|
(11) | EP 1 454 724 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
|||||||||||||||||||||||
| (54) | Method of manufacturing panels and panels thus obtained |
(57) Method to obtain hardboard panels or MDF panels, and panels obtained by means of
such method. The panels have at least an outer layer, to which a mixture based on
ammonium salts is added.
FIELD OF THE INVENTION
[0001] The present invention concerns a method to obtain panels of fiber or particles of wood, which will allow to paint them uniformly, using powder-type paints.
[0003] The articles, individual or assembled, made with said panels, whether painted or not, totally or partly, also come within the field of the present invention.
[0004] The present invention is mainly but not exclusively applied to panels identified by the acronym MDF (Medium Density Fiberboard), that is, panels of wood fiber produced by means of a dry process, also known as "dry process fiberboard".
BACKGROUND OF THE INVENTION
[0005] With the evolution of powder paint technology, for some time now powders have been available that can be applied using a temperature of around 100-150°C.
[0006] Powders used for painting metals liquefy at around 190°C. After liquefaction there is the catalysis step using UV rays.
[0007] The temperature of around 100-105°C allows to use the powders also for painting materials of fibers or particles of wood since, at that temperature, the fibers or particles of wood do not carbonize.
[0008] However, the use of powders for painting panels made of fiber or particles of wood has not so far led to good results, since the corners and the edges, whether positive or negative, are covered differently.
[0009] Moreover, the surfaces are not painted uniformly, but a so-called orange peel effect is achieved. This is the main limitation since surfaces with this defect are not acceptable for the medium to high band of the market.
[0010] The Applicant has surprisingly embodied the present invention, after long studies and experiments intended to overcome these problems, which entails further advantages and allows to achieve other purposes.
[0011] The present invention allows to obtain hardboard panels, advantageously but not exclusively MDF panels, suitable to be painted with powders, so as to obtain a substantially uniform cover on all the surfaces, edges and corners.
[0012] Another advantage is that said panels, once painted, have a particularly uniform and smooth cover, without the typical marks of the so-called "orange peel effect".
[0013] Another advantage is also that the panels obtained according to the invention have the same characteristics of machine workability as normal panels.
[0014] Another advantage is that the panels obtained according to the invention have the same chemical-physical characteristics as normal panels.
[0015] It is therefore one purpose of the invention to obtain panels of wood particles, advantageously but not exclusively MDF panels, that can be painted with powders so as to obtain a substantially uniform and smooth cover.
[0016] Another purpose of the present invention is to obtain hardboard panels of wood, advantageously but not exclusively MDF, that can be worked on the machine and painted on every part, even worked, so as to obtain a substantially uniform and smooth cover.
[0017] Another purpose of the present invention is to obtain said panels with the plants that are usually used.
[0019] Another purpose is to produce panels that can be obtained using the current production plants, without needing to modify them.
[0020] The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art, and to obtain these and other advantages.
SUMMARY OF THE INVENTION
[0021] The present invention is set forth and characterized in the respective main claims, while the dependent claims describe, each time, developed variants of the invention.
[0022] Applicant has surprisingly discovered that, by adding a basic mixture of ammonium salts, advantageously distributed uniformly, to the usual mix with which the panels are made, whether it is in the form of hardboard or fiber, and then by proceeding using the usual technique to obtain panels, a panel according to the invention is obtained.
[0023] According to the invention, the mixture is inserted at least into the surface layers of the panel that is to be painted.
[0024] To be more exact, if the panel is hardboard, it is better to insert the mixture only in the outer layers.
[0025] On the contrary, if the panel is MDF, it is better to insert the mixture into the entire mix of the panel.
[0026] Applicant has also surprisingly discovered that the minimum quantity of the mixture of ammonium salts is 20 Kg per m3 of the panel part involved. Applicant has also surprisingly discovered that the quantity of ammonium salts must not be excessive, and therefore it is enough to consider, as maximum value of ammonium salts, 42 Kg per m3 of panel involved.
[0027] From subsequent studies and experiments, Applicant has discovered that the content of ammonium salts in the mix involved in the treatment must be maintained preferably between 20 and 40 Kg per m3.
[0028] Advantageously, as ammonium salts those of strong acids are preferably used, particularly the ammonium salts of nitric, phosphoric or sulphuric acid.
[0029] Experiments have shown that, in the case of MDF panels, the best product is obtained when the granulometry of the fibers is thin and fine, which fibers can be obtained only by using specific mixtures of wood perfected for that purpose and worked according to the state of the art.
1. Method to obtain hardboard panels or MDF panels having at least an outer layer, characterized in that a mixture based on ammonium salts is inserted at least into said layer.
2. Method as in claim 1, characterized in that said mixture is distributed substantially uniformly in the part of the panel involved
in the treatment.
3. Method as in any claim hereinbefore, characterized in that the quantity of said ammonium salts introduced is about 20-42 Kg per m3 of said part of the panel involved in the treatment.
4. Method as in any claim hereinbefore, characterized in that said ammonium salts are of strong acids, such as ammonium salts of nitric, phosphoric
or sulphuric acid.
5. Method as in any claim hereinbefore, characterized in that if the panel is MDF, said mixture is inserted into the entire mix that makes up the
panel.
6. Method as in any claim hereinbefore, characterized in that said mixture is inserted by means of spraying in powder or liquid form.
7. Method as in claim 6, wherein a step is provided to press said panel, characterized in that said spraying is effected on one or more outer surfaces of the panel downstream of
said pressing step.
8. Method as in any claim hereinbefore, characterized in that said mixture is inserted into the mix that makes up the panel before said mix is
deposited on the usual work planes to obtain the panels.
9. Hardboard panel or MDF panel, having at least an outer layer, characterized in that at least said outer layer comprises a mixture based on ammonium salts.
10. Panel as in claim 9, characterized in that said mixture is distributed substantially uniformly in the part of the panel involved
in the treatment.
11. Panel as in claim 9 or 10, characterized in that the quantity of said ammonium salts present in said mix is about 20-42 Kg per m3 of panel part involved.
12. Panel as in any claim from 9 to 11 inclusive, characterized in that said ammonium salts are of strong acids, such as ammonium salts of nitric, phosphoric
or sulphuric acid.
13. Panel as in any claim from 9 to 12 inclusive, characterized in that if the panel is MDF, said mixture is inserted into the entire mixture that makes
up the panel.