DESCRIPTION Field of the Invention

The present invention relates to the field of coating or decorating wood- derived composite products, especially MDF panels.

More specifically, the present invention relates to a primer that can be applied to a product made of wood-derived composite material, such as an engineered wood panel, which allows such a product to be coated or decorated by powder paint thus achieving a quality result.

The present invention also relates to a method and machine for coating such a product.

Background Art Products, especially in the form of panels made of wood-derived composite material, that is, panels made by joining wood-derived chips, particles, fibers or flours through an appropriate adhesive compound, are often used in the construction field.

These panels are also known as engineered wood panels precisely because they are the result of a process consisting of gluing together wood particles to form a composite material.

Some of the best-known engineered wood panels include the MDF ( medium-density fiberboard) panels, the LDF ( low-density fiberboard) panels and the FIDF {high-density fiberboard) panels. These panels differ in the density of the material they are made of. For example, LDF panels have a density of about 550-650 Kg/m ³ , MDF panels have a density of about 650-800 Kg/m ³ and HDF panels have a density of about 800- 1050 Kg/m ³ .

Compared with non-engineered wood panels, that is, solid wood, the engineered wood panels have many advantages. For example, they can be made with the specific characteristics required by the customer depending on the particular panel application, and are easier, faster and cheaper to make than non-engineered wood panels.

In particular, the MDF panels are used to make home or workplace furniture, that is, to make shelving, furniture, doors, tables or to cover walls, precisely because they can be made so to have a structure as uniform as possible, with an adequate thermal and acoustic insulation and significant impact resistance. Furthermore, the engineered wood panels are recyclable and environmentally friendly. In general, however, the engineered wood panels have the disadvantage of being aesthetically unappealing because they have a brownish color and surfaces with uneven textures, due to the wood-derived composite material they are made of. For similar reasons, such panels are also unattractive to the touch (a not insignificant aspect precisely because of their use in the home or work environment).

Therefore, after being made, the engineered wood panels are often coated or decorated to cover the coloring and irregularities of the surface.

For example, the engineered wood panels are in most cases coated or decorated by liquid coating or lamination, consisting in gluing a decorated laminated article on the panel.

Flowever, these coating methods of the engineered wood panels have drawbacks.

In particular, the liquid coating is not very environmentally friendly because it is associated with a high release of VOCs ( Volatile Organic Compounds) as the paint evaporates. This is because liquid paints are made of up to 70% of organic solvents.

Furthermore, the use of liquid paints does not allow the reuse of the paint fraction which does not remain adhered to the panel during the application step. In practice, about 50% of the liquid paint used does not adhere to the panel and cannot be reused (or however, if it can be reused this is not done easily, cheaply and quickly).

The same disposal of the paint is not very environmentally friendly, because it involves emulsifying the liquid paint in water and decanting the emulsion into appropriate basins. Overall, therefore, in addition to being not very environmentally friendly, the use of the liquid paint is also uneconomical.

This aspect is also related to the need, given the high production of VOCs, to carry out liquid coating at environments equipped with special air extraction systems, specially trained technical personnel and precise fire prevention protocols. The coating method with liquid paint further provides several cycles of paint application and hand sanding. These cycles make this coating or decorating method expensive and inefficient.

Finally, the liquid coating does not allow panels to be coated with a homogeneous layer of paint, nor does it allow elaborate, good-quality decorations to be made easily, simply and quickly.

In particular, at the edges, an appropriate application of liquid paint with an associated edging operation must be carried out. In other words, the liquid coating does not allow a panel, including the edges, to be coated in a single application but involves multiple applications to separate portions of the panel. Regarding the lamination, however, it should be noted that such method may not give satisfactory results because, over time, the decorative layer may peel off the product, especially at the edges.

In the light of the above, it is therefore clear that there are no products and methods to date to coat, or decorate, a panel made of wood-derived composite material in a simple, fast, effective, economical and environmentally friendly way.

In an attempt to solve the limitation of the solutions mentioned above, various attempts have been made to coat panels made of wood-derived composite material by using alternative methods, such as for example, using the powder paint. For example, US 6,296,939 describes a water-based primer applicable to products made of materials that are heat sensitive, such as wood-derived composite materials. Such a primer is electrostatically conductive and is applied to the product prior to the powder paint. The primer comprises, in addition to other components, titanium oxide at

28% by weight. In order not to reach too high temperatures during the primer solidification, US 6,296,939 teaches to use a matrix that is solidified by ultraviolet radiation (column 8, rows 18-20).

US 2009/0297818 describes a water-based primer comprising a thermoplastic acrylic polymer and titanium oxide from 0.1 % to 20% by weight.

Such a primer is intended to be applied to a thin-layer lignocellulosic composite material comprising isocyanate-based resins. Such a primer allows to cover the resin spots that result from the coagulation of the resin inside the material (paragraph 18). CN 102492342 describes a white water-based primer for MDF panels.

Such a primer is made white by the addition of titanium oxide (paragraph 15).

The Applicant found that primers made according to the known art do not allow a quality powder paint coating to be achieved due to the excessive heating the panels undergo during the subsequent polymerization step of the powder paint, or, during the various steps of panel processing.

In fact, for example, the polymerization step generally provides for heating the panel to a temperature of at least 130°C for about three minutes in an air oven.

For example, in US 6,296,939, the polymerization of the paint is achieved by heating the panel, during the sintering step, in a hot air oven at 160°C for 2-3 minutes and, subsequently, during the hardening step, at 140°C for 30 minutes or by UV light at 120°.

It is known that due to the heat to which the panel is subjected, there is overheating of the material the panel itself is made of. Such overheating occurs mainly through two mechanisms. A first mechanism is that directly related to radiation used to polymerize the powder paint. In essence, the radiation, once it impacts the panel surface on which the powder paint has been deposited, penetrates inside the panel itself causing it to overheat. Such mechanism can be identified as "radiation overheating".

The second mechanism is related to the first one and consists in overheating the panel interior due to thermal conduction phenomena between the panel surface heated directly by radiation, and the panel interior. Such mechanism can be identified as "conduction overheating". In general, overheating associated with the polymerization step of powder paint causes the water and other volatiles contained in the panel to evaporate. As they evaporate, the water and other substances exert pressure on the outside of the panel and cause cracks in the panel and/or layer of powder paint. Such cracks impair the very quality of the powder paint coating and force the panel to be discarded or the process to be repeated.

Therefore, the need emerges to identify a solution that allows a panel made of wood-derived composite material to be powder paint coated thereby achieving a quality result, minimizing or eliminating the formation of cracks due to internal overheating of the panel. Summary of the invention

Object of the present invention is to provide a primer that allows a panel made of wood-derived composite material to be coated, or decorated, in a simple, fast, effective, inexpensive and environmentally friendly way thus achieving a quality coating, or decoration. Also object of the present invention is to provide a primer that allows the limitations of the known art to be overcome, that is, that allows to powder paint coat a wood-derived composite product while avoiding, or minimizing, the formation of fissures o cracks in the panel or coating layer.

Further object of the present invention is to provide a primer that allows to limit the overheating of the wood-derived composite product, that is, which limits the overheating by radiation and conduction.

For the purposes of this invention, a wood-derived composite product means any product made of engineered wood, that is, made by gluing together wooden sheets or particles to form a composite material. In particular, a wood-derived composite product may mean a composite product made of wood fibers ( fiberboard/fibreboard ), such as an MDF ( medium- density fiberboard) panel, or an LDF ( low-density fiberboard) panel, or an FIDF ( high-density fiberboard) panel, or a particleboard, or an OSB ( Oriented Strand Board) panel, or a plywood product. For the purposes of the present invention, it is not necessary for the product to have particular shape or size; in fact, the product can be flat, curved, corrugated, or can be made as a panel or beam.

