EP4054500A1

EP4054500A1 - Elastic laminate and method for producing the elastic laminate

Info

Publication number: EP4054500A1
Application number: EP20803106.2A
Authority: EP
Inventors: Jan Michael Trinkaus; Marcus Schönbeck
Original assignee: Mondi AG
Current assignee: Nitto Advanced Film Gronau GmbH
Priority date: 2019-11-08
Filing date: 2020-10-30
Publication date: 2022-09-14
Also published as: WO2021089436A1; DE102019130246A1

Abstract

The invention relates to an elastic laminate comprising two nonwoven layers (1), which form opposing outer faces, and strips (2) of an elastic film, said strips running in a stretching direction (D) and being incorporated between the nonwoven layers (1). The strips (2) are incorporated between the nonwoven layers (1) under pretension, and the nonwoven layers (1) are laid in folds along the stretching direction (D) in a non-stretched state by means of the restoring forces of the strips (2) incorporated under pretension, wherein the strips are arranged in a mutually spaced manner transversely to the stretching direction (D) along a transverse direction (Q), and the strip (2) width (q₁), which is defined perpendicularly to the stretching direction (D) along the transverse direction (Q), is between 3 mm and 15 mm. According to the invention, the nonwoven layers (1) are connected together and/or to the strips (2) of the elastic film at discreet connection points (3) which are free of adhesive.

Description

Elastic laminate as well as process for the production of the elastic

Laminates

Description:

The invention relates to an elastic laminate, a method for producing the elastic laminate and a disposable diaper formed with the elastic laminate.

The elastic laminate is particularly suitable for disposable articles from the hygiene sector such as disposable diapers, disposable pants or disposable incontinence products for adults. With these products, on the one hand, there is a need for a simple, inexpensive and resource-saving structure, while on the other hand, a good and reliable fit is necessary. For this purpose, elastic areas, for example diaper ears, waistbands or the like, can be formed with the elastic laminate. It can also be used for certain medical applications such as bandages or heat belts. If diapers are referred to in particular below, this application is to be regarded as an example.

Diapers, especially for babies and toddlers, are produced as single-use mass-produced articles, so that there are special requirements for efficient material utilization and low production costs.

In addition, however, a large degree of functionality is also necessary at the same time, so that a high degree of safety and reliable protection of the person wearing the diaper are ensured under all conditions of use. Large amounts of excrement have to be absorbed and safely retained overnight, with the aim of avoiding impairment of the wearer's skin as well as possible. For sealing at the waist as well as the legs of a user, disposable diapers are therefore provided with elastic elements and sections. At the same time, however, a high level of comfort must be ensured even when the user moves. In particular, constrictions and skin irritations due to the elastic sections and elements are to be avoided.

In order to form elastic side parts and in particular side diaper closures, elastic laminates are known which have layers of nonwoven on their opposite outer sides and an elastic core in between. According to the prior art, the elastic core can, for example, be formed by an elastic film or elastic strands integrated over the entire surface.

The present invention is based specifically on an elastic laminate, in particular for diaper fasteners, which is known from EP 3 228 292 A1. The elastic laminate comprises two opposite outer sides forming nonwoven layers and strips of an elastic film that run in a stretching direction and are bound between the nonwoven layers, the strips being bound under pretension between the nonwoven layers and the nonwoven layers in a relaxed state are laid in folds along the stretching direction by the restoring forces of the pre-tensioned strips and wherein the strips are arranged transversely to the stretching direction along a transverse direction at a distance from one another and where the width of the strips determined perpendicular to the stretching direction along the transverse direction is between 3 mm and 15 mm.

By specifying the strip width of 3 mm to 15 mm, it is also clear that typical sections of the laminate for forming elastic functional elements, such as diaper ears, each run several next to one another Have stripes. The elastic properties of such a blank are then provided jointly by all the strips.

In order to be able to form the elastic laminate according to the generic prior art and, in particular, to incorporate the elastic strips, an adhesive is provided which preferably itself has elastic properties so that the elastic properties caused by the strips of the elastic film are not excessively impaired by the gluing .

Even if the laminate known from EP 3 228 292 A1 has good functional properties, certain disadvantages arise, in particular with regard to production. When using adhesive, undesirable solvents, plasticizers or similar additives are often necessary. Since the elastic strips are glued to the nonwoven layers in the stretched state, a comparatively fast-hardening adhesive must generally also be provided in order to avoid that only the elastic strips contract without the nonwoven layers that are not yet sufficiently attached to them. The material must therefore be kept under tension over a certain distance during production and the web speed must not exceed a certain value. In an essentially tension-free lamination, these aspects usually do not play a special role.

The present invention is based on the object of specifying a generic elastic laminate which is characterized by good functional properties, has a simple structure and can be manufactured efficiently. Furthermore, a method for producing the elastic Laminates as well as a disposable diaper formed with the laminate can be specified.

