EP2827999B1 - Device and method for spray coating a work with a hot-melt adhesive - Google Patents

Description

The invention relates to an apparatus and a method for spray coating an article with a hot melt adhesive. From the US 5,020,723 For example, a device for spray coating an article with a hot melt adhesive is known. The device comprises a nozzle through which a melt jet is ejected under pressure. The nozzle is surrounded by an annular nozzle in the region of its nozzle opening, through which compressed air is ejected. The effect of the compressed air creates a ring or spiral spray. - For many applications, a ring or spiral spray is unsuitable. By the action of compressed air, although the finest hot melt adhesive droplets are formed. Investigations have shown, however, that the droplets thus produced have on their surface a solid skin, whereby the strength of an adhesive bond produced therewith is reduced. Apart from that, the spray does not have a particularly exact geometric shape. Ie. a portion of the spray, the so-called "overspray", does not reach the portion of the article to be coated, but undesirably enters the environment. As a result, the environment becomes polluted. Apart from that, hot glue is lost.

From the DE 10 2010 001 454 A1 an arrangement for spray coating an article with a hot melt adhesive is known. The emerging from the nozzles melt jets are not sharply defined, since it is spray cone. Also, no arrangement is disclosed in which a spray fan forming downstream of a meeting point impinges upon an object to be coated.

The object of the invention is to eliminate the disadvantages of the prior art. In particular, a device and a method are to be specified, which enable a precise application of a hot melt adhesive to an object by means of spraying. For a further object of the invention the strength of an adhesive bond should be improved.

This object is solved by the features of claims 1 and 10. Advantageous embodiments of the invention will become apparent from the features of claims 2 to 9 and 11 to 17.

According to the invention, a device for spray-coating an article with a hot-melt adhesive is proposed, comprising a first nozzle and a second nozzle, the first and second nozzles being arranged such that a first melt jet emerging from the first nozzle and one from the second nozzle emerging second melt jet at an acute angle meet in a meeting point, so that forms a spray fan downstream of the meeting point, and wherein a temperature holding means for holding the first and the second nozzle at a predetermined target temperature in the range of 80 ° C to 250 ° C is provided ,

With the proposed device, in contrast to the prior art, it is possible for the first time to apply a hot glue in the form of a flat spray fan to an object arranged downstream of the point of contact. This creates new freedom when applying a hot melt adhesive by means of spray coating. It is possible, for example, to apply the hot melt linearly. Furthermore, relatively well-defined coating areas can be produced on the article. The Sprühfächer is inventively produced by a meeting of two ejected under pressure from the nozzle melt jets. In contrast to the prior art, no compressed air or compressed gas is used to produce the spray fan. An adhesive bond made using the proposed device has a improved strength. - Apart from that can be minimized with the invention of the "overspray". The proposed device thus enables a particularly efficient spray coating of an article with a hot melt adhesive.

According to an advantageous embodiment of the invention, the acute angle is 10 ° to 80 °, preferably 20 ° to 60 °. The first and the second melt jet are further advantageously arranged symmetrically with respect to a meeting point of the two melt jets, d. H. the first and second melt streams have substantially the same length to the meeting point. As a result, they hit each other at about the same temperature, which forms a particularly homogeneous Sprühfächer.

According to an advantageous embodiment, the temperature-retaining device comprises a thermal insulation surrounding the nozzles. It has been shown that even a thermal insulation of the nozzles can be sufficient for holding the nozzles at the predetermined setpoint temperature. For thermal insulation, it is possible to use conventional temperature-resistant insulating materials whose thermal conductivity is lower than the thermal conductivity of a material used to produce the first and / or second nozzle. The insulating material may be mineral wool, ceramic fiber mats or the like, for example.

The temperature retaining device may further comprise a heating device, e.g. As heating bands or the like., Which surround the nozzles at least in sections. Thus, the nozzles are maintained at a temperature necessary for applying the hot melt adhesive.

According to a further embodiment, the first and the second nozzle are each connected at their upstream end with a valve. The valve makes it possible, for example, to generate the spray fan intermittently. Thus, a variety of objects can be successively coated with hot melt at high speed.

According to a particularly advantageous embodiment of the invention, a further heating device for heating the valve is provided. The valve provided on the other heater can, for. B. for heating, preferably provided with a thermal insulation, nozzles are used. In this case, the heater for heating the nozzles may also be omitted. This simplifies the structure of the device.