Therefore, in its first aspect, the present invention relates to a primer according to claim 1. In particular, claim 1 is addressed to a primer applicable to a wood- derived composite product comprising a resin matrix, a matrix solvent and a mixture of titanium oxide and aluminum oxide.

The titanium oxide and aluminum oxide are dispersed in the primer itself.

The primer first of all allows a product made of wood or its derivatives, hereinafter denoted only as "product," to be powder paint coated.

In fact, the mixture of titanium oxide and aluminum oxide firstly has the function of creating an electrostatically charged layer on the surface of the product and allowing the powder paint to adhere; secondly, advantageously, the mixture of titanium oxide and aluminum oxide allows for the reduction of the overheating of the product during the polymerization process of the paint because it allows the overheating by radiation and conduction to be reduced.

In practice, by limiting the overheating of the product, the primer allows to limit the evaporation of the water or other substances inside the product, or the migration of the moisture towards the panel surface. This way it is less likely that cracks will be created in the product or paint layer, and the quality of the coating process is assured.

From the analysis of the comparative data described below with reference to Table 1 and Table 2, it is possible to see that the primer according to the present invention, if compared to a primer exclusively comprising titanium oxide (such as that described in the known art), does indeed allow the internal overheating of the product to be limited. These data will be more pointedly commented on below.

In essence, the primer described herein allows to overcome the limitations found in the known art that until now prevented satisfactory, quality results from being achieved in the coating of products made of wood-derived composite material.

This way, it is possible to coat or decorate such products by achieving the advantages given by the powder paint coating listed below.

First of all, the powder paint coating offers advantages from the point of view of the environmental sustainability because it allows the use of solvents and VOC emissions to be eliminated, compared to the liquid coating. Furthermore, the use of the powder paint coating is not associated with disposal problems because, unlike the liquid paint, the powder paint does not have to be emulsified in water for disposal.

Furthermore, the powder paint coating does not require intermediate sanding, that is, multiple applications and one sanding performed by hand between one application and the next.

This aspect is particularly advantageous because it allows to reduce the panel handling, to be able to reserve a smaller space of the processing site for the product coating (no need to set aside a special area for sanding), and to preserve the health of workers because, in the absence of sanding, there is no fine dust that could be inhaled by them.

Furthermore, the use of powder paint coating reduces fire hazards, so much that facilities where powder paints are applied are not subject to specific regulations such as those for flammable liquids. In general, all conditions being equal, the time required to perform a powder paint coating is 50% less than the time required to liquid paint a product, and less energy is required.

The powder paint coating ensures a superior quality of the decoration and allows any errors in the coating process to be corrected because, by using an air gun, the powder paint applied to the product can be removed.

The powder paint coating is associated with wastes of up to 5% of the powder paint used and allows for a homogeneous layer on the product to be obtained, thanks to the self-levelling properties of the powder paint. Finally, operationally speaking, the powder paint coating systems require less maintenance, are associated with lower operating costs and do not require particularly skilled operators.

Thanks to the reflective properties of the metal oxides and/or metal silicates, it is also possible to limit or eliminate the number of products discarded due to damage caused by heating in the polymerization step of the powder paint.

The present primer is also itself capable of imparting a definite color characteristic to the product, that is, of giving a uniform coloring to the product, preferably white in color, and making the product pleasant to the touch, smooth and uniform.

In essence, by applying the primer to the product provides decoration to the product per se, by covering the coloring of the wood-derived composite material, and makes the surface to be powder paint coated more uniform. For example, the primer can give the product a white color, making it easier later to coat the product with other colors, if desired.

In essence, the product to which the primer is applied according to the present invention appears to be of a uniform color (preferably white) and with a uniform coating and/or decorative layer even at the edges.

Preferably, the primer layer on the product is at least 10 μm, and preferably between 10 μm and 30 μm. Preferably, the mixture of titanium oxide and aluminum oxide is present in the primer in total at 20-45% by weight, even more preferably at 23-29% by weight.

Thanks to the presence of the mixture of titanium oxide and aluminum oxide, the primer has IR reflective and thermo-insulating properties, that is, it has both the ability to reflect infrared radiation, thus limiting the radiation overheating, and the ability to thermally insulate the wood-derived composite material the product is made of, thus limiting the conduction overheating.

In practice, the primer applied to the product allows the product's interior to be shielded from heat and radiation that is applied to its exterior, such as for example to the layer of the powder paint left adhered to the primer itself.

In particular, the mixture can reflect infrared radiation with wavelengths between 2 μm and 10 μm.

In particular, the product coated with the primer has preferably an IR reflection coefficient of at least 0.10, and more preferably between 0.10 and 0.31. In other words, preferably the product coated with the primer allows at least 10% of the IR rays incident on the product to be reflected, and more preferably allows 10% to 31% of the IR rays incident on the product to be reflected. The reflection coefficient can be estimated by using the method described below, with reference to Test III.

Preferably, the resin is at 30-40% by weight.

Preferably, the resin matrix is a polyester resin or an acrylic resin.

Preferably, the mixture of titanium oxide and aluminum oxide has electrostatic properties or is electrostatically chargeable. In practice, by coating the product with the primer, it is possible to charge the product electrostatically and make any possible powder paint applied later adhere to the product.

In essence, it is described herein a primer with IR reflective, thermo- insulating and electrostatic properties.

Preferably, the solvent used in the primer is water. Preferably, these metal oxides are initially dispersed in the resin matrix. Preferably, the titanium oxide is in total at 8-17% by weight and the aluminum oxide is in total at 12-28% by weight (that is, relative to the entire mass of the primer), more preferably the titanium oxide is at 9-11% by weight and the aluminum oxide is at 14-18% by weight. Preferably, the primer comprises an amine-based, cross-linking agent that promotes the cross-linking of the resin matrix and/or a surfactant/dispersing agent and/or a rheology/levelling agent to improve the viscosity of the primer and allow it to be applied by spraying on a product.

In an embodiment the primer may comprise an allotropic form of graphite, that is electrostatically charged or can be electrostatically charged. Such characteristic can contribute to electrostatically charge the product to which the primer is applied, in order to facilitate any subsequent possible powder paint coating.

Preferably, the allotropic form of graphite is present at 1% by weight in the primer.

In addition to or as an alternative to the allotropic form of graphite, the primer may also comprise ions of a dissolved salt, in order to electrostatically charge the product. For example, sodium chloride NaCI can be dissolved in the primer. In an embodiment, the primer consists exclusively, except for impurities, of a resin matrix, a solvent and a mixture of titanium oxide and aluminum oxide. Additives may be present in other embodiments.

The present invention relates to a method for coating a product made of wood or its derivatives, according to claim 16. In particular, the method comprises the steps of: a) providing a product made of wood or its derivatives; b) applying a primer with IR reflective, thermo-insulating and electrostatic properties to said product; c) heating the product to solidify the primer applied during step b).

In other words, in the method described herein, a primer with the characteristics described above is preferably applied.

The present method allows, firstly, to coat a product with the primer described above and, secondly, to powder paint coat the product to which the primer is applied while achieving a quality result.

In other words, the method allows to create a base on which to carry out a powder paint coating of a wood-derived composite material.

The present method preferably comprises one or more of the characteristics, or steps, described in claims 17-26.

In particular, prior to step b), the product can be heated to a temperature between 50°C and 80°C for 1-2 minutes, and then possibly cooled to decrease, or eliminate, the water content in the product, preferably below 5% by weight. The treatment temperature and duration are selected depending on the size of the panel 1 , the material it is made of, and the water content.

