WO2020144042A1

WO2020144042A1 - Roller application of coatings to wood surfaces

Info

Publication number: WO2020144042A1
Application number: PCT/EP2019/086364
Authority: WO
Inventors: Dirk Conrad; Marcel DÜLGE; Tim LOHRSTRÄTER; Didier NOREILLIE; Stefan Rose; Pawel Salamonowicz
Original assignee: Hesse Gmbh & Co. Kg
Priority date: 2019-01-08
Filing date: 2019-12-19
Publication date: 2020-07-16
Also published as: EP3680028B1; EP3680028A1; PL3680028T3

Abstract

The invention relates to a method for coating substrates that have open pores and/or substrates that have a structured surface.

Description

Roller application of paints on wooden surfaces

The present invention relates to a method for applying paints to wooden surfaces with rollers.

State of the art

Varnish can be applied to wooden surfaces (solid wood, veneered wood materials) using different methods. Both spraying, casting and rolling processes are known, particularly in the field of coating application on an industrial scale. Spraying methods are used most frequently, since all shapes and colors can be processed. Disadvantages such as high paint losses etc. are accepted. In the case of casting processes, essentially flat and less shaped substrates pass through a paint curtain in order to ensure a uniform application of paint. This process is used, for example, to achieve high-quality, smooth topcoat applications, for example in the industrial manufacture of doors and furniture fronts. Roller application processes are used in the coating of flat substrates. The paint is typically applied to the substrate using a rotating rubber roller (applicator roller). The dosing takes place with the aid of a dosing roller and / or by adjusting the contact pressure of the rubber roller or the gap width between the dosing and application roller. The coating application can be carried out in the same or opposite direction in the case of roller application processes. Both systems can also be used in combination. In a first parallel roller application step, the lacquer is applied to the substrate, so that in particular wood pores and veneer joints are filled. In the subsequent counter-rotating roller application step, the applied lacquer layer is optimally smoothed, so that high-quality, structure-free, smooth surfaces are obtained.

Today, wooden surfaces should look like untreated wood, but they should have the durability and quality of lacquered or plastic surfaces. This can only be achieved if the lacquers used have a high degree of mattness and completely and completely enclose the wood surface. When coating open-pore wood (especially brushed oak), coating the deep pores is problematic. Either the depth of the pore is not wetted and thus unprotected even after painting, or the pore is completely filled with paint and the wood surface no longer reveals any pore structure. The same applies to structured surfaces where conventional surfaces are used Paint application can either result in partial areas not being covered or only insufficiently covered with paint, or that the structuring of the surface is lost due to an excessive application of paint.

Aim of the invention

The object of the present invention is therefore to provide a method for coating substrates, in particular wood or wood materials, with open pores and / or structuring, in which the pore structure or the structuring remains optically visible even after coating, although the pores are sealed with a closed lacquer film and protected against the ingress of moisture or dirt or all areas of the structured surface are sealed with a closed lacquer film. In particular, the present invention relates to the coating of substrates with open pores, whereby the pores are filled with lacquer in such a way that they meet the requirements for a lacquered wooden surface (for example DIN EN 68861-1 furniture surfaces, behavior in the event of chemical stress), but nevertheless optically open pore structure remains visible.

Brief description of the invention

This object is achieved by the method according to claim 1. Preferred embodiments can be found in subclaims 2 to 15 and in the description below. Brief description of the figures

Figures 1 a) and 1 b) schematically show partial areas of a paint application device, suitable for performing the method according to the invention.

Detailed description of the invention

The invention provides a method for coating substrates (wood or wood materials) as defined in claim 1. Preferred configurations are specified in the subclaims and the description below. Possible applications are the coating of plate-shaped materials with a structured or pore-containing surface, such as parquet, veneered chipboard or fiber board (MDF or HDF board). The wood material of the surface to be coated is preferably oak or ash. The The method according to the invention is particularly suitable for coating oak parquet and oak veneers.

A possible embodiment of the method for coating substrates with open pores and / or substrates with a structured surface can be the following

Process steps include: a) providing a substrate with open pores and / or a structured surface, b) applying a sealing layer, preferably by means of rollers A and / or B (as in a spatula or reversing machine) or b1) by only one roller A, this roller A particularly preferably has a Shore A hardness of 80 or less, or b2) by a combination of roller A with a Shore A hardness of 80 or less and then one

Combination of roller A and roller B, c) partial removal of the sealing layer from the pores and / or from the structured surface by means of at least one roller C, and d) treatment of the sealing layer with a brush roller.

