Elastic laminate

Abstract

The invention relates to an elastic laminate having at least one top layer made of a non-woven fabric and an elastic film, the at least one top layer having a plurality of wrinkles extending in a machine direction in an unstretched state in a transverse direction, and the at least one top layer and the elastic film being bonded to each other at a plurality of spaced-apart bonding points. In an unstretched state in the transverse direction, at least two wrinkles between the bonding points have different cross sections.

Description

TECHNICAL FIELD

[0001] The present invention relates to an elastic laminate having at least one top layer made of a nonwoven and an elastic film, wherein the at least one top layer in the un-stretched state has a plurality of pleats extending in the machine direction in the cross direction. In this context, the un-stretched state means the state in which the nonwoven is essentially free of forces. On this basis, the at least one top layer and the elastic film are subsequently joined to each other at a plurality of spaced-apart bonding points. As a result, there is no full-surface connection between the top layer and the elastic film. Rather, there can be a plurality of bonding points in the machine direction and in the cross direction, which fix the elastic film on the top layer. BACKGROUND

[0002] Such laminates are known in principle from the prior art, although the folding in the cross direction makes it possible to achieve stretchability in the cross direction despite the top layer being essentially inelastic nonwoven, while the elastic film provides the restoring behavior. In contrast, the elastic laminate does not exhibit significant stretchability in the machine direction, since the folding is only done in the cross direction, so that at most only slight stretching is used in the machine direction due to the nonwoven for the top layer. However, since the nonwoven is usually made of inelastic material, the stretchability in the machine direction is significantly lower than in the cross direction.

[0003] Various methods are known in practice to achieve elasticity in the cross direction in laminates made of nonwoven and elastic film. For example, so-called neck bonding is known, different embodiments of which are explained in documents EP 0 707 106 B1, EP 1 458 565 B1 and US 7 008 496 B2.

[0004] In the case of neck bonding, the nonwoven is guided after unwinding at an increased pull-off speed. This leads to the length of the nonwoven being stretched and contracted. This results in pleats which are arranged next to each other in the cross direction and aligned in the machine direction. The nonwoven must have a corresponding fiber structure in order for the fibers to align and be able to stand up during the necking process. The nonwoven folded in this way is then joined with the elastic film.

[0005] US 2006 / 003656 A1 teaches a design in which the entire laminate after lamination of the nonwoven web with the elastic film is further stretched by ring rolling.

[0006] Although this technique has proven successful in principle, it has also shown that setting certain elastic parameters is problematic, because the mere collapsing of the nonwoven web alone means that the stresses at the edges of the material are significantly smaller than in the center of the nonwoven web, resulting in a non-uniform collapsing of the nonwoven web over its width. At the same time, the elastic parameters can only be adjusted within a limited range, since the adhesive points are independent of the collapsing of the nonwoven web. The elastic parameters therefore differ to some extent over the width of the nonwoven web.

[0007] Another method of achieving the elastic properties in the transverse direction is so-called stretch bonding. In this process, the nonwoven web is fed essentially in the untreated state, while the elastic film is stretched in the transverse direction by the desired amount. The nonwoven web is then joined to the elastic film in the stretched state of the elastic film, and as the elastic film returns to its original state, the elastic laminate forms the pleats. The pleats are therefore not actively introduced into the nonwoven web, but are formed entirely by the transverse direction elasticity of the elastic film. The formation of the adhesive points is then preferably carried out in the stretched state of the elastic film in order to achieve a uniform adhesive pattern in the stretched state.

[0008] The advantage of this design is that the elasticity and the collapsing in the non-stretched state are more defined than in the previously described neck-bonding. In this design, however, the elastic parameters are almost entirely influenced by the pattern of the adhesive points.

[0009] There is therefore an increasing demand for elastic laminates which have a greater variability of the elastic parameters compared to previously known laminates. SUMMARY

[0010] The present invention is based in this case on the task of specifying an elastic laminate which has a high transverse direction elasticity, while at the same time having a good hand.

[0011] The object and solution of this task is an elastic laminate according to patent claim 1. It is therefore essential for the present invention that at least two pleats between the adhesive points have different cross-sections in the non-stretched state in the transverse direction.

[0012] Compared to the laminates known to date, the laminate according to the present invention is characterized by an irregular structure, which becomes visible in the case of pleats between the transversely arranged adhesive points which differ from one another in cross-section. These differences are embodied in particular in the shape and / or size of the pleats. While it is sufficient for the purposes of the present invention if only two pleats have different cross-sections, it is preferable for a plurality of pleats, in particular more than three, preferably more than five, to have different cross-sections. Furthermore, the different pleats are preferably arranged at least partially directly adjacent to one another.

[0013] According to a preferred embodiment, the cross-sectional areas of at least two of the pleats differ from each other by at least 25%, particularly preferably by at least 35%. The area is defined by the width, the height and the cross-sectional shape of the pleat.

[0014] According to another preferred embodiment, at least two of the pleats have different heights, which preferably differ from each other by at least 25%, preferably by at least 35%.

[0015] According to another embodiment, which also has its own inventive concept, in the stretched state, in which at least one of the top layers is essentially free of pleats in the direction of stretching, the surface weight of the laminate and / or of at least the top layer at the points of adhesion is greater than the surface weight between the points of adhesion. The surface weight in this case mainly refers to the direction of expansion in the transverse direction and provides information about how much material, in particular of at least one of the top layers, is provided at the points of adhesion. This stretched state is reached when the laminate is stretched to the so-called "bulge effect". If this point is exceeded, the material of the top layer will be stretched and destroyed. The bulge effect is therefore characterized by a sharp increase in force.

[0016] In this case, it should be noted that although the points of adhesion are introduced into the laminate at discrete points, due to the alignment of the pleats in the machine direction, areas with a higher and lower surface weight are formed, which also extend in the machine direction. The areas with a higher surface weight are formed in the areas where the points of adhesion are provided at points in the transverse direction of the laminate, while the areas with a lower surface weight are completely free of points of adhesion. In order to determine the difference in surface weight, strips of the same length in the machine direction (e.g. 1 m) can be cut from both areas and the surface weight determined by taking into account the effect of stretching to the wall.

