METHOD FOR PRODUCING AN ELASTIC LAMINATE AND LAMINATE OBTAINED BY THE METHOD

Description

[0001] The invention relates to a method for producing an elastic laminate comprising at least a first cover layer and an elastic film. The invention further relates to a laminate obtainable by the method.

[0002] The elastic laminate is particularly preferred for use as the elastic section of a disposable hygiene product. The elastic laminate is particularly intended as the elastic closure band of a conventional diaper or as the elastic side section of a training diaper, which is also known in practice as a training pants. In addition to diapers for babies, corresponding elastic materials are also used in incontinence products for older children and adults.

[0003] With regard to the described applications, various constraints must be considered. On the one hand, disposable items aim to be as cost-effective as possible and utilize materials as efficiently as possible. Manufacturing and processing should also be as simple and cost-effective as possible.

[0004] Furthermore, the described applications are technically demanding because they require high reliability and good comfort. In particular, the hygiene products described must fit well, even when the user moves, so that absorbed excreta are safely contained. Furthermore, the hygiene products described should not be perceived as uncomfortable or even cause discomfort to the user.

[0005] For this purpose, known elastic laminates typically have at least one nonwoven cover layer, which forms a soft, comfortable, textile-like surface and can be produced cost-effectively. With such a typically non-elastic cover layer, the desired elastic recovery properties for a secure fit are achieved by the elastic film. With the cover layer, it is only necessary to ensure that the resulting laminate is sufficiently stretchable.

[0006] To achieve these laminate properties, various approaches are known in practice. For example, a pre-produced elastic film and a pre-produced nonwoven cover layer can be bonded together in a largely tension-free manner using pressure and temperature, adhesive, or ultrasonic welding, preferably with a pattern of bonded and unbonded areas. If the nonwoven then has only low strength, the laminate thus formed can be used directly for the purposes described above.

[0007] Frequently, however, activation of the formed laminate is provided during the manufacturing process. For this purpose, the laminate is stretched in a desired stretching direction, for example transversely to a production direction. For this purpose, the laminate can be fed, for example, into a stretching device with ring rollers. Due to the undulating or zigzag course of the nip between intermeshing ring rollers, the introduced material is extended in a transverse direction, whereby the stretchable, but not elastic, nonwoven cover layer is overstretched, permanently deformed, and possibly even partially destroyed. Upon leaving the nip, an elastic recovery occurs due to the elastic films, whereby the laminate is then slightly stretchable up to the degree of the previous stretching.Due to the plastic deformation and / or partial destruction of the cover layer, the elastic properties are then largely determined by the elastic film.

[0008] The approach described is described, for example, in EP 0 573 586 B1 and is widely used in practice.

[0009] Since the elastic films and at least one cover layer are largely unstretched during lamination and subsequent activation is usually also required, corresponding materials are also referred to as activatable laminates, zero-strain laminates or latent-elastic laminates.

[0010] Even though the laminates described have proven their worth, specific disadvantages must be considered. Since the nonwoven fabric is overstretched and often partially destroyed during activation, the laminate can be stretched relatively easily during use to the point of complete destruction. There is no clearly perceptible yield point for the user.

[0011] A variant of a zero-strain laminate is described in EP 2 177 654 B1, in which a nonwoven layer is formed directly on the elastic films, at least on one side. The nonwoven can also be so slightly stretchable that prior activation is not necessary. This is precisely why, in this case, there is no perceptible stretch limit for the user.

[0012] According to alternative approaches, a nonwoven cover layer, whose structure is not significantly impaired, is bonded to the elastic film only at individual, particularly linear or point-shaped sections, with a wave-like surface between them. In principle, such a structure can also be achieved if, in the previously described laminates, only a section-by-section bond is made, for example, using an adhesive, and the nonwoven material is not destroyed during activation.

[0013] This structure can also be achieved, however, if the elastic film is stretched along the desired stretch direction during lamination and is then bonded section by section to the cover layer. Once the tensile forces are removed, the elastic film then returns to its original position and thus also pushes the attached cover layer together in a wave-like manner. This has the advantage that the nonwoven still largely retains its original structure and is only pushed together along the preferred stretch direction. The laminate formed in this way can then be stretched very slightly up to the degree of stretch during lamination until the cover layer, which initially lies in a wave-like manner on the elastic film, is then, so to speak, straightened again. Depending on the design of the cover layer, a very clear yield point can be achieved in a particularly advantageous way.In the force-strain diagram of the laminate, there is then a clearly perceptible steep increase in the force required for further stretching.

[0014] Since the elastic film is stretched during lamination, this process is also called stretch bonding.

[0015] A material with comparable properties can be formed if, according to a further variant, the cover layer is formed into a corrugated shape along the desired stretching direction before being bonded to the elastic film and then bonded to the elastic film. Handling the cover layer in this way can be challenging, particularly because the edges of the corresponding material web must be positioned with sufficient precision. However, the advantage is that no significant tensile forces need to be applied to the elastic film during lamination along the desired stretching direction. Since the cover layer is folded into its corrugated shape for lamination, this process is also referred to as neck bonding.

