EP1872864A2 - Device and method for applying a liquid coating to a surface - Google Patents

Abstract

The device (1) has a nozzle (2) and a surface that are moved relatively to each other, where the nozzle applies a fluid (3) on the surface by an air flow (5). A unit produces the air flow, which deflects the fluid between the nozzle and the surface. A collecting unit is provided for collecting the fluid, where the air flow deflects the fluid in the collecting unit. The nozzle distributes a coating composition perpendicular to an application direction over an application breadth. An independent claim is also included for a method for applying a fluid coating on a surface.

Description

The present invention relates first to a device for applying a liquid coating to a surface according to the preamble of claim 1 and to a method for applying a liquid coating to a surface according to the preamble of claim 8.

Such devices are known. They may include a robot that can move a nozzle to deliver the liquid to the surface to be coated. This nozzle can apply the liquid to the surface, for example, by means of an air jet called horn air. The devices are used for example for applying paint or release agents on a surface, in particular a body of a motor vehicle. Furthermore, with such a device also protective coverings, such as an underbody protection, or adhesive can be applied to a surface.

The problem with devices known from the prior art is the dripping of, for example, the nozzle discharge means after the completion of the application process. For example, in the application of paint, dripping turns out to be extremely disturbing, because the already painted surface is visually impaired by subsequently applied drops.

The problem underlying the present invention is thus to provide a device of the type mentioned, which can prevent a disturbing dripping. Furthermore, a method of the aforementioned type is to be specified, with which the dripping can be prevented.

This is according to the invention in terms of the device by a device of the type mentioned above with the characterizing features of claim 1 and in terms of the method by a method of the type mentioned achieved with the characterizing features of claim 8. The subclaims relate to preferred embodiments of the invention.

Although from other areas an atomization of small amounts of liquid is known, for example. From the DE 3809517 A1 , The atomization desired there, however, is unsuitable for the precision required here. The generated air flow can prevent the droplets formed at the end of the application process from reaching the surface in an uncontrolled manner. For example, the air flow can direct the drops on the already applied coating. Alternatively, the air flow can also direct the drops into a separate collecting container or into the collecting area for paint provided in the painting booths.

Fig. 1

eine schematische Seitenansicht einer erfindungsgemäßen Vorrichtung;

Fig. 2

eine um 90° gedrehte schematische Seitenansicht der Vorrichtung gemäß Fig. 1;

Fig. 3

eine schematische Seitenansicht einer Vorrichtung gemäß dem Stand der Technik.

Further features and advantages of the present invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings. Show in it

Fig. 1

a schematic side view of a device according to the invention;

Fig. 2

a rotated by 90 ° schematic side view of the device of FIG. 1;

Fig. 3

a schematic side view of a device according to the prior art.

From Fig. 3, the prior art is shown schematically. From the known device, which may be arranged on a robot, only a part is shown, which includes a nozzle 2. From this nozzle 2, for example, liquid 3 can emerge, which can produce a coating on the schematically indicated workpiece 4. This nozzle 2 can apply the liquid to the surface of the workpiece 4, for example by means of an air flow. Fig. 3 shows the state after the stopping of the robot or after the termination of the actual Application process. Liquid 3 still drips out of the nozzle in small quantities. These drops of the liquid 3 can fall uncontrollably next to or on the workpiece 4, which is to be coated. This suggested dripping can thus cause the disadvantages already described.

From the illustrated in Fig. 1 and Fig. 2 embodiment of a device 1 according to the invention, which may also be arranged on a robot, a slightly larger part is indicated. This device 1 also comprises a nozzle 2 or a plurality of nozzles 2. The nozzle 2 can emit a liquid 3, which can produce a coating on the workpiece 4. In this case, the robot carrying the device 1 can be moved along the arrow 6 relative to the workpiece.

The apparatus 1 further comprises means for generating an additional air jet 5 different from the air jet used by the nozzle 2 for applying the coating. These means comprise a compressed air connection 7 and a nozzle, from which the air jet 5 can emerge. The air jet 5 is turned on when the robot stops, that is, when the application process is terminated. In contrast to the state of the art depicted in FIG. 3, the drops of the liquid 3 no longer fall down in an uncontrolled manner, but are deflected by the air jet 5 in a targeted manner. This can, as shown in FIG. 2, take place in such a way that the drops are guided directly onto the coating already produced on the surface of the workpiece 4. Alternatively, the drops can also be specifically directed into appropriate collecting means.

Another invention relates to a method of making a removable surface protection. This further invention, which is sought for protection alone and in combination with the invention set forth above, relates to a process for making a removable surface protection by applying a liquid, curable coating composition (liquid film) to painted surfaces wherein the liquid coating composition is applied through an application die, the relative over a predetermined, to be protected surface area in an application direction is moved and the liquid coating composition is supplied under pressure, sprayed distributed across the application surface across an application width on the surface, the application by starting and stopping the supply of coating composition to the application nozzle in coordination with their relative movement in the application direction to the predetermined surface area in Application is limited. The movement of the application nozzle is referred to here as relative, since the surface to be coated can be moved when the application nozzle is stationary.

Such a procedure is over DE 198 54 760 Al discloses a method of making a removable surface protection (liquid film) on a painted automotive body. A liquid is sprayed onto the painted body surface. This liquid solidifies into a peelable film. The application of the liquid via an application nozzle in the form of a fan nozzle to avoid so-called overspray and to achieve edge-sharp application. The application nozzle is moved by a robot arm over the predetermined surface area to be protected in an application direction. The application is limited by starting and terminating the supply of coating composition to the application nozzle in coordination with their movement in the application direction to the given surface area in the application direction, so that only the predefined surface areas are coated.