Preferably, a cleaning step may be also performed on the product, prior to step b).

Preferably, subsequent to step c), the product is coated or decorated with a powder paint coating in order to achieve the benefits mentioned above.

This provides that the powder paint coated product undergoes a polymerization process of the paint, preferably carried out by setting one or more infrared lamps to a temperature of at least 180°C and exposing the powder paint coated product to the lamp, or lamps, so set for at most 180 seconds.

In practice, the polymerization can be preferably carried out by setting one or more infrared lamps to a temperature between 180°C and 500°C and exposing the powder paint coated product to the lamp, or lamps, so set for a time interval, inversely corresponding to the temperature range, between 30 seconds and 180 seconds. For example, the temperature can be set to 250°C and the product can be exposed for 90 seconds.

The technician in the field will know how to select the temperature and time interval depending to the thickness of the product, its density and the distance from the infrared lamp, or lamps.

The present invention is directed also to a machine for coating a product made of wood-derived composite material according to claim 27.

In particular, the machine comprises:

- a loading section for loading the product to be coated;

- an unloading section for unloading the coated product;

- a feed way of the product from the loading section to the unloading section;

- a station for applying the primer with electrostatic properties, in particular with one or more of the characteristics described above in relation to claim 1 ; and

- a station for heating the product coated with a primer with electrostatic properties, preferably as described above with reference to claim 1 and configured to perform the primer solidification on the product.

The Applicant reserves the right to file a Divisional Patent Application directed to the machine described herein, regardless of how the applied primer is made.

The product feed way runs from the loading section to the unloading section and passes through the primer applying station and the product heating station.

Such stations are therefore functionally interposed between the product loading section and the product unloading section, in the sense that regardless of the respective positions of the stations in relation to the product loading and unloading sections, considering the operation of the machine, such stations are located between the two sections, such that the product is loaded in the loading section, is coated at these stations and finally reaches the unloading section.

Downstream of the primer applying station and the station for heating the primer-coated product, the product can be subjected to coating, polymerizing and possibly even a sublimation printing process.

The machine may also comprise one or more characteristics, or stations, described with reference to claims 28-33.

It is clear that other possible stations provided in the machine are also functionally interposed between the loading section and the unloading section.

The present invention also relates to a wood-derived composite product provided with a surface layer of the primer described above, according to claim 34. Preferably, the product has a surface layer of solidified primer.

Preferably, the thickness of the primer layer is at least 10 μm, even more preferably it is between 10 μm and 30 μm.

The present invention also relates to a wood-derived composite product provided with a layer of primer and powder paint coated, according to claim 36. In other words, it relates to a wood-derived composite product comprising a primer layer and a polymerized layer of powder paint.

Preferably, the layer of powder paint is at least 80 μm; even more preferably the layer of powder paint is between 80 μm and 110 μm. The present invention also relates to a wood-derived composite product according to claim 37 coated with the coating method described above.

Finally, the present invention describes the use of the primer described above for electrostatically charging a product made of wood-derived composite material and as a base for powder paint coating such a product. Brief list of the figures

Further characteristics and advantages of the invention will be better highlighted by examining the following detailed description of its preferred, but not exclusive, embodiments depicted by way of non-limiting example, with the support of the appended drawings, wherein: - Figure 1 is a schematic view of a panel made of wood-derived composite material on which the primer according to the present invention is applicable;

Figure 2 is a flowchart of a preferred embodiment of the method to coat the panel shown in Figure 1; - Figure 3 is a schematic view of a loading section of a machine for coating the panel shown in Figure 1 ;

Figure 4 and Figure 5 are schematic views of a cleaning station of a machine for coating the panel in Figure 1 ;

Figure 6 and Figure 7 are schematic views of two versions of a station for applying the primer according to the present invention on the panel in Figure 1 ;

Figure 8 and Figure 9 are schematic views of two versions of a station for heating the panel shown in Figure 1 on which the primer has been applied; Figure 10a and Figure 10b are schematic views of two versions of a station for powder paint coating the panel shown in Figure 1 to which the primer according to the present invention has been applied;

Figure 11 and Figure 12 are schematic views of two versions of a station for polymerizing the panel shown in Figure 1 which has been powder paint coated; Figure 13 is a schematic view of a portion of the machine comprising a polymerizing station and a sublimation station;

Figure 14 is a schematic view of an unloading section of the panel shown in Figure 1 , which has been decorated;

Figures 15 and 16 show graphs, respectively, as a function of time, of the change in the internal temperature and surface temperature of MDF panels subjected to IR rays for 90 seconds at a temperature of 180°C. The graphs compare with each other raw panels without any primer (panel A), panels coated with primer comprising a mixture of titanium oxide and aluminum oxide (panel C), panels coated with primer comprising aluminum oxide only (panel E), and panels with primer comprising titanium oxide only (panel G);

Figures 17 and 18 show graphs, respectively, as a function of time, of the internal temperature and surface temperature of MDF panels subjected to IR rays for 90 seconds at a temperature of 210°C. The graphs compare with each other raw panels without any primer (panel B), panels coated with primer comprising a mixture of titanium oxide and aluminum oxide (panel D), panels coated with primer comprising aluminum oxide only (panel F), and panels with primer comprising titanium oxide only (panel H).

Detailed description of the invention

A primer applicable to a wood-derived composite product and preferably applicable to a panel made of wood fiber composite material MDF is described below.

For simplicity, the invention will be described below with reference to an MDF panel shown in Figure 1 and identified as "panel 1," but without intending to limit the invention to a product of this particular type.

Before going into the essence of the invention, with reference to Figure 1 , a panel 1 is shown. The panel 1 has a top face 2 and a bottom face 3 not visible in the figure, and a set of side faces arranged in pairs on opposite sides of the panel, of which the front face 4 and the side face 5, in the figure located on the right, are visible in Figure 1.

Figure 1 shows a panel placed horizontally, that is, with the faces 2, 3 arranged horizontally and the side faces 4, 5 arranged vertically. In contrast, a vertically positioned panel 1 has the faces 2, 3 arranged vertically and one of the pairs to which the side faces 4, 5 belong arranged horizontally, e.g., with the side face 5 arranged at the bottom and the opposite side face at the top. For example, the panel 1 has a length of 300 mm, depth of 200 mm, thickness of 19.4 mm and a weight of 620 grams (density of about 0.51 grams per cm ³ ).

Flowever, it is clear that for the purposes of the present invention it is possible to coat a wood-derived composite product of any shape or size. Therefore, what has been described below with reference to the panel 1 can be extended to any wood-derived composite product.

The primer described herein comprises a resin matrix and related solvent, which form the base component of the primer, and a mixture of titanium oxide and aluminum oxide.

In the preferred embodiment of the invention, the primer comprises, as a matrix, a polyester or acrylic resin and, as a solvent, water. In practice, the polyester or acrylic resin is present in a weight percentage of 30% to 40%.

The presence of the mixture of titanium oxide and aluminum oxide allows the primer, when applied to an MDF panel, to be able to powder paint coat the panel 1 by forming a suitably thick and durable layer of paint. In fact, the mixture of titanium oxide and aluminum oxide in the primer allows the surface of the panel 1 to be electrostatically charged, in order to overcome the inability of the raw panel 1 to be adequately charged electrostatically.

Furthermore, the titanium oxide and aluminum oxide allow to achieve a quality coating thanks to the properties of this mixture to limit the panel overheating, as it allows both to thermally insulate the MDF panel on which the primer is applied and to reflect the IR rays used to polymerize the powder paint.

In practice, the primer described herein, once applied to a panel 1 to be coated or decorated, allows the powder paint to adhere to the surface of the panel 1, so as to preferably form a paint layer of at least 80 μm and, advantageously, it ensures that the panel does not overheat excessively, so as to limit or nullify the possibility of cracks in the paint layer and/or material of which the panel 1 is made.