[0016] Such a neck bonding is known from EP 0 985 394 B1, although this describes the connection of the cover layer with individual elastic strands rather than with a film. However, designs are also known in practice in which at least one cover layer made of nonwoven is laminated with an elastic film by means of neck bonding.

[0017] Whether a material web is stretched or simply folded using intermeshing ring rollers depends on various factors, such as the shape of the ring rollers and the friction involved. Stretching often also requires holding the material webs at their edges, as is also provided for in the finished laminate according to the aforementioned EP 0 573 586 B1.

[0018] Stretching a cover layer prior to further processing using ring rolls is known, for example, from WO 2017 / 184542 A1. With a consistent ring roll structure around the circumference, a continuous wave shape is created. Alternatively, the structure of the individual protruding rings can also be varied along the circumference in order to create different structures along the production direction. Corresponding measures are known from WO 2017 / 184542 A1.

[0019] Against the background of the prior art, the present invention is based on the object of providing a method for producing an elastic laminate, wherein the resulting laminate is particularly cost-effective and has good functional properties. Furthermore, a laminate obtainable by the method is to be provided.

[0020] The subject matter of the invention and the solution to the problem are a method for producing an elastic laminate according to patent claim 1 and a laminate obtainable by the method according to patent claim 16.

[0021] The invention thus relates to a method for producing an elastic, in particular a transversely elastic laminate with at least a first cover layer and an elastic film, wherein the first cover layer is fed as a material web along a production direction to a first stretching device, the first cover layer is subsequently stretched by means of the first stretching device transversely to the production direction and is thereby folded, and the folded first cover layer is subsequently connected in the folded state either to an extrusion web provided for the formation of the elastic film in such a way that the cover layer is connected to the extrusion web only at sections on its side facing the extrusion web or is connected to a prefabricated elastic film by at least partially melting the elastic film on its side facing the first cover layer,that the first cover layer is pressed only in sections against the at least partially melted side of the elastic film and that the first cover layer is at least partially embedded in a polymer matrix of the elastic film.

[0022] According to a first aspect of the invention, it is therefore provided that the first cover layer is also folded during its stretching by means of the first stretching device, wherein the folds are then at least partially and preferably at least largely retained until the lamination. During the lamination, the first cover layer is still folded, so that a material supply is provided by the folds for the intended elastic stretching of the formed laminate.

[0023] According to a preferred embodiment of the invention, the first stretching device is formed by two intermeshing annular rollers, whereby the first material web can then be guided along one of the annular rollers until it is laminated. This initially ensures that the first material web initially remains unchanged in its structure even after stretching, with a precisely predetermined width, in particular the initial width of the material web, whereby the material web is then held and guided by the projections of the associated annular roller.

[0024] In order to keep the first material web at exactly or at least approximately a predetermined width, it is expediently held by the first stretching device at its edges and in particular clamped against annular edges of the ring rollers. If alternately intermeshing rings projecting beyond a central plane are then arranged equidistantly between the edges, an averagely uniform stretch results between the edges, although the friction and support of the first material web on the individual rings, which are also referred to as teeth, makes it possible to modulate the stretch according to the distance between the successive rings. In particular, this can result in the first material web being stretched less at the points of contact with the rings and more between the rings.

[0025] Against this background, however, the invention is not limited to expansion devices in which the rings are arranged equidistantly. Rather, the spacing between successive rings can also be varied to create specific areas with different extensibility and thus adapt the mechanical properties of the laminate even more precisely to specific requirements.

[0026] Additionally or alternatively, the first material web can be held not only at its edges but also at at least one intermediate section to prevent it from being stretched and folded there. Such a process can be useful, for example, to enable the laminate to be further processed in multiple ways, i.e., to form at least two consecutive strips in the transverse direction. The separation of the at least two consecutive strips is then conveniently carried out at the intermediate section. Since the first material web is then flat and unstretched at the intermediate section, the strips thus formed can be easily further processed and, for example, glued together during the manufacture of a hygiene article.

[0027] If individual rings or ring segments can be adjusted, the gap for the connection to the extrusion web or the elastic film can also be optimized if necessary.

[0028] Particularly preferably, the first material web and the extrusion web or the elastic film can then be joined in a roll gap between the corresponding annular roller and a counter-roller. At the individual projections, the cover layer can then be pressed effectively and with a comparatively large force against the extrusion web or the elastic film, resulting in a particularly tight and reliable connection. Between the projections, the cover layer remains spaced apart from the extrusion web of the elastic film, thus preventing any connection there.

[0029] According to a preferred embodiment, the extrusion web intended for forming the elastic film is only formed inline in the process for producing the elastic laminate immediately before lamination. In particular, it can be provided within the scope of the invention that the single- or multi-layer extrusion web, at least on its side facing the first cover layer, is still molten or at least not yet completely solidified from the immediately preceding extrusion process. Even if the corresponding surface initially solidifies after the extrusion process, the surface can then be reheated and at least partially melted for lamination, whereby lamination is then possible without additional adhesive and thus without the introduction of further chemical components. In a multi-layer design of the extrusion web, different melting points can also be provided for the different layers.For example, it may be useful for the process if, during lamination, a layer facing away from the first cover layer or a core layer of the extrusion web has already completely or largely solidified and thus already gives the extrusion web a certain strength.

