DE8815242U1 - Device for applying an adhesive to elastic threads - Google Patents

Description

The invention relates to a device for applying an adhesive to elastic threads of the type specified in the preamble of claim 1.

Web-like fabrics that curl when heated are used in particular as elastic waistbands for disposable clothing _> e.g. for nuclear facilities, but also for elastic bandages, dressings and hygiene articles, such as diapers, in order to achieve tight, yet elastically deformable closures.

The basic structure of such a fabric is shown, for example, in US-PS 4,640,859 and comprises a substrate and pre-stretched elastomer threads embedded in an adhesive, namely so-called "spandex fibers", i.e. polyurethane elastomer fibers.

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TW: (OW) 4707064 (6S, 66,67) _F ä _X: Bank accounts: Bayef. Vefeinsbank Munich 453100 (ÖLZ 7ÖÖ2O270)

Telex: 5 24 560 Swan d (039j -170 71-20

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The known fabrics use films or foils made of an inelastic, thermoplastic polymer, in particular based on ethylene vinyl acetate (EVA) copolymers, which are laminated onto the pre-stretched elastomer threads from both sides. The lamination takes place while heating, with the heat energy being supplied via a heating roller; the laminate must then be cooled again in order to stop the adhesive from reacting.

The production of this surface structure is very complex due to the heating and subsequent cooling of the adhesive; in addition, adhesive films must be used, which are very expensive and complicated to handle.

Furthermore, DE-GM 88 06 965 discloses a device for producing such a surface structure, in which a layer of hot melt adhesive is applied at least partially to the unwound substrate or to the elastic threads by means of a melting device. The associated application head can be provided with a melting nozzle or a spray nozzle for applying the hot melt adhesive.

Finally, DE-PS 37 07 349 describes a method for permanently bonding stretchable thread- or ribbon-shaped elements to a flat substrate, in which the thread- or ribbon-shaped element arranged or fixed on the flat substrate is covered or sprayed with a sprayed hot-melt adhesive; the hot-melt adhesive also covers the neighboring areas of the thread- or ribbon-shaped element, i.e. the adjacent substrate areas, so that the hot-melt adhesive consumption is relatively high, since hot-melt adhesive is also present on the areas between the threads, which are not actually required for the bonding.

The invention is therefore based on the object of creating a device for applying a hot melt adhesive to elastic threads of the type specified, in which the disadvantages mentioned above do not occur. In particular, an application device is to be proposed which, in comparison with the previously usual embodiments, enables a significant saving in adhesive.

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This is achieved according to the invention by the features specified in the characterizing part of claim 1.

Appropriate embodiments are described by the features of the subclaims.

The advantages achieved with the invention are based on the fact that at the time of applying the adhesive, the elastic threads are guided and positioned very precisely, so that the adhesive can be applied specifically to the threads and not to the surface areas between the individual threads. This allows adhesive savings of 30 to 40 % to be achieved compared to conventional techniques.

At the same time, it is ensured that the threads are evenly stranded with the adhesive over their entire surface, as is necessary for the required, highly durable connection between the threads and the corresponding substrates for the production of hygiene articles, e.g. diapers.

If colored adhesives are used, the elastic threads coated with the adhesive can be optically marked; this allows additional quality control to be implemented, for example by assigning different thread types to different colored adhesives, so that you can immediately tell from the color whether it is a certain type.

And finally, there is also a comparatively low thermal load on the usually pre-stretched and thus particularly sensitive elastic threads; this is primarily due to the fact that a minimal amount of heated adhesive can be used, so that only a correspondingly small amount of heat is transferred to the threads.

In addition, the application head can now be positioned in the immediate vicinity of the substrate to be coated with the threads, so that the heat emitted by the warm adhesive is immediately dissipated via the threads to the substrate to be coated.

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For this purpose, according to a preferred embodiment, the application head is arranged at a distance of maximum 2 mm above the web of material to be coated, for example a polyethylene web in the manufacture of diapers, whereby even with mechanical contact between the web and the application head, the perfect coating of the individual threads located in the guide grooves of the application head is possible.

In principle, the guide grooves can have any cross-section, for example semicircular or rectangular shapes. However, particularly at high thread speeds, there is a risk that the threads will be pushed from one side to the other by the "hydraulic effect" of the adhesive in such guide grooves and thus coated unevenly.

For this reason, according to a preferred embodiment, guide grooves are used which have the shape of an isosceles, in particular equilateral triangle in cross section, since this results in an automatic centering of the elastic threads in the triangular guide grooves.

At the same time, such triangular guide grooves allow a very even coating of the elastic threads with the adhesive by arranging the feed openings for the adhesive at the three corners of the triangle.

The invention is explained in more detail below using exemplary embodiments with reference to the accompanying schematic drawings. They show

Fig. 1 is a perspective schematic representation of a device for producing a fabric that curls when heated, with an integrated device for applying an adhesive to the elastic threads used here,

Fig. 2 is a sectional view of detail X of Figure 1,

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Fig* 3 is a sectional view corresponding to figure 2 of another embodiment of the guide grooves,

Fig * 4 is a sectional view corresponding to Figure 2 of a third embodiment of the guide grooves, and

Fig. 5 is a sectional view of detail Y of Figure 1.

The device shown in Figure 1 and generally indicated by reference numeral 10 for producing a fabric that curls when heated, such as is used for hygiene articles, has a rotatable roller 12 to which a polyethylene web 14, a nonwoven web 16 and pre-stretched elastic threads 18 are fed in the direction of the arrows and are thereby connected to one another.