[0017] It is clear that according to the preferred embodiment, the points of adhesion define areas of increased surface weight, according to the preferred embodiment, the surface weight of all the points of adhesion is greater than the surface weight of the areas between the points of adhesion. The design of the points of adhesion can therefore be used to adjust the elasticity of the elastic laminate in a targeted manner, while in laminates produced by neck-bonding, the surface weight is essentially arbitrarily set at the points of adhesion or between the points of adhesion due to the excessive stretching of the nonwoven.

[0018] In order to produce such an elastic laminate, a method for producing such an elastic laminate can comprise the following steps:

[0019] a) feeding at least one web of nonwoven and one web of elastic film in the machine direction,

[0020] b) forming pleats at least by pre-folding the at least one web of nonwoven in the transverse direction

[0021] Preferably, the pre-folding occurs when the at least one nonwoven is guided in a supporting manner along a longitudinal section. In this case, the longitudinal section refers to the section along which the nonwoven web is guided in the machine direction during the folding process. In contrast to ring rolling, the nonwoven web is thus guided essentially without force along fins extending in the longitudinal direction, which engage with one another in the same way as the rings of a ring rolling, thus enabling the nonwoven to be folded. However, instead of being placed between two rollers at a single point, the nonwoven is placed along a longitudinal section, which must be sufficiently long to allow the formation of the pleats, even though the speed of the web is high. The axial longitudinal section can thus be at least 500 mm, preferably at least 600 mm long. It is also important that the nonwoven web is guided without force between the fins, so that the width of the nonwoven web is significantly reduced during the folding process, whereas in the case of ring rolling the nonwoven web is fixed at the lateral edges. This leads to the nonwoven being pleated, but the material is not stretched or over-stretched in the transverse direction. At the same time, the longitudinal support ensures that the material has sufficient time to form a uniform pleat over the entire width of the nonwoven web.

[0022] c) in a subsequent step, forming an elastic laminate by bonding the substantially un-stretched elastic film web to the folded nonwoven web, at least one of the nonwoven webs, at a plurality of bonding points.

[0023] In this manufacturing process, the top layer of the nonwoven is only folded, but is essentially not stretched in the transverse direction, and the connection to the elastic film web occurs in an essentially unaffected state, so that when the laminate is stretched in the transverse direction, only the elastic film web is stretched in the area between the bonding points, whereas the laminate itself remains unaffected at the bonding points. The elasticity is thus largely determined by the bonding points, although there is greater variability in the adjustment of the elasticity parameters compared to the case of stretch bonding.

[0024] As mentioned above, during production, the elastic film is not stretched in the machine direction, although of course a small amount of stretching does occur, which is necessary to maintain the process stability. However, this elongation is less than 10%, and is therefore not significant in the context of the present application.

[0025] A further development of the present application provides that the surface weight of at least the top layer of the elastic laminate at the bonding points is at least 10% greater than the surface weight between the bonding points in a stretched state with essentially no pleats between the bonding points.

[0026] The surface weight of the top layer at the bonding points is 10% to 100%, in particular 15% to 50%, greater than the surface weight between the bonding points. For the elastic laminate, the surface weight at the bonding points can be at least 20% higher than the surface weight between the bonding points. In this case, particular reference is made to all the bonding points.

[0027] However, in order to achieve such a high difference, not only the elastic film but also the top layer of the nonwoven must be taken into account.

[0028] The above process allows, in particular compared to the solutions known to date, very fine micro-creases to be formed in the transverse direction. This is achieved, for example, by stretching the nonwoven web in the machine direction after the pre-folding. This stretching has the effect not only of refining the coarse pre-fold structure formed in the longitudinal support process beforehand. At the same time, the stretching in the machine direction also stabilizes the creases in the nonwoven web. It is crucial, however, that the stretching is used only to preserve the crease structure. There is no structural change in the material of the nonwoven web in the machine direction.

[0029] The result of the process is the formation of a very fine micro-crease structure in the nonwoven web, the micro-creases being significantly narrower than the bond points. In the bonding process, the bond points can contain a large number of creases in the transverse direction. For example, just one bond point can comprise 6 to 14 creases, in particular 8 to 12 creases. This leads to the material being further compressed by the creases at the bond points in the bonding process, so that the elasticity is determined to a greater extent by the bond points. Thus, for example, greater stretch and higher tensile strength can be achieved with a small number of integrated creases. By contrast, a greater number of integrated creases increases the restoring force from the stretched to the unstretched state. Depending on the application, the elasticity of the laminate is significantly influenced, in particular by the design of the bond points.

[0030] The preferred further development of the application also provides that, in the unstretched state, the maximum thickness of the laminate between two bond points corresponds to at least 1.5 times the thickness at the bond points, whereby this refers both to two bond points arranged one behind the other in the machine direction and to two bond points arranged one behind the other in the transverse direction, wherein, in the case of the transverse direction, the maximum thickness between the two bond points can correspond to at least twice the thickness at the bond points. Thus, a relatively dense material is formed for the user, although a material with increased loft and thus better haptics can also be provided. The particularly high thickness can be due to the fact that, on the basis of the manufacturing process described above, the nonwoven web is only folded and not stretched and thinned. It thus virtually remains unchanged in the corrugated state between the bond points, resulting in an increase in the thickness between the bond points.

[0031] According to a preferred embodiment of the present application, the transverse strain is at least 100% at a load of 1000 g. Most preferably, the strain at a load of 1000 g is at least 150%. This refers to a test procedure according to DIN ISO 527, wherein a sample of 50.8 mm width (2 inches) is loaded with a weight of 1000 grams. The length change (AL) determined in this measurement can be compared to the original length (LO), wherein an elongation of 100% means that the length change AL is equal to the original length LO. Thus, a material having an initial length of 10 mm will have an extended length of 20 mm due to the load of 1000 g.

[0032] In addition to the extensibility of the elastic laminate, the so-called permanent set is also important, which provides information about how permanently the elastic laminate is extended after an initial stretching. For this purpose, the material sample of 50.8 mm width (2 inches) is clamped again and stretched by 150% in the transverse direction. Then, the material is returned to the unstretched or force-free state, and the difference in length to the original clamping length defines the permanent set. Based on such a measurement, the permanent set after an initial stretching of 150% in the transverse direction is at most 30%, preferably at most 25%.