In practice, the primer described herein, being sandwiched between the MDF and the surface layer of powder paint, allows to limit the overheating of the MDF because it inhibits both the radiation overheating and conduction overheating.

In fact, the mixture of titanium oxide and aluminum oxide has thermo- insulating properties (i.e. , limiting the induction overheating by thermally insulating the panel 1) and IR reflecting properties, that is, if irradiated with infrared rays it reflects part of the radiation with this wavelength. This results in a panel 1 to which the primer is applied which is overheating less than a raw panel 1 , that is, to which the primer described herein is not applied.

This will be evident from the evidence and results described below.

The base component of the primer is supplemented with a mixture of titanium (IV) oxide T1O2 and aluminum oxide AI2O3. Titanium oxide and aluminum oxide are preferably present in a weight percentage between 8% and 17% and between 12% and 28% respectively, relative to the total mass of the primer. More preferably, titanium oxide and aluminum oxide are present in a weight percentage between 9% and 11% and between 14% and 18%, respectively, relative to the total mass of the primer.

In general, the metal oxides are preferably present in the primer between 20% and 45% by weight, and preferably between 23% and 29% by weight.

Depending on the overall concentration of titanium oxide and aluminum oxide, the field technician will select the other components, such as the matrix, water, or any other possible components.

In addition to the components mentioned above, the primer may comprise one or more of the following substances that can be defined as adjuvants: a crosslinking reagent and/or a surfactant/dispersant and/or a rheology/levelling agent.

These substances are not essential to make the primer according to the present invention, but their presence in the mixture is preferable to improve the dispersion of the metal oxides in the base component of the primer or to enable the primer to be applied on the panel 1 by spraying means. In particular, the crosslinking reagent is present in a percentage of 3% to

5% by weight, the surfactant/dispersing agent between 1% and 4% by weight, and the rheology/levelling agent between 1% and 2%, relative to the total mass of the primer.

For example, in a particular embodiment of the primer described herein, the primer comprises Joncryl 79 at 35% by weight as resin, Zinc Oxide Solution #1 at 2% by weight as catalyst, Plastopal BTM at 3% by weight as crosslinker, Hydropal WE 3500 at 2% by weight as surfactant, Dispex Ultra FA 4480 at 1.5% by weight as dispersant, Rheovis AS 1130 at 2% by weight as rheology agent, titanium (IV) oxide at 11% by weight and aluminum oxide at 15% by weight as metal oxides, and an amount of water as solvent to get to 100% by weight. In general, the primer may comprise Joncryl 79 at 30-40% by weight as resin, Zinc Oxide Solution #1 at 1-2% by weight as catalyst, Plastopal BTM at 3- 5% by weight as crosslinker, Hydropal WE 3500 at 1-2% by weight as surfactant, Dispex Ultra FA 4480 at 1-2% by weight as dispersant, Rheovis AS 1130 at 1-2% by weight as rheology agent, titanium (IV) oxide at 9-11% by weight and aluminum oxide at 14-18% by weight as metal oxides, and an amount of water as solvent to get to 100% by weight.

The primer can be prepared by adding the metal oxides to the base component and adjuvants, if any, and by mixing everything until a suspension or dispersion is obtained, or the metal oxides can be added from the beginning directly into the resin matrix that is then used in the preparation of the primer along with the other components.

As mentioned above, tests have been carried out to demonstrate that the primer allows, firstly, to powder paint coat a panel 1 and, secondly, that it has the ability to thermally insulate the panels and reflect, at least partially, the IR rays used in the polymerization process of the powder paint.

Test I

The test was carried out on three MDF panels.

In particular, MDF panels each having a length of 300 mm, depth of 200 mm and thickness of 19.4 mm, having a weight of 620 grams (density of about 0.51 grams per cm ³ ), were used.

A first panel was used raw, that is, not coated with the primer, a second panel was coated with Joncryl 79 resin in the absence of metal oxides, whereas a third panel was coated with the primer described below. In particular, for coating the third panel a primer was used, comprising

Joncryl 79 at 35% by weight as resin, Zinc Oxide Solution #1 at 2% by weight as catalyst, Plastopal BTM at 3% by weight as crosslinker, Hydropal WE 3500 at 2% by weight as surfactant, Dispex Ultra FA 4480 at 1.5% by weight as dispersant, Rheovis AS 1130 at 2% by weight as rheology agent, titanium (IV) oxide at 11% by weight and aluminum oxide at 15% by weight as metal oxides, and an amount of water as solvent to get to 100% by weight.

The primer was applied to the MDF panel with a Wagner W100 gun and allowed to solidify, so that it formed a primer layer of at least 10 μm, and preferably a primer layer between 10 μm and 25 μm. A powder paint was subsequently applied to all three panels by a Corona

CP-2100 gun.

The powder paint is a polyester-based paint sold under the code PGE22 001 by Sublitex S.r.l.

Similar data can be obtained by using any other known powder paint. This test showed that the powder paint did not adhere to the raw panel and the panel with Joncryl 79 resin only, whereas it adhered to the panel coated with the primer comprising metal oxides.

This demonstrates that the primer described herein allows the surface of an MDF panel to be electrostatically charged and can serve as a base for powder paint coating an MDF panel.

Test II

Polymerization tests of the powder paint were carried out under the conditions described in Test I. Although the manufacturer's instructions were to perform the polymerization of the powder paint in an air oven at 130°C for 3 minutes, surprisingly, it has been found that even by setting the temperature of the IR lamps to a temperature of at least 180° and exposing the powder paint coated panel to the so set lamps for at most 180 seconds, the powder paint has polymerized adequately, forming a layer of at least 80 μm.

In other words, the Applicant has identified a new method for polymerizing the powder paint.

In particular, the tests have demonstrated that by setting the IR lamps to a higher temperature, the exposure time can be decreased.

For example, it is possible to set the lamps to a temperature of 210°C or 250°C and achieve the polymerization at about 90 seconds of exposure, or to set the lamps to a temperature of 450°C or 500°C and achieve the polymerization at about 70 seconds or 30 seconds of exposure, respectively.

This means that the polymerization of the powder paint can be achieved a shorter time interval than traditionally thought necessary to achieve the polymerization. This method is independent of the presence or absence of the primer, in the sense that excellent results were obtained with this method even when performing the polymerization of the powder paint applied on a metal product in the absence of a primer layer.

Test III The third test was carried out to demonstrate the ability of the primer described herein to thermally insulate the MDF panel and reflect IR rays.

The test was carried out on eight separate MDF panels denoted by the letters A-H.

Also in this case, identical MDF panels each having a length of 300 mm, depth of 200 mm and thickness of 19.4 mm, having a weight of 620 grams (density of about 0.51 grams/cm ³ ), were used.

In particular, Test III was carried out by setting, in a first case (Test IMA) the temperature to 180°C and in a second case (Test IIIB) the temperature to 210°C. In Test IIIA, panels A, C, E, G were used, while in Test IIIB panels B, D,

F, FI were used.

Panels A and B were used as raw panels, that is, not coated with the primer; panels C-H were used after the primer comprising a mixture of titanium oxide and aluminum oxide, was applied. In particular, as for Test I, for the coating a primer was used, comprising

Joncryl 79 at 35% by weight as resin, Zinc Oxide Solution #1 at 2% by weight as catalyst, Plastopal BTM at 3% by weight as crosslinker, Hydropal WE 3500 at 2% by weight as surfactant, Dispex Ultra FA 4480 at 1.5% by weight as dispersant, Rheovis AS 1130 at 2% by weight as rheology agent, titanium (IV) oxide at 11% by weight and aluminum oxide at 15% by weight as metal oxides, and an amount of water as solvent to get to 100% by weight.

