WO2010112511A1

WO2010112511A1 - Adhesion promoter for painting and printing

Info

Publication number: WO2010112511A1
Application number: PCT/EP2010/054217
Authority: WO
Inventors: Jens Fandrey; Klaus Becker-Weimann
Original assignee: Klebchemie M. G. Becker Gmbh & Co. Kg
Priority date: 2009-03-31
Filing date: 2010-03-30
Publication date: 2010-10-07
Also published as: DE102009002048A1

Abstract

The present invention relates to an object, the surface of which is at least partially painted or printed, and to methods for painting or printing the object, wherein an adhesion promoter layer containing a reactive melt mass is used.

Description

Adhesion promoter for coatings and prints

The present invention relates to an article whose surface is at least partially painted or printed and methods for its coating or printing.

In the most diverse fields of application, lacquers or prints are currently used on the surface of objects in large quantities, for example in the furniture and woodworking industry.

However, this often results in problems that are due to the chemical and / or physical nature of the article surface and the paint or ink.

Thus, the adhesion often has to be increased, which can be achieved by pretreatment of the article surface. Typically, special basecoats or primers are used for bonding, to which topcoats are then applied or these are printed.

The primer layer can also serve other purposes beyond. Thus, with the help of the primer layer, an undesirable interaction between paint or

Pressure and object surface are avoided. Especially with woody

Object surfaces can be avoided, for example, the so-called Anreibuerungseffekt, ie the enhancement of the natural color and structure of

Object surface. With regard to fueling, a contrary market trend can now be observed, since wood is an inhomogeneous one

Naturstoff acts and therefore on a given wooden surface the intensity of

Cheering effect can vary greatly and so to an uneven

Appearance leads. Accordingly, it is required of basecoats that they do not lead to any often uncontrolled Auffeuerungseffekt. - -

Furthermore, the primer layer can serve to level out unevenness on the article surface, thus achieving a more homogeneous appearance of the topcoat or the print.

Widely used (base) coating systems are UV-curing coatings, which are usually applied by roller application, more rarely by spray application to the parts. The subsequent curing process is carried out with UV light or UV lamps. The machine

Effort in the coating with UV coatings is very high and requires a very large

Space requirements. The large space requirement is also due to the fact that painting with

UV-curing systems usually require several jobs - in practice, three to four jobs are commonly required. Due to the viscosity, but especially due to the UV curing, only about 10 to 20 μm thick layers per application can be applied with each coating application, which is why several coating jobs are generally required.

Other (base) paint systems, such. B. 2-K PUR coatings, nitro paints or water-based paints must also be applied in several layers. Filler, primers and possibly intermediate cuts are also usually necessary here. In particular, in the case of waterborne or generally solventborne paints, any impairment of the surface by the solvent must as far as possible be avoided.

One advantage of paints, however, is that they dry relatively quickly and can then have a high resistance to moisture and cleaning agents.

Due to the required multi-layer application of the lacquer layers, methods have been sought which make the application of lacquer layers more efficient, in which adhesion promoter layers are used.

Suitable paints are described for example in DE-A 196 47 982. Multilayer coatings are described, for example, in DE-A 100 55 549.

An aqueous dispersion as adhesion promoter for a topcoat is described in DE-T 601 30 251.

But also multi-layer systems in which a layer is formed by a reactive melt, are known in the art. In WO-A 2006/066954, for example, such a layer is described in a multilayer system, wherein the melt mass should have a thickness of 20 to 150 microns. The hotmelt layer has the advantage that the desired layer thicknesses can be applied in one operation. In addition, the cured melt still provides sufficient flexibility to avoid the formation of Sprödrissen. Here, the melt-mass layer is used as a substitute for one or more lacquer layers, so that preferably a single lacquer layer is sufficient to obtain a desired coating. However, WO-A 2006/066954 does not describe the use of a reactive melt in the form of a thin adhesion promoter layer, which allows a conventional coating or printing of an object surface.

There is therefore a need for alternative methods and layer systems which avoid the abovementioned disadvantages or achieve requirements which are particularly effective.

The present invention is therefore based on the object to provide an improved method for painting or printing, in which the disadvantages described above are at least partially avoided.

The object is achieved by a method for painting or printing on at least part of the surface of an article containing the steps

(a) applying a primer layer containing a polyurethane-based reactive melt to at least a portion of the article surface;

(B) applying a lacquer layer or a print on the adhesion promoter layer, wherein the adhesion promoter layer has a thickness of less than 20 microns.