In various embodiments, this method can include the following method steps: a) providing a substrate, in particular in the form of a carrier plate made of wood or wood-based material, with open pores and / or a structured surface. With a

Coating device for applying lacquer, as shown schematically in FIG. 1 a), a sealing layer can be applied to such a substrate. The term “sealing layer” denotes, for example, a lacquer layer that completely protects the substrate, for example against the influence of water. A formulation of a suitable composition is usually applied, which after an additional treatment, such as curing, gives the final sealing layer. b) Application of a sealing layer, for example a UV-curing lacquer, by means of at least and preferably exactly one roller A. For this purpose, for example, as schematically shown in FIG. 1 a), the substrate is brought into contact with the application roller A in a transport direction. The metering of the material for the sealing layer can be carried out by the metering roller also shown in FIG. 1 a) (roller D in the figure to the left of roller A). This roller A can be designed as specified in the claims, ie in accordance with one of the variants b), b1) and b2). c) The sealing layer is preferably distributed by means of a roller B, as a result of which, in particular, the wetting of the wood pore down to the depth can be improved by excess sealing material. In Figure 1 a) this trowel roller B is shown to the right of the application roller. As shown schematically, this roller is preferably provided in the immediate vicinity of roller A. As an alternative or in addition, this roller can already serve to remove part of the applied material of the sealing layer. A combination of application roller, roller A and B, is also known as a spatula machine. A reversing machine can also be used at this point. d) Partial removal of the sealing layer from the pores by means of a roller C, as a result of which the pore structure of the wood becomes visible again. This roller, shown in Figure 1 b), is preferably designed as a smooth roller. Here, too, a metering roller can preferably be provided in combination with roller C, the application quantity of the material for the sealing layer being particularly preferably set such that only a minimal application is carried out, so that in total material is removed. In Figure 1 b), the direction of transport of the substrate is indicated by the arrow. e) treatment of the sealing layer with a brush roller. This treatment can be carried out in all variants b) and / or b1) and / or b2) of the process according to claim 1. However, this is not absolutely necessary. This additional treatment leads to an equalization of the sealing layer by a further distribution of the material of the sealing layer on the surface, so that smaller unevenness is leveled out. As a result, the image of the pore structure in particular becomes particularly uniform. The brush roller is generally any roller with a highly structured surface and preferably material sections protruding from the surface. Brushes are particularly preferably arranged on the surface of the brush roller, and very particularly preferably the surface of the brush roller is formed exclusively from brushes. A preferred brush roller is formed from a natural fiber material, in particular from sisal or as a sisal brush, and / or from a plastic material. f) curing the sealing layer, for example with UV light.

Surprisingly, it has been shown that by using an additional roller C, part of the amount of lacquer that has penetrated into the pores can be removed again easily before curing, without the sealing of the pores as such being impaired, so that the desired open-pore structure is obtained. After the sealing layer has hardened, the pore is wetted in depth and thus coated with a waterproof coating, but the pore structure is still visible and corresponds optically to a natural wood surface. The above-mentioned object is therefore achieved by using an additional roller in the coating process. This roller removes excess lacquer from the wood pore after it has been completely filled with lacquer. According to the invention, one roller C or more, that is to say 2 or more, can be used.

The amounts of material to be applied for the sealing layer depend on the viscosity of the lacquer, the feed speed of the rollers and / or the absorbency or porosity of the substrate. It is essential to use the roller C in order to remove material for the sealing layer which has penetrated into the pores before the hardening, in order to make the structure / open porosity visible without adversely affecting the sealing. In the context of the investigations leading to the present invention, it has been shown in this connection that the use of roller C is of particular importance (and not the amount of application that ultimately remains), since, for example, comparative investigations only with roller A and / or with roller A and B ( with the same remaining application quantity) does not show the effect according to the invention.

Suitable materials for providing a roller A with a Shore A hardness of less than 80, preferably less than 20, particularly preferably less than 10 are, for example, elastomers or thermoplastics, optionally adapted through the use of suitable additives, such as plasticizers, these preferably being applied Material for the sealing layer must not interfere, so as to result in a sufficiently soft surface.