Panels E and F were used after applying a primer comprising aluminum oxide only (i.e. , free of titanium oxide) as metal oxide.

In particular, this primer comprises Joncryl 79 at 35% by weight as resin, Zinc Oxide Solution #1 at 2% by weight as catalyst, Plastopal BTM at 3% by weight as crosslinker, Hydropal WE 3500 at 2% by weight as surfactant, Dispex Ultra FA 4480 at 1.5% by weight as dispersant, Rheovis AS 1130 at 2% by weight as rheology agent, aluminum oxide at 26% by weight, and an amount of water as solvent to get to 100% by weight. Panels G and H were used after applying a primer comprising titanium oxide only (i.e., free of aluminum oxide) as metal oxide.

In particular, this primer comprises Joncryl 79 at 35% by weight as resin, Zinc Oxide Solution #1 at 2% by weight as catalyst, Plastopal BTM at 3% by weight as crosslinker, Hydropal WE 3500 at 2% by weight as surfactant, Dispex Ultra FA 4480 at 1.5% by weight as dispersant, Rheovis AS 1130 at 2% by weight as rheology agent, titanium oxide at 26% by weight, and an amount of water as solvent to get to 100% by weight.

The primer was applied to the panels with a Wagner W100 gun and allowed to solidify, so to form a primer layer of at least 10 μm, and preferably a primer layer between 10 μm and 25 μm.

The panels were subsequently powder paint coated by using a Corona CP-2100 gun.

The powder paint is a polyester-based paint sold under the code PGE22 001 by Sublitex S.r.l. Similar data can be obtained by using any other known powder paint.

In order to demonstrate the properties of the primer containing the mixture of titanium oxide and aluminum oxide, panels A-H were heated by IR lamps under conditions such to polymerize the powder paint on the panels, and the internal temperature and external temperature reached by panels A-H were measured at 15 s intervals. In particular, a temperature control instrument equipped with 2 thermocouples from the company Tersid and 4 temperature controllers from the company Ascon Tecnologic S.r.l., and a temperature control system using static relay and holding timer, were used. 12 ceramic-type infrared lamps from the Lorenzoni S.r.l. Company were used to heat the panels; these lamps were arranged along a plane vertical to the ground so as to form two opposing groups that were each 8 cm away from the panel 1. Each group comprised 6 lamps. In each group, the lamps were arranged in two rows of three: a top row and a bottom row so that the top row and bottom row of one group faced the top row and bottom row of the other group of lamps, respectively.

The two thermocouples were from time to time associated with panels A- H in the following way: a first thermocouple was inserted inside the panel in a blind hole formed in a side face (e.g., in the face 4 or 5 shown in Figure 1) and placed at a distance, in depth, of 10 cm from the corresponding side face; a second thermocouple was instead placed at an upper or lower face (e.g., at the face 2 or 3 shown in Figure 1), just below the primer layer. In practice, the first thermocouple was set up to measure the temperature reached by panels A-H in depth (identified herein as the internal temperature), while the second thermocouple was set up to measure the surface temperature, below the primer layer, of panels A-H (identified herein as the surface temperature).

In this test, each opposing group of IR lamps had a surface emitting IR rays of about 1500 cm ² , and the area of each face of the panel 1 irradiated by IR rays was about 650 cm ² . In order to carry out the test, eight tests were done consecutively, one for each A-H panel.

In each test, the corresponding A-H panel was placed with the corresponding thermocouples between the IR lamps turned off, the IR lamps were set to the predetermined temperature, and at to the IR lamps were turned on for 90 seconds. After this time interval, the lamps were turned off and moved away from the corresponding A-H panel, and by means of a special fan, the cooling of panels A-H was speeded up.

From time to to at least 285 seconds, internal temperature (T ₁ ) and surface temperature (T ₂ ) were recorded every 15 seconds. The results obtained by setting the temperature to 180°C are set forth in the following table:

Table 1

The results obtained by setting the temperature to 210°C are set forth in the following table:

Table 2

As shown in Table 1, by setting the lamps to 180°C, the raw panel A reached a maximum internal temperature of 55°C after 210 s, while panel C, provided with a primer layer according to the present invention, reached a maximum internal temperature of 47°C after 225 s, which is 8°C lower than the internal temperature of panel A.

The maximum internal temperature reached by panel C is also lower than the maximum internal temperature reached by panel G, on which the primer comprising titanium oxide only was applied. In fact, panel G reaches a maximum internal temperature of 55°C after 210 seconds.

This can also be appreciated from the graph in Figure 15, in which it can be seen that in the curve of the measured internal temperatures in panels A and G they can be overlapped with each other and are both found to have higher values than those in panel C. This means that, if compared to a primer made according to the known art, that is, with titanium oxide only, the primer comprising a mixture of titanium oxide and aluminum oxide allows to significantly limit the internal overheating of the product.

Still from Table 1 it is shown that raw panel A reached a maximum surface temperature of 118°C, while panel C, provided with a primer layer according to the present invention, reached a maximum surface temperature of 106°C, which is 12°C lower than the temperature of panel A.

The maximum surface temperature reached by panel C is also lower than the maximum surface temperature reached by panel E, on which the primer comprising aluminum oxide only was applied. In fact, panel E reaches a maximum surface temperature of 111°C.

This can also be appreciated from the graph in Figure 16, in which it can be seen that in the curve of the measured surface temperatures in panels A and E they are both found to have higher values than those in panel C. Overall, the above data show that the primer comprising the mixture of titanium oxide and aluminum oxide allows the panel to limit overheating both in depth (reduction of the internal temperature) and at the surface (reduction of the surface temperature) if compared with a raw panel, that is, without any type of primer. The same data show that the primer comprising the mixture of titanium oxide and aluminum oxide is able, compared with the primer with aluminum oxide only, to limit the surface overheating and, compared with the primer with titanium oxide only, to limit the internal overheating.

Similar conclusions also emerge from the analysis of Table 2, which refers to the tests carried out by setting the lamps at 210°C.

It is possible to see that the raw panel B reached a maximum internal temperature of 56°C after 210 s, while panel D, provided with a primer layer according to the present invention, reached a maximum internal temperature of 53°C after 210 s, which is 3°C lower than the internal temperature of panel A. The maximum internal temperature reached by panel D is also lower than the maximum internal temperature reached by panel H, on which the primer comprising titanium oxide only was applied. In fact, panel H reaches a maximum internal temperature of 55°C after 210 s.

This can also be appreciated from the graph in Figure 17, in which it can be seen that in the curve of the measured internal temperatures in panels B and H they can be overlapped with each other and are both found to be higher than those in panel D.

Still from Table 2 it is shown that raw panel B reached a maximum surface temperature of 142°C, while panel D, provided with a primer layer according to the present invention, reached a maximum surface temperature of 127°C, which is 15°C lower than the temperature of panel B.

The maximum surface temperature reached by panel D is also lower than the maximum surface temperature reached by panel F, on which the primer comprising aluminum oxide only was applied. In fact, panel F reaches a maximum surface temperature of 132°C.

This can also be appreciated from the graph in Figure 18, in which it can be seen that in the curve of the measured surface temperatures in panels B and F they are both found to have higher values than those in panel D.

Also these data show that the primer comprising the mixture of titanium oxide and aluminum oxide allows the panel to limit overheating both in depth (reduction of the internal temperature) and at the surface (reduction of the surface temperature) if compared with a raw panel, that is, without any type of primer.