[0030] According to an alternative embodiment, a prefabricated elastic film is fed in and then, prior to bonding to the cover layer, at least partially melted on the side facing the cover layer. The actual bonding then occurs, as previously described in connection with the extrusion web, simply by pressing the layers to be joined together, without additional adhesive and thus without the introduction of further chemical components. Due to the identical bonding process, the measures described below in connection with the extrusion web are typically also suitable for the process in which a prefabricated elastic film is fed in.

[0031] The increased contact forces acting on the individual projections compared to full-surface pressure are particularly advantageous for achieving high local bond adhesion. While the unconnected, wrinkle-forming areas remain soft and flexible, the increased contact forces create a particularly tight bond. In particular, local contact forces can be achieved which are difficult to apply in a flat connection or which could damage the material. Within the scope of the invention, a certain amount of compression of the first cover layer can be tolerated only in the connected sections. With regard to the contact forces, a larger permissible parameter range, which can also be referred to as the process window, results compared to full-surface pressure. This also results in a wider selection of materials for the first cover layer. However, different aspects can play a role in the details.Thus, it is possible that the first cover layer is pressed to a certain extent into the extrusion web or the elastic film or at least an associated layer of the extrusion web or the elastic film.

[0032] If, for example, according to a preferred embodiment of the invention, a nonwoven is supplied as the first material web, the individual fibers of the nonwoven can then be enclosed by the polymer of the extrusion web or the at least partially melted elastic film, so that separation is then only possible by destruction or at least partial destruction of the first cover layer with maximum composite adhesion.

[0033] Alternatively, the first material web can also be made of a film, a woven fabric, or a knitted fabric. It is only necessary to ensure that the first material web can be stretched and folded transversely to the production direction.

[0034] If the first material web has openings, perforations, or free spaces, a connection can be achieved through a type of positive locking, as previously described in connection with a nonwoven, when the polymer of the extrusion web or of the at least partially melted elastic film penetrates into the openings, perforations, or free spaces.

[0035] In all possible configurations of the first material web, it can additionally or alternatively be provided that components of the first material web melt or melt due to pressure and temperature during lamination with the extrusion web or the elastic film. If the first material web is formed from a film, for example, this can have a low-melting cover layer. If the first material web is formed from fibers or threads, these can also have low-melting and high-melting components, for example as a fiber-thread mixture, through various filaments, or a bicomponent structure.

[0036] Additionally or alternatively, it can also be provided that the first cover layer is at least partially melted or at least partially melted due to the temperature of the extrusion web or the at least partially melted elastic film, so that the materials are reliably welded together. If - as described above - a nonwoven is used as the first material web, the fibers forming the nonwoven can also be optimized in this regard.

[0037] For example, a nonwoven fabric can be made from different fibers with different melting or softening temperatures. The process can then be conducted in such a way that only a portion of the fibers melts or partially melts, enabling a particularly reliable bond, while another portion of the fibers remains unmelted or partially melted, thus ensuring the structural integrity of the nonwoven fabric.

[0038] Additionally or alternatively, at least some of the fibers can also be in the form of multicomponent fibers, particularly bicomponent fibers. In a bicomponent fiber, for example, a high-melting core can be combined with a low-melting cladding. In this case, it is expedient to melt or partially melt only the low-melting cladding.

[0039] The counter roll described above is also called a smoothing roll because the extrusion web is guided and supported by it. The counter roll can be conveniently temperature-controlled to achieve the desired properties during lamination and further transport of the formed laminate. For example, it is advisable to at least prevent excessive flow of the corresponding polymer after the extrusion web has been bonded to the first cover layer. The smoothing or counter roll is therefore often referred to as a chill roll in practice.

[0040] Preferably, a cover layer is arranged on each side of the extrusion web or the elastic film, with various variants being possible. For example, a second cover layer is arranged opposite the previously described first cover layer. The second cover layer, as described above, is also expediently fed along a production direction to a second stretching device, stretched transversely to the production direction by the second stretching device, and folded in the process. The second cover layer is subsequently folded and joined to the extrusion web.

[0041] It must be taken into account that the extrusion web, which preferably emerges from a cast nozzle, cools down after leaving the extrusion gap, so that the two cover layers must be fed in and laminated in good time before the polymer melt has cooled down too much.

[0042] In principle, it is conceivable that for a design with two cover layers, an exactly or essentially symmetrical process could be carried out, with the two cover layers being laminated in a roll gap formed by two opposing ring rollers. For such a process, however, the teeth of the ring rollers must be positioned exactly opposite one another, with the extrusion web not being guided between the teeth. In order to enable the simultaneous symmetrical or essentially symmetrical feeding and lamination of two cover layers, various specific adaptations may be expedient. For example, it is expedient if the extrusion web is still soft enough for an intimate bond with the cover layers, but already has a certain melt strength. Otherwise, the melt web could become too thin between the opposing teeth.A multilayer design with at least three layers, as described further below, may also be expedient, in which case, for example, during lamination, a core layer essentially retains its previous thickness even at the connection points due to the cooling that has already taken place and / or its viscosity. In the case of opposing ring rollers, the rings can also be flat or at least flattened on their outer circumference to achieve a reliable connection even in the event of slight misalignment.