A disadvantage of the method described is the uneven layer thickness of the applied liquid film. Thus, the layer thickness at the edges of the applied liquid web is higher than in the middle of the web. The width of the liquid web applied with a fan nozzle varies as a function of the material pressure under which the liquid is discharged from the nozzle. In order to cover larger surfaces with a closed liquid film, the liquid paths discharged from the fan nozzle must be applied overlapping. The layer thickness of the applied film is additionally increased in the overlapping areas.

Uneven layer thicknesses of the applied film lead to uneven drying behavior of the liquid film. In order to obtain a completely through-dried film at all points of the coated surface, it is necessary to orient the drying conditions at the greatest possible layer thickness. This leads either to high drying temperatures or to longer drying times.

DE 10 2004 018 597 B3 describes the application of a liquid film along a web direction with an application head, which consists of a plurality of chambers, which are arranged one behind the other in the flow direction, and one or more in the application direction arranged behind one another rows of adjacent round jet nozzles has (multi-jet). The use of the multi-jet nozzle in the liquid film application has the following advantages: At the same time a large number of liquid beads are discharged side by side. These liquid beads flow into each other immediately after application and form a fluid path. The layer thicknesses of the caterpillars deposited within the liquid web and the caterpillars deposited at the edge of the liquid web are the same. Ie. the layer thickness of the liquid web thus applied is more uniform across the width of the web than when using a fan nozzle.

When using a multi-jet nozzle, the width of the applied liquid web is less dependent on the material pressure than when using a fan nozzle. Therefore, it is not necessary to overlap the individual liquid webs to coat larger areas with a closed film. The layer thickness distribution is therefore more uniform than when using a fan nozzle.

A common disadvantage of both of the previously described methods is the following: Before the start of the application process, the application nozzle is separated from the line supplying the liquid coating composition by a closed valve. The material is already under the line for the application necessary pressure. The dead volumes of the nozzle at this time are either not yet filled with material or contain material that is under lower pressure than the pressure selected for application.

At the beginning of the application, the valve is opened. The liquid coating composition flows into the nozzle of the application head and there is an increase in the material pressure within the dead volume of the nozzle. Depending on the shape of the flow paths within the nozzle structure, this can lead to an abrupt increase in material pressure in the dead volume of the nozzle. Only in the course of the application, then under constant flow conditions, a constant material pressure.

The pressure surges occurring at the beginning of the application could lead to the material being discharged from the nozzle at an undesirably high speed and to splash back after being hit on the surface to be coated.

The flying material droplets contaminate the vehicle surface outside the predetermined surface area to be protected which is to be coated. These impurities must be removed by hand after drying the liquid foil.

Moreover, it is possible that upon impact of the material on the surface to be coated air is trapped in the applied film, and film defects such. As foam and bubbles leads.

During application, the overpressure prevailing in the dead volume of the nozzle in comparison with the ambient pressure generates the material flow through the outlet openings of the nozzle. The material pressure in the dead volume of the nozzle remains constant.

The speed of the material discharged from the nozzle is proportional to the material overpressure prevailing in the dead volume of the nozzle in the jet direction.

The speed of the material discharged from the nozzle is in the direction of application, i. parallel to the plane of the surface to be coated (horizontal), proportional to the speed of movement of the robot arm, which guides the application head with the nozzle over the surface to be coated.

At the end of the application, the valve, which separates the material supply from the dead volume of the nozzle, is closed. Thereafter, the material pressure in the dead volume of the nozzle decreases due to the still ongoing material discharge from the nozzle to ambient pressure.

As a result, the vertical speed of the material discharged from the nozzle is lower than during the application. The material flies longer through the air until it hits the surface to be coated. However, the horizontal speed of the discharged material is unchanged by the feed speed of the robot arm.

Therefore, at the end of the application, the material discharged from the nozzle flies farther in the feed direction of the robot arm than during the application. This leads especially at high application speed, i. high feed rate of the robot arm, to impurities beyond the specified surface area on surfaces that are not supposed to be coated.

Although these impurities occur predominantly in the use of multi-jet nozzles, but can not be completely avoided by the use of fan nozzles.

The removal of these impurities can only be done manually after drying the liquid film, and is therefore very expensive.

It is an object of the present invention to counteract impurities that were previously unavoidable in the robot-assisted application of liquid film with spray nozzles of different construction at the beginning and at the end of the application.

In addition, a possibility should be found to be able to use the advantages of the application of liquid film with the multi-jet nozzle, without having to take a comparison with the application with the fan nozzle increased effort to clean the coated car body shop in purchasing.

In addition, the application rate, which was previously limited by the occurrence of impurities at high speeds when using the multi-jet nozzle, should be increased.

To solve this problem, the characterizing features of the independent claims. Advantageous embodiments of the invention are listed in the subclaims.

According to the invention, provision is made for nozzle devices in the direction of application in front of and behind the application nozzle, which are designed to direct a gas flow over the application width when the application is started, to be directed from the back at an angle to the spray jet of the application nozzle in the direction of application, and on termination the application a gas flow distributed over the application width, in the application direction from the front at an angle to the spray jet of the application nozzle to each to prevent overspraying of coating composition beyond the predetermined surface area and to direct the spray jet in the predetermined surface area.

By a respective nozzle device which is in the application direction (= feed direction of the robot arm, if the relative movement is effected) in front of and behind the application nozzle and at the beginning of the application in the feed direction and at the end of the application against the feed direction, preferably laminar, gas flow produced, impurities can be avoided. It is advantageous if the gas flow generated by the nozzle device is directed at an angle of 25 to 35 degrees to the spray jet.