Furthermore, the temperature-retaining device may comprise a control device connected to the heating devices and / or the further heating device for holding the nozzles at the desired temperature. Thus, the device can be kept ready for use at any time. If the spray coating is interrupted, the hot glue will not freeze in the nozzle channels. By means of the proposed regulation, moreover, overheating of the nozzles is avoided.

Upstream of the nozzles is advantageously provided a melting device for melting a solid hot melt starting material.

Further, upstream of the nozzles, a pressure generating device may be provided for generating a predetermined pressure on the melt. It may be a suitable for promoting thermoplastic melts conventional Act pump. The pressure generating device is expediently connected between the valve and the melting device. By means of the pressure generating device, a pressure of 2 to 10 bar, preferably 3 to 6 bar, is applied to the melt.

• Schmelzen eines Heißkleberausgangsmaterials,
• Ausstoßen des geschmolzenen Heizklebers durch eine erste Düse und eine zweite Düse,
• so dass ein aus der ersten Düse austretender erster Schmelzestrahl und ein aus der zweiten Düse austretender zweiter Schmelzestrahl in einem spitzen Winkel in einem Treffpunkt derart aufeinandertreffen, dass sich stromabwärts des Treffpunkts ein Sprühfächer ausbildet,
• wobei die Düsen auf einer vorgegebenen Solltemperatur im Bereich von 80°C bis 250°C gehalten werden.

In accordance with another aspect of the invention, a method is provided for spray coating an article with a hot melt adhesive, comprising the steps of:

• Melting a hot melt starting material,
• Ejecting the molten heating adhesive through a first nozzle and a second nozzle,
• so that a first melt jet emerging from the first nozzle and a second melt jet emerging from the second nozzle meet at an acute angle at a meeting point in such a way that a spray fan is formed downstream of the meeting point,
• wherein the nozzles are maintained at a predetermined set temperature in the range of 80 ° C to 250 ° C.

For the purposes of the present invention, the "hot melt starting material" is a physically setting adhesive. Such an adhesive is usually at room temperature in solid, one-component form. It usually contains no or only small proportions of solvent. Preferably, the hot melt starting material is a thermoplastic, for example polyamide, saturated polyester or ethylene-vinyl acetate copolymers. The hot melt starting material may contain additives such as tackifying resins, Plasticizers, stabilizers, antioxidants, fillers, extenders or waxes included. Furthermore, the term "hot melt starting material" is also understood to mean reactive hot melt adhesives which bind physically and chemically. These are one-component systems in which the hot melt z. B. cures under the action of UV light, moisture or water vapor, which is present in the article to be coated or in the environment. As a reactive hot melt adhesive, for example polyurethane (PUR) hot melt adhesive can be used, which hardens chemically under the action of moisture.

Because of the advantageous design features of the method, reference is made to the features described for the device, which may equally form embodiments of the method.

Fig. 1

eine schematische Darstellung einer erfindungsgemäßen Vorrichtung,

Fig. 2

eine Ausgestaltung der Vorrichtung gemäß Fig. 1 und

Fig. 3

die Schmelzestrahlen sowie den Sprühfächer gemäß Fig. 1 oder 2.

Embodiments of the invention will be explained in more detail with reference to the drawings. Show it:

Fig. 1

a schematic representation of a device according to the invention,

Fig. 2

an embodiment of the device according to Fig. 1 and

Fig. 3

the melt jets and the Sprühfächer according to Fig. 1 or 2 ,

At the in Fig. 1 A device 1 is provided with a supply device 2 for supplying hot melt starting material. The hot melt starting material can be present for example as granules. The reference numeral 3 is a first heating device for heating the container 1 denotes. The container 1 contains a melt S formed from the hot-melt starting material. The melt S can be formed, for example, from a thermoplastic polymer. A leading away from the container 1 first line 4 is connected to a, preferably heatable, pump 5. It may be, for example, a gear, diaphragm or piston pump. By means of the pump 5, the melt S in a downstream of the pump 5 provided second line 6 is brought to a pressure in the range of 2 to 10 bar. The first 4 and the second line 6 are expediently heated. Reference numeral 7 denotes a valve which is provided with a second heating device 8. From the valve 7 branch off two third lines 9, which open into a first nozzle 10 and a second nozzle 11. The first 10 and second nozzles 11 are each provided with a third heater 12. Although not shown in the figures, it may also be that the first 10 and second nozzles 11 are each provided with a valve. In this case, the first 10 and the second nozzle 11 may each form a structural unit with the respective valve. The assembly may in this case include the second 8 and / or third heater and / or thermal insulation.