[0043] If, according to the variants of the invention described above, a prefabricated elastic film is supplied instead of the extrusion web, then, for example, even with heating on both sides for melting the surfaces, the energy input can also be provided in such a way that at least one core or one core layer of the elastic film does not melt and can thus withstand the compressive forces on the sections.

[0044] According to a preferred embodiment of the invention, the first cover layer and the second cover layer are successively fed with an offset to one another and bonded to the extrusion web or the elastic film. Naturally, the distance between the two locations for lamination with the two cover layers is then kept as small as possible.

[0045] In order to enable a connection by means of thermal bonding on both sides of the extrusion web or the elastic film with a certain offset, a polymer material can also be provided for the extrusion web or the elastic film, which can be processed over a wider temperature range, so that at least slightly different temperatures can be accepted when laminating the first cover layer on the one hand and the second cover layer on the other.

[0046] It should also be noted that the extrusion web or the elastic film can be constructed in multiple layers, although different thermal behavior is advantageous for the different layers. For example, if a core layer and a low-melting cover layer on each side are used to form the elastic film, the solidification of the core layer after extrusion can achieve sufficient stability of the polymer melt, the resulting elastic film, and the laminate, while the low-melting cover layers initially enable bonding with the cover layers, which are preferably made of nonwoven fabric. Such cover layers can also be remelted more easily if necessary.

[0047] If, according to the described preferred embodiment of the invention, two cover layers are laminated in successive steps with the extrusion web of the elastic film, then, before the second cover layer is laminated, the corresponding side of the extrusion web or the elastic film can also be heated again to a desired temperature, for which purpose, for example, hot air or infrared radiation can be considered.

[0048] As already described at the beginning, the first cover layer and, if applicable, the second cover layer are stretched in the same way using the associated stretching device and simultaneously folded. It is possible for the cover layer(s) to extend over the same width before and after stretching, even if the cover layer(s) actually have a larger width after stretching due to their corrugated shape.

[0049] Thus, the first cover layer and, if applicable, also the second cover layer can be fed to the respectively assigned stretching device with a width which corresponds approximately to the width and preferably exactly to the width of the extrusion web or the elastic film during lamination.

[0050] It is also expedient if the first material web and, if applicable, the second material web are held at their edges in the associated stretching device in order to keep the width covered by the material web constant transversely to the production direction. The desired extension of the cover layer itself, which provides the laminate's stretchability, is then achieved by stretching the corresponding cover layer and folding it into wave-like folds.

[0051] According to a further variant, an elastic laminate with two opposing cover layers can also be formed by bonding two sections of the previously described elastic laminate with the elastic film and only the first cover layer to the elastic film. For better differentiation, such a configuration is also referred to as a double laminate within the scope of the invention.

[0052] The double laminate can be formed by feeding two webs of the laminate with the elastic film and only the first cover layer, with the sides each containing the elastic film facing each other. The elastic films are then bonded there. The two supplied laminates can generally be different or identical. For example, different cover layers can be provided depending on the intended application. The elastic films of the two laminates supplied as a web are preferably made of the same material so that they can be easily bonded to one another and, furthermore, form a largely uniform elastic core in the double laminate. A bond is possible in different ways depending on the material used.If the elastic film is also comparatively soft and sticky due to its elastic properties, a sufficient bond may be achieved under certain circumstances through pressure alone, for example, by pressing it together in a roller nip. For lamination, the facing elastic films can preferably be heated at least superficially to achieve a firm and reliable bond using simple means. Such heating is possible, for example, with infrared radiation and / or hot air.

[0053] The double laminate described above can also be formed by folding a web of the laminate comprising the elastic film and only the first cover layer onto itself on the side of the elastic film, in particular along a fold edge running in the direction of production. If this occurs immediately after the extrusion web of the first cover layer has been joined, the elastic film or the extrusion web may still be so warm and sticky that a bonding of the double-layered elastic film in the folded state to itself is possible without further heating. Of course, heating by means of infrared radiation and / or hot air can be provided within the scope of the described embodiment.

[0054] In this context, it is important to note that the formation of the double laminate from two sections of the laminate can be completely separate (offline) from the formation of the laminate itself. The laminate can be formed in a separate and complete process and, if necessary, outsourced. One web of the laminate can then be folded to form the double laminate or cut into two half-width webs. Furthermore, two webs of the previously manufactured laminate can also be provided for the formation of the double laminate, so that no folding or cutting is necessary.