The subject of the invention and the solution to the problem are an elastic laminate according to claim 1, a method for producing the elastic laminate according to claim 18 and a disposable diaper according to claim 20.

With regard to the elastic laminate itself, starting from a generic embodiment, provision is made for the nonwoven layers to be connected to one another and / or to the strips of the elastic film at discrete, adhesive-free connection points.

According to a preferred embodiment of the invention, the discrete, adhesive-free connection points can be designed as ultrasonic welds.

Surprisingly, by ultrasonic welding, it is also possible to incorporate only strips in the stretched state, whereby the person skilled in the art can easily select suitable patterns for this by means of orienting experiments, which are also explained further below.

If, with a selected connection pattern, the integrated strips of the elastic film do not tear immediately during the formation of the laminate due to at least partial melting at the connection points, then, surprisingly, there is not a great risk of tearing to be expected in later use either. The specific properties of the laminate also play a role here, because the lamination of the elastic strips in the stretched state and the subsequent folds of the nonwoven layers due to the elastic recovery, the elastic laminate is often not stretched over the length present during the lamination when used as intended. When used as intended, the folds of the nonwoven layers formed by the elastic recovery are often pulled straight again, with preferred materials for the nonwoven layers then generating a clearly perceptible stretch resistance. A user will then refrain from further stretching, so that the strips of the elastic film are protected from excessive stretching and then tearing, in particular at the connection points.

In the context of the invention, the strips of the elastic film each have a width between 3 mm and 15 mm. In principle, it is possible to match a pattern of connection points precisely to the position of the individual strips. Along the individual strips it could be provided, for example, that connection points are only provided in the middle and not at the edge of the individual strips in order to avoid undesired weakening precisely at the edge.

Such a repeat-accurate alignment of a plurality of strips on a pattern of connection points is also covered by the present invention and is extremely advantageous for certain applications, according to a preferred embodiment of the invention, however, a repeat-accurate alignment of the strips on the one hand and the connection points on the other hand is dispensed with. A connection pattern is then selected which, on the one hand, ensures a secure integration of all strips regardless of their exact position along the transverse direction and, on the other hand, also avoids excessive weakening of the strips of the elastic film. In particular are To do this, adjust the size and position of the connection points to the width of the strips and the distance between them.

At the edges of the strips and between the strips, the nonwoven layers are connected directly to one another by the connection points.

In contrast, different types of connection are possible in the area of the strips of the elastic film. The nonwoven layers can be attached directly to the strips at the discrete, adhesive-free connection points, which are preferably formed by ultrasonic welding. The strips then remain as a layer between the two nonwoven layers.

The energy input during ultrasonic welding results in a local load due to pressure and temperature. Precisely because the strips of the elastic film are under tensile stress along the stretching direction during lamination, the strips can also thin out or even form openings directly at the connection points. In such a case it is then also possible for the nonwoven layers to be connected directly to one another through such an opening. In such a case, the nonwoven layers are connected to the individual strips not by a material connection or an adhesion, but ultimately mechanically by a form connection. If the nonwoven layers are connected to one another through openings in the strips, they are inevitably fixed there. The type of connection that is established can be influenced both by how the process is carried out and by the materials used, which is explained in more detail below. In addition, different patterns of connection points can also be useful for the different types of connection. Even if openings are formed during ultrasonic welding, a type of bead is then often observed at the openings, on which the melted material withdraws and collects. Such a bead can at least partially compensate for the actual weakening caused by the opening.

Different types of connection can also be achieved through the design of the elastic film from which the strips are cut. For example, a multi-layer elastic film can be provided, in which case not all film layers have to be elastic. Suitable embodiments are explained in more detail below. In the context of such a configuration, it is also possible, for example, for the nonwoven layers to be connected only to outer layers of the elastic film.

Typically, the strips are equidistant and parallel to one another with straight edges. Preferably the stripes are immediate, i.e. H. connected to the nonwoven layers or arranged between them without further intermediate layers.

By integrating the strips of the elastic film in a stretched state, a clearly defined yield point is given. After the tensile forces have ceased to exist after the laminate has been produced, it essentially resets itself until the strips of the elastic film have again reached their original length in the force-free state. A certain permanent extension compared to the original length can, however, result precisely from a stiffening at the connection points. As will be explained in more detail below, such a stiffening, which is undesirable per se, can be limited to certain areas. According to the corresponding pretensioning of the strips of the elastic film, the elastic laminate can be stretchable, for example, up to an elastic limit with an elongation between 30% and 300%, in particular between 50% and 250%. In the context of the invention there is the advantage that the stability and tensile strength of the elastic laminate when the yield point is reached is largely determined by the nonwoven layers. Even if the strips themselves are particularly easily stretchable and thus the elastic laminate can be stretched to the yield point with little effort, the nonwoven layers, whose structure is not damaged by activation, which is often provided according to the prior art, can provide high strength. This means that, in contrast to an activated elastic laminate, particularly easily stretchable elastic films with a comparatively low tensile strength can be used.