The following embodiments can be used in particular for the individual process steps mentioned above or in the claims (in each case individually or in combination): a) The substrate provided is preferably made of oak or a wood material with a wooden surface made of oak, in particular veneer. Alternatively, it can also be ash or a surface made of ash, in particular veneer. Before the lacquer application, however, this can also preferably be subjected to any other surface treatment described here, such as a grinding treatment, for example raw wood sanding, in particular with a grain size of 120, 150 and / or 180. The surface to be coated can also be coated with an adhesive primer or a Be treated beforehand. b) The application of a sealing layer, in particular a UV-curing lacquer, preferably with a typical lacquer application quantity of 10-200 g / m ² , particularly preferably 60 to 120 g / m ² , can be carried out using a spatula (applicator roller A and spatula roller B) or using a procedure similar to that of a reverse machine. This application of material is also referred to here as the application of a material for the sealing layer. As a result, the surface is coated with a lot of excess material (lacquer), so that the pore is sealed. In particular, the second roller B ensures that a sufficient amount of the lacquer penetrates into the pores. In one embodiment, this second roller only serves to ensure the penetration of the material for the sealing layer into the pores of the substrate. However, this treatment is preferably carried out in such a way that at the same time a certain amount of the applied lacquer is removed again. In this preferred embodiment, about 10% to 40%, preferably 15% to 25%, of the coating amount applied by roller A is removed again. This ensures sufficient wetting of the pores, but at the same time ensures the desired lively structure of the coated substrate. Such a removal of part of the applied amount of lacquer can be carried out by a spatula roller, which is also particularly suitable for achieving the penetration of the material for the sealing layer into the pores. The spatula roller is particularly preferably designed with suitable further devices in order to absorb the removed amount of lacquer or the removed material for the sealing layer and in particular to prevent it from coming into contact with the substrate again. c) In a preferred process variant with a soft roller A with a Shore A hardness of 80 or less, the amount of material to be applied for the sealing layer is as described above under b). This also applies to variant b2) according to the invention, in which the total application quantity is applied by the different rollers A and, if appropriate, also roller B. d) The further, ie in addition to removal by roller B, partial removal of the sealing layer from the pores is preferably carried out by means of at least one roller, in particular a smooth roller C. This is typically set such that it uses the same material, for example a UV-curing lacquer, how the application roller applies, but is set to the smallest or smallest possible application quantity. This effectively removes excess material from the pores and the pore Structure of the wood visible again. In a preferred embodiment, if a first amount of the material for the sealing layer has already been removed again by roller B, about 5% to 30% of the original application amount is preferably by means of roller C, in particular by roller A and particularly preferably 10% to 20 % away. If no material has been removed by roller B, the amount of material to be removed by roller C can also be higher. Suitable percentage values for this material removal are preferably 15% to 70% and particularly preferably 25% to 45%. In general, it is preferred that either 15% to 70% and particularly preferably 25% to 45% of the originally applied amount of material for the sealing layer is removed again by roller C alone or by rollers B and C together. Alternatively, a second roller C can also be provided, it being possible for the amounts of material to be removed by the rollers C to be the same or different. If, for example, 2 rolls C are used, these are preferably set such that the percentage values for the material removal are cumulated as described above. The rollers C can be adjusted so that the same amounts are removed by both and in particular by all the rollers C. However, it is also possible for different amounts to be removed. It is preferred if the first roller C removes more material than the second and / or each additional roller C. e) In addition to the sealing layer, further layers can also be applied, such as topcoat layers, effect lacquer layers, etc. These are preferred after complete curing applied to the sealing layer. f) Both the sealing layer and the optional further layers can be subjected to additional treatments. An example of this is a matting treatment, which is preferably carried out before the layer has fully hardened. This is preferably carried out using a 172 nm excimer laser. This has the advantage that matting, which is based on the microstructuring of the surface of the treated layer, takes place without the use of matting additives. Such a matting treatment is suitable for materials, for example for the sealing layer, which are reactive towards the laser, for example acrylates, which show a crosslinking reaction with such a treatment. Matting with an excimer laser also has the advantage that this step can be combined well with curing by UV radiation etc. Such matting also results in very reproducible, identical surface properties. The matted surfaces obtained are often particularly pleasant with regard to their Haptic, advantageous with regard to anti-fingerprint properties and very good matting effect can be set with very low gloss levels. g) The sealing layer is cured in a conventional manner, e.g. B. with UV light and preferably by means of a mercury lamp, especially with 80-

120 W / cm when using a UV-curable lacquer. Lacquers of this type and thus curing with UV light are preferred, since a hard-wearing, solid lacquer film can be obtained very quickly. Curing can vary when using other types of lacquer; for example, thermally curing lacquers can be cured by means of IR radiation.

Particularly preferred configurations of the method are as follows:

(1) Application with a roller A with a Shore A hardness of 80 or less and use of a roller B. (2) Application with two rollers A and B and use of a brush roller.