At the time of switching (on or off) of the valve in the Material supply to the application nozzle, the respective nozzle device with compressed gas, eg compressed air, applied. The air flowing out of the nozzle openings forms an "air curtain" which blows the liquid emerging from the spray nozzle onto the surface to be coated or already coated. At the beginning of the application, after reaching a constant flow of material through the application nozzles, the supply of compressed air to the rear nozzle device is terminated. At the end of the application, the compressed air supply to the front nozzle device is started at a predetermined time with respect to the closing of the valve in the material supply.

It has also surprisingly been found that many advantages can be achieved by treating the surface to be coated with water or an aqueous solution of one or more surface-active substances and then applying the coating composition. By treating the surface, for example a painted vehicle body, with water or aqueous solutions of surface-active substances and applying the liquid film to the pretreated surfaces, a closed course and a corresponding film are obtained even at lower layer thicknesses than when the liquid film is applied to dry surfaces. This reduces the material consumption per unit area and still creates a closed film. In addition, the material pressure can be reduced so far that the back-spraying of the coating material can be avoided.

A significant advantage of this embodiment with pre-wetting compared to application methods without pre-wetting is the material savings of 15 to 20% per unit area, which is achieved in the preferred method.

Although washing surfaces to be coated with water or aqueous cleaning agents is known as pretreatment prior to coating. It removes impurities that could interfere with the adhesion of the coating to the surface. The water or the aqueous cleaning agent but before the application of the Coating material completely removed from the surface.

1. a) die Oberfläche zunächst mit Wasser oder einer wässrigen Lösung einer oder mehrerer grenzflächenaktiver Substanzen behandelt,
2. b) eine Beschichtungszusammensetzung auf die behandelte Oberfläche mit dem erfindungsgemäßen Verfahren aufgebracht, bevor das Wasser vollständig von der behandelten Oberfläche abgetrocknet ist, und
3. c) die Beschichtungszusammensetzung gehärtet, um eine gehärtete Beschichtung mit einer Schichtdicke von höchstens 200 pm zu bilden.

Accordingly, in the preferred embodiment, a method of making a removable surface protection

1. a) first treating the surface with water or an aqueous solution of one or more surface-active substances,
2. b) a coating composition is applied to the treated surface by the method of the invention before the water has completely dried from the treated surface, and
3. c) curing the coating composition to form a cured coating having a layer thickness of at most 200 μm.

In a further preferred embodiment, the surface is treated in step a) with water, which can optionally be condensed by condensation on the surface of water supersaturated air. The pretreatment by condensation has the advantage that the generated water layer thicknesses are uniform and low. In addition, it can be dispensed with application technology for the spraying of water. In a further preferred embodiment, the treatment with water or the aqueous solution of surface-active substances takes place on the surface by spraying.

In a further preferred embodiment, the temperature of the surface in step a) is 1 ° C to 50 ° C, preferably 5 ° C to 40 ° C, more preferably 10 ° C to 30 ° C, especially 15 ° C to 25 ° C.

The coating structure on the vehicle surface is preferably a typical car body painting, which consists for example of a cathodic dip coating, optionally a filler, a basecoat and additionally a clearcoat as topcoat. But it is also possible that a pigmented topcoat is used instead of basecoat and transparent clearcoat. The used as a final topcoat transparent or pigmented lacquer may be a lacquer based on, for example, a one- or two-component polyurethane system, or a melamine resin / polyol system. The polyols used to formulate the topcoat lacquer can be polyester, polyacrylate or polycarbonate polyols.

Preferably, the coating composition is applied less than 25 minutes after step a), more preferably 0.1 second to 25 minutes, especially 0.1 second to 15 minutes, such as 0.1 second to 10 minutes, or 1 second to 1 minute, for example 1 second to 45 seconds, or 1 second to 30 seconds after step a).

The coating composition is preferably a water-dilutable coating material based on e.g. As polymer dispersions, in particular polyurethane dispersions and more preferably dispersions of polyesterurethanes.

In applying the coating composition, it is preferable to use a multi-jet nozzle having 1 to 6 rows of 5 to 500 nozzles each, more preferably 10 to 320 nozzles, particularly 20 to 160 nozzles, such as 40 to 80 nozzles.

In preferred pre-wetting processes, higher viscosity coating compositions can be used as compared to the non-wetting process. Preferred viscosity ranges are 5 to 40, preferably 10 to 35, in particular 15 to 30 Pa ● s.

The layer thickness of the cured coating composition is preferably 40 to 170 μm, more preferably 50 to 160 μm, especially 60 to 130 μm, for example 70 to 120 μm, such as 80 to 110 μm or 90 to 100 μm.

The curing in step c) can be carried out at elevated temperature, for example at 10 ° C to 90 ° C, preferably 15 ° C to 80 ° C, especially 15 ° C to 60 ° C, such as 20 ° C to 50 ° C.

• Figur 4 eine Applikationsdüse mit daran angebrachten Düseneinrichtungen in seitlicher Ansicht (in der Darstellung oben) und in Draufsicht von unten (in der Darstellung unten) zeigt, und
• Figur 5 eine seitliche Ansicht der Baueinheit aus Applikationsdüse und Düseneinrichtungen mit angedeutetem Spritzstrahl und Gasströmen zeigt.

The invention will be described in more detail below on the basis of exemplary embodiments in the drawings, in which:

• FIG. 4 shows an application nozzle with nozzle devices attached thereto in a lateral view (in the illustration above) and in a plan view from below (in the illustration below), and
• Figure 5 shows a side view of the assembly of application nozzle and nozzle means with indicated spray jet and gas flows shows.