In the relaxed state, the elastic film preferably has a thickness of only 30 μm to 80 μm, the width of the strips formed therefrom being between 3 mm and 15 mm, in particular between 5 mm and 12 mm. The strips of the elastic film thus lie flat between the two nonwoven layers and consequently do not significantly increase in thickness. Due to the flat arrangement of the strips, the elastic properties of the material can also be optimally used, whereby the area coverage between 20% and 80%, preferably between 50% and 75% not only has uniform elastic properties, but also an advantageous fold structure of the nonwoven layers is achieved between the elastic strips in the relaxed state. The arrangement of the nonwoven layers in the relaxed state can also be referred to as a ruffle effect, resulting in a particularly soft and pleasant surface that is optimally gentle on the user even in the event of direct skin contact.

In the context of the invention, the discrete adhesive-free connection points can be formed in different shapes and patterns. In the following, various preferred configurations are explained for this purpose, which are considered to be particularly expedient. Of course, however, the invention is not restricted to these specific configurations, even if these are associated with particular specific advantages.

The connection points preferably have a rounded base area to which a long side and a short side can be assigned. The base can thus be oval and in particular elliptical, for example, with the main axis then forming the long side and the minor axis forming the short side in the case of an ellipse. According to another preferred shape, two semicircles are spaced from one another and connected by a rectangular intermediate section. Such a shape can be referred to in the broadest sense as "pill-shaped" or "stadium-round". Finally, for example, a rectangular basic shape with clearly rounded corners is also possible. The ratio of the long side to the short side can for example be between 1.1: 1 and 3: 1, in particular between 1.3: 1 and 2: 1.

According to a further development of the invention, it is provided that the long side described above is inclined with respect to the direction of expansion. Whether an inclined position of the long side is appropriate for a particular embodiment can also depend on the type of connection. If the elastic film is intact or only thinned at the connection points between the nonwoven layers, a larger area can also be covered along the transverse direction due to the inclination. If, on the other hand, openings arise in the elastic film at the connection points, it can be useful to make the connection points as narrow as possible in the transverse direction so that the individual strips are only interrupted over a small proportion of their width. With such a type of connection, it can advantageously be provided that the long side is aligned along the direction of expansion.

When characterizing the elastic laminate, it should be noted that the dimensions and also the angular orientations change with regard to the relaxed state and the stretched state. In a stretched state, when the nonwoven layers are smooth and, moreover, unstretched, the structure is achieved again during production. The connection points are then in a configuration, orientation and size, as was also intended during manufacture. To characterize the elastic laminate, reference can therefore be made to the stretched state described when the nonwoven layers are smooth and unstretched.

In relation to this stretched state, the long side can be inclined with respect to the stretching direction, for example between 30 ° and 60 °. In particular, it can be expedient if a first group of connection points, starting from a central axis, is inclined in a first direction and a second group of connection points is inclined opposite in a second direction by the specified value. In particular, the long side should be angled by +/- 45 ° in relation to the stretched state. As explained above, such an inclination can be useful when the elastic film is retained at the connection points.

As already mentioned before, the strips of the elastic film cover between 20% and 80%, in particular between 50% and 75% of the total area in the relaxed state. Based on the claimed strip width and an equidistant arrangement, a typical distance between adjacent strips in the relaxed state is then between 1 mm and 30 mm. It should be noted that the area proportion of the elastic strips and the spacing change only to a limited extent when they are stretched, because the strips essentially change in their thickness when they are stretched. However, certain constrictions of the strips during stretching or widening during elastic recovery are possible.

In the context of the invention, it should be noted that adhesive-free connection points and in particular ultrasonic weld points can contribute both to stiffening and to weakening.

Against this background, it is provided according to a preferred embodiment of the invention that in a stretched state, when - as described above - the nonwoven layers are smooth and unstretched, extending strip-shaped expansion areas are provided which are free of connection points, the ratio of one The width of the expansion regions determined along the direction of expansion and the length of the connection points determined along the direction of expansion is between 0.5 and 6, in particular between 2 and 5. Even if the expansion areas run in the transverse direction, they do not have to be aligned exactly parallel to the expansion direction. From a manufacturing point of view, it can be useful if the expansion areas run with a slight inclination in the transverse direction. If the individual expansion areas with no connection points were aligned exactly along the transverse direction, there would then be no support between the anvil roller and the sonotrode in the case of ultrasonic welding with an anvil roller and a sonotrode at the expansion areas, or there would be an increased distance between the sonotrode and the back areas of the anvil roller between the projections provided for the formation of the connection points. If, on the other hand, the expansion areas run somewhat obliquely with respect to the transverse direction, as described, a practically continuous support between the anvil roll and the sonotrode can be achieved. This can reduce the risk of damage and wear and tear on the system.