In fact, it has been found that, surprisingly, the positive properties which the use of lacquer or reactive enamel composition layers bring about for sealing can be retained if a reactive enamel composition is used merely as an adhesion promoter layer. Here, it is particularly surprising that the reactive melt can cure, although it is covered by the paint layer of the surrounding air, whose moisture is usually required for cross-linking and thus for curing, and although the thickness of the melt layer is very low. In particular, by the use of the reactive melt as a primer in addition to the increase in adhesion and a smooth article surface, resistance to water vapor, moisture and - -

Chemicals, insensitivity to mechanical stress, avoidance of impurities, cracks, tempering effects or color impairments possible or given.

A further aspect of the present invention is an article having a lacquer layer or printing on at least part of its surface containing a primer layer containing a polyurethane-based reactive melt on at least a portion of the article surface and a lacquer layer or a print on the primer layer, wherein the primer layer has a Thickness of less than 20 mm.

The polyurethane-based reactive melt is preferably a commercially available polyurethane-based reactive melt which normally reacts with the aid of the moisture present in the ambient air and hardens. Preferably, this reactive melt is free of water and solvent. Such reactive enamels represent hot-liquid components, solid hotmelt adhesives which are solid at room temperature and are known as such in the prior art. They are often called "hot melts" or "hotmelts". Reactive hotmelts are sold, for example, as PUR-SK series by the company Klebchemie M.G. Becker GmbH & Co. KG, Weingarten (Germany).

Preferably, the entire adhesion promoter layer consists of the melt.

The preferably water- and solvent-free reactive melt is usually applied to the surface to be coated at a temperature of at least 100 ⁰ C, about 100 ⁰ C to 150 ⁰ C, preferably 120 ⁰ C to 150 ⁰ C. Normally, about 5 to 20 g of reactive melt can be applied per square meter of surface to be coated. The reactive melt usually has a density of about 1.1 g / m ² and a viscosity according to BROOKFIELD at 120 ⁰ C in the range of about 1000 mPas to 30,000 mPas, preferably 4,000 mPas to 10,000 mPas. It is advantageous to apply the reactive melt under exclusion of air and shielding from atmospheric moisture to prevent premature Ausreagieren. The layer can, for example, be doctored, rolled, sprayed or applied by means of a nozzle or slot die. Similarly, a curtain coating or by fiber (thread application) is possible. Even when cured, the reactive melt layer still has some residual elasticity. Preferably, the reactive melt layer has a thickness in the range of 5 to 15 microns.

The application of the adhesion promoter layer does not have to take place over the entire surface, so that partial areas occur at which the layer is interrupted. This can occur, for example, when using gravure rollers. Nevertheless, the value of the mediator layer thickness should not be exceeded, at least on average. Preferably, the thickness is not exceeded over the entire surface to be painted or printed.

Since complete curing of the reactive melt layer is not required before the lacquer layer is applied to it, it is preferred if the lacquer layer or the pressure is applied before complete curing of the melt. This can be a huge time saver.

The lacquer used can be any lacquer which advantageously hardens quickly in order to allow the earliest possible further processing. When printing conventional dye and paint systems are used.

The coating or the printing can be done by conventional methods such as with the help of rollers, spraying, inkjet or digital printing.

By way of example, 2-component polyurethane paints, nitro paints or water-based paints may be mentioned. The paints can be present, for example, as clear, white or colored lacquer.

Preferably, however, UV-curing paints are used. This widespread coating system can be applied to the objects by roller application or spray application. The subsequent curing process is carried out with UV light or UV lamps. Due to the viscosity and UV curing, only approx. 10 to 20 μm thick layers can be applied with each coat of varnish, which is why several varnish jobs are usually necessary.

More preferably, the application of a printed image by means of digital printing process.

Although it is also possible in the context of the present invention to apply the lacquer layer in one layer. Preferably, however, this is applied in multiple layers. - -

In this case, the lacquer layer preferably has a thickness in the range from 5 .mu.m to 25 .mu.m, more preferably from 5 .mu.m to 10 .mu.m. For a multi-coat layer, this value typically multiplies. It is possible, for example, a single, two times, three times or four times application and to form the paint layer.