[0055] According to the invention, the laminate has at least a first cover layer. Based on this, variants with two cover layers have also been described previously, which are folded and thus connected to the extrusion web of the elastic film. In principle, however, other variants are also possible in which the first cover layer is folded as described, but a second cover layer has a different design. For example, a weakly bonded, easily stretchable material, in particular a nonwoven, can be provided as the second cover layer. Such an easily stretchable material then does not need to be folded to enable sufficient stretchability of the entire laminate.The mechanical properties of the laminate, such as the force required for stretching, the elastic recovery forces, and a perceptible yield point, are then essentially provided or determined by the elastic film and the pleated first cover layer. When producing the variant described, it can preferably be provided that the second cover layer is first bonded flat to the extrusion web while the latter is still largely molten and thus very sticky after emerging from a die gap. A reliable bond can then be achieved even with comparatively low surface or section-by-section pressure. The pleated first cover layer is subsequently bonded to the extrusion web, whereby the bond can then easily provide relatively large local pressure forces only in linear sections.

[0056] The first material web and, if applicable, the second material web can be stretched with the associated stretching device, for example, by a value between 100% and 400%, in particular between 150% and 350%, relative to an initial length. If the material web(s) are then laminated with a corresponding waveform, this value also roughly corresponds to the extensibility of the laminate until the cover layer, initially resting in a waveform on the elastic film, is essentially straightened again. A stretch limit is then typically clearly perceptible to a user.

[0057] In this context, another advantage of the present invention arises. On the one hand, the stretching of at least the first cover layer according to the invention allows the material, particularly the nonwoven, to be thinned, thereby reducing the basis weight of the cover layer (relative to the stretched state of the laminate). On the other hand, the stretching in the stretching device also takes place in such a way that the structure of the associated cover layer, preferably formed from a nonwoven, is not destroyed.

[0058] The effect of the stretching of the cover layer(s) depends not only on the degree of stretching but also on the material of the cover layer, whereby different types of nonwoven can also have different properties.

[0059] For example, nonwoven materials are available which initially exhibit relatively slight stretchability in a force-strain diagram, with the fiber structure being pulled apart like a net. The material then thins out, but its actual structure is not destroyed. In some cases, a relatively abrupt increase in force can be observed in the force-strain diagram with increasing stretch; this area of ​​the curve can also be referred to as the knee. For further stretching, significantly greater forces are then required, which can also be accompanied by destruction of the material. Before the nonwoven finally tears, the force required for further stretching usually drops significantly again.

[0060] The previously described characteristic with the formation of a knee can also be characterized by the force-strain diagram exhibiting an inflection point. Thus, according to a preferred embodiment of the invention, a nonwoven fabric is used with a force-strain diagram in which an inflection point occurs in a range between 100% elongation and 300% elongation. The elongation at break of the nonwoven fabric is typically at least 300%, preferably at least 400%, and in particular at least 500%.

[0061] Taking into account the previously described characteristics, the initially slight stretch can easily be used to thin the material and thus produce a particularly soft and cost-effective laminate. If, within the scope of the invention, the stretch is then carried out approximately to the previously described inflection point or knee, the subsequent steep increase in force in the force-strain diagram is maintained upon additional stretching and acts as a clearly perceptible yield point in the laminate thus formed.

[0062] The described characteristic occurs particularly in bonded nonwoven materials, whereby according to a first preferred embodiment of the invention, the nonwoven has at least one spunlace layer. A spunlace nonwoven is a nonwoven that is bonded or needled by water jets.

[0063] Additionally or alternatively, the nonwoven fabric may also comprise at least one spunbond layer. Particularly preferred in this context is a configuration in which the corresponding spunbond layer comprises crimped fibers or consists entirely of crimped fibers. The crimping may be due, for example, to mechanical crimping and / or the use of bicomponent fibers with an eccentric material structure. For example, if polymer materials with different shrinkage behavior are arranged side by side in bicomponent fibers (side-by-side arrangement), crimping may occur during cooling or as a result of additional heat treatment.

[0064] The crimping of the fibers can be advantageous within the scope of the invention for various reasons. For example, corresponding spunbond layers are pleasantly soft for the user due to the crimping of the fibers. For this reason, such nonwoven materials are also referred to in practice as high-loft nonwovens. The high softness is particularly evident when the spunbond layer with crimped fibers forms a surface of the laminate. Corresponding nonwovens and their advantages are described, for example, in EP 3 246 444 A1.

[0065] Spunbond layers made of crimped fibers are also characterized by good stretchability. Upon stretching, the crimped fibers can easily be straightened to a certain extent along the stretching direction without destroying the structure of the corresponding nonwoven layer. If only a portion of the fibers in a nonwoven or a layer of the nonwoven are crimped as described, at least this portion can be stretched to a certain extent without causing damage.

[0066] In principle, other nonwoven materials are also possible, especially multilayer nonwovens. The mechanical and haptic properties of the nonwoven can be precisely adjusted and selected, especially in a multilayer structure.

[0067] In principle, it is also possible for the entire nonwoven, a layer of the nonwoven, or at least a portion of the fibers of a layer to be made of non-melting fibers such as viscose, cotton, or cellulose. Non-melting fibers can be used, for example, to increase the proportion of renewable raw materials or to impart specific properties to the laminate, such as a certain degree of absorbency.