The degree of inclination also depends on the width of the laminate. The inclination is usually chosen so that the anvil roller is supported practically continuously with respect to the sonotrode by at least one projection. With the usual widths of the laminate, the inclination can be, for example, between 1 ° and 20 °, in particular between 2 ° and 10 °.

With regard to the expansion of the material along the expansion direction, the expansion areas are not affected by stiffening or weakening due to the omission of connection points at the expansion areas. Surprisingly, it can also be accepted that the nonwoven layers and the strips of the elastic film are not directly connected to one another over the corresponding length. In contrast, for some of the embodiments it is preferably provided that the connection points in a projection cover the transverse direction to at least 80%, preferably completely. This means that there are no larger linear sections along the longitudinal direction at which no connection points are provided at all along the stretching direction. If, on the other hand, larger free spaces running in the direction of elongation would remain, the secure integration of the strips of the elastic film could not be ensured if, according to a preferred embodiment of the invention, no precise repeat or precise alignment of the strips to the pattern of the connection points is provided. With regard to the projection described, the transverse direction can also be completely covered by connection points. In this case, no straight line can be found running along the stretching direction that does not intersect individual connection points. With regard to the projection described, the connection points can of course also be provided with a certain overlap in order to completely cover the transverse direction. The described at least extensive coverage of the transverse direction can advantageously also be achieved in that successive connection points are offset along the transverse direction. The described cover in the transverse direction is provided in particular when the elastic film is retained at the connection points and does not form any openings there.

According to a preferred embodiment it is provided that the connection points are arranged in rows which run exactly parallel to the transverse direction or preferably with a certain inclination in the transverse direction. As already indicated above, an offset can then also occur in the case of rows directly following one another along the stretching direction be provided to each other. For example, successive rows can be arranged with gaps so that exactly every second row again has the same alignment with regard to the transverse direction.

According to a further aspect of the invention, the rows following one another in the direction of elongation can also have different spacings. In particular, it can be provided that the rows have a first spacing and a larger second spacing in a recurring sequence along the stretching direction. For example, in the case of pairs of two rows or groups of at least three rows, the small first spacing can be provided between the rows of the pair or the group. If the rows are then offset in the transverse direction, there may be some overlap with respect to the individual pairs or groups even along the direction of elongation. Due to the locally closer arrangement of the connection points, a particularly reliable connection of the laminate is achieved, with a certain impairment of the ductility and elasticity also being accepted there due to the usual stiffening of the material by the connection points. The larger, second distance is then provided between the pairs or groups, in particular in order to form the expansion areas described above. In a simple embodiment, a first distance and a second distance can always alternate along the stretching direction.

The individual connection points typically have an area between 0.2 mm ² and 5 mm ² , in particular between 0.3 mm ² and 2 mm ² .

It is preferably provided that the connection points in the stretched state, when the nonwoven layers are smooth and unstretched, cover between 3% and 40%, in particular between 25% and 50% of the total area. The invention also relates to a method for producing the elastic laminate described above, comprising the steps: a) extruding an elastic film; b) cutting the elastic film to form strips; c) introducing the strips in a stretched state with an elongation between 30% and 300% and with a distance from one another between two nonwoven layers; d) producing discrete adhesive-free connection points by ultrasonic welding; e) Relaxation of the laminate formed from the nonwoven layers and the strips.

The production direction in which the elastic film is extruded as a monofilm or preferably coextruded as a multilayer film is also referred to as the machine direction. The film is preferably cut into strips in such a way that the individual strips also run along the machine direction, which is advantageous in terms of process management alone because the strips can then also be formed as continuous material and can easily be further processed.

When the film is stretched for the first time in particular, a significantly greater force is often necessary for stretching than for subsequent stretches. This applies in particular if, as described in detail below, the elastic film is provided with thin, non-elastic cover layers, so that the elastic film itself must first be activated to a certain extent in order to provide slight stretchability. Against this background, a preferred embodiment of the method provides that either the extruded film or the strips cut therefrom are initially pre-stretched before being introduced between the nonwoven layers. In particular, this first pre-stretching is preferably greater than the pre-stressing with which the elastic strips are laminated with the nonwoven layers in the stretched state. The greater pre-stretching ensures that a particularly slight stretching of the elastic film or the strips formed from it is possible at least up to the stretch limit specified by the method.

For example, it can be provided that the extruded elastic film or the strips cut therefrom are pre-stretched by 300% to 500% before being introduced between the nonwoven layers, the length then resulting after tension with a permanent deformation (permanent set) as The starting length for the subsequent expansion during lamination is to be used as a basis.

