhesive masses. [11] Method according to claim 10, wherein the irradiation with a radiation dose in the range of 1 to 12 J / cm² 2 This has been done. [12] Method according to one of claims 10 or 11, wherein the dwell time of a point of the web-shaped adhesive tape (12) in the device (10) is in the range of 0.5 to 60 s. [13] Method according to any one of claims 10 to 12, wherein the UV-curable adhesive is cured to more than 50% after process step c), based on the maximum possible degree of curing.

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