[0068] If thermal bonding is performed using pressure and temperature within the scope of the invention, an additional adhesive can be dispensed with. In addition to the corresponding cost savings, other disadvantages sometimes associated with adhesives, such as the release of volatile components, are also avoided.

[0069] As already described, the extrusion sheet or elastic film can have a multi-layer structure. For example, in a three-layer structure, a core layer of thermoplastic elastomer can be combined with non-elastic cover layers.

[0070] For a single- or multi-layer design of the extruded sheet or elastic film, conventional styrene block copolymers, as well as thermoplastic elastomers based on polyolefin (TPE-O), can be considered as thermoplastic elastomers, whereby these are often formed from a polypropylene copolymer. In a multi-layer structure, at least one elastic layer must be provided. For example, a core layer made of elastic polyolefin can be arranged between thin cover layers, which are also made of polyolefin. Especially with comparatively thin cover layers, it is then not necessary for the cover layers to be made of an elastic polyolefin.

[0071] The invention also relates to a laminate which is obtainable by the process described above.

[0072] The laminate has a first cover layer made of nonwoven and an elastic film, wherein the first cover layer and the elastic film are connected to the film by thermal bonding only at continuous or interrupted sections running along a longitudinal direction, wherein the first cover layer is arranged on the film in a wave-like manner along a transverse direction with arches between the connected sections and wherein the first cover layer, including the wave shape with the exposed arches along the transverse direction, has at least twice the width of the film and wherein the film is unstretched after the laminate has been formed by thermal bonding and preferably also starting from the production of the film itself. The arches are usually exposed between the connected sections.Especially with a comparatively low elongation and thus a less pronounced wave shape, it cannot be ruled out that at least individual fibers of a nonwoven are slightly bonded to the film as the preferred cover layer on the sheets.

[0073] Preferably, the cover layer, based on the base area of ​​the laminate in the unstretched state, has a basis weight of between 10 g / m² and 80 g / m². If, as previously described in connection with the method, the cover layer is held at its edges during stretching and the area covered in the transverse direction remains unchanged, the specified basis weight also corresponds to the basis weight initially intended for the corresponding material web. Based on the stretched state of the laminate or taking into account the actual length of the cover layer, a significantly lower basis weight results. This also leads to particularly efficient material utilization within the scope of the invention.

[0074] As is also evident from the process, the first cover layer is corrugated by stretching. Further design options for the laminate itself are also evident from the process description.

[0075] The invention is explained below with reference to a drawing illustrating only one exemplary embodiment. The drawings show: Fig. 1 Essential steps of a method for producing an elastic laminate, Fig. 2 the method step of stretching a cover layer, Fig. 3a a schematic view of an elastic laminate in a cross section, Fig. 3b the laminate according to the Fig. 3a in the stretched state, Fig. 4 a cross section according to the Fig. 3a for an alternative design of the elastic laminate, Fig. 5 a force-strain diagram for a cover layer of the laminate, Fig. 6 a further development of the method according to the Fig. 1 , Fig. 7the formation of a double laminate.

[0076] The Fig. 1 shows a method for producing an elastic laminate 1 with a first cover layer 2 and an elastic film 3. A spunlace nonwoven is provided as the first cover layer 2. The first cover layer 2 is fed along a production direction to a stretching device 4. In the context of the invention, the production direction refers to the advancement direction of the material web of the first cover layer 2, whereby the production direction naturally changes accordingly when deflected by rollers. The assignment of the production direction serves to delimit and define a transverse direction Q. Therefore, if several sections or material webs are fed as a continuous web, there is no need to distinguish between the different feeding devices.

[0077] The first stretching device 4 has two intermeshing ring rollers 5a, 5b, which, with the cover layer 2 arranged therebetween, are Fig. 2 are shown in a cross-section. From a comparative analysis of the Figuren 1 and 2 It can be seen that the material web of the first cover layer 2 is held at edges 6a, 6b of the ring rollers 5a, 5b, with rings 7a, 7b in the form of teeth being provided between the edges 6a, 6b of the ring rollers 5a, 5b, each projecting relative to a central plane M. Since the material web of the first cover layer 2 is held at the edges 6a, 6b, the width covered in the transverse direction Q by the first cover layer 2 does not change in the first stretching device 4. However, the intermeshing rings 7a, 7b cause an extension, i.e. stretching, of the material web of the first cover layer 2. The degree of stretching results from the shape of the rings 7a, 7b and from the offset relative to the central plane M.

[0078] The elongation is usually between 50% and 400%, in particular between 100% and 350%, preferably between 150% and 300%.

[0079] The first cover layer 2 is guided on the first stretching device 4 in such a way that even after leaving the roll gap, the first cover layer 2 continues to rest on one of the ring rollers 5a and is guided. Thus, even after leaving the roll gap, the first cover layer essentially retains the Fig. 2 shown structure.