FIG. 4 shows the application nozzle 2a, on whose sides a nozzle device 10 and 20 is mounted. The application nozzle 2a may have a tube closed at one end and substantially rectangular in cross section; alternatively, the tube may also be open on both sides and provided with a coating composition port. On the underside of the tubular body are in a row along the longitudinal axis of the tubular body, a plurality of holes. The diameter of the holes can be up to 2 mm.

The nozzle device 10 (20) also has an elongated tubular hollow body, which comprises on its underside a fan nozzle in the form of an elongated slot 12 (22) which extends parallel to the application nozzle row. The nozzle devices 10, 20 are in each case mounted inclined to the application nozzle 2a in such a way that the gas streams emerging from the slots 12, 22 of the nozzle devices 10, 20 are inclined to the spray jet 4a issuing from the application nozzle, this angle of inclination preferably being in the range from 25 to 35 °.

The nozzle devices 10, 20 are supplied with compressed air by supply lines (not shown) which are connected to the hollow bodies at both ends.

As an alternative to the slots 12, 22 for discharging the gas streams, it is also possible to provide rows of individual nozzles instead of the slots on the nozzle devices, these nozzle rows then being approximately Overall size and arrangement as the fan slots 12, 22 have. In the case of such a design of the nozzle device with a series of individual nozzles, it may be useful to select the diameter of the individual nozzles in the row from the ends with air supply starting to the center of the tubular body progressively smaller, so as to obtain a most laminar air flow. Accordingly, it can be useful, when forming the nozzle devices 10, 20 with continuous slots 12, 22, to decrease the width of the slots from the air supply ends to the center of the tubular body of the nozzle device in order to obtain a laminar and homogeneous air flow.

FIG. 5 schematically shows the arrangement of the application nozzle 2 with the nozzle devices 10, 20 mounted thereon in a lateral view. The application direction, i. the direction in which the application nozzle is moved over the surface to be coated is indicated by the horizontal arrow. The spray jet of the application nozzle 2a is denoted by 4a. At the beginning of the application, the nozzle device 20 is supplied with compressed air, so that the air flow indicated by dashed lines impinges on the spray jet 4 of the application nozzle 2a and deflects it into the jet 4 '. Conversely, shortly before the end of the material discharge from the application nozzle 2a, the nozzle device 10 is actuated and generates an air flow indicated by dashed lines, which is emitted at an angle b to the spray jet 4a of the application nozzle 2a and deflects the spray jet 4a into the spray jet 4 ", thus overspraying at the end of the application of material to avoid the coating surface.

The control of the movement of the application nozzle 2a in the application direction, the coating material supply to the application nozzle 2a and coordinated with the control of the compressed air supply to the nozzle means is performed by a programmed control device, in the control parameters on the coating material supply, compressed air supply to the nozzle devices and information about the to be coated, predetermined surface can be entered.

Examples of preferred embodiments with pre-wetting of the paint surface are described below.

Another invention relates to a method for applying a liquid film after aqueous pretreatment of the surface to be coated. This further invention, for which protection is desired on its own and in combination with the inventions presented above, relates in particular to a process for the production of a removable surface protection by application of a liquid, curable coating composition (also called liquid film) in which the surface to be protected with water or an aqueous solution of surfactants treated and then the coating composition is applied. This further invention further relates to the use of water or aqueous solutions of surfactants in such a process. Finally, the invention also relates to such a removable surface protection.

Usually motor vehicles are provided after production with a surface protection that protects the topcoat from damage such as scratching. This surface protection is removed before handing over the vehicle to the buyer. For example, wax coatings are known which must be removed with solvents and have therefore proved to be disadvantageous. Furthermore, the sticking of films has been proposed, but the application is associated with a disproportionate amount of time. In addition, it can lead to damage of the surface when sticking, which should actually be avoided. On the basis of this is in the DE 196 52 728 A1 described a liquid which cures to a film, wherein the film is removed before delivery to the customer.

• Die ungleichmäßige Schichtdicke der applizierten Beschichtungszusammensetzung. Die Schichtdicke ist an den Rändern der applizierten Bahn höher als in der Mitte der Bahn.
• Die Breite der mit einer Fächerdüse applizierten Bahn schwankt in Abhängigkeit vom Druck, unter dem die Zusammensetzung aus der Düse ausgetragen wird. Um größere Flächen mit einem geschlossenen Film aus einzelnen Bahnen zu belegen, müssen die aus der Fächerdüse ausgetragenen Bahnen überlappend appliziert werden. Dadurch wird die Schichtdicke des applizierten Filmes in den Bereichen der Überlappung der Bahnen zusätzlich erhöht.
• Ungleichmäßige Schichtdicken des Filmes führen zu einem ungleichmäßigen Trocknungsverhalten. Um an allen Stellen eine vollständig durchgetrocknete Folie zu erhalten, ist es notwendig, die Trocknungsbedingungen an der größtmöglichen auftretenden Schichtdicke zu orientieren. Das erfordert höhere Trocknungstemperaturen und/oder längere Trocknungszeiten.

The DE 198 54 760 A1 describes such a method of making a removable surface protection on a painted automotive body. A liquid is sprayed onto the painted body surface. This liquid solidifies to a peelable film, therefore, such a liquid Coating composition also referred to as liquid film. According to the DE 198 54 760 A1 the application of the liquid film is carried out with two fan nozzles of different widths in order to avoid accidental spraying of surface areas which are not to be coated (overspray) and to achieve an edge-sharp application. Disadvantages of in the DE 198 54 760 A1 described method are:

• The uneven layer thickness of the applied coating composition. The layer thickness is higher at the edges of the applied web than in the middle of the web.
• The width of the web applied with a fan nozzle varies depending on the pressure at which the composition is discharged from the nozzle. In order to cover larger surfaces with a closed film of individual webs, the webs discharged from the fan nozzle must be applied overlapping. As a result, the layer thickness of the applied film in the areas of overlap of the webs is additionally increased.
• Uneven layer thicknesses of the film lead to an uneven drying behavior. In order to obtain a completely through-dried film at all points, it is necessary to orient the drying conditions to the greatest possible layer thickness. This requires higher drying temperatures and / or longer drying times.