[0033] On the one hand, this laminate has a high extensibility in the transverse direction, while at the same time having a low permanent set, which is suitable for various products. For example, a suitable laminate is used for so-called paper nappy ears, wherein the high extensibility ensures a particularly high comfort and a secure closure. At the same time, the low permanent set makes it possible to close the nappy several times without causing a problematic elongation of the paper nappy ear. Thus, the present application not only relates to the elastic laminate, but also to products made from such a laminate, in particular sanitary products, such as paper nappy ears.

[0034] In addition, the elastic laminate can have a relatively high tensile strength in the transverse direction due to the essentially unprocessed top layer. This is at least 25 N, particularly preferably at least 30 N, in the transverse direction according to DIN ISO 527. For this measurement, a sample of 50.8 mm (2 inches) width is continuously stretched at a speed of 500 m / min, and the force-strain diagram is recorded. The maximum force corresponds to the tensile strength. This can be achieved in particular by the laminate produced by the method of the present application when the laminate is stretched to such an extent that essentially no folds are visible on the nonwoven top layer. Thus, in this state, the transverse elastic creases are exhausted. In comparison to a laminate produced using neck-bonding, the top layer made of nonwoven now has a relatively high resistance, since the nonwoven does not have areas of thinning due to the folds alone. Thus, a product can be formed from the elastic laminate which is particularly resistant to external stresses.

[0035] The elongation at break in the transverse direction is preferably at least 200 %, particularly preferably at least 250 %, according to DIN ISO 527.

[0036] Although it is sufficient in the context of the present application to connect only one nonwoven cover layer to the elastic film, it is preferred to arrange the elastic film between at least two nonwoven top layers. Thus, the elastic film is enclosed between two nonwoven top layers, both of which have a plurality of pleats extending in the machine direction in an un-stretched state and thus are free of forces in the transverse direction. Thus, both sides of the laminate have a soft, fluffy surface, which leads to a better feeling for the user, in particular in the design of hygiene products.

[0037] Based on this design, the top layers and the elastic film can be directly bonded to each other. On the one hand, this can be achieved by applying a point-like adhesive, for example a hot-melt adhesive. However, it is particularly preferred to form the bond points by ultrasonic welding. In this process, the laminate is pressed at the intended bond points by so-called ring rolls with protrusions and ultrasonic welding heads, the ultrasonic energy being used to melt the top layers and / or the elastic film. It is conceivable in this case that only the elastic film is melted to some extent, the two nonwoven top layers being bonded together by the molten material. However, at the same time, it is also conceivable that the introduction of pressure and energy in combination with the web tension of the elastic film leads to the elastic film tearing at the bond points, the nonwoven cover layers then being at least partially or completely bonded directly to each other at the bond points. This naturally presupposes that the nonwovens are formed from a material consisting at least partially of thermoplastic filaments and / or fibers. In particular, filaments and / or fibers made from polyolefins, for example polypropylene (PP) or polyethylene (PE), are suitable for this.

[0038] The formation of the bond points is crucial for the elastic behavior of the laminate, the size of the bond points and their distance from each other being particularly important. According to a preferred embodiment, the bond points are arranged in longitudinal rows extending in the machine direction and in transverse rows extending in the transverse direction. In this respect, the arrangement in the transverse direction is particularly important, since the material is essentially elastic only in the transverse direction. The bond points can be circular, oval, square or rectangular, wherein the width in the transverse direction is particularly important for how many pleats can be fixed on the bond point. In this case, a particularly preferred embodiment provides that the width of the bond points in the transverse direction is between 0.8 mm and 2 mm, in particular between 1 mm and 1.6 mm. The length in the machine direction is preferably between 0.1 mm and 0.5 mm.

[0039] Another important factor related to the elasticity is not only the width of the adhesive points and thus the number of integrated folds possible, but also the distance of the adhesive points along the transverse direction. This distance is preferably between 1 mm and 2.5 mm, in particular between 1.4 mm and 2 mm. The ratio between the distance of the adhesive points along the transverse direction and the width of the adhesive points also determines the ratio between fully free pleats and pleats fixed in the adhesive points. Thus, the elasticity of the laminate along the transverse direction can be adjusted by specifically selecting this ratio, and thus the selection of the pattern of pleats and adhesive points is crucial compared to previously known laminates manufactured using neck-bonding or stretch-bonding methods.

[0040] According to preferred embodiments of the present application, the longitudinal rows among them and the transverse rows among them are identical in terms of arrangement and design of the adhesive points. However, it is also useful to have different sizes for the adhesive points of longitudinal rows and / or transverse rows directly adjacent to each other.

[0041] Furthermore, it is also possible to arrange the adhesive points of two longitudinal rows next to each other in the machine direction and / or in the transverse direction, such that they are staggered in the machine direction.

[0042] The position and design of the adhesive points are also crucial for the pleat structure in the laminate. The pleats extending from the adhesive points in the machine direction are usually much narrower than the pleats that are not integrated by adhesive points in the machine direction. It should be noted that in the folded state of the nonwoven, a large number of microscopic pleats are arranged next to each other, which are introduced during the production process by the adhesive points. By introducing the adhesive points, the microscopic pleats are then fixed at the adhesive points, while outside the adhesive points the microscopic pleats essentially come together to form macroscopic pleats, which is caused by at least partial unfolding. Thus, the pleats integrated in the adhesive points in the transverse direction are microscopic pleats, while the pleats between the adhesive points are macroscopic pleats. In this context, microscopic pleats refer to pleats with a width of less than or equal to 1 mm, respectively less than 0.5 mm, while macroscopic pleats have a width of more than 0.5 mm, in particular more than 1 mm. Furthermore, microscopic pleats usually do not have as clear a pleat formation as macroscopic pleats, which include a more random and non-linear pleat structure.

[0043] While the pleats between the adhesive points are macroscopic pleats, a closer examination also reveals a microscopic pleat structure. Usually, the microscopic pleats are relatively uniformly arranged along the transverse direction before the adhesive points are applied. However, it is also possible that several microscopic pleats form some kind of macroscopic pre-structure, which has an influence on the structure of the laminate after the adhesive points have been applied.

[0044] Due to the fact that the folds are integrated into the adhesive points, the material density of the laminate and / or at least the top layer at the adhesive points is higher compared to the material density of the area between the adhesive points in the stretched state. In the stretched state, where the top layer is essentially free of folds, the ratio between the density in the adhesive points and the fold density outside the adhesive points is at least 0.1 and 0.6, preferably between 0.15 and 0.5.

