EP0380781A2 - Device for applying glue to elastic threads - Google Patents

Abstract

A device for applying glue to elastic threads has an application head and outlet openings for the glue in the application head; a further application head is provided for the intermittent or continuous application of a colouring agent to the individual threads. <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 are made from an inelastic, thermoplastic polymer, in particular on the basis of ethylene vinyl acetate (EVA) copolymers, 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.

Furthermore, 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 detects 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 in themselves required for the bonding .

Finally, from the older German utility model application G 88 15 242.1 of December 7, 1988, a device for application an adhesive on elastic threads, the applicator head has guide grooves for the individual threads. At least one outlet opening for the adhesive opens into each guide groove. As a result, the elastic threads can be guided and positioned very precisely at the time the adhesive is applied, so that the adhesive is applied specifically to the threads and not to the surface areas between the individual threads. 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.

Especially in the production of baby diapers, there is now a desire to color-code the elastic threads. An advantage of such colored marking is that you can quickly check the presence or the perfect quality of the glued threads from the outside of the finished product; In addition, the manufacturers of baby diapers are increasingly moving towards marking certain types of diapers, for example diapers for boys or girls but also private labels, by appropriately coloring the threads. Compared to the other marking methods that have been customary to date, this represents a very simple and therefore inexpensive method.

In principle, it is possible to use appropriately colored adhesives and, for example, to use the device according to German utility model application G 88 15 242.1 to apply such colored adhesives. However, it is disadvantageous that the glue also has to be exchanged when the color changes, which generally requires expensive retrofitting work. In addition, relatively large amounts of adhesive are required.

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 by the invention are based on the fact that the elastic threads are first provided with a suitable paint application continuously or intermittently and then the hot melt adhesive is applied.

As a result, the coloring, that is to say a specific dye, can be changed or changed as desired, without the hot melt adhesive application device being touched thereby.

Any thermoplastic material without adhesive properties, for example based on so-called "microwaxes", which contains no expensive resins, can be used as the paint. This material becomes liquid when heated and can therefore be applied to the threads in the desired, relatively small amounts.

The order quantity for the relatively expensive colored material can be reduced by about 50%. The overall costs are comparatively low, in particular when the hot melt adhesive is applied by a spraying method, since only extremely small amounts of the undyed adhesive are required for the spraying.

Another advantage of this applicator is that existing elastic thread gluing devices, for example in diaper machines, do not have to be laboriously replaced, but the previous diaper machines have to be used further and only have to be supplemented by the coloring device for the threads.

Both the coloring of the elastic threads with a suitable dye and the application of the adhesive and the subsequent gluing to the substrate can be carried out continuously. In the manufacture of hygiene articles, in particular diapers, great importance is attached to the fact that the coloring is carried out only in the area of the bond, since the cut off, non-bonded ends of the elastic threads are virtually invisible without coloring. This advantage arises in particular in comparison with the previously used, pre-dyed elastic threads, which are generally dyed over their entire length, so that their cut off, non-glued ends remain clearly visible.

Because of the simple conversion of the production to different color types and the individual "in-line coloring" during diaper production, the manufacturer can buy and process the same white elastic thread for all diaper types, so that essentials also with regard to purchasing, warehousing and production Advantages.

And finally, the elastic threads, which are dyed intermittently and then provided with the hot melt adhesive, act as real threads and not as dyed broad blue traces due to the economical application on the finished product, for example a diaper, so that this also results in an aesthetic improvement.

The application device for the dye can essentially have the structure as found in utility model application G 88 15 242.1 emerges, namely with guide grooves for the individual threads and with at least one outlet opening for the dye in each guide groove.

The hot melt adhesive can be applied practically by any method, e.g. B. spray, roller application, slot nozzle application, but also with an application head with guide grooves for the individual threads and with an outlet opening for the hot melt adhesive in each guide groove.

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

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the attached, 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 a dye and an adhesive to the elastic threads used here,
• 2 is a sectional view of the device for applying the dye,
• 3 shows a sectional view corresponding to FIG. 2 of a further embodiment of the guide grooves,
• Fig. 4 is a Fig. 2 corresponding sectional view of a third embodiment of the guide grooves, and
• Fig. 5 is a sectional view of the finished fabric.

The device shown in FIG. 1, generally indicated by the reference numeral 10, for producing a device that heats up curling fabric, as is used for example for hygiene articles, has a rotatable roller 12 which, via a deflection roller 13, has a polyethylene web 14 in the direction of a first arrow 15, a nonwoven web 16 in the direction of a second arrow 17 and pre-stretched elastic threads 18 fed in the direction of a third arrow 19 and thereby connected to each other.