In front of the roller 12, as seen in the transport direction of the polyethylene web 14, there is an application head 20 to which a liquefied and thus flowable adhesive, in particular a hot melt adhesive, is fed from an adhesive source (not shown).

The underside of the application head 20 is located at a distance of maximum 2 mm above the top of the polyethylene sheet 14.

As can be seen from the sectional views of detail X of Figure 1 in Figures 2 to 4, the application head 20 is provided on its underside with guide grooves for the threads 18. These guide grooves are slightly larger in cross-section than the threads 18, so that the threads 18 are largely accommodated in the guide grooves and only protrude slightly downwards beyond the underside of the application head 20.

As can be seen from Figures 2 to 4, the guide grooves in the underside of the application head 20 can have different shapes; for example, Figure 2 shows two guide grooves 22a with a semicircular cross-section, Figure 3 shows two guide grooves 22b with a rectangular cross-section and Figure 4 shows two guide grooves 22c with a triangular cross-section.

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Figures 2 to 4 also show the outlet gates 24a (Figure 2), 24b (Figure 3) and 24c (Figure 4) as well as several feed openings 26a (Figure 2), 26b (Figure 3) and 26c (Figure 4) for the adhesive in each guide groove 22a, 22b and 22c.

As can be seen from Figures 1 to 4, the polyethylene web 14 is guided under the underside of the application head 20 at a small distance, which should be a maximum of 2 mm. At the same time, the threads 18 run individually through the corresponding guide grooves 22a (Figure 2), 22b (Figure 3) or 22c (Figure 4), so that the threads are evenly coated on all sides by the adhesive 28 indicated by the hatched area, which emerges from the slots 24a, 24b or 24c and the openings 26a, 26b or 26c. Each thread 18 is thus embedded in an adhesive tube that forms between the guide groove and the polyethylene web 14.

The adhesive is supplied in a timed manner so that only short pieces of thread are provided with the adhesive, as can be seen in Figure 1, where the individual adhesive areas on the threads 18 are indicated by the reference numerals 30.

The threads 18 coated with the adhesive 28 come into contact with the polyethylene web 14 either directly below the application head 20 or, as seen in the transport direction, just behind the application head 20 and are then fed together to the roller 12, where the nonwoven web 16 is laminated onto the top of the polyethylene web 14; as a result, the elastic threads 18 provided with the adhesive are located between the nonwoven web 16 and the polyethylene web 14.

The resulting sandwich structure can be seen in Figure 5, which shows two elastic threads 18, the polyethylene web 14, the nonwoven web 16 and the adhesive 28 which connects the threads 18 to the two webs 14, 16.

As can be seen from Figures 2 and 3, the threads 18 have a relatively large amount of play in semicircular or rectangular guide grooves,

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so that they can be displaced in the guide grooves by the hydraulic effect of the adhesive and thus coated unevenly.

A preferred embodiment is therefore shown in Figure 4, namely guide grooves 22c, which in cross section have the shape of an isosceles, in particular equilateral triangle. The feed openings 26c for the adhesive are located at the three corners of the triangle in order to ensure a uniform coating of the elastic threads 18 over their entire surface.

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Claims (9)

SCHWABE, · ^NDMAIB. ^. .MARX ^ j i .'' . PAfENTAKWALTE'."'. STUm2STRÄSä^f6'-'8000 RiÜNC&EN Attorney's file 36 469 X Henning J. Ciaassen Industrial area Hafen 2120 Lüneburg Device for applying an adhesive to elastic threads Patent claims 1. Device for applying an adhesive to elastic threads a) with an application head, and b) with outlet openings for the adhesive in the application head, characterized in that c) the application head (20) has guide grooves (22a, 22b, 22c) for the individual threads (18), and that d) at least one outlet opening (26a, 26b, 26c) for the adhesive (28) opens into each guide groove (22a, 22b, 22c). 2« Device according to claim 1, characterized in that the guide grooves (22a) have a semicircular shape in cross section. (089) 4707084 (W, M, 87) ^. Bank accounts: Bayer. Vereinsbank Munich 4531ÖÖ (bank code 7ÖÖ2Ö2 70) Telex: 5 24 560 Swan d (089)4707120 , ,,,, ,, &igr; HypojBänk Mühchen 4410122850 (bank code 70020011) Switt Code: HYPO DE MM " ■ " !,, ' J lDeutsch^Bank Munich 3743440 (BU 70Ö7ÖÖ1Ö) ¹ ''pis(Biro|Munich 65343^808 (bank code 7Ö010Ö80) till ' t i" > I I I >«ff·· SCHWABE · SANDMAIR ■ MAR}<·;" · * 2 w' . ."··' 3. Device according to claim 1, characterized in that the guide grooves (22b) have a rectangular cross-section. 4. Device according to claim 1, characterized in that the guide grooves (22c) have a triangular shape in cross section. 5. Device according to claim 4, characterized in that the guide grooves (22c) have the shape of an isosceles, in particular equilateral triangle in cross section. 6. Device according to one of claims 1 to 5, characterized in that several outlet openings (26a, 26b, 26c) for the adhesive open into each guide groove (22a, 22b, 22c). 7. Device according to claim 6, characterized in that an outlet opening (26c) for the adhesive is provided at each corner of the triangle. 8. Device according to one of claims 1 to 7 for applying an adhesive to elastic threads to be connected to a material web, characterized in that the application head (20) is located a maximum of 2 mm above the material web (14). 9. Device according to claim 8, characterized in that the distance between the material bed (14) and the application head (20) is zero to 2 mm.