[0045] However, it is also conceivable that the height and / or width of the single folds between the adhesive points is significantly larger than the height and / or width of the folds within the adhesive points.

[0046] The fact that the cross-sections of the folds between the adhesive points differ from each other is caused by two different aspects. Initially, the pre-folding process can lead to the fact that a single pre-fold is overfolded and thus, due to the position of the adhesive points, captured in the adhesive points over a comparatively large area. This naturally means that the adjacent folds outside the adhesive points can essentially fold the material, resulting in different sizes of the folds between the adhesive points. The other aspect is achieved in particular by subsequently activating the elastic laminate in the transverse direction, pulling the single folds out of the adhesive points.

[0047] In this case, the fold height of the single fold is at least 10%, preferably at least 20% larger than the average fold height and / or width in the laminate. This refers to the average fold width or height, which is averaged over all folds outside the adhesive points.

[0048] The preferred embodiment of the present invention provides that the opening hole force (OHF) is between 30 N and 140 N. This parameter is determined using a measuring device, which will be explained in more detail below in connection with Figure 7 . When measuring this parameter, the sample is fixed on a sample holder with an inner diameter D H of 35 mm. Then a stress is applied to the laminate with a mechanical finger, the size of which is based on a human finger. The mechanical finger is conical, with a base region with a diameter D T of 20 mm and a length Z T of 15 mm. At the tip, the mechanical finger is rounded with a radius R T of 5 mm. The surface material of this mechanical finger is made of neoprene with a hardness of between 5 HRC and 20 HRC. Then, the mechanical finger is guided in the direction of the sample holder and the elastic laminate is pressed through the tip into the opening area of the sample holder formed by the inner diameter. The speed of the insertion of the mechanical finger is 1260 mm / min. Then the force is recorded until the limit of the elongation at break is reached, the maximum measured force corresponding to the opening hole force (OHF).

[0049] The further development of the application also provides that the elastic film has an elastic film layer and at least a first non-elastic outer layer which is co-extruded with the elastic film layer. Preferably, the first non-elastic outer layer and the second non-elastic outer layer are co-extruded with the elastic film layer, the elastic film layer being arranged between the first outer layer and the second outer layer. In principle, various materials are suitable for forming the outer layers and the elastic film layer. The elastic film layer is preferably made of a polyolefin elastomer or a styrene block copolymer compound. The styrene block copolymer compound can be, for example, a styrene-isoprene-styrene block polymer (SIS), a styrene-butadiene-styrene block copolymer (SBS), a styrene-ethylene-butylene-styrene (SEBS) or a styrene-ethylene / propylene-styrene block copolymer (SEPS). Furthermore, the styrene block copolymer compound can be mixed with a polyolefin, i.e. a polyolefin elastomer, or a polyolefin mixture. It is particularly preferred that the styrene block copolymer is a styrene-ethylene-propylene-styrene block polymer (SEEPS), which is special in that it can be mixed particularly well with polyolefins. As a result, processing aids such as mineral oil can be dispensed with.

[0050] The second polymer component is preferably present in the elastic film layer in a proportion of 25% to 90%. In addition to the polyolefin or polyolefin mixture, polystyrene or processing aids can also be provided. The processing aids can in particular be mineral oil.

[0051] In a preferred embodiment, the first outer layer and / or the second outer layer is formed from a polyolefin as the main component. By "main component" is meant that the polyolefin is present in the first outer layer and / or the second outer layer in a proportion of at least 30% by weight. It is particularly preferred that at least 45% by weight, particularly preferably at least 50% by weight, of the polyolefin is present in the respective first outer layer and / or second outer layer. The polyolefin of the outer layer and / or the elastic film layer is preferably polyethylene, polypropylene or a mixture thereof. In the case of polyethylene, this is in particular low-density polyethylene (LDPE) or linear low-density polyethylene (LLDPE). The first outer layer and / or the second outer layer can also contain 2% to 15% of a filler, such as chalk or talc.

[0052] In this case, a particularly preferred embodiment provides that the ratio of the thickness of the elastic film layer to the thickness of the first outer layer and / or the second outer layer is between 6:1 and 15:1, in particular between 7:1 and 12:1. In particular, a thickness of the first outer layer and / or the second outer layer of between 1 μm and 5 μm, preferably between 1.5 μm and 4 μm, particularly preferably between 2 μm and 3.5 μm, is envisaged. In contrast, the thickness of the elastic film layer is between 15 μm and 40 μm, in particular between 20 μm and 30 μm.

[0053] The laminated article of the application can in particular be obtained by the following method. The method comprises at least the following steps:

[0054] a) supplying at least one nonwoven web and one elastic film web in the machine direction,

[0055] b) forming pleats at least by pre-pleating the at least one nonwoven web in the cross direction while guiding the nonwoven web in a supporting manner along a longitudinal section,

[0056] c) forming an elastic laminate by connecting the substantially un-stretched elastic film web with the at least one nonwoven web which is pleated at a plurality of bonding points.

[0057] In this context, a substantially un-stretched elastic film means that the elastic film web is stretched less than 10% in the machine direction. In this context, it should be noted that due to the web tension, the elastic film can experience a certain stretch, but this unintended stretch does not exceed a value of 10%, depending on the thickness and stiffness of the skin.

[0058] The pre-pleating during the supporting guiding occurs on a longitudinal section having a length between 500 mm and 1500 mm, in particular between 600 mm and 1200 mm. In contrast to the so-called ring-rolling process, the pre-pleating on the longitudinal section is performed in a static manner, whereby the nonwoven web is guided between a series of mutually interlocking upper and lower fins. The distance between the fins and the degree of interlocking of the fins has a decisive influence on the pleats formed thereby.

[0059] In particular, the distance between two consecutive fins arranged in the cross direction is between 5 mm and 50 mm. The degree of engagement of the upper fins and the lower fins with each other is preferably between 5 mm and 40 mm. The upper row of fins and the lower row of fins are part of a folding device, whereby the nonwoven web, after leaving the fins, has pleats which are usually too coarse for the intended laminate.

[0060] This type of pre-pleating, in which the nonwoven is guided on the fins in a straight line and without tension, also differs significantly from the pleating of the material web in the roll gap or around a forming roll.