(3) Like (1) with a brush roller insert.

(4) Like (1), (2) or (3), but with a matting treatment for the sealing layer with a 172 nm excimer laser.

(5) Like (1), (2), (3) or (4), in addition with the application of at least one further layer to the sealing layer.

example

An adhesive primer (eg Hesse HUW 8831) with a coating quantity of 10-15 g / m ^{2 is} applied to oak parquet (finished, sanded 180, dedusted), then it is completely dried. A roller A applies a UV lacquer (for example Hesse UG 7328) at an application rate of 50 g / m ² . Using a spatula roller B removes 10-15 g, but at the same time ensures a good penetration depth of the applied lacquer into the pores, so that an application amount of 35-40 g / m ² remains, which made the pore structure partially visible, but not yet a sufficient degree. A further 5-10 g / m ^{2 are} removed by using a smooth roller C, so that a coating amount of 30 g / m ² remains. The layer is then treated with a sisal roller. The pore structure is then particularly clearly visible. This is followed by curing by UV radiation (3 Hg emitters with 80 W / cm) at 18 m / min feed. Doing so will be a high quality Obtain paint coating with the pores sealed but the pore structure visible as desired. A comparative example with a paint application of 30 g / m ² in a process without the use of a smooth roller (same amount of coating) showed an inadequate and uneven paint coating. A reliable sealing of the pores could not be achieved and the open-pore structure was not evenly visible as desired. In particular, a completely smooth lacquer film was obtained in some cases, which left no pore structure visible.

The sealed parquet was evaluated with regard to the sealing of the pores to ensure that the parquet treated in this way not only leaves the pore structure visible, but also enables a reliable and complete sealing.

The test results showed no staining of the pore by methylene blue solution and no discoloration (wetting) of the wood after the water test, e.g. for 16 h. This proves reliable and complete sealing down to the depths of the pores.

Claims

Expectations

1. Method for coating substrates with open pores and / or substrates with a structured surface, with the following method steps:

a) providing a substrate with open pores and / or a structured surface,

b) applying a material for a sealing layer by means of at least one first roller A,

c) distributing the applied material of the sealing layer and / or removing a part of the applied material of the sealing layer by means of a second roller B, and subsequently

d) partial removal of the applied amount of the material of the

Sealing layer from the pores and / or from the structured surface by means of at least one further roller C, and

e) treating the applied material of the sealing layer with a

Brush roller.

2. The method according to claim 1, further comprising curing and / or drying the sealing layer and / or applying further layers to the

Sealing layer.

3. The method according to any one of claims 1 or 2, wherein the amount of material for the sealing layer by means of a metering roller and / or by the

Displacement speed of the substrate in the area of the roller A is controlled.

4. The method according to at least one of the preceding claims, wherein the

Sealing layer is formed from a UV-curing lacquer.

5. The method according to at least one of the preceding claims, wherein a roller A is used to apply the sealing layer, said roller A having a Shore A surface hardness of 80 or less.

6. The method according to at least one of the preceding claims, wherein roller C is a smooth roller and / or wherein two rollers C are used.

7. The method according to at least one of the preceding claims, wherein the substrate is selected from parquet, veneered chipboard, fiberboard, MDF or HDF boards and / or wherein the substrate has a surface made of oak or ash wood.

8. The method according to at least one of the preceding claims, wherein the

applied amount of the material of the sealing layer is from 10 to 200 g / m ² .

9. The method according to at least one of the preceding claims, wherein the

applied amount of the material of the sealing layer is from 60 to 120 g / m ² .

10. The method according to at least one of the preceding claims, wherein the substrate is subjected to a pretreatment before being selected, selected from primer application and / or pickling application and / or primer and / or grinding treatment.

11. The method according to at least one of the preceding claims, wherein by the roller B already 10% to 40% of the applied amount of the material for the

Sealing layer can be removed again.

12. The method according to at least one of the preceding claims, wherein by the

at least one roller C of 5% to 30% of the applied amount of the material for the sealing layer is removed again.

13. The method according to at least one of the preceding claims, wherein by means of

Roller B wooden pores of the substrate are completely filled with material of the sealing layer and subsequently the excess material of the sealing layer is removed from the wooden pore by means of roller C in order to make the pore structure of the wood visible again.

14. The method according to at least one of the preceding claims, wherein the

Brush roller is a sisal brush.

15. The method according to at least one of the preceding claims, further comprising treating the sealing layer and / or further layers, in particular topcoat layers, with an excimer laser, preferably a 172 nm excimer laser.