EP0372120A2 - Device for applying glue to elastic threads - Google Patents

Abstract

A device for applying a glue to elastic threads has an application head and outlet openings for the adhesive in the application head; the application head contains guide grooves for the individual threads; and in each guide groove there opens out at least one outlet opening for the glue. <IMAGE>

Description

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

Rippled, sheet-like structures when heated are used in particular as elastic bundles for disposable clothing, for example for nuclear facilities, but also for elastic bandages, bandages and hygiene articles, such as diapers, in order to achieve tight, but elastically deformable closures.

The basic structure of such a flat structure is evident, for example, from US Pat. No. 4,640,859 and has a substrate and pre-stretched elastomer threads embedded in an adhesive, namely so-called “spandex fibers”, that is to say polyurethane elastomer fibers.

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

The production of this fabric is very complex because of the heating and then cooling of the adhesive; In addition, adhesive films have to be used, which are very expensive and complicated to handle.

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

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

The invention is therefore based on the object of providing 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 customary embodiments, enables relevant adhesive savings.

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. In this way, an adhesive saving of 30 to 40% can be achieved in comparison with the conventional techniques.

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

If colored adhesives are used, the elastic threads coated with the adhesive can be optically identified; This enables an additional quality control to be implemented, for example by assigning different thread types to differently colored adhesives, so that one can immediately see from the coloring whether it is a specific type.

And finally there is also a comparatively low thermal load on the usually pre-stretched and thus particularly sensitive elastic threads; This is based first of all on 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 arranged in the immediate vicinity of the substrate to be coated with the threads, so that the heat emanating from the warm adhesive is immediately dissipated via the threads to the substrate to be coated.

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

In principle, the guide grooves can have any cross sections, for example semicircular or rectangular shapes. Particularly at high thread speeds, however, there is a risk that the threads will be pressed from one side to the other side by the "hydraulic effect" of the adhesive in such guide grooves and thereby 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, with such triangular guide grooves, a very uniform coating of the elastic threads with the adhesive can be achieved by arranging the feed openings for the adhesive at the three corners of the triangle.

• Fig. 1 eine perspektivische Schema-Darstellung einer Vorrichtung zur Herstellung eines sich bei Erwärmung kräuselnden Flächenge­bildes mit einer integrierten Vorrichtung zum Auftragen eines Klebstoffes auf die hierbei verwendeten, elastischen Fäden,
• Fig. 2 eine Schnittdarstellung des Details X von Figur 1,
• Fig. 3 eine Figur 2 entsprechende Schnittansicht einer weiteren Aus­führungsform der Führungsnuten,
• Fig. 4 eine Figur 2 entsprechende Schnittansicht einer dritten Aus­führungsform der Führungsnuten, und
• Fig. 5 eine Schnittansicht des Details Y von Figur 1.

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

• 1 is a perspective schematic representation of a device for producing a sheet that curls when heated with an integrated device for applying an adhesive to the elastic threads used here,
• 2 shows a sectional illustration of the detail X from FIG. 1,
• 3 shows a sectional view corresponding to FIG. 2 of a further embodiment of the guide grooves,
• Fig. 4 is a sectional view corresponding to Figure 2 of a third embodiment of the guide grooves, and
• 5 shows a sectional view of the detail Y from FIG. 1.

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

In the transport direction of the polyethylene web 14, in front of the roller 12, 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 at a maximum distance of 2 mm above the top of the polyethylene web 14.

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

As can be seen from FIGS. 2 to 4, the guide grooves in the underside of the application head can have 20 different shapes; two guide grooves 22a with a semicircular cross section are shown in FIG. 2, two guide grooves 22b with a rectangular cross section are shown in FIG. 3, and two guide grooves 22c with a triangular cross section are shown in FIG.

FIGS. 2 to 4 also show the outlet slots 24a (FIG. 2), 24b (FIG. 3) and 24c (FIG. 4) and a plurality of feed openings 26a (FIG. 2), 26b (FIG. 3) and 26c (FIG. 4) for the adhesive indicated in each guide groove 22a, 22b and 22c.

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

The adhesive supply is clocked, so that only short pieces of thread are provided with the adhesive, as can be seen in FIG. 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 either directly below the application head 20 or, viewed in the transport direction, just behind the application head 20 into contact with the polyethylene web 14 and are then fed together to the roller 12, where the nonwoven web 16 is on the top the polyethylene web 14 is laminated on; 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 FIG. 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 FIGS. 2 and 3, the threads 18 have a relatively large play in semicircular or rectangular guide grooves, 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 FIG. 4, namely guide grooves 22c, which have the shape of an isosceles, in particular equilateral triangle in cross section. The feed openings 26c for the adhesive are located at the three corners of the triangle, in order in this way to ensure a uniform coating of the elastic threads 18 over their entire surface.

Claims (9)

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. 3. Apparatus according to claim 1, characterized in that the guide grooves (22b) have a rectangular shape in cross section. 4. The device according to claim 1, characterized in that the guide grooves (22c) have a triangular shape in cross section. 5. The device according to claim 4, characterized in that the guide grooves (22c) in cross section have the shape of an isosceles, in particular equilateral triangle. 6. Device according to one of claims 1 to 5, characterized in that in each guide groove (22a, 22b, 22c) a plurality of outlet openings (26a, 26b, 26c) open for the adhesive. 7. The device according to claim 6, characterized in that an outlet opening (26 c) is provided for the adhesive 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 at most 2 mm above the material web (14). 9. The device according to claim 8, characterized in that the distance between the material web (14) and the application head (20) is zero to 2 mm.

Images