[0061] In view of this, it is necessary to convert the coarse pre-pleats into finer micro-pleats. Therefore, the pleats in step b) during the supporting guiding only form a pre-pleat, the width and height of which is significantly smaller than the width and height of the pre-pleat.

[0062] To achieve such microfolds, the already pre-folded nonwoven web can be stretched in the machine direction by at least 10% during step b). This stretching has to be performed after the pre-folding, which ensures that the microfolds are formed uniformly over the width of the nonwoven web in the cross direction. If the nonwoven web is stretched during the folding process, the folds in the center of the nonwoven web will be significantly larger than at the edges, because the material cannot be fed uniformly into the area between the fins, and thus will be stretched more at the center. The subsequent stretching converts the pre-folds into microfolds, while the width of the nonwoven web does not change anymore. At the same time, the application of the stretching also stabilizes the folds in the nonwoven web, so that the folded nonwoven web can be bonded to the elastic film. However, the pre-folds can still exist as an overall structure containing microfolds.

[0063] It is particularly preferred that the nonwoven web is stretched between 10% and 30%, in particular between 15% and 25%. The stretching can be achieved by means of rollers running at different speeds. However, it has to be ensured that the stretching only stabilizes and reshapes the folds, while the structure of the nonwoven web in the machine direction remains unchanged.

[0064] The nonwoven web is bonded to the elastic film web in the folded state of the nonwoven web, the bonding points being larger than the microfolds of the nonwoven web. Thus, the bonding points can contain a large number of microfolds. This leads to an increase in the material density, in particular by the surface weight, of the area of the bonding points compared to the area between the bonding points in the stretched state in the cross direction, because it is not possible to unfold the folds in the area of the bonding points during the stretching process.

[0065] A further development of the method envisages a step e) after step d): activating the elastic laminate in the cross direction. Thus, after the bonding of the nonwoven web to the elastic film web, the elastic laminate can be activated in the cross direction. This is done, for example, by means of the ring-rolling process already explained. The activation rate can be between 100% and 400%. This is a relatively high degree of cross-directional strain, which can lead to the formation of a hole structure at the bonding points or to the reinforcement of an already formed hole structure. This hole structure is in particular the result of the melting and / or tearing of the elastic film web during the formation of the bonding points, whereby the openings of the hole structure either directly adjoin the bonding points or even completely surround them. Thus, for example, the cross-directional activation can improve the air permeability.

[0066] Furthermore, the transverse direction activation can also be used exclusively to influence the elasticity of the laminate in the transverse direction. In this case, it has already been explained that a large number of microfolds can be captured in the bond points during the formation of the bond points. In particular, the number of microfolds per bond point is between 6 and 14. Due to the subsequent activation of the laminate in the transverse direction with a high transverse strain, individual microfolds can be pulled out of the bond points. Furthermore, the microfolded material can be oriented, worn and / or partially torn. In accordance therewith, the number of microfolds captured in the bond points is reduced, which leads to the fact that in particular the folds directly adjacent to the bond points have a greater cross section in height and / or width, since the pulled-out microfolds can merge with the adjacent folds. During the activation in the transverse direction, two to four microfolds can be released from the individual or all bond points. In this respect, the transverse direction activation represents a further means of adjusting the elasticity in the transverse direction in a targeted manner. A further aspect of the irregular formation of the fold structure is that the independent arrangement between the bond points and the pre-folded structure of the nonwoven web also leads to the fact that the folded regions of the nonwoven web are enclosed in the bond points. This can also lead to a change in the cross section of the finished laminate.

[0067] For the formation of the elastic laminate, it is also essential that the width of the nonwoven web and the elastic film web in the supplied state is precisely dimensioned, whereby particular consideration must be given to the reduction in the width of the nonwoven web during the folding process. Preferably, the width of the folded nonwoven web is between 40% and 80% of the width of the nonfolded nonwoven web.

[0068] The bond points are preferably produced by ultrasonic welding. Alternatively, however, it is also possible to use bond points to join the nonwoven web to the elastic film web, in which case a bond pattern is applied between the nonwoven web and the elastic film.

[0069] A further development of the application also provides for the elastic laminate to be wound up in the final step f).

[0070] Furthermore, it is possible to supply and fold at least two nonwoven webs, whereby the elastic film web is inserted between the folded nonwoven webs in an essentially unstretched state and connected to them at the bond points. In general, the two nonwoven webs are crimped in the same way, but in principle it is also conceivable to use nonwoven webs with different crimping on both sides of the laminate, so that a different hand feel is obtained on both sides of the laminate.

[0071] For the formation of the bond points, it can also be useful for the nonwoven webs to be connected directly to one another through the holes in the elastic film. This requires the nonwoven webs to be formed at least partially from a thermoplastic material. However, it is also conceivable for the material of the elastic film to remain at the bond points, which also acts as a kind of hot-melt adhesive. BRIEF DESCRIPTION OF DRAWINGS

[0072] The application will be explained in more detail below with the aid of exemplary figures and examples. The figures show:

[0073] Figure 1 is a cross-sectional view of an elastic laminate according to the application,

[0074] Figure 2 is a schematic view of a manufacturing process for forming Figure 1 a laminate according to the application,

[0075] Figure 3 is a schematic view of a folding device for creping a nonwoven web,

[0076] Figures 4A to 4D is a schematic view of a creping formation,

[0077] Figures 5A to 5D is a variety of patterns of bond point formation and arrangement,

[0078] Figure 6A , 6B is a schematic view of the effect of subsequent ring rolling on material density, and

[0079] Figure 7 is a schematic view of a hole force measurement. DETAILED DESCRIPTION

[0080] Figure 1 An elastic laminate 1 is shown, which has a first and a second top layer 2, 3 made of a nonwoven fabric and an elastic film 4 arranged between the top layers 2, 3. Figure 1 The elastic laminate 1 is shown in a cross direction CD, which is arranged perpendicular to the machine direction MD during the course of the manufacturing process.

[0081] The top layers 2, 3 have a plurality of crepes 5, each of which extends in the machine direction MD, whereby the crepes 5 form a wave shape in the cross direction CD in cross section. The elastic film 4 is connected to the top layers 2, 3 at a plurality of bond points 6 spaced apart in the machine direction MD and the cross direction CD.