The first 10 and the second nozzle 11 are arranged so that ejected melt jets St1, St2 meet at an angle α of about 60 °. The nozzles 10, 11 expediently have straight cylindrical nozzle channels whose axes intersect or almost intersect. A meeting point of the melt jets St1, St2 is designated by the reference symbol T. Due to the meeting of the melt jets St1, St2 forms a downstream of the meeting point T a Spray fan SF, which impinges on an object to be coated 13.

Fig. 2 shows a further embodiment of the invention. As far as the components used therein in Fig. 1 Corresponding components correspond, the same reference numerals have been chosen. In deviation from Fig. 1 Here, the first 10 and the second nozzle 11 are not provided with third heaters 12. By the reference numeral 14, a thermal insulation is referred to, which surrounds both the valve 7 and the first 10 and the second nozzle 11 substantially. In this case, the second heater 8 for heating the valve 7 is also used for heating the first 10 and second nozzles 11. The thermal insulation 14 may also be advantageously used to maintain the third lines 9 at a predetermined temperature.

The function of the devices will now be described with additional reference Fig. 3 explained in more detail.

By means of the first heating device 3, hot adhesive starting material supplied to the container 1 is melted. The temperature of the melt S is 120 ° to 250 ° C depending on the hot melt starting material. Conveniently, the temperature of the melt S is kept constant by means of a (not shown here) control. By means of the downstream downstream pump 5, the supplied melt S is brought to a pressure of, for example, 3 to 6 bar. With the valve 7, it is possible to interrupt a connection to the third lines 9. The valve 7 is also maintained at a suitable temperature in the range of 120 to 250 ° C by means of the second heater 8. With the second heating device 8, a temperature can be set, which expediently 10 ° C to 20 ° C higher than the temperature of the melt S in the container. 1

The melt S passes downstream of the valve 7 via, preferably heated, third lines 9 to the first 10 and the second nozzle 11. From the first nozzle 10 exits under the pressure generated by the pump 5, a first melt jet St1; from the second nozzle 11, a second melt jet St2 exits under pressure. The melt jets St1, St2 expediently have at the outlet opening of the nozzles 10, 11 - depending on the application - a diameter in the range of 0.5 to 3.0 mm. The sharply limited melt jets St1, St2 meet at the meeting point T at the angle α to each other. The angle α is selected so that a spray fan SF is formed. The spray fan SF strikes with a predetermined impact width B on the downstream of the meeting point T arranged object 13. A distance between the meeting point T and a surface of the object to be coated is z. B. 1 cm to 20 cm.

The spray fan SF generated with the device according to the invention is "flat", d. H. a perpendicular to the Auftreffbreite B extending thickness is advantageously 1 to 10 times, preferably 2 to 6 times the diameter of the melt jets St1, St2 at the outlet of the nozzles 10, 11. The not shown here thickness of the Sprühfächers SF runs perpendicular to the paper plane.

The reference character Z denotes a plane of symmetry. At the in Fig. 3 In the embodiment shown, the nozzles 10, 11 are arranged symmetrically to one another. A first length L1 of the first melt stream St1 and a second length L2 of the second Melt stream St2 are the same. In this case, a symmetrical spray fan SF is formed.

In the context of the present invention, however, it may also be that the first 10 and the second nozzle 11 are not arranged symmetrically to each other. Further, it may be that the first length L1 is different from the second length L2. This makes it possible to produce asymmetric Sprühfächer SF.

The proposed method or "airless spray method" is particularly suitable for applying a hot melt adhesive to nonwoven or woven articles 13. The proposed method hot melt adhesive bonds excellent strength can be achieved. Furthermore, it is possible with the proposed device to apply hot melt linearly or in the form of defined rectangular coating surfaces on objects 13. In the case of a rotation of the article 13 during the spray coating also circular application surfaces or circular sector-shaped application surfaces can be generated.