[0080] While the first cover layer is then guided along the associated ring roller 5a, the first cover layer 2 is laminated with an extrusion web 8 emerging from a casting die 9. The first cover layer 2 is laminated with the extrusion web 8 between a nip of the associated ring roller 5a and a counter roller 10, which cools the extrusion web 8 and thus smooths and fixes it. The counter roller 10 can therefore also be referred to as a smoothing roller or chill roller.

[0081] Since the first cover layer 2 is guided on one of the ring rollers 5a during lamination with the extrusion web 8, the first cover layer 2 and the extrusion web 8 are only connected at linear sections 11, while between the sections 11 the first cover layer 2 essentially also has the Fig. 2 shown wave shape with folds. Between the connected sections 11, exposed arches 12 remain, which contribute to a particularly soft and pleasant feel (see Fig. 3a ).

[0082] According to the Fig. 3a The sections 11 are continuous in the production direction and thus in a longitudinal direction L of the laminate 1. In principle, however, it is also possible for the sections 11 to be interrupted along the longitudinal direction L. This can be achieved by interrupting, i.e., segmenting, the individual rings 7a, 7b along the circumferential direction of the associated ring rollers 5a, 5b.

[0083] According to the Fig. 3b the laminate 1 is stretched so far that the Fig. 3a The sheets 12 shown are pulled apart, so that the first cover layer 2 lies largely flat on the elastic film 3. The width of the laminate along the transverse direction Q then corresponds to the total width of the first cover layer, taking into account the corrugation. Fig. 2 The degree of elongation shown in the first stretching direction 4 also specifies a yield point for the entire laminate 1. Until the Fig. 3b In the configuration shown, the laminate is relatively easily stretchable, with the elastic film 3 being essentially decisive for the elastic properties and the forces necessary for stretching.

[0084] When the Fig. 3b In the configuration shown, the first cover layer 2 is then pulled tightly, creating a clearly perceptible yield point, which the user perceives as a kind of stop. These measures can prevent the laminate 1 from being accidentally overstretched during use and thus potentially destroyed.

[0085] The extrusion web 8 or the elastic film 3 formed therefrom can be single-layered or multi-layered without restriction. Fig. 4 shows in this context, by way of example, a three-layer structure of the elastic film 3, wherein a core layer 13 made of thermoplastic elastomer is arranged between cover layers 14, which are preferably not or less elastic. At least in the case of thin cover layers 14, elasticity is not necessary for the basic function of the laminate. It can also be provided that the cover layers 14 are made of a low-melting material, so that after emerging from the cast nozzle 9, the core layer 13 forms a closed, homogeneous layer relatively quickly, while the cover layers 14 are still available for good lamination of at least the first cover layer 2. It can also be provided that the first cover layer 2, which is preferably made of nonwoven, penetrates into the extrusion web 8 and in particular the cover layers 14 through the lamination.At the connected sections 11, the nonwoven is thus particularly reliably embedded in the elastic film 3 and can then only be separated again by destruction.

[0086] Additionally or alternatively, it can also be provided that the cover layers formed from nonwoven fabric comprise fibers with different melting points and / or bicomponent fibers. In the case of bicomponent fibers, for example, a low-melting sheath can be provided around a high-melting core, so that melting of the sheath upon connection to the extrusion web 8 also contributes to a particularly high bond strength. In the case of a fiber mixture, a similar effect can be achieved by a proportion of low-melting fibers. Within the scope of the invention, non-melting fibers such as viscose or cotton can also be provided, which are pressed into the extrusion web during production and thus mechanically bonded.

[0087] As already explained, a spunlace nonwoven is particularly suitable as cover layer 2. For this purpose, according to the Fig. 5 A typical force-strain diagram is shown as an example, where the nonwoven has an inflection point WP in a range between 100% and 300% elongation. Following the inflection point WP, the force F required for further elongation increases sharply, so that the force-strain diagram has a kind of knee 15. The nonwoven is expediently stretched to approximately the inflection point WP or the knee 15 as shown in Fig. 2 As shown, the nonwoven fabric is stretched prior to lamination, so that the material is advantageously thinned without losing its structure. However, the significant increase in force following the knee 15 is still maintained with respect to the laminate 1, ensuring the clearly perceptible yield point described above. The elongation at break of the nonwoven fabric is typically above 100%, preferably above 150%, and especially above 200%. Depending on the design of the nonwoven fabric, the elongation at break can also be above 300%, 400%, or even 500%.

[0088] According to a further development of the invention, the laminate also has a second cover layer 16 opposite the first cover layer 2, which can be formed as previously described in connection with the first cover layer 2. Accordingly, the second cover layer 16 is fed to a second stretching device 17 with annular rollers 18a, 18b, with reference to the explanations regarding the first stretching device 4 for further details.

[0089] The second cover layer 16 is laminated with a slight offset to the extrusion web 8. It must be ensured that the extrusion web 8 has not solidified to such an extent that a connection is no longer possible, even when laminated with the second cover layer 16. For this purpose, reference can be made to Fig. 4 It can also be advantageous if a core layer 13 made of thermoplastic elastomer is combined with cover layers 14 which have a lower melting point and thus remain liquid or at least soft even when the temperature decreases.