[0082] The elastic laminate 1 is special in that, in the unstretched state, the crepes 5 between the bond points 6 in the cross direction are shaped as macro crepes 5b having different cross sections. As Figure 1 shown, the macro crepes 5b differ in their shape and / or form, wherein the form of the macro crepes 5b can be described in terms of their area F or height H. Thus, the laminate 1 has an irregular wavy surface, which is formed on both sides by the top layers 2, 3.

[0083] Furthermore, in the stretched state in the transverse direction CD, in which the top layer 2, 3 is essentially free of macrofolds 5c in the direction of stretching, the surface weight at the adhesive points 6 is greater than the surface weight between the adhesive points 6. This is essentially achieved in two different ways.

[0084] In one aspect, the top layer 2, 3 is folded. However, no material-technical treatment is carried out on the nonwoven web 8 forming the top layer 2, 3. In this case, the top layer 2, 3 is only laid in the microfolds 5b without any material treatment, so that the nonwoven or the top layer 2, 3 has the same surface weight in the unstretched state, regardless of the position in the transverse direction CD. However, when stretched, the elastic film 4 becomes thinner, whereas in the unstretched state it has to be fixed in the adhesive points 6.

[0085] A second, even more decisive aspect is that the width of the adhesive points 6 is greater than the width of the microfolds 5b in the area of the adhesive points 6. This effect will be described further in the course of the manufacturing process. However, the width of the microfolds 5b in the adhesive points 6 can be less than 0.5 mm. These microfolds 5b are shown in more detail in Figure 5B . The width of the adhesive points 6 is between 1 mm and 6 mm. Thus, usually several microfolds 5b are enclosed at each adhesive point 6. In Figure 1 the example shown, two or three folds 5 are schematically integrated into each adhesive point 6. However, this is only a schematic representation to better illustrate the fact. Usually, between 6 and 14 folds 5 are arranged within the adhesive points 6.

[0086] By integrating several microfolds 5b into the adhesive points 6 and subsequently stretching the laminate 1 in the transverse direction, the material density or surface weight is significantly increased in the area of the adhesive points 6 U compared to the area W between the adhesive points 6, as Figure 6B is shown in the representation according to Figure 1 and Fig. 6. It is clear from the representation that due to the melting of the top layer 2, 3 at the adhesive points 6, these adhesive points 6 are essentially free of any folds 5. However, the microfolds 5c captured at the adhesive points 6 are spanned in the machine direction MD and thus visible behind the adhesive points 6. Thus, Figure 1 the microfolds 5c at the adhesive points 6 are shown, wherein these microfolds 5c actually start behind the adhesive points 6 in the machine direction MD.

[0087] The measures described above make it possible to design the basis weight at the adhesive points 6 to be at least 10% greater than the basis weight between the adhesive points 6 in the stretched state. The basis weight of the entire elastic laminate can be between 70 gsm and 110 gsm, the basis weight being determined primarily by the top layer 2, 3.

[0088] Top layer 2, 3

[0089] Nonwovens are particularly used for the top layer. These nonwovens can be spunbond nonwovens, hydroentangled nonwovens, carded nonwovens, air-laid nonwovens or meltblown nonwovens. Spunbond nonwovens are preferred. In the spunbond process so-called spun filaments are spun from a melt or solution and are stretched in the longitudinal direction. Then, using appropriate measures, the individual filaments are fused to form a nonwoven from the initially loose filament arrangement.

[0090] Furthermore, it is advantageous if the fibers are generally formed from thermoplastic material, so that the filaments can also be fused together by the application of heat. To this end, the nonwoven web can be passed through an oven, for example, in which hot air is applied to the nonwoven web. The hot air penetrates the nonwoven web, causing the filaments to partially melt. This does not significantly destroy the structure of the filaments. Rather, the surface melts, causing the filaments to bond to one another. Furthermore, it is also conceivable to use a so-called hot-embossing process to bond the nonwoven web together at discrete points. In this process, by applying pressure and temperature in a targeted manner, melting points are produced at discrete points, the size and number of which play a decisive role for the strength of the nonwoven. In addition to fibers made entirely of thermoplastic material, it is also possible to combine different materials into the fibers. One possibility is so-called bicomponent fibers, which are made of two different materials, wherein a first polymer forms the core and a second polymer forms the coating, wherein it is sufficient when only the second polymer is selected as a thermoplastic polymer. Alternatively, it is possible to use fiber mixtures, in which thermoplastic fibers and non-thermoplastic fibers are mixed. In this case, it is even possible to use natural or semi-synthetic fibers.

[0091] The top layer 2, 3 made of nonwoven is preferably formed from filaments, which in turn consist of polypropylene or polyethylene. In the case of polyethylene, low-density polyethylene (LDPE) or linear low-density polyethylene is preferred.

[0092] Of course, it is also conceivable to add other types of fibers or filaments that are not made of thermoplastic material to the nonwoven top layer 2, 3. These can be natural fibers, such as cotton fibers. However, the predominant component of the thermoplastic filaments ensures that the cover layer 2, 3 can be treated with heat, in particular can be fixed to the elastic laminate 1 in the subsequent bonding process with the elastic film 4. Predominant component is understood to mean that the continuous filaments of thermoplastic material are present in the top layer 2, 3 in an amount of at least 30 wt.-%, in particular at least 50 wt.-% in each case.

[0093] Elastic film 4

[0094] The elastic film consists of an elastic film layer and at least a first non-elastic outer layer which is co-extruded with the elastic film layer.

[0095] The non-elastic outer layer is particularly used for the production of elastic films. The non-elastic layer ensures that the co-extruded material interlocks during the co-extrusion process, which greatly simplifies the handling of the elastic film. In addition, the non-elastic outer layer is also used to maintain web tension. It should be noted that during manufacture and handling, the film is usually transported in the machine direction (MD), whereby web tension must be applied to the elastic film in the machine direction. If the elastic film is formed only by an elastic film layer, this web tension would lead to a material elongation, at least in certain areas, and complicate handling. In this case, the elastic film would be joined to the top layer 2, 3 in a substantially unstretched state, whereby a substantially unstretched elastic film is understood to be a film that is stretched by a maximum of 10% in the machine direction. In particular, the non-elastic film layer is intended to influence the material of the elastic film layer in some way.