• Es wird gleichzeitig eine Vielzahl von Flüssigfolienraupen nebeneinander ausgetragen. Diese Raupen verfließen unmittelbar nach der Applikation ineinander und bilden eine Flüssigfolienbahn. Die Schichtdicke der in der Mitte einer Bahn abgelegten Raupen und der am Rand einer Bahn abgelegten Raupen ist gleich, d.h. die Schichtdicke der so applizierten Bahn ist über die Bahnbreite gleichmäßiger als bei Verwendung einer Fächerdüse.
• Bei Verwendung einer Multistrahldüse ist die Breite der applizierten Bahn weniger stark vom Materialdruck abhängig als bei Verwendung einer Fächerdüse. Deshalb ist es zur Beschichtung größerer Flächen mit einem geschlossenen Film nicht notwendig, die einzelnen Bahnen überlappend aufzutragen. Die Schichtdickenverteilung ist deshalb gleichmäßiger als bei Verwendung einer Fächerdüse.

The DE 10 2004 018 597 A1 describes for the application of a liquid film along a web direction an application head with a plurality of successively arranged rows of adjacent round jet nozzles (multi-jet nozzle). The use of the multi-jet nozzle in liquid film application has several advantages:

• At the same time, a large number of liquid foil beads are discharged side by side. These caterpillars flow into each other immediately after the application and form a Liquid film web. The layer thickness of the caterpillars deposited in the middle of a web and the caterpillars deposited on the edge of a web are the same, ie the layer thickness of the web thus applied is more uniform over the web width than when using a fan nozzle.
• When using a multi-jet nozzle, the width of the applied web is less dependent on the material pressure than when using a fan nozzle. Therefore, to coat larger areas with a closed film, it is not necessary to overlap the individual webs. The layer thickness distribution is therefore more uniform than when using a fan nozzle.

• Zur Bildung einer gleichmäßig geschlossenen Bahn müssen die einzelnen nebeneinander abgelegten Raupen ineinander verlaufen. Deshalb müssen die einzelnen Raupen eine relativ hohe Schichtdicke aufweisen. Der Materialverbrauch ist dementsprechend höher als bei Verwendung einer Fächerdüse.
• Um hinreichend hohe Schichtdicken der einzelnen Materialraupen zu erzeugen, ist wiederum ein relativ hoher Materialdruck notwendig. Das führt dazu, dass das Material mit vergleichsweise hoher Geschwindigkeit aus der Multistrahldüse ausgetragen wird und nach dem Auftreffen auf die zu beschichtende Oberfläche zurückspritzt. Die herumfliegenden Materialtröpfchen verunreinigen die Fahrzeugoberfläche außerhalb des Bereichs, der beschichtet werden soll. Diese Verunreinigungen müssen nach der Trocknung/Aushärtung der Flüssigfolie aufwendig von Hand entfernt werden.

However, the use of a multi-jet nozzle also involves disadvantages:

• To form a uniformly closed path, the individual caterpillars deposited next to one another must run together. Therefore, the individual caterpillars must have a relatively high layer thickness. The material consumption is correspondingly higher than when using a fan nozzle.
• In order to produce sufficiently high layer thicknesses of the individual material beads, in turn, a relatively high material pressure is necessary. As a result, the material is discharged from the multi-jet nozzle at a comparatively high speed and injected back onto the surface to be coated after impact. The flying material droplets contaminate the vehicle surface outside the area to be coated. These impurities must be removed by hand after drying / curing of the liquid film.

The object of the present invention is to provide a method with which the advantages associated with the use of a multi-jet nozzle can be exploited. At the same time the disadvantages should be avoided with such Use of a multi-jet nozzle are connected, in particular the associated increased material consumption and overspray. Finally, there is always a need for a process with lower material requirements and a correspondingly thinner removable surface protection.

It has now surprisingly been found that these objects are achieved and further problems of the prior art are avoided by treating the surface to be coated with water or an aqueous solution of one or more surface-active substances and then applying the coating composition. By treating the surface, for example a painted vehicle body, with water or aqueous solutions of surface-active substances and applying the liquid film to the pretreated surfaces, a closed course and a corresponding film are obtained even at lower layer thicknesses than when the liquid film is applied to dry surfaces. This reduces the material consumption per unit area and still creates a closed film. In addition, the material pressure can be reduced so far that the back-spraying of the coating material can be avoided.

A significant advantage of the application method according to the invention with prewetting compared to the non-inventive application method without prewetting is the material savings of 15 to 20% per unit area, which is achieved in the inventive method.

Although washing surfaces to be coated with water or aqueous cleaning agents is known as pretreatment prior to coating. It removes impurities that could interfere with the adhesion of the coating to the surface. However, the water or the aqueous cleaning agent is completely removed from the surface before the application of the coating material.

1. a) die Oberfläche mit Wasser oder einer wässrigen Lösung einer oder mehrerer grenzflächenaktiver Substanzen behandelt wird,
2. b) eine (flüssige, härtbare) Beschichtungszusammensetzung auf die behandelte Oberfläche aufgebracht wird, bevor das Wasser vollständig von der behandelten Oberfläche abgetrocknet ist, und
3. c) die Beschichtungszusammensetzung gehärtet wird, um eine gehärtete Beschichtung mit einer Schichtdicke von höchstens 200 µm zu bilden.