In particular, a smooth surface can be achieved in that after application to the (partial) surface of the article, the reactive enamel or the adhesion promoter layer is smoothed. This is not always mandatory. As a result, surface irregularities are avoided, which could result from the mere application of the hot reactive melt.

It is advantageous to once again apply heat to the surface of the primer layer between the application and the smoothing (if this is carried out), in order to further improve the result of the smoothing. Conveniently, the smoothing by means of a smoothing roll, for example a steel roller, or a smoothing belt, which may optionally be provided with a polyurethane coating.

It is particularly advantageous if the means for smoothing during wetting is wetted with a release agent. In this way it is effectively prevented that the not yet cured reactive melt breaks off on the object and sticks to the roller.

As a release agent, a solvent-free and low-viscosity paraffin wax-based agent can be used. By using such an agent, the surface of the reactive melt can become even smoother.

The release agent based on paraffin wax may be clear and, for example, have a density of about 0.85 g / cm ³ and a viscosity at 20 ⁰ C according to BROOKFIELD of about 34 mPas. A viscosity range between 30 and 500 mPas is also conceivable. The order amount may be, for example, about 20 to 35 g / m ² .

The release agent is applied to the means for smoothing, for example, by the spray method or vacuum spray method. The release agent can also be impregnated by means of a Felt be applied, which is a particularly simple and secure way to create a uniform, thin release agent during the smoothing of the reactive melt.

Preferably, the paint to be applied to the article is used as a release agent. As a result, the smoothing of the reactive enamel and the application of the lacquer layer can be done in a working gang, which shows, inter alia, the further advantage of a fast and inexpensive coating.

With the method according to the invention, a wide variety of object surfaces or at least parts thereof can be coated, these objects also being an aspect of the present invention.

In addition to element surfaces for floorboards or parquet floors so that, for example, the surfaces of furniture or furniture parts can be at least partially coated. It remains to emphasize, however, that in principle the surface of any object can be coated by the method according to the invention or each article can have a layer system according to the invention.

Preferably, the articles are elements for plank and parquet floors, to which particularly high demands are made with respect to a seal.

The surface of the article may consist of wood or a wood-like material, such as paper, cardboard, papier-mâché, veneers, wood-plastic composites (WPC), and may be made of plastic or ceramic, preferably of wood or plastic wood-like material, in particular of wood or a veneer.

Examples

A chipboard with 18 mm thickness and the dimensions 1.20 mx 2 m is coated with a hot melt adhesive from the company Klebchemie MG Becker GmbH & Co KG (VP 9383/190) by means of roller application (5 g / m ² ) and then on the one hand by digital printing printed with a water-based ink (Example 1) and on the other hand painted with a UV-curing acrylic paint by roller application (Example 2). The adhesion is checked by cross-hatching.

In both examples, an excellent adhesion results. In addition, the overall structure has a high water resistance.

Claims

claims

A method of painting or printing at least a portion of the surface of an article comprising the steps

(b) applying a paint layer or a print on the

Adhesive layer, wherein the adhesion promoter layer has a thickness of less than 20 microns.

2. The method according to claim 1, characterized in that the lacquer layer or the pressure is applied before the complete curing of the melt.

3. The method according to claim 1 or 2, characterized in that the paint is UV-curing.

4. The method according to any one of claims 1 to 3, characterized in that the lacquer layer has a thickness in the range of 5 microns to 25 microns.

5. The method according to any one of claims 1 to 4, characterized in that the object surface to be coated consists of wood, a wood-like material, plastic or ceramic.

6. The method according to any one of claims 1 to 5, characterized in that the

Subject of a parquet or wooden floor element, a piece of furniture or furniture is.

7. An article having a lacquer layer or printing on at least a portion of its surface containing a primer layer containing a polyurethane-based reactive melt on at least a portion of the article surface and a lacquer layer or print on the primer layer, wherein the primer layer has a thickness of less than 20 mm having.

8. An article according to claim 7, characterized in that the lacquer is UV-curing.

9. Article according to one of claims 7 to 8, characterized in that the

Paint layer has a thickness in the range of 5 microns to 25 microns

10. An article according to any one of claims 7 to 9, characterized in that the article Oberfiäche to be sealed consists of wood, a wood-like material, plastic or ceramic.

11. The article according to one of claims 7 to 10, characterized in that it is a parquet or plank floor element, furniture or furniture part.