[0096] Preferably, the elastic film is formed by two non-elastic film layers, which are co-extruded with the elastic film layer and sandwich the elastic film layer between them. The present invention is not limited to any particular design with regard to the precise design of the elastic film.

[0097] Table 1 and Table 2 show particularly preferred designs of the elastic film 4 for the elastic laminates 1 in the examples.

[0098] Table 1

[0099]

[0100] Table 2

[0101]

[0102] As can be seen from the tables, the non-elastic outer layer is significantly thinner than the elastic film layer, the elastic film 4 of type A uses a 28 pm thick elastic film layer and a 3.5 pm wide non-elastic outer layer. In contrast, the elastic film of type B is generally thinner, the non-elastic film layer is 3 pm thick and the elastic film layer is 24 pm thick.

[0103] The non-elastic outer layer consists mainly of polyolefins, in both examples a polyolefin blend of 57% polyethylene and 35% polypropylene is used. In addition, 8% talcum is present in the non-elastic outer layer.

[0104] The elastic film layer of type A and type B differs in that type A uses a styrene-butadiene-styrene copolymer (SBS) and 12% polystyrene. In addition, 8% mineral oil is found in the film elastic layer as a processing aid.

[0105] According to type B, the elastic film layer is formed from 60% polyolefin blend and 40% styrene-ethylene-propylene-styrene block copolymer (SEEPS). Due to the good miscibility between SEEPS and polyolefin, no processing aid is required in this case.

[0106] Manufacturing process

[0107] Figure 2 Fig. 1 shows a schematic view of an elastic laminate 1 according to the present application. Figure 1 Fig. 2 shows a schematic view of a manufacturing process for forming the elastic laminate 1.

[0108] In a first step, the elastic film 4 is supplied in the form of an elastic film web 7. The cover layers 2, 3 are also supplied as nonwoven webs 8, respectively, and are moved along with the elastic film web 7 in the machine direction MD.

[0109] The nonwoven webs 8 are then fed into a folding device 9, respectively, which pre-folds the nonwoven webs 8 in the cross direction CD. This pre-folding process is illustrated in Figure 3 Fig. 3, wherein the width of the nonwoven web 8 is converted from the original width A to the folded width A' during the pre-folding process. The ratio of the folded width A' to the unfolded width A is preferably between 0.4 and 0.9.

[0110] In this context, the folding device 9 is of particular importance, Figure 3 which is explained in more detail in the form of a schematic view. Contrary to the solutions known in the prior art, the nonwoven webs 8 are pre-folded, whereby the pre-creases are subsequently transformed into creases 5 in the form of micro-creases 5b. The pre-creases lead to a particularly uniform distribution of the creases 5.

[0111] To this end, the nonwoven web 8 is supplied to the folding device 9 and the nonwoven web 8 is guided between an upper row of fins 13 and a lower row of fins 14, which guide the nonwoven web 8 in a supporting manner along the longitudinal section L in the machine direction MD. The length of the longitudinal section L is preferably 800 mm. This length is of crucial importance for ensuring that the respective creases can occur between the upper row of fins 13 and the lower row of fins 14. The upper row of fins 13 and the lower row of fins 14 are preferably arranged opposite to each other in an interlocking manner, the degree of interlocking x preferably being between 5 mm and 50 mm. The distance y between the two spaced-apart fins is preferably between 5 mm and 40 mm. Due to this configuration, pre-creases are formed in the nonwoven web 8.

[0112] The nonwoven web 8, which has been pre-folded in the cross direction CD, is then stretched in the machine direction MD in a stretching device 16. This is basically achieved by different roller speeds. Due to these different speeds, the nonwoven web 8, which has been pre-folded, is stretched by at least 10%. This ensures that the initially very roughly formed pre-folds are transformed into micro-creases 5b, as illustrated in Figure 4A Fig. 4. At the same time, the web tension, which causes the stretching, ensures that the nonwoven web 8, which has been folded, also remains in the folded state and does not spread out.

[0113] The nonwoven web 8 is then bonded to the elastic film web 7 in the bonding device 10. This is advantageously effected by ultrasonic welding. In this case, the pattern of the bond points 6 is generated by the ring roller 15 shown, and the nonwoven web 8 and the elastic film web 7 are bonded to one another by means of these bond points 6. In this case, the elastic film web 8 is preferably melted, so that the two nonwoven webs 8 are then welded directly to one another. This also results in openings being formed at the bond points 6, which lead to particularly high air permeability. Figure 4A

[0114] In this case, it is important to note that the structural position of the pleats 5 after the folding device 9 is not specified specifically to the position of the bond points 6. Thus, according to Figure 4D , a plurality of micro-pleats 5b can form a macro-structure 5a, which can also be overfolded. The bond points 6 can then be introduced in the region in which the overfolding takes place.

[0115] The result of the overfolding is that, in the finished laminate 1, the cross-sectional area of the single macro-pleats 5c between the bond points 6 differs from the cross-sectional area of the other macro-pleats 5c. These differences are evident in the difference in the area F or height H of the macro-pleats 5c outside the bond points 6.

[0116] According to Figure 4B , the micro-pleats 5b outside the bond points 6 together form a macro-pleat 5c. Thus, the pleats 5 which extend in the machine direction MD and are captured in the bond points 6 are designed as micro-pleats 5b, wherein the pleats 5 which are not captured in the bond points 6 are designed as macro-pleats 5c as a result of the unfolding of the micro-pleats 5b.

[0117] Figure 5A , 5B , 5C, 5D show various patterns of bond points 6 which can be used in the bonding device 10 for attaching the nonwoven web 8 and the elastic film web 7.

[0118] Figure 5A Rectangular bond points 6 are shown which are regularly arranged in the machine direction MD and in the cross direction CD. Thus, the bond points 6 are provided at all positions in the machine direction CD and in the cross direction CD. The width of these bond points 6 in the cross direction CD is W, and the depth in the machine direction MD is t.

[0119] According to Figure 5B , the bond points 6 are arranged offset to one another in the design in Figure 5A , there is only one bond point 6 every second position in the machine direction MD and in the cross direction CD. Figure 5D Based on Figure 5B , the depth of the bond points 6 is greater than the width W. According to Figure 5C , the bond points are circular.