Accordingly, the invention relates to a method for producing a removable surface protection, in which

1. a) the surface is treated with water or an aqueous solution of one or more surface-active substances,
2. b) applying a (liquid, curable) coating composition to the treated surface before the water is completely dried from the treated surface, and
3. c) the coating composition is cured to form a cured coating having a layer thickness of at most 200 μm.

In a preferred embodiment, the surface is treated in step a) with water, which can optionally be condensed by condensation on the surface of water supersaturated air. The pretreatment by condensation has the advantage that the generated water layer thicknesses are uniform and low. In addition, it can be dispensed with application technology for the spraying of water. In a further preferred embodiment, the treatment with water or the aqueous solution of surface-active substances takes place on the surface by spraying.

In a further preferred embodiment, the temperature of the surface in step a) is 1 ° C to 50 ° C, preferably 5 ° C to 40 ° C, more preferably 10 ° C to 30 ° C, especially 15 ° C to 25 ° C.

In all embodiments of the invention, it is preferred that the surface is a surface of a motor vehicle painted with topcoat. The coating structure on the vehicle surface is preferably a typical car body painting, which consists for example of a cathodic dip coating, optionally a filler, a basecoat and additionally a clearcoat as topcoat. But it is also possible that a pigmented topcoat is used instead of basecoat and transparent clearcoat. The transparent or pigmented lacquer used as a final topcoat can be a lacquer based on, for example, a single or a lacquer be a two-component polyurethane system, or a melamine resin / polyol system. The polyols used to formulate the topcoat lacquer can be polyester, polyacrylate or polycarbonate polyols.

Preferably, the coating composition is applied less than 25 minutes after step a), more preferably 0.1 second to 25 minutes, especially 0.1 second to 15 minutes, such as 0.1 second to 10 minutes, or 1 second to 1 minute, for example 1 second to 45 seconds, or 1 second to 30 seconds after step a).

The coating composition is preferably a water-dilutable coating material based on e.g. As polymer dispersions, in particular polyurethane dispersions and more preferably dispersions of polyesterurethanes.

The coating composition is z. B. by pouring, the deposition of material beads, by hydraulic spraying (airless), by hydraulic spraying with pneumatic assistance (Airmix), or applied by pneumatic atomization. These different nozzle designs can be used, such. B. fan nozzles, slot nozzles and round jet nozzles.

In applying the coating composition, it is preferable to use a multi-jet nozzle having 1 to 6 rows of 5 to 500 nozzles each, more preferably 10 to 320 nozzles, particularly 20 to 160 nozzles, such as 40 to 80 nozzles.

In the process according to the invention, higher-viscous coating compositions can be used in comparison with the process without pre-wetting. Preferred viscosity ranges are 5 to 40, preferably 10 to 35, in particular 15 to 30 Pa · s.

The layer thickness of the cured coating composition is preferably 40 to 170 μm, more preferably 50 to 160 μm, especially 60 to 130 μm, for example 70 to 120 μm, such as 80 to 110 μm or 90 to 100 μm.

The curing in step c) can be carried out at elevated temperature, for example at 10 ° C to 90 ° C, preferably 15 ° C to 80 ° C, especially 15 ° C to 60 ° C, such as 20 ° C to 50 ° C.

The invention further relates to a removable surface protection made according to the method of the invention. This further invention, for which alone and in combination with the above-presented inventions protection is sought, is characterized in particular by the fact that the surface protection in a comparatively small layer thickness of (in the cured state) is at most 200 microns, which provides sufficient mechanical strength ensures the removal of the (cured) surface protection without an unnecessarily high amount of coating composition must be used, which would be disadvantageous because of the associated higher costs and longer curing / drying times.

Moreover, the invention relates to the use of water or aqueous solutions of one or more surfactants in a method of making a removable surface protection in which the water or solution of surfactants is applied to the surface and then a coating composition is applied to the treated surface before the surface is completely dried, to reduce the necessary amount of coating composition as compared with a method without treatment with water or solution of surfactants. Also for this further invention alone and in combination with the inventions presented above protection is desired.

Another invention sought to be protected alone and in combination with the inventions set forth above relates to the use of water or aqueous solutions of surfactants in a process for making a removable surface protection wherein the water or solution surfactant is applied to the surface and then a coating composition is applied to the treated surface before the surface is completely dried, to avoid the undesirable coating of certain areas of the surface with the coating composition (overspray).

Figur 6

das Aufbringen der Beschichtungszusammensetzung gemäß Schritt b) zeigt,

Figur 7

zwei gehärtete Beschichtungen zeigt, wobei rechts eine erfindungsgemäß hergestellte Beschichtung gezeigt ist und links eine Beschichtung gezeigt ist, die gemäß einem Verfahren ohne Schritt a) erzeugt wurde, und

Figur 8

das Entfernen einer erfindungsgemäß hergestellten Beschichtung gezeigt ist.

The advantages of the above-described inventions can also be seen in FIGS. 6 and 7, in which

FIG. 6

the application of the coating composition according to step b) shows,

FIG. 7

shows two cured coatings, wherein on the right a coating produced according to the invention is shown and on the left a coating is shown, which was produced according to a process without step a), and

FIG. 8

the removal of a coating produced according to the invention is shown.

In Figure 6 it is illustrated that the coating composition is conveyed by means of a suitable metering device (pump) and discharged through a nozzle consisting of a plurality of holes. The individual beads forming on exit from the nozzle combine to form a closed film upon impact with the surface. In this case, a certain overpressure is required, which allows the merging of the individual tracks and tracks into a film.