According to a preferred embodiment of the invention, it is provided that the elastic film has a multi-layer structure with an elastic core layer and at least one outer layer, even if an embodiment as a monofilm is also possible. It must be taken into account that typical elastic materials such as styrene block copolymers or elastic thermoplastic olefins often have considerable tack, so that monofilms formed with them cannot easily be wound up and unwound for transport, storage and processing. In addition to increased tensile forces due to the stickiness described, there is even the risk of blocking, so that a corresponding roller can no longer be used. In the case of a monofilm, there is also the disadvantage that it stretches its transport very greatly due to the necessary tensile forces when it is handled during manufacture. If, on the other hand, a multi-layer structure with at least one non-elastic, usually thin cover layer is used, such a film can be handled very well and without any significant elongation, at least with moderate tensile forces during production.

In addition to a two-layer configuration with a core layer and an outer layer, a three-layer structure and, in particular, a symmetrical three-layer structure with a core layer between two outer layers is particularly advantageous.

Typical materials for the core layer are styrene block copolymers, such as SIS, SBS and SEBS (see for example "Saechtling Kunststoff Taschenbuch", 31st edition, 2013, Carl Hanser Verlag) or thermoplastic elastomers based on polyolefin copolymers, which in practice also called TPE-0.

The outer layers, on the other hand, are preferably formed from conventional, non-elastic polyolefins such as polyethylene, polypropylene and their copoly mers, various types of density being considered for this purpose. For example, LDPE and LLDPE are suitable, it being possible for these to be mixed with other components, such as, for example, PP / PE copolymer or typical additives and aggregates, such as, for example, talc. Furthermore, other additives, such as antiblocking agents, color pigments or the like, can also be provided.

For the films described, it is usually sufficient and expedient if the outer layers are made very thin. The outer layers can, for example, each have a thickness between 1 μm and 10 μm, in particular between 2 μm and 5 μm. The core layer responsible for the elastic properties, on the other hand, is thicker and, depending on the choice of material, typically has a thickness between 15 μm and 60 μm, in particular between 20 μm and 50 μm.

The thickness ratio of the core layer to one of the outer layers is typically in a range between 5: 1 and 12: 1.

As described above, different types of connection at the connection points are possible within the scope of the invention in order to bind the strips of the elastic film into the laminate. The nonwoven layers can be connected to one another on the strips with the elastic film or through openings in the elastic film. In addition, various intermediate stages or locally different connections are also possible in a laminate.

A connection of the nonwoven layers with the elastic film without the formation of openings, pores or strong material constrictions can be achieved, for example, by the fact that in a multi-layer, in particular at least three-layer elastic film, the core layer or an inner layer compared to the outer layers Melting point and / or has a higher viscosity, so that the core layer or the inner layer also with the Ultrasonic welding or a comparable energy effect is retained.

Additionally or alternatively, the materials of the elastic film or, in the case of a multi-layer structure, at least the outer layers of the elastic film on the one hand and the nonwoven layers on the other hand, can be matched to one another in such a way that a material connection is promoted by fusing.

In this context, the fibers of the nonwoven can also be specially adapted or selected. For example, the nonwoven can be formed from bicomponent fibers or at least have bicomponent fibers which have a low-melting component, in particular as a sheath in a core-sheath structure. The high-melting component, in particular the core, then preferably remains in its structure, while the low-melting component enables a reliable material connection. Similar advantages can also be achieved if a mixture of high-melting and low-melting fibers is present in the nonwoven.

According to the invention, the outer sides of the laminate are formed from nonwoven layers. Various currently common nonwoven types come into consideration, such as spunbond nonwovens, carded nonwovens and meltblown nonwovens. It is particularly preferable to use a multilayer structure which combines the various types of nonwoven with one another. Such a multi-layer structure allows very good properties in terms of strength and haptics to be achieved even with a low weight per unit area. For example, a nonwoven with a layer structure SMS, SSMMS or the like can be provided. How previously described, the individual layers can also have a fiber mixture and / or bicomponent fibers.

The weight per unit area of the nonwoven is typically between 10 g / cm ² and 35 g / cm ² , in particular between 13 g / m ² and 25 g / cm ²

The invention is explained below with reference to a drawing showing only one embodiment. They show: FIG. 1 an elastic laminate for diaper closures in a state that has been created, FIG.

FIG. 2 shows the elastic laminate according to FIG. 1 in a completely stretched state at an elastic limit,

3 shows a pattern of discrete, adhesive-free connection points of the laminate in the stretched state according to FIG. 2 or during production, FIG. 4A shows the production of the elastic laminate in a schematic representation,

FIG. 4B shows a process step for the formation of spaced-apart foils,

5 shows the schematic representation of a disposable diaper,

FIGS. 6a to c show alternative configurations to the pattern according to FIG. 3, 7 shows a schematic representation of an ultrasonic welding in a plan view,

8a, b show further alternative configurations to the pattern according to FIG. 3.

Fig. 1 shows a plan view of an elastic laminate, which is provided in particular for diaper closures. As can also be seen in a comparison with FIG. 4a, the elastic laminate comprises two nonwoven layers 1, which also form the outside of the elastic laminate. Strips 2 of an elastic film run along a stretching direction D.