The same data show that the primer comprising the mixture of titanium oxide and aluminum oxide is able, compared with the primer comprising aluminum oxide only, to limit the surface overheating, and, compared with the primer with titanium oxide only, to limit the internal overheating.

The data set forth above can be used to provide an estimate of the primer refraction coefficient. First, it should be considered that the heat which is incident on a panel A, B without primer is

Q = KΔt where K is a constant of proportionality that takes into account the heat emitted by the lamps and by the incident surface of the panel, and At is the exposure time of the panel to the heat flow.

From the laws of thermology, it is possible to state that heat can also be expressed as absorbed heat

Q = mcΔT where m is the mass of the panel, c is its specific heat, and AT is the temperature difference measured inside the panel between the maximum temperature reached and that of the initial state.

In case the primer is applied to the panel, it is possible to write that the heat absorbed by the panel, that is, not reflected by the primer, is a fraction of the incident heat produced by the lamps:

Q _p = (1- α) KΔt where a, the reflection coefficient of the primer, is a number between 0 and 1 , whereas the subscript p depicts the magnitudes obtained by the primer application.

Since all the heat which is incident on the panel (and transmitted by the primer) causes an increase in temperature inside the panel itself, it is possible to state

(1 — α) KΔt = mcΔT _p KΔt = mcΔT and, by dividing member by member, we obtain the expression for the primer reflection coefficient:

Reporting the values measured in the tests at 180°C and 210°C, with and without primer, it can be derived that:

- by considering that in tests at 180°C, panel C, with the primer, has a rise in the internal temperature from 27°C to 47°C, while the raw panel A has a rise in the internal temperature from 26°C to 55°C, the reflection coefficient a is equal to 0.31. From the above it can be derived that 31 % of IR rays is reflected;

- considering that in the tests at 210°C, panel D, with the primer, has a rise in the internal temperature from 26°C to 53°C, while the raw panel B has a rise in the internal temperature from 26°C to 56°C, the reflection coefficient a is equal to 0.10. From the above it can be derived that 10% of the IR rays is reflected.

The results of Test III show that the primer described herein has a reflection coefficient of at least 0.10, and preferably between 0.10 and 0.31 , and therefore the primer described herein allows at least 10% of the incident IR radiation to be reflected, and preferably allows to reflect incident IR radiation in the range of 10% to 31 %.

As mentioned above, the advantages of the primer emerge when considering the primer applied to a panel 1 to be coated.

First of all, thanks to the presence of the mixture of aluminum oxide and titanium oxide, the primer allows to powder paint coat an MDF panel with excellent results, that is, it allows creating a layer of powder paint preferably of at least 80 μm, more preferably between 80 μm and 110 μm, on the MDF panel. Flowever, most importantly, the primer limits the overheating of the MDF panel and limits, or prevents altogether, thanks to the IR reflective and thermo- insulating properties demonstrated above, the formation of cracks in the panel itself and/or in the layer of powder paint, due to the evaporation of water, or other components, caused by the heating of the panel during the polymerization process. In fact, thanks to the presence of the mixture of aluminum oxide and titanium oxide, not only is the IR radiation used to polymerize the powder paint are reflected by the primer and does not reach, or reaches only to a limited extent, the MDF panel, but there is also the thermal insulation of the MDF panel against heat transmission by conduction.

In essence, thanks to the primer described herein, not only it is made possible to powder paint coat an MDF panel, thus achieving the advantages described above, but the occasions for panel damage are limited or eliminated, the coating process is made faster because it is not necessary to perform checks for the possible damage to the panels due to heat, and the costs for coating the panels are cut because the amount of panels discarded due to damage from overheating of the wood fibers is significantly reduced.

The primer also allows giving to the panel 1 a better aesthetic appearance because the presence of aluminum oxide and titanium oxide in the primer gives to the panel 1 a uniform coloration, preferably white, and a texture that is pleasant to the touch.

If necessary, it is possible to add color pigments to the primer to give it a very precise coloring.

In practice, the primer can be used to coat and/or decorate a panel 1 , both in the sense that it can itself constitute a product to coat and/or decorate a panel 1 , and in the sense that it can constitute a base on which to perform the powder paint coating.

Optionally, the primer may also comprise a dissolved salt, such as sodium chloride, or an allotropic form of graphite to give the primer more electrostatic properties. For example, the allotropic form of graphite may be present in the primer at 1 % by weight.

With reference to the flowchart shown in Figure 2, a method is described for coating or decorating a panel 1 by using the primer described above.

In particular, the method provides a step a) in which a panel 1 to be coated is provided; the panel 1 can be provided manually or via an automated system, such as a Cartesian system or an anthropomorphous robot.

In practice, in step a), the panel 1 is placed at a workstation to perform step b), which involves applying the primer described above to the panel 1. The primer can be applied by immersing the panel in a basin containing the primer itself, or by applying the primer with a brush or, preferably, by spraying the primer on the panel using suitable spraying media, such as spray ramps or spray guns.

In the next step c), the panel 1, with the primer applied, is heated to solidify the primer and create a primer layer on the panel 1. Preferably, the solidified primer has a thickness of about 10 μm-30 μm and preferably 20 μm.

It should be noted that the panel 1 with the solidified primer can be called a decorated panel 1 , because even the primer alone is able to give a pleasing appearance to the panel 1 thanks to the presence of the metal oxides, as described above. Step c) can be achieved by heating the panel by infrared radiation and/or by hot air. For example, it is possible to heat with infrared lamps for about 30-40 seconds at 80°C-90°C, or it is possible to heat by a hot air oven for 1 -2 minutes at a temperature between 70°C and 90°C.

In the preferred embodiment of the method, after step a), the panel 1 is subjected to a cleaning process to remove any possible dust on the panel. This process may also have the purpose of smoothing the surfaces of the panel 1, that is, to eliminate any possible surface irregularities given by the wood fibers the panel 1 is made of.

Preferably, the cleaning process is implemented by using cleaning means comprising, for example, one or more brushes and/or a high-pressure air jet. The panel can be held in place on the work surface with vises or by providing holes in the work surface and creating a negative pressure at the work surface itself by suction means, such as a suction pump.

In practice, the negative pressure ensures that the panel 1 does not move on the work surface as a result of the stresses exerted on it by the cleaning means, and it also allows the dust generated by the cleaning process to be sucked so that it does not escape into the environment.

Prior to step b), the panel 1 can be heated and subsequently cooled so as to decrease, or eliminate, the water content in the panel 1. This further decreases the possibility of cracks forming in the panel 1 as a result of the subsequent steps involving the heating of the panel 1.

In this step, the panel is heated on average to 50°C-80°C for 1-2 minutes.

As mentioned above, the panel 1 can also be considered coated and/or decorated at the end of step c). However, in case it is necessary to decorate and/or cover the panel 1 in a more elaborate way, it is possible to provide additional steps for decorating the panel 1.

In particular, it is possible to carry out a step d) that involves applying a powder paint to the panel. It is possible to apply the powder paint to the panel 1 in a known way.

However, it is preferable to powder paint coat a panel 1 in a workstation equipped with powder paint coating guns and providing suction means of the powder paint that has not adhered to the panel 1.

For the powder paint coating it is possible to use, for example, the powder paint based on polyester sold under the code PGE22 001 by Sublitex S.r.l. Or it is possible to use the powder paint sold by Sublitex under the code PGE22 401, which is a polyester powder paint, and PGU22 502, which is a polyurethane powder paint.

In general, any other known powder paint can be used. As it is known, means for electrostatically charging the powder paint may be provided. Known ways to electrostatically charge the powder paint involve the use of triboelectric or corona effect guns or fluidized bed systems.