FIG. 7 illustrates the advantages of the method according to the invention and correspondingly produced coatings. The aim of the invention is inter alia the reduction of the applied amount of coating composition per unit area. The applied caterpillars and webs of coating composition do not form a closed film (left). Only the pre-wetting leads by passing the single tracks to a movie (right). According to the invention, the surface to be protected is pre-wetted, which leads to its uniform flow in the subsequent application of the liquid film, namely at lower application pressures and thus also amounts of coating composition.

Figure 8 illustrates the peeling of a coating made according to the invention according to an embodiment of the invention, showing the step of peeling off a hood. A water-dilutable one-component coating composition based on a polyurethane dispersion for the preservation of surfaces such as e.g. Car bodies applied. The composition forms after drying (even at room temperature) a mechanically and chemically highly resistant protective layer (dried liquid film). This can be removed by hand (peel off), as it is only connected by relatively weak adhesion forces with the surface to be protected. The dried composition is typically removed from the surface by simply peeling it off immediately prior to delivery of the automobile, exposing the underlying topcoat.

Claims (44)

Apparatus for applying a liquid coating, for example a lacquer and / or a preferably peelable film, to a surface, comprising liquid dispensing means (3) capable of forming the liquid coating on the surface, the dispensing means and the surface can be moved relative to each other and wherein the output means, in particular by means of an air flow, the liquid (3) can apply to the surface, characterized in that the device (1) comprises means for generating a, in particular additional, air flow (5), the Fluid (3) between the output means and the surface can distract. Apparatus according to claim 1, characterized in that the air flow can direct the liquid (3) on the surface, in particular in the region in which the coating is applied. Device according to one of claims 1 or 2, characterized in that the device comprises collecting means for the liquid (3), wherein the air flow (5) can deflect the liquid (3) into the collecting means. Device according to one of claims 1 to 3, characterized in that the device comprises control means which can turn on and / or off the air flow (5) in a predetermined period of time, for example, shortly before, while, in particular, at, and / or shortly after the completion of the dispensing of the liquid (3), preferably about, more preferably exactly towards the end of the application process. Device according to one of claims 1 to 4, characterized in that the output means comprise at least one nozzle (2). Device according to one of claims 1 to 5, characterized in that the liquid coating is a protective coating, such as an underbody protection, or an adhesive. Device according to one of claims 1 to 5, characterized in that the liquid coating is a paint or a release agent. Apparatus for carrying out a method according to any one of claims 10-42. Device according to claim 8, comprising an application nozzle (2a), a robot which is adapted to move the application nozzle over a predetermined surface area to be protected in an application direction, to a supply device which supplies the application nozzle with the liquid coating composition under pressure the application nozzle distributes the coating composition transversely to the application direction over an application width, substantially perpendicular to the surface, the controller of the robot being adapted to apply by starting and stopping the supply of coating composition to the application nozzle in coordination with its movement in the direction of application to limit the predetermined surface area in the application direction, nozzle devices (10, 20) which are present in the application direction in front of and behind the application nozzle (2a) and by the robot control be operated so that when starting the application a gas flow distributed over the application width, in the application direction from the rear at an angle (c) on the spray jet of the application nozzle (2a) to direct, and when the application is terminated a gas flow over the application width, in the application direction from the front at an angle (b) on the spray jet Application nozzle to each to prevent overspraying of coating composition beyond the predetermined surface area addition. A process for applying a liquid coating to a surface, for example a paint and / or a preferably peelable film, in particular with a device according to one of claims 1 to 9, characterized by the following process steps: - Of the output means liquid (3) is applied to the surface to form there the liquid coating; - The delivery of the liquid (3) from the output means is terminated; - Short before, during, especially, exactly, and / or shortly after the completion of the delivery of the liquid (3), an air stream (5) is turned on to prevent residues of the liquid (3) go uncontrolled on the surface. A method, in particular according to claim 10, for producing a removable surface protection by applying a liquid, curable coating composition (liquid film) to painted surfaces, wherein the liquid Coating composition through an application nozzle, which is relatively moved over a predetermined surface area to be protected in an application direction and the liquid coating composition is supplied under pressure, distributed across the application width across the application width, is sprayed substantially perpendicular to the surface, the application by starting and terminating the supply of coating composition to the application nozzle in coordination with its relative movement in the application direction is limited to the predetermined surface area in the application direction, characterized in that nozzle devices (10, 20) in the application direction in front of and behind the application nozzle (2a) present and prepared are, when starting the application, a gas flow distributed over the application width, in the application direction from behind at an angle (c) on the spray jet of the application nozzle (2 a) to direct, and at the termination of the application, a gas flow distributed over the application width, in the application direction from the front at an angle (b) on the spray jet of the application nozzle (2a) to each overspray (overspraying) of coating composition over the given Surface area to counteract. A method according to claim 11, characterized in that the gas flow of the nozzle means is in each case at an angle (b, c) of 25 to 35 degrees with respect to the spray jet of the application nozzle is directed. Method according to one of the preceding claims 10-12, characterized in that the nozzle means (10, 20) are supplied with compressed air, so as to generate an air flow as a gas stream. A method according to claim 13, characterized in that the nozzle means (10, 20) are supplied with compressed air at an overpressure of 0.01 to 6 bar, preferably 2 bar to 4 bar. Method according to one of the preceding claims 10-14, characterized in that the nozzle devices (10, 20) are designed to