[0090] In principle, it is also possible to heat up the corresponding surface of the extrusion web 8 again to a certain extent before laminating the extrusion web 8 with the second cover layer 16, for which purpose Fig. 6 A heating device 19 is shown as an example. The heating device 19 can, for example, provide heating by means of hot air and / or infrared radiation.

[0091] Through the Fig. 6 In the embodiment shown, it is possible to arrange the first cover layer 2 and the second cover layer 16 on both sides of the extrusion web 8. The Fig. 7Against this background, shows an alternative embodiment, wherein two previously formed laminates 1, each comprising only the elastic film 3 and the first cover layer 2, are fed in such a way that the elastic films 3 face each other. After at least superficial heating by means of heating devices 19, a bonding takes place in a roll nip. The two superimposed elastic films 3 thereby interlock to form a largely uniform elastic core 20. Thus, a type of double laminate 21 is formed from two sections of the laminate 1.

Claims

1. Method for the production of an elastic laminate (1) with at least a first top layer (2) and an elastic film (3), wherein a) the first top layer (2) is fed into a first stretching device (4) as the first material sheet along a direction of production, b) the first top layer (2) is subsequently stretched using the first stretching device (4) transversely to the direction of production and thereby folded, and either c) the first top layer (2) laid in folds is subsequently connected to an extrusion sheet (8) intended for the formation of the elastic films (3) in such a way that the top layer (2) is connected to the extrusion sheet (8) on its side facing the extrusion sheet (8) only at sections (11), or d) the folded first top layer (2) is subsequently connected to a prefabricated elastic film (3) by at least melting the elastic film (3) on its side facing the first top layer (2), that the first top layer (2) is pressed against the at least melted side of the elastic film (3) only at sections (11) and that the first top layer (2) is at least partially embedded in a polymer matrix of the elastic film (3).

2. The method according to Claim 1, wherein the first stretching device (4) is formed by two interlocking ring rollers (5a, 5b).

3. The method according to Claim 2, wherein the first material sheet and the extrusion sheet (8) or the elastic film (3) are connected in a roller gap between one of the ring rollers (5a) and a counter roller (10).

4. The method according to any one of the Claims 1 to 3, wherein a second top layer (16) is fed into a second stretching device (17) as a second material sheet and is stretched transversely to the direction of production by means of the second stretching device (17), thereby being folded, and wherein the second top layer (16) is subsequently folded and connected to the extrusion sheet (8) or the elastic film (3).

5. The method according to any one of the Claims 1 to 4, wherein the first material sheet is stretched by a value between 100 % and 400 % by means of the first stretching device (4).

6. The method according to any one of the Claims 1 to 5, wherein a nonwoven-material sheet is fed as the first material sheet.

7. The method according to claim 6, wherein the nonwoven material comprises at least one spunlace layer.

8. The method according to Claim 6 or 7, characterized in that the nonwoven material comprises at least one spunbond layer.

9. The method according to Claim 8, characterized in that the spunbond layer contains crimped fibres and is made of crimped fibres in particular.

10. The method according to any one of the Claims 6 to 9, wherein the nonwoven material comprises an elongation at break of at least 300 % and wherein a stress-strain diagram of the nonwoven comprises a inflection point (WP) at a range between 100 % elongation and 300 % elongation.

11. The method according to any one of the Claims 6 to 10, wherein the nonwoven material contains bicomponent fibres.

12. The method according to any one of the Claims 1 to 11, wherein the extrusion sheet (8) or the elastic film (3) is formed in multi-layer manner with a layer of thermoplastic elastomer and at least one surface layer (14).

13. The method according to any one of the Claims 1 to 12, wherein the extrusion sheet (8) or the elastic film (3) is made of polyolefin.

14. The method according to any one of the Claims 1 to 13, wherein the first top layer (2) is fed into the first stretching device (4) with a width equal to between 90 % and 110 % of the width of the extrusion sheet (8) or the elastic film (3) during lamination.

15. The method according to any one of the Claims 1 to 14, wherein the first sheet of material is held at its edges in the first stretching device (4).

16. A laminate available according to the method according to any one of the Claims 1 to 15 comprising at least a first top layer (2) of nonwoven material and an elastic film (3), i) wherein the first top layer (2) and elastic film (3) are connected to the film (3) only at sections (11) running along a longitudinal direction (L) without a separate adhesive; ii) wherein the first top layer (2) is arranged in an wave-like manner along a transverse direction (Q) with exposed arches (12) between the connected sections (11) on the film (3); iii) wherein the first top layer (2), including the waveform with the exposed arches (12) along the transverse direction (Q), comprises at least twice the width of the film (3), and iv) wherein the film (3) is unstretched after its formation.

17. The laminate according to Claim 16, wherein the first top layer (2) comprises a basis weight between 15 g / m2 and 80 g / m2 in relation to the base surface of the laminate in the unstretched state.

18. The laminate according to Claim 16 or 17, wherein the first top layer (2) is made into the wave shape by stretching it.