The sucked powder paint is concentrated by a cyclone system and then conveyed back to the powder paint coating guns. This way, thanks to the advantages associated with the use of the powder paint (elimination of VOC emissions, elimination or reduction of the need for intermediate sanding, application of the powder paint to the side surfaces in a single step), the powder paint that has not been adhered to the panel 1 can be reused, so that the costs related to the purchase of the powder paint itself can be cut. Following the coating steps, the panel is subjected to a polymerization step e), in which the polymerization of the powder paint is caused.

The polymerization of the powder paint causes the formation of a seamless coating on the panel 1.

In practice, in this step, the paint on the panel hardens and forms a uniform layer between 80 μm and 110 μm that covers the entire surface of the panel 1, without the need for intermediate sanding and without the need to make special applications of paint on the edges of the panel 1 or to perform edging.

The polymerization can be caused by heating the coated panel by using infrared rays, such as those emitted by an "infragas" or ceramic lamp, to a temperature of about 180°C or 210°C for 90 seconds.

More advantageously, it is possible to cause the polymerization by setting the temperature of the lamp, or lamps, to 250°C and exposing the powder-coated panel to the so set lamp, or lamps, for 90 seconds. Preferably, the panel has a distance from the lamp, or lamps, of 8 cm.

This halves the time required for the powder paint to polymerize, compared to the time required by the traditional methods.

It is possible to carry out step e) by arranging the infrared lamps at opposite sides with respect to the panel 1 , that is, by arranging one or more infrared lamps toward the face 2 and arranging one or more infrared lamps toward the face 3.

Furthermore, it is possible to provide temperature detection means to measure the temperature at the panel 1 so that the heating of the panel 1 can be adjusted depending on the detected temperature. For example, it is possible to retrofit adjust the heating automatically, by attaching the infrared lamps to a corresponding frame susceptible to reciprocal movements towards and away, that is, relative to the panel 1. This way, when it is necessary to increase the temperature at the panel 1, one or both frames move towards each other, and when it is necessary to decrease the temperature, one or both frames move away from each other. In practice, if the temperature is outside a predefined range both at the level of the face 2 or face 3, both the frames move towards or away to bring the temperature back into the desired range, whereas if the temperature is outside the predefined range at only one of the faces, e.g., the face 2, only the corresponding frame, with its infrared lamps, moves towards or away from the panel 1. Therefore, the retrofit control can be performed selectively for each frame and each face of the panel 1.

With retrofit control, it is also possible to provide for adjusting the intensity of the infrared lamps and, if panel handling means are provided, the speed of the panel handling means can be modified.

Such heating method can also be used in step c).

After the polymerization step, the panel 1 can be cooled with air, preferably cold air.

As mentioned above, the panel 1 can also be decorated by sublimation printing. In fact, the method may provide for a step f) in which a sublimation, batch or continuous printing process is carried out on the powder paint coated panel.

In essence, the powder paint has the advantage of being able to operate as a base on which the decoration during the sublimation printing process is imprinted.

The sublimation printing can be carried out according to a method known in the field, either on a single panel 1 at a time or on more than one panel 1 at once, by using a sublimation film known in the field and having the sublimation take place in a negative pressure environment (-100 millibars to -360 millibars) at a temperature between 140°C and 180°C for between 1 minute 30 seconds and 3 minutes 30 seconds.

At the end of the sublimation step, the panel is decorated with a particular pattern, or design, initially present on the sublimation film and then transferred to the panel 1.

At this point, the decorated panel 1 can be unloaded from the workstation, either manually or via a Cartesian system or an anthropomorphous robot.

Overall, the method described above allows to coat and/or decorate a panel 1 in an easier, faster, cheaper and more efficient way than methods known to date, thanks to the application of the primer described above and the possibility of powder paint coating the MDF panel.

The coating method of a panel 1 according to the present invention comprises the steps a), b), c) and optionally, as needed, also the steps d), e), f).

The method can also be better understood by considering the machine for decorating a panel 1 , that will be described below with reference to Figures 3-14.

Such a machine is set up to decorate a panel 1 by employing a primer that can electrostatically charge the panel itself. Preferably, the primer is a primer according to the present invention described above.

The machine has a loading section 11 of one or more panels 1, which is shown in Figure 3, and an unloading section 90 of one or more panels 1 , which is shown in Figure 14.

The machine can be set up to coat one panel 1 at a time or, preferably, to coat more than one panel 1 at once.

The machine also has a panel feed way 1 that can also be configured as a supporting and feeding plane for the panels 1.

In essence, the machine can provide for the movement of the panels 1 on a supporting and feeding plane, by holding the panels 1 in a horizontal position, or it can provide for the movement of the panels 1 by the hooking means described below, by holding the panel 1 in a vertical position. Alternatively, it is possible to provide some stations where the panel 1 is positioned horizontally and others where it is positioned vertically.

In particular, the loading section 11 shown in Figure 3 has a supporting plane 12 on which the panels 1 to be decorated are placed and a handling system 13 comprising a guide rail 14 for a manipulator 15 fitted, for example, with a suspension device 16 to the lower end of which is attached a suction cup intended to abut onto a panel 1 to move it from a pickup station, such as from a pallet 17, to the supporting plane 12.

The manipulator 15 is susceptible to movements along the guide rail 14 parallel to the ground, in a first direction and in a second direction opposite the first one, and to movements orthogonal to the ground, downward or upward, as shown by the respective arrows in Figure 3.

Alternatively, it is possible to use an anthropomorphous robot, such as a collaborative robot not shown in the figure, in place of the manipulator.

Once placed on the supporting plane 12, the panel 1 is moved, for example by a conveyor belt, to a cleaning station 20 shown in Figures 4-5.

The cleaning station 20 has a supporting and feeding plane 21 on which the panels 1 are placed. The supporting and feeding plane 21 is arranged to move the panels 1 along a longitudinal axis, in the direction of the arrow shown in Figure 4.

The supporting and feeding plane 21 is drilled at least at one portion of the surface, that is, it has a set of through holes 22 visible in Figure 4.

Underneath the supporting and feeding plane 21 there is a retaining basin 23 that opens to the external environment just at the through holes 22. The retaining basin 23 is also in fluid communication with a suction pump 24 capable of generating negative pressure at the through holes 22 of the supporting and feeding plane 21.

The cleaning station 20 is equipped with cleaning means 25 to clean the panels 1. Preferably, such cleaning means 25 comprise one or more brushes 26 and/or one or more nozzles 27 arranged to deliver a pressure air jet schematically shown in Figure 5.

The brush, or brushes, 26 and nozzles 27 can be placed in series above the supporting and feeding plane 21 so that the panels 1 can first be cleaned by brush(es) 26 and then cleaned by pressurized air fed by the nozzles 27. It is also possible to provide one or more brushes 26 facing upward, as shown in Figure 5, before the supporting and feeding plane 21. This way, the manipulator 15, before placing the panel 1 back on the supporting and feeding plane 21 , can position it at said brush(es) 26 so as to provide for cleaning the face intended to abut onto the supporting and feeding plane 21 as well.

The fact that the supporting and feeding plane 21 has through holes 22, at which negative pressure is applied to the panel 1 , allows both to ensure that the panel 1 remains in place on the supporting and feeding plane 21 during the cleaning, that is, it does not move in response to the stresses imparted by the cleaning means 25, and to suck the residues from the cleaning of the panel 1 in the retaining basin 23, preventing them from being dispersed into the environment.

The machine is also equipped with a primer applying station 30 capable of electrostatically charging a panel 1. Preferably, the station 30 is set up for the application of the primer described above. Figures 6 and 7 show two embodiments of a primer applying station 30: the one shown in Figure 6 has a supporting and feeding plane 21 on which the panels 1 are stored and moved to a horizontal position in the direction depicted by the arrow, while Figure 7 shows a station 30 in which the panels 1 are moved in a feeding way provided with means for hooking the panels 1 , not shown in the figure, that hold the panels 1 in the vertical position. Such means may comprise suspended tray conveyors and conveyors known in the field.