[0120] ​Regardless of the specific design, as Figure 4B illustrated, a large number of microfolds 5b always join in the adhesive points 6. This leads to an increase in the surface weight in the area of the adhesive points 6 in the stretched state, wherein the area between the adhesive points 6 is essentially free of folds 5. This relationship is illustrated in Figure 6A . In the stretched state, a width W u is formed between the adhesive points 6, at which time the essentially flat folds 5 are still indicated.

[0121] At the same time, the activation device 12 can be used to activate the elastic laminate 1 in the transverse direction CD. This is used in particular to expose the holes at the adhesive points 6. At the same time, it can also be used to pull the individual microfolds 5b out of the adhesive points 6. Activation of the laminate 1 in the transverse direction CD Figure 4C and 6B pulls the individual microfolds 5b out of the adhesive points 6. Alternatively, it is also conceivable that the microfolds 5b tear or swell in the area of the adhesive points 6. These microfolds 5b lead to the macrofolds 5c outside the adhesive points 6 having an irregular cross-sectional shape Figure 4C , which has already been explained. At the same time, the width W u of the area between the adhesive points 6 is enlarged compared to the unactivated laminate 1. The combination of the folding device 9, the stretching device 16, the adhesive device 10 and the activation device 12 allows the elasticity of the elastic laminate 1 to be adjusted in a targeted manner.

[0122] The advantage of this design is that it allows particularly uniform stretching in the transverse direction CD.

[0123] The web tension can be set in a controlled manner by the tension control unit 11.

[0124] Examples of embodiments

[0125] Table 3 shows various design examples of the elastic laminate 1, which differ essentially in the pattern of the cover layers 2, 3, the elastic film 4, the adhesive points 6 and the material for the transverse activation. The transverse activation is related to the depth of engagement (DOE). This parameter defines the distance of the disc overlap of the ring rolls. It is thus a parameter which is described in a similar manner to the value x of the folding device 9. However, in contrast to the folding device 9, the insertion of the laminate 1 is not force-free, so that the laminate 1 is stretched between the successive discs. The extent of this stretching is related to the parameter DOE, wherein a higher DOE leads to greater stretching.

[0126] Table 3 lists the different examples. According to the various examples, different measurements were made, as shown in Tables 4 and 5.

[0127] The measurement results show that the elastic laminate 1 has a particularly high elongation under a load of 1000 g in the transverse direction (CD), of more than 100% and even more than 150%. At the same time, the permanent set after an initial transverse strain of 150% is relatively low, with a maximum of 25%. The values determined in this case were obtained using the measurement method described above.

[0128] Table 3

[0129]

[0130] Table 4

[0131]

[0132] Table 5

[0133]

Claims

1. An elastic laminate having at least one top layer made of a nonwoven fabric and an elastic film, the at least one top layer having a plurality of corrugations extending in a machine direction in an unstretched state in a cross direction, and the at least one top layer and the elastic film being joined to each other at a plurality of spaced apart bond points, characterized in that at least two of the corrugations between the bond points have different cross sections in the unstretched state in the cross direction.

2. The elastic laminate article of claim 1, wherein, the cross sectional areas of the at least two corrugations differ from each other by at least 25%.

3. The elastic laminate of claim 1 or 2, wherein, the at least two corrugations have different heights, the heights preferably differing from each other by at least 25%.

4. An elastic laminate having at least one top layer made of a nonwoven fabric and an elastic film, the at least one top layer having a plurality of pleats extending in a machine direction in an unstretched state in a cross direction, and the at least one top layer and the elastic film being connected to each other at a plurality of spaced apart bonding points or according to one of the preceding claims, characterized in that, in a stretched state, in which the at least one top layer is essentially free of corrugations in a stretching direction, the surface weight at the bond points is greater than the surface weight between the bond points.

5. An elastic laminate having at least one top layer made of a nonwoven and an elastic film, the at least one top layer having a plurality of pleats extending in the machine direction in the unstretched state in the cross direction, and the at least one top layer and the elastic film being joined to each other at a plurality of spaced apart bond points or according to one of the preceding claims, characterized in that, in a stretched state, in which the at least one top layer is essentially free of corrugations in a stretching direction, the surface weight of the at least one top layer at the bond points is greater than the surface weight between the bond points.

6. The elastic laminate of Claims 4 or 5, wherein, in the stretched state, the surface weight at the bond points is at least 10% greater than the surface weight between the bond points.

7. The elastic laminate article of any of the preceding claims, wherein, the bond points comprise a plurality of corrugations.

8. The elastic laminate article of any of the preceding claims, wherein, the strain under a load of 1000 g in the cross direction is at least 100% according to DIN ISO 527.

9. The elastic laminate article of any of the preceding claims, wherein, the permanent set after an initial cross direction strain of 150% is at most 30%.

10. The elastic laminate article of any of the preceding claims, wherein, the tensile strength in the cross direction is at least 25 N according to DIN ISO 527.

11. The elastic laminate article of any of the preceding claims, wherein, the elongation at break in the cross direction is at least 200% according to DIN ISO 527.

12. The elastic laminate article of any of the preceding claims, wherein, the elastic film is arranged between at least two nonwoven top layers.

13. The elastic laminate of claim 12, wherein, the nonwoven top layers are at least partially directly joined to each other at the bond points.

14. The elastic laminate article of any of the preceding claims, wherein, the bond points are formed by ultrasonic welding.

15. The elastic laminate article of any of the preceding claims, wherein, the bond points are arranged in longitudinal rows extending in the machine direction and in transverse rows extending in the cross direction.

16. The elastic laminate of claim 15, wherein, the bond points of longitudinal rows and / or transverse rows directly adjacent to each other have different sizes.

17. The elastic laminate of Claims 12 or 13, wherein, the bond points of two longitudinal rows directly adjacent to each other in the cross direction are staggered in the machine direction.

18. The elastic laminate article of any of the preceding claims, wherein, the bond points are circular, rectangular and / or elliptical.

19. The elastic laminate of any of the preceding claims, wherein, the elastic film has an elastic film layer and at least a first non-elastic outer layer co-extruded with the elastic film layer.

20. The elastic laminate of claim 19, wherein, a second non-elastic outer layer is co-extruded with the elastic film layer, the elastic film layer being arranged between the first outer layer and the second outer layer.

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