Water-Vapor Assisted Lacquering Method

Abstract

The invention relates to a method or a system for coating substrates with at least one coating material which comprises at least one organic component, wherein the coating material is applied to the substrate by means of atomization and spray-painting. The invention is characterized in that the coating material is atomized by means of water vapor.

Description

BRIEF DESCRIPTION OF DRAWINGS

Further advantages, characteristics and features of the present invention are apparent from the following detailed description of an embodiment using the enclosed drawings. The purely schematic drawings show in

FIG. 1 a) and b) are schematic diagrams of nozzle arrangements with internal mixing (a) and external mixing (b) of the coating material with the water vapor used as auxiliary gas for application;

FIG. 2 is a schematic diagram of a system for coating substrates in accordance with the present invention;

FIG. 3 is a schematic diagram of the water-vapor feed line in the spray gun; and

FIG. 4 is a schematic diagram of a second embodiment of the water-vapor feed line in the spray gun.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows in two schematic diagrams two different nozzle arrangements 1, which, for example, can be realized in a spray gun in order that the method of the invention may be performed.

In the nozzle arrangement 1 of sub-diagram a), the nozzle arrangement has an inner nozzle 2 and an outer nozzle 3, with the nozzle opening 4 of the inner nozzle 2 arranged inside the outer nozzle arrangement 3 directly in front of the nozzle opening 5 of the outer nozzle arrangement 3. In this way, the coating material transported in the internal nozzle arrangement 2 is mixed with the water vapor transported in the outer nozzle arrangement 3 prior to finally leaving the nozzle arrangement 1 through the nozzle opening 5 of the outer nozzle arrangement 3 (internal mixing).

As opposed to this, in the nozzle arrangement 1 of sub-diagram b), in which the nozzle opening 4 of the inner nozzle arrangement 2 is arranged at the same level as the nozzle opening 5 of the outer nozzle arrangement 3, mixing of the coating material located in the inner nozzle arrangement 2 with the water vapor, which has left the outer nozzle arrangement 3 through the nozzle opening 5, occurs only after said coating material has left nozzle arrangement 1 (external mixing).

These two types of spray coating of the coating material with the aid of water vapor can be used for the present invention.

FIG. 2 is a purely schematic drawing of a system for coating substrates in accordance with the present invention, wherein a nozzle arrangement 1 is connected in accordance with the nozzle arrangements of FIG. 1 via a first feed line 6 to a first supply device 8 for providing and feeding the coating material to the nozzle arrangement 1, with the coating material being conveyed in the feed line 6 by a pump 10.

The nozzle arrangement 1 is further connected via a second feed line 7 to a second supply device 9 which comprises a water-vapor generator, by means of which the water vapor required for the invention can be generated and conveyed to the spray gun 1.

As part of the second supply device 9 or, as shown in FIG. 2, as a separate device, a pressure-increasing or compression device, such as a pump 11, may be provided in the second line 7 to bring the water vapor to the corresponding operating pressure range of 0.5 to 10 bar or 1 to 2 or 4 to 8 bar.

In the same way, it goes without saying that the corresponding pressure-increasing or compression device or pump 10 may also be integrated in the first supply device for the coating material or be provided separately in the first supply line 6 (as illustrated).

It goes without saying that the pump 10 in the supply line 6 for the coating material can also be dispensed with if the suction of the water vapor ensures adequate transport of the coating material.

FIGS. 3 and 4 schematically show the preferred embodiments of the nozzle arrangement 1 and the water-vapor feed line 7.

In accordance with FIG. 3, the cross section of the feed line is reduced in the vicinity of the delivery opening or nozzle opening 5 such that the pressure directly in front of the nozzle opening 5 increases, so that even the tiniest quantities of water droplets, which may have precipitated out of the water vapor, are vaporized again and thus almost pure water vapor is available for application of the coating material. In the embodiment shown in FIG. 3, this is achieved by a conical region 13 in the feed line 7, said conical region reducing the first cross section of the line 7 in region 12 to a second cross section in region 14.

FIG. 4 shows a further possibility for counteracting the formation of water droplets in the water vapor. For this purpose, an additional heating device 15 is provided directly in front of or at the nozzle opening 5, by means of which said device the water vapor can be correspondingly heated and superheated such that all of the water is present in water vapor form. All known devices, such as electrical resistance heaters with windings around line 7 or cartridge heaters with exothermic materials or fuels for use in a cavity of the spray gun, can serve as the heating device 15.

Claims

1-10. (canceled)

11. Method for coating substrates with at least one coating material comprising providing at least one organic component and applying the coating material to the substrate by atomization and spraying, wherein the coating material is atomized by water vapor.

12. Method in accordance with claim 11, wherein the coating material is a water-based paint or an essentially solvent-free hot melt paint.

13. Method in accordance with claim 11, wherein the coating material is applied as primer, top coat, filler or clearcoat.

14. Method in accordance with claim 11, wherein the coating material, by flowing through a nozzle arrangement, is atomized with the water vapor acting as auxiliary gas and is sprayed onto the substrate.

15. Method in accordance with claim 11, wherein the water vapor flows out of a nozzle arrangement, with or adjacent to the coating material, with the water vapor of the nozzle arrangement being fed at a pressure of 0.5 to 10 bar.

16. Method in accordance with claim 11, wherein metals, plastics or wood materials are used as the substrate.

17. A system for coating substrates in accordance with claim 11, with at least one nozzle arrangement for atomizing and spraying the coating material onto the substrate and including at least a first supply device for providing and feeding the coating material to the nozzle arrangement and at least a second supply device for preparing and feeding an auxiliary gas to the nozzle arrangement for atomizing the coating material, wherein the second supply device comprises a water-vapor generator.

18. System in accordance with claim 17, wherein the second supply device and/or a feed line to the nozzle arrangement comprises a pressure-increasing or compression device, with which the water vapor can be brought to operating pressure in the range of 0.5 to 10 bar.

19. System in accordance with claim 7, wherein the spray gun has a heating device and/or a pressure-increasing device for converting nearly all of the water into the vapor phase.

20. System in accordance with claim 17, wherein the pressure-increasing device is formed by a reduction in cross section of a feed line.