At the station 30 shown in Figure 6, the primer is applied to the panels 1 via spray ramps or spray guns 31 positioned above the supporting and feeding plane 21. In Figure 6 the primer sprayed by the respective spray guns 31 is shown schematically.

In Figure 6, it is possible to see that under the supporting and feeding plane 21, on the side opposite the spray ramps or spray guns 31, there is a retaining basin 32 that collects the excess primer that has not adhered to the panels 1.

The retaining basin 32 is also provided with a primer recovery system; in fact, the retaining basin 32 has an outlet channel 33 connected to a delivery pump 34 that feeds the excess primer collected in the retaining basin 32 to the spray ramps or spray guns 31. The station 30 is also equipped with one or more tanks not shown in the figure, in which the primer is prepared and collected and which are also connected to the spray ramps or spray guns 31.

A filter assembly 35 is preferably provided between the retaining basin 32 and the delivery pump 34, which filters the primer collected in the retaining basin 32 from any panel fragments.

Preferably, the station 30 is also equipped with a tipper device not shown in figure, which allows the panels 1 to be tipped so that primer can be applied both to the face 4 and the face 5 of the panels 1.

As mentioned above, it is possible to make a station 30 arranged to hold and move the panels 1 in the vertical position, as shown in Figure 7. In this version, the station is provided with two sets of spray ramps or spray guns 31 facing each other: the panels 1 are moved between the two spray ramps or between the two sets of spray guns 31 , so that each of the two faces 2 and 3 of the panels 1 faces one of the two spray ramps or one of the sets of spray guns 31.

The machine also comprises a station 40 for heating the panels 1 coated with the primer in the previous station 30. Also this station can be made in such a way as to move the panels arranged forward horizontally or vertically.

In particular, Figure 8 shows a version of the station 40 equipped with a supporting and feeding plane 21 configured as a conveyor belt on which one or more panels 1 can be placed, which are movable in the direction shown by the arrow.

The station 40 is provided with heating means 41 to obtain the solidification of the primer and, preferably, to evaporate the water in the primer as a solvent.

Such heating means 41 preferably comprise infrared lamps 42 preferably arranged in series above and below the supporting and feeding plane, and/or a hot air oven 43. Such heating means 41 are arranged to heat both faces 2, 3 of the panels 1 so as to solidify the primer.

Figure 9 shows a station 40 in which the panels 1 are moved vertically by appropriate hooking means 44. This station also comprises infrared lamps 42 and/or a hot air oven 43 which are set up to heat both faces 2, 3 of the panels 1 to which the primer was applied.

The heating of the panels, if performed by infrared lamps, takes place at a temperature of 80-90 degrees for 30-40 seconds; in case it is performed by an air oven, the panels are heated for 1-2 minutes at 80-90°C. The machine preferably comprises, with reference to Figure 10a, a powder paint coating station 50. The station 50 shown in Figure 10a provides for moving the panels 1 horizontally and, therefore, comprises a supporting and feeding plane 21 preferably configured as a movable Teflon mat, which moves the panels 1 in the direction depicted by the arrow. Above the supporting and feeding plane 21 there are one or more coating guns 51 for powder paint coating the panels 1. Instead, there is a fume hood 52 connected to a suction fan 56 under the supporting and feeding plane 21, which sucks the powder paint that has not been adhered to the panels 1 and conveys it to a recirculation system of the powder paint. The recirculation system comprises a doctor blade 53, a cyclone 54 and a power center 55 and allows the powder paint collected at the fume hood 52 to be conveyed to the coating gun 51 via related ducts.

Prior to the suction fan 56, it is preferable to install a filter 57 to block any possible particles of powder paint that have not been collected by the cyclone 54.

Optionally, it is possible to make the powder paint coating station 50 to coat the panels 1 in vertical position, as shown in Figure 10b.

For the powder paint coating it is possible to use, for example, the powder paint based on polyester sold under the code PGE22 001 by Sublitex S.r.l. Or it is possible to use the powder paint sold by Sublitex under the code PGE22 401, which is a polyester powder paint, and PGU22 502, which is a polyurethane powder paint.

In general, any known powder paint can be used.

Preferably, the machine also comprises a polymerizing station 60 shown in Figure 11, whose function is to cause the polymerization of the powder paint remaining adhered to the panels 1.

The polymerizing station 60 comprises a supporting and feeding plane 21 configured as a movable Teflon mat with warp and weft covered with a glass- filled PTF material so that it is resistant to high temperatures. Such a supporting and feeding plane 21 moves the panels 1 in the direction depicted by the corresponding arrow.

The polymerization is obtained by infrared lamps 61 positioned above and below the supporting and feeding plane 21.

The infrared lamps 61 are mounted in series on respective frames 62a, 62b. In practice, the polymerizing station 60 comprises an upper frame 62a and a lower frame 62b, each equipped with a set of infrared lamps 61.

Each frame 62a, 62b is arranged movable with respect to the supporting and feeding plane 21, that is, each frame 62a, 62b is susceptible to movements towards and away from the supporting and feeding plane 21, in the direction depicted by the respective arrows.

The polymerizing station 60 also comprises temperature detection means 63 at the supporting and feeding plane 21. Preferably, such temperature detection means 63 are placed both above and below the supporting and feeding plane 21. They can be configured as optical pyrometers or as temperature sensors and have the function of detecting the temperature at the faces 2, 3 of the panels 1.

Such temperature value is sent to a control unit not shown in the figure, which compares the temperature value with a predetermined temperature range. If the detected temperature deviates from the predetermined temperature range, the control unit drives the movement of one or both frames 62a, 62b towards and away from the supporting and feeding plane 21. In essence, the control unit drives the movement of one or both frames 62a, 62b in such a way as to allow the temperature to fall within the predetermined range. Preferably, the control unit also takes into account, in this calculation, the feeding speed of the panels and the intensity of the radiation emitted by the infrared lamps.

The frames 62a, 62b are arranged to move selectively, that is, independently of each other, depending on the temperature detected by the corresponding temperature detection means 63.

The polymerizing station 60 is also provided with a hot air ventilation system 64.

Also in this case, the above can be done by holding the panels in the vertical position, as shown in Figure 12. Such a station can also be provided as a heating station 40 of the panels

1 to solidify the primer.

The machine preferably also comprises a sublimation printing station 70 on the panel 1, that is, a station in which an image previously present on a sublimation film is printed on the panels 1. The station 70 is shown schematically in Figure 13 downstream of the polymerizing station 60 and consists of a sublimation printing station known in the field.

Finally, the machine comprises a section 90, shown in Figure 14, for unloading the coated and/or decorated panels 1, the section being equipped with a system similar to that described with reference to the loading section 11 but arranged to unload the decorated panels from the supporting plane 91 and stack them, for example, on a pallet 92.

In general, the machine according to the present invention comprises at least the loading section 11, the primer applying station 30, the heating station 40 to heat the panels 1 for solidifying the primer on the panels, the unloading section 9 and a panel feeding way that can be configured as a supporting and feeding plane 21, which plane can be shared among the different stations or that can be made differently at the different stations. A machine with these stations allows a panel 1 coated with the primer described above to be made.

The other stations described above of the machine are to be considered optional in the sense that the machine may comprise one or more of the other stations, preferably, however, the machine comprises at least one powder paint coating station and a related station polymerizing the powder paint, so as to provide a powder paint coated panel 1 that allows the above advantages to be achieved.