According to the invention, the strips 2 are bound under pretension between the nonwoven layers 1, the nonwoven layers 1 being folded in a relaxed state shown in FIG. H. are gathered along the strips 2. The nonwoven layers 1 are connected to the strips 2 and to one another between the strips by discrete adhesive-free connection points 3. For the sake of clarity, the connection points 3 are not shown in FIGS. 1 and 2. For this purpose, reference is made to FIG. 3, in which the pattern of the connection points 3 is reproduced as a detail, with two strips 2 being dashed as an example.

The illustration in FIG. 3 relates to a stretched state of the laminate according to FIG. 2 or to the configuration of the laminate during production, in which the film strips 2 are stretched along the stretching direction D. FIG. In the relaxed state, the strips of the elastic film typically cover between 20% and 80%, in particular between 50% and 75% of the total area, this value generally not changing significantly as a result of the stretching, because a thinning of the strips 2 of elastic film usually takes place mainly in the direction of the thickness. The thickness of the strips 2 in the relaxed state is usually between 30 μm and 80 μm.

As can be seen from FIG. 3, the connection points 3 each have a rounded base area with a long side a and a short side b. The connection points 3 can for example be oval and in particular elliptical. The exemplary embodiment in FIG. 3, on the other hand, shows an embodiment in which the connection points are each formed by crank circles which are connected by a rectangular intermediate section.

The ratio of the long side a to the short side b can for example be between 1.1: 1 and 3: 1, in particular between 1.3: 1 and 2: 1.

It can also be seen from FIG. 3 that the connection points 3 are arranged in rows running along a transverse direction Q, the rows immediately following one another along the stretching direction D being offset from one another with gaps. It can also be seen that the connection points 3 are inclined alternately to the left and right with their long sides a with respect to the direction of elongation D.

Due to the inclination, the long side a and the short side b do not correspond to the length d2, the width covered by the individual connection points 3 along the stretching direction and the width q2 determined along the transverse direction. From Fig. 3 it can be seen that in the stretched State when the nonwoven layers 1 are smooth and unstretched (according to the structure during production), strip-shaped stretching areas 4 running along the transverse direction Q are provided, at which there are no connection points 3. The ratio of the width of the expansion regions di determined along the expansion direction D to the length d2 of the connection points determined along the expansion direction D is typically between 0.5 and 6, in particular between 2 and 5.

It can also be seen that the connection points 3 cover the transverse direction Q to at least 80% in a projection. With regard to FIG. 3, such a projection is to be formed on a horizontal base line, for example. While there are strip-shaped expansion areas running along the transverse direction Q, there are only very narrow linear areas between the connecting points 3 along the stretching direction. In particular, when the connecting points 3 are made somewhat larger, the transverse direction Q can be completely covered in the projection. As a result, regardless of the exact alignment of the individual strips 2, adequate integration by the connection points 3 is always guaranteed.

It can also be seen from FIG. 3 that no precise repeat is provided for the arrangement of the individual strips 2 with respect to the connection points 3. In practice, it is to be expected that each strip 2 is arranged somewhat differently from the pattern of connection points 3. The pattern of connection points 3 is to be selected in such a way that it does not depend on a specific orientation and a sufficient connection and strength is always ensured. The ratio of the width qi of the elastic strips 2 determined along the transverse direction to the width q2 of the connection points determined along the direction Q is typically between 2: 1 and 9: 1.

The individual connection points 3 can, for example, have an area between 0.2 mm ² and 5 mm ² , in particular between 0.3 mm ² and 2 mm ² .

With regard to the stretched state, the connection points 3 can cover, for example, an area between 3% and 40%, in particular between 5% and 25% of the total area.

FIG. 4A shows, by way of example, individual steps for the lowering position of the elastic laminate. Accordingly, a previously extruded elastic film is supplied and cut into strips 2 with knives 5. The cut strips 2 are fanned out equidistantly, which is not evident from the schematic illustration in FIG. 4A. For example, according to FIG. 4B, the strips 2 can be guided around an inclined roller 6.

The strips 2 are then introduced between two nonwoven layers 1 at a distance from one another.

4A also shows that the elastic film for forming the strips 2 is fed at a first speed vi, while the two nonwoven layers 1 and also subsequently the laminate formed are transported at a greater speed V2. The degree of elongation of the individual strips 2 during the connection results from the speed difference between vi and V2. The actual formation of the laminate takes place through the creation of the connection points described in detail above on an anvil roller 7 and a sonotrode 8 that interacts therewith.

5 shows a preferred use of the elastic laminate according to FIGS. 1 and 2. FIG. 5 shows a disposable diaper with a diaper base body 9 which has a liquid-absorbing core 10 between a liquid-tight outer layer and a liquid-permeable inner layer, wherein two sections 11 of the elastic laminate described above are connected to the diaper body 9 and are provided as lateral connections between a front part and a rear part of the diaper body 9. Specifically, the sections 11 are each connected at a first end to the diaper base body 9 and at a second end carry a closure element 12, for example a hook material. The closure elements 12 are provided in order to be fastened to a front section of the diaper base body when the disposable diaper is put on, for which purpose a support surface, also referred to as a landing zone, is provided there.