Seen in the direction of transport of the polyethylene web 14 in front of the roller 12 is an application head 20, from which a liquefied and thus flowable dye from a dye source (not shown), namely a suitable thermoplastic material without adhesive properties, e.g. B. is supplied on the basis of so-called "microwaxes".

As can be seen from the sectional views of the application head 20 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 several Feed openings 26a (FIG. 2), 26b (FIG. 3) and 26c (FIG. 4) for the dye are indicated in each guide groove 22a, 22b and 22c.

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 dye 28 indicated by the hatched area the slots 24a, 24b and 24c and the openings 26a, 26b and 26c emerges. Each thread 18 is therefore embedded in a dye tube, which forms between the guide groove and the polyethylene web 14.

The dye supply is clocked, so that only short pieces of thread are provided with the dye, as can be seen in FIG. 1, where the individual dye regions on the threads 18 are indicated by the reference symbols 30.

The threads coated with the dye 28 are brought into contact with the polyethylene web 14 on the deflecting roller 13 and are provided with the hot melt adhesive in this area approximately by means of an application device 31. In Fig. 1, this application device is shown as a spray device; However, other application techniques are also possible, namely roller application, slot nozzle application and the like.

The hot-melt adhesive is also applied intermittently, synchronized with the dye application, i.e. that is, the regions 30 of the elastic threads which are provided with the dye are also coated with the hot-melt adhesive, as indicated in FIG. 1 by the thread regions 32.

The threads 18 coated with the dye 28 and the hot-melt adhesive on the polyethylene web 14 are fed together to the roller 12, where the nonwoven web 16 is laminated onto the top of the polyethylene web 14; this means that they are with the Dye 28 and the elastic threads 18 provided with the adhesive between the nonwoven web 16 and the polyethylene web 14.

The resulting sandwich structure can be seen from FIG. 5, which shows the two elastic threads 18, the polyethylene web 14, the nonwoven web 16 and the dye / adhesive layer 29, which the threads 18 with the two webs 14, 16 connects.

As can be seen from FIGS. 2 and 3, the threads 18 in semicircular or rectangular guide grooves have a relatively large amount of play, so that they can be shifted by the hydraulic effect of the dye in the guide grooves and thus coated unevenly.

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

Instead of the spray device 31, an application device 20 can also be used to coat the threads with the hot melt adhesive.

As tests have shown, the distance between the application head 20 for the dye and the application head 31 for the hot melt adhesive should be a maximum of 500 mm, in particular a maximum of 300 mm. Particularly good results were achieved when this distance was approximately 100 mm. Because on the corresponding conveyor line the dye applied by the application device 20 has reached such a consistency that there is now a particularly good connection with the adhesive. At the same time, the installation or integration of the application device 20 into a stationary machine presents no problems if a distance in this area is selected.

Claims (12)

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) a further application head (20) is provided for the intermittent or continuous application of a dye to the individual threads (18). 2. Device according to claim 1, characterized in that the further application head (20) in the direction of movement (19) of the threads (18) is in front of the application head (31) for the adhesive. 3. Device according to one of claims 1 or 2, characterized in that the applicator head (20) for the dye guide grooves (22a. 22b, 22c) for the individual threads (18) and that at least one outlet opening (26a, 26b, 26c) for the dye (28) opens into each guide groove (22a, 22b, 22c). 4. Device according to one of claims 1 to 3, characterized in that the guide grooves (22a) have a semicircular shape in cross section. 5. Device according to one of claims 1 to 4, characterized in that the guide grooves (22b) have a rectangular shape in cross section. 6. Device according to one of claims 1 to 5, characterized in that the guide grooves (22c) have a triangular shape in cross section. 7. The device according to claim 6, characterized in that the guide grooves (22c) in cross section have the shape of an isosceles, in particular equilateral triangle. 8. Device according to one of claims 1 to 7, characterized in that in each guide groove (22a, 22b, 22c) several outlet openings (26a, 26b, 26c) open for the dye. 9. The device according to claim 8, characterized in that an outlet opening (26 c) is provided for the dye at each corner of the triangle. 10. Device according to one of claims 2 to 9, characterized in that the distance between the application head (20) for the dye and the application device (31) for the adhesive is a maximum of 500 mm, in particular a maximum of 300 mm. 11. The device according to claim 10, characterized in that the distance between the application head (20) for the dye and the application head (31) for the adhesive is in the range of about 10 mm to about 200 mm, in particular about 100 mm. 12. The device according to one of claims 1 to 11, characterized in that the application head for the adhesive is designed as a spray head (31).

Images