LIST OF REFERENCE NUMBERS

1

container

2

feeder

3

first heating device

4

first line

5

pump

6

second line

7

Valve

8th

second heating device

9

third line

10

first nozzle

11

second nozzle

12

third heating device

13

object

14

thermal insulation

S

melt

SF

spray fan

St1

first melt jet

St 2

second melt jet

T

meeting point

α

angle

Claims (17)

1. An arrangement for spray-coating an object (13) with a hot-melt adhesive (S),
   comprising an apparatus for spray-coating the object (13) with the hot-melt adhesive having a first nozzle (10) and a second nozzle (11),
   wherein the first (10) and the second nozzle (11) are arranged such that a clearly delimited first melt jet (St1) exiting from the first nozzle (10) and a clearly delimited second melt jet (St1) exiting from the second nozzle (11) contact one another at an acute angle (α) at a contact point (T), such that a fan-shaped spray (SF) is formed,
   wherein a temperature-holding device (8, 12, 14) for holding the first (10) and the second nozzles (11) at a predefined target temperature in the range from 120 °C to 250 °C is provided, and
   wherein the object (13) to be coated is arranged downstream of the contact point (T), such that the fan-shaped spray contacts the object (13) with a predefined contact width (B).
2. The arrangement according to Claim 1, wherein the acute angle (α) is 10 to 80°, preferably 20 to 60°.
3. The arrangement according to one of the preceding claims, wherein the temperature-holding device comprises a thermal insulation (14) surrounding the nozzles (10, 11).
4. The arrangement according to one of the preceding claims, wherein the temperature-holding device comprises a heating apparatus (12) which the nozzles (10, 11) surround at least in portions.
5. The arrangement according to one of the preceding claims, wherein the first (10) and the second nozzle (11) are each connected via their upstream end to a valve (7).
6. The arrangement according to one of the preceding claims, wherein a further heating apparatus (8) for heating the valve (7) is provided.
7. The arrangement according to one of the preceding claims, wherein the temperature-holding device comprises a regulation device connected to the heating apparatuses (12) and/or the further heating apparatus (8) for holding the nozzles (10, 11) at the target temperature.
8. The arrangement according to one of the preceding claims, wherein a melting apparatus (3) for melting a solid hot-melt adhesive starting material is provided upstream of the nozzles (10, 11).
9. The arrangement according to one of the preceding claims, wherein a pressure-generating apparatus (5) for generating a predefined pressure at the melt (S) is provided upstream of the nozzles (10, 11).
10. A method for spray-coating an object with a hot-melt adhesive, said method comprising the following steps:

    melting a hot-melt adhesive starting material,

    ejecting the molten hot-melt adhesive (S) through a first nozzle (10) and a second nozzle (11), wherein the nozzles (10, 11) are held at a predefined target temperature in the range from 120 °C to 250 °C,

    such that a clearly delimited first melt jet (St1) exiting from the first nozzle (10) and

    a clearly delimited second melt jet (St2) exiting from the second nozzle (11) contact one another at an acute angle (α) at a contact point (T) in such a way that a fan-shaped spray (SF) is formed, and

    arranging the object (13) to be coated downstream of the contact point (T), such that the fan-shaped spray contacts the object (13) with a predefined contact width (B).
11. The method according to Claim 10, wherein the acute angle (α) is 10 to 80°, preferably 20 to 60°.
12. The method according to Claim 10 or 11, wherein the nozzle channels are held at the target temperature with use of a thermal insulation (14).
13. The method according to one of Claims 10 to 12, wherein the nozzles (10, 11) are held at the target temperature by means of a heating apparatus (12).
14. The method according to one of Claims 10 to 14, wherein a further heating apparatus (8) is used to heat the nozzles (10, 11) and is part of a valve (7) provided upstream of the nozzles (10, 11).
15. The method according to one of Claims 10 to 13, wherein the nozzles (10, 11) are held at the target temperature with use of a regulation.
16. The method according to one of Claims 10 to 15, wherein the solid hot-melt adhesive starting material is melted by means of a melting apparatus (3) provided upstream of the nozzles (10, 11).
17. The method according to one of Claims 10 to 16, wherein a predefined pressure is exerted onto the melt (S) by means of a pressure-generating apparatus (5) provided upstream of the nozzles (10, 11).

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