The elastic laminate is characterized by a low use of material, low manufacturing costs and yet good functional properties. The elastic laminate is therefore also very suitable for other disposable items. With the elastic laminate, for example, waist bands of an incontinence product or a disposable warming belt can also be formed.

The pattern of discrete, adhesive-free connection points 3 shown in FIG. 3 is particularly useful when the elastic film does not have any in the area of the strips 2 at the connection points 3 there Forms openings so that the nonwoven layers 1 are attached to the elastic film.

If, on the other hand, the energy input from the ultrasonic welding to the strips 2 of the elastic film leads to the formation of holes and the nonwoven layers 1 are then connected to one another in the area of the strips through the holes formed, other patterns may be useful which weaken the strips 2 less .

Thus, FIGS. 6a to 6c show an alternative pattern of connection points 3, which is particularly useful in such a case. FIGS. 6a and 6c differ in the different widths of the strip 2, the distance between adjacent strips 2 corresponding, by way of example, exactly to the width of the strip 2. The strips 2 then cover (at least based on the stretched state during manufacture) 50% of the total area. Of course, this area coverage is only an example, the distance between adjacent strips 2 within the scope of the invention being able to be larger and smaller than the width of the strips 2.

In order not to weaken the strips 2 too much along their width, the non-round connection points 3 are aligned with their long side a along the stretching direction D, so that then the strips 2 at the individual connection points 3 are only weakened over the length of the short side b are.

As with the pattern according to FIG. 3, the connection points are arranged in rows which are offset from one another.

According to FIGS. 6a to 6c, however, the rows alternately have a first spacing and a larger second spacing along the stretching direction D on. The rows following one another with the first small spacing form a type of double row 13, which enables a particularly reliable connection. The strip-shaped expansion regions 4, which run in the transverse direction Q, are provided by the larger second spacing.

On closer inspection of FIGS. 6a to 6c it can be seen that the rows and thus also the expansion areas D are slightly inclined with respect to the transverse direction Q, which in particular offers advantages in terms of manufacturing technology.

For this purpose, FIG. 7 shows the area of the sonotrode 8 (see FIG. 4a) in a highly schematic top view, the double rows 13 being indicated in their inclined position on the laminate. According to FIG. 7, the inclination is adapted to the width of the laminate in such a way that there is always support between the anvil roller 7 and the sonotrode 8 by at least one projection of the anvil roller 7 provided for the formation of the connection points. Such an inclination is also useful in the pattern according to FIG. 3, even if it is not shown there.

According to FIG. 6a, the distance between two adjacent connection points 3 in a row, in each case based on the center of the connection point 3, corresponds exactly to the width and the spacing of the strips 2. As a result, all strips 2 are fixed in the same way .

Since, however, as a rule the individual strips 2 cannot or should not be aligned exactly with respect to the pattern of connection points 3, the configuration according to FIG. 6a can be disadvantageous in practice. If the (not precisely specified) alignment for a strip 2 is disadvantageous with regard to the mechanical properties, then this applies to all strips 2. According to FIGS. 6b and 6c, it is therefore provided that the strips 2 and the distance between the strips 2 are either slightly larger (FIG. 6b) or slightly smaller (FIG. 6c) than the distance (center to center) between adjacent connection points 3 . The distance between adjacent connection points 3 can be, for example, 5% to 20% greater than the width of the strips 2.

In FIGS. 8a and 8b it is shown by way of example that the connection points 3 can also be made circular, with rows of connection points 3 also then being arranged along the stretching direction D, for example, equidistantly (FIG. 8a) or in double rows 13 (FIG. 8b) can.

According to a specific test sample, a carded nonwoven with a weight per unit area of 22 g / m ^{2 is} provided. For example, a carded nonwoven, which is sold under the name "ThermoStrain" by Mondi Ascania GmbHFI, is suitable. The strips 2 are formed from an elastic film based on SBS, which can be stretched by 250% along a machine direction MD, which here coincides with the stretching direction D. The strip width in the unstretched state is 3 mm for the specific sample.

The film has a symmetrical structure with an elastic core layer. The core layer has a thickness of 42 μm, whereby SBS is mixed with polystyrene (PS) and oil and titanium dioxide (T1O2) is also contained as a white batch. The symmetrically provided outer layers each have a thickness of only 4 μm, a blend of polyethylene (PE) and polypropylene (PP) additionally containing talc. As already explained at the beginning, the elastic properties of the laminate are determined by the strips 2 of the elastic film. It goes without saying that the elastic properties can also be varied substantially by the width of the strips and the distance between the strips and thus ultimately the degree of coverage by the strips and can be adapted to the respective requirements.