generate a laminar gas flow in the intended pressure range, with which the nozzle devices are acted upon. Method according to one of the preceding claims 10-15, characterized in that the nozzle device (10, 20) used is an elongate tubular body which, in addition to a gas supply connection, has an elongate slot-shaped nozzle outlet opening (12, 22) extending in the longitudinal direction of the tubular body for dispensing the Gas stream has. Method according to one of claims 10 to 16, characterized in that as the nozzle device in each case an elongate tubular body is used, which in addition to a gas supply port, a plurality of rows arranged in the longitudinal direction of the tubular body having individual nozzles, which together output the gas flow. Method according to one of the preceding claims 10-17, at the a) the surface is treated with water or an aqueous solution of one or more surface-active substances before application of the coating composition, b) then the coating composition is applied to the treated surface by a method according to any one of the preceding claims before the water is completely dried from the treated surface, and c) the coating composition is cured to form a cured coating having a layer thickness of at most 200 pm. The method of claim 18, wherein the surface is treated with water in step a). The method of claim 18 or 19, wherein the water is condensed. The method of claim 18, wherein the water or the aqueous solution of surfactants is sprayed onto the surface. Method according to one of claims 10 to 21,
characterized in that the temperature of the surface at step a) is up to 50 ° C, for example 1 ° C to 50 ° C, preferably 5 ° C to 40 ° C, more preferably 10 ° C to 30 ° C, especially 15 ° C to 25 ° C is. Method according to one of claims 10 to 22,
characterized in that the surface is painted with topcoat surface of a motor vehicle is. Method according to one of claims 10 to 23, characterized in that step b) is carried out less than 25 minutes after step a), more preferably 0.1 seconds to 25 minutes, in particular 0.1 seconds to 15 minutes, such as 0.1 second to 10 minutes, or 1 second to 1 minute, for example 1 second to 45 seconds, or 1 second to 30 seconds after step a). A method according to claim 10 or 24, characterized in that the topcoat is selected from topcoats based on a one- or two-component polyurethane system or a melamine resin / polyol system, preferred polyols being polyester, polyacrylate or polycarbonate polyols. Method according to one of claims 10 to 25, characterized in that the coating composition is selected from water-dilutable coating materials based on, for example, polymer dispersions, in particular polyurethane dispersions and particularly preferably dispersions of polyesterurethanes. Method according to one of claims 10 to 26, characterized in that the coating composition from a multi-jet nozzle with 1 to 6 rows of 5 to 500 nozzles, more preferably 10 to 320 nozzles, in particular 20 to 160 nozzles, such as 40 to 80 nozzles applied , Method according to one of claims 10 to 27,
characterized in that the layer thickness of the cured coating is 40 to 170 μm, preferably 50 to 160 μm, more preferably 60 to 130 μm, in particular 70 to 120 μm, such as 80 to 110 μm or 90 to 100 μm. Method according to one of claims 10 to 28,
characterized in that the curing in step c) takes place at elevated temperature. Method, in particular according to one of Claims 10 to 29, for the production of a removable surface protection, in which a) the surface is treated with water or an aqueous solution of one or more surface-active substances, b) applying a (liquid, curable) coating composition to the treated surface before the water is completely dried from the treated surface, and c) the coating composition is cured to form a cured coating having a layer thickness of at most 200 μm. The method of claim 30, wherein the surface is treated with water in step a). The method of claim 31, wherein the water is condensed. The method of claim 30, wherein the water or aqueous solution is surface active Substances are sprayed onto the surface. Method according to one of the preceding claims 10-33, characterized in that the temperature of the surface at step a) to 50 ° C, for example 1 ° C to 50 ° C, preferably 5 ° C to 40 ° C, more preferably 10 ° C to 30 ° C, in particular 15 ° C to 25 ° C. Method according to one of the preceding claims 10-34, characterized in that the surface is a painted with topcoat surface of a motor vehicle. Method according to one of the preceding claims 10-35, characterized in that step b) is carried out less than 25 minutes after step a), more preferably 0.1 seconds to 25 minutes, in particular 0.1 seconds to 15 minutes, such as 0.1 Second to 10 minutes, or 1 second to 1 minute, for example 1 second to 45 seconds, or 1 second to 30 seconds after step a). A method according to claim 35 or 36, characterized in that the topcoat is selected from topcoats based on a one- or two-component polyurethane system or a melamine resin / polyol system, preferred polyols being polyester, polyacrylate or polycarbonate polyols. Method according to one of the preceding claims 10-37, characterized in that the coating composition is selected from water-dilutable coating materials based on, for example, polymer dispersions, in particular Polyurethane dispersions and particularly preferably dispersions of polyesterurethanes. Method according to one of the preceding claims 10-38, characterized in that the coating composition of a multi-jet nozzle with 1 to 6 rows of 5 to 500 nozzles, more preferably 10 to 320 nozzles, in particular 20 to 160 nozzles, such as 40 to 80 nozzles applied becomes. Method according to one of the preceding claims 10-39, characterized in that the layer thickness of the cured coating is 40 to 170 microns, preferably 50 to 160 microns, more preferably 60 to 130 microns, especially 70 to 120 microns, such as 80 to 110 microns or 90 up to 100 μm. Method according to one of the preceding claims 10-40, characterized in that the curing in step c) takes place at elevated temperature. Removable surface protection, for example lacquer and / or, preferably strippable, film produced according to a method of one of claims 10 to 41. Use of water or aqueous solutions of surfactants in a process for producing a removable surface protection, in particular in a process according to any one of claims 10-41, wherein the water or solution of surfactants is applied to the surface and then a coating composition is applied to the surface Surface is applied before the water is completely removed from the treated surface dried to reduce the necessary amount of coating composition, compared with a method without treatment with water or solution of surfactants. Use of water or aqueous solutions of surfactants in a process for producing a removable surface protection, in particular in a process according to any one of claims 10-41, wherein the water or solution of surfactants is applied to the surface and then a coating composition is applied to the surface Surface is applied before the water is completely dried from the treated surface, to avoid the unwanted coating of certain areas of the surface with the coating composition (overspray).

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