Claims

Patent claims:

1. Elastic laminate with two opposing outer sides forming nonwoven layers (1) and with strips (2) of an elastic film which run in a stretching direction (D) and are bound in between the nonwoven layers (1), the strips (2) being pretensioned are bound between the nonwoven layers (1) and the nonwoven layers (1) in a relaxed state by the restoring forces of the pretensioned strips (2) are laid in folds along the stretching direction (D) and the strips transverse to the Stretching direction (D) are arranged along a transverse direction (Q) at a distance from one another and wherein the width (qi) of the strips (2) determined perpendicular to the stretching direction (D) along the transverse direction (Q) is between 3 mm and 15 mm, characterized in that the nonwoven layers (1) are connected to each other and / or to the strips (2) of the elastic film at discrete adhesive-free connection points (3).

2. Elastic laminate according to claim 1, characterized in that the connection points (3) are designed as ultrasonic welds.

3. Elastic laminate according to claim 1 or 2, characterized in that in the relaxed state the thickness of the strips (2) is between 30 pm and 80 pm.

4. Elastic laminate according to one of claims 1 to 3, characterized in that the strips (2) of the elastic film in the relaxed state cover between 20% and 80%, in particular between 50% and 75% of the total area.

5. Elastic laminate according to one of claims 1 to 4, characterized in that the connection points (3) each have a rounded base area with a long side (a) and a short side (b).

6. Elastic laminate according to claim 5, characterized in that the long sides (a) are inclined with respect to the direction of elongation (D).

7. Elastic laminate according to one of claims 1 to 6, characterized in that the distance between adjacent strips determined along the transverse direction (Q) in the relaxed state is between 1 mm and 30 mm.

8. Elastic laminate according to one of claims 1 to 7, characterized in that in a stretched state, when the nonwoven layers (1) are smooth and unstretched, strip-shaped expansion areas (4) extending in the transverse direction (Q) are provided which are free of connection points (3), the ratio of a width (di) of the expansion areas determined along the expansion direction (D) to the length (d2) of the connection points (3) determined along the expansion direction (D) between 0.5 and 6, in particular between 2 and 5.

9. Elastic laminate according to one of claims 1 to 8, characterized in that the connection points (3) in a projection cover the transverse direction (Q) to at least 80%, preferably completely.

10. Elastic laminate according to one of claims 1 to 9, characterized in that the connection points (3) are arranged in rows which run in the transverse direction (Q).

11. Elastic laminate according to claim 10, characterized in that the rows immediately following one another along the stretching direction (D) are offset from one another.

12. Elastic laminate according to claim 10 or 11, characterized in that the rows along the stretching direction (D) have a first spacing and a larger second spacing in a recurring sequence.

13. Elastic laminate according to one of claims 1 to 12, characterized in that the ratio of the width (qi) of the elastic strips (2) determined along the transverse direction (Q) to the width (q2) determined along the transverse direction (Q) the connection points (3) is between 2: 1 and 9: 1, in particular between 3: 1 and 6: 1.

14. Elastic laminate according to one of claims 1 to 13, characterized in that the connection points (3) each have an area between 0.2 mm ² and 5 mm ² , in particular between 0.3 mm ² and 2 mm ² .

15. Elastic laminate according to one of claims 1 to 14, characterized in that the connection points (3) in the stretched state cover between 3% and 40%, in particular between 5% and 25% of the total area.

16. Elastic laminate according to one of claims 1 to 15, characterized in that the elastic film has a multi-layer structure, in particular an at least three-layer structure with a core layer between two cover layers.

17. A method for producing an elastic laminate according to any one of claims 1 to 16 comprising the steps: a) extruding an elastic film; b) cutting the elastic film to form strips (2); c) introducing the strips (2) in a stretched state with an elongation between 30% and 300% and with a distance from one another between two nonwoven layers (1); d) producing discrete adhesive-free connection points (3) by U Itraschal Ischweiß ßen; e) Relaxation of the laminate formed from the nonwoven layers (1) and the strips (2).

The method of claim 17, wherein the elastic sheet is extruded in a machine direction (MD) and wherein the elastic sheet is cut into the strips (2) along the machine direction (MD).

19. The method according to claim 17 or 18, wherein the extruded elastic film or the strips (2) cut therefrom is or are pre-stretched before being introduced between the nonwoven layers (2).

20. Disposable diaper with a diaper base body (9) which has a liquid-absorbing core (10) between a liquid-tight outer layer and a liquid-permeable inner layer, wherein two sections (11) of an elastic laminate according to one of claims 1 to 16 are attached to the diaper base body ( 9) connected and as a side connection between a front part and a rear part of the diaper base body (9) are provided.

21. Disposable diaper according to claim 20, wherein the sections (11) are each connected at a first end to the diaper base body (9) and at a second end carry a closure element (12).