METHOD FOR FINISHING A LARGE-SIZE SUPPLIED BUILDING PANEL

Abstract

The disclosure relates to a method for finishing a panel, the method includes a) a relief embossed into the upper side in the form of at least one strip-shaped depression with a depth (T), b) a decorative paper applied to the upper side, c) an overlay paper applied to the decorative paper as an abrasion-resistant layer, d) the lower side provided with a backing layer, e) the structure pressed at a high pressure and temperature, and f) during the pressing, at least one strip-shaped depression is again embossed in a second embossing without changing the depth (T). Also, the upper side features a press skin that has a thickness of 0.3 to 0.5 mm, the bulk density of the panel in a top layer is between 950 and 1,000 kg/m.sup.3, and an aqueous melamine resin is applied to the upper side as a tempering agent before or after embossing.

Claims

1. A method for finishing a supplied building panel with an upper side and a lower side, the method comprises: a) in a first embossing step, embossing a relief at least into the upper side in a form of at least one strip-shaped depression comprising a bottom wall with a depth (T), b) applying a decorative paper to the upper side; c) applying an overlay paper to the decorative paper an abrasion-resistant layer; d) feeding the thus-prepared structure to a press and pressing the structure; e) during the pressing, at least one strip-shaped depression is again embossed in a second embossing step without changing the depth (T), wherein f) the upper includes a press skin that has a thickness of 0.3 to 0.5 mm; g) the bulk density of the building panel the top layer that forms the upper side is between 950 and 1.000 kg/m.sup.3, h) the lower side includes a backing layer prior to pressing; and further comprising: i) heating the building panel using steam prior to the embossing until it reaches a surface temperature of 30 to 50° C.; j) applying an aqueous melamine resin to the upper side as a tempering agent before or immediately after the embossing; and k) the press is a short-cycle press with pressure and temperature.

2. The method according to claim 1, wherein at least one further depression is embossed at an angle (α) transverse to the at least one depression.

3. The method according to claim 1, wherein the first embossing step is carried out with at least one embossing calender roll which operates under application of a pressure of up to 300 N/mm.sup.2 and a surface temperature of up to 220° C.

4. The method according to claim 1, wherein the first embossing step is carried out in a short-cycle press with a deeply structured press plate.

5. The method according to claim 1, wherein the depth (T) is up to 0.7 mm.

6. The method according to claim 1, the depth (T) is in a form of steps, so that the bottom wall is designed in the form of the steps.

7. The method according to claim 1, further comprising embossing markings on a region of the bottom wall.

8. The method according to claim 7, wherein the markings, which comprise lines, circles, dots, crosses or other graphic characters, are printed on the decorative paper where it reaches the base walls of the at least one depression.

9. The method according to claim 4, wherein re-embossing in the depression in the second embossing step is conducted by strip-shaped elevations the press plate of the short-cycle press.

10. The method according to claim 1, wherein a structure is embossed into the upper side which is at least partially synchronous with the decorative pattern.

11. The method according to claim 1, further comprising dividing the large size building panel into individual panels by carrying out a saw cut in and along each of the depressions.

12. The method according to claim 4, wherein the first embossing step is carried out in the short-cycle press by means of strip-shaped elevations on the press plate.

13. The method according to claim 1, wherein the supplied building panel is made of HDF.

Description

DETAILED DESCRIPTION FO THE DRAWINGS

[0031] In the following, an example of an embodiment of the invention will be explained in more detail with the aid of a figure: They show:

[0032] FIG. 1—a perspective partial image of a large-size building panel;

[0033] FIG. 2—the top view of the building panel according to FIG. 1;

[0034] FIG. 3—a schematic partial image before the second embossing step;

[0035] FIG. 4—an enlarged partial image during the second embossing step;

[0036] FIG. 5—a schematic partial image during the first embossing step;

[0037] FIG. 6—a schematic image of the building panel in the short-cycle press;

[0038] FIG. 7—a typical bulk density profile of an HDF panel;

[0039] FIG. 8—the bulk density profile of a first large-size building panel;

[0040] FIG. 9—the bulk density profile of a second large-size building panel;

DETAILED DESCRIPTION

[0041] The starting point is a large-size HDF panel with a length of 2800 or 1860 mm, a width of 2070 mm and a thickness of 7 to 14 mm. The bulk density is lower than that of a conventional HDF panel, as a comparison of FIG. 7 with FIGS. 8 and 9 shows. In order to form a weak top layer that can be plastically deformed, the peaks of the top layer have been lowered by at least 40 kg/m.sup.3 compared to the standard. Good results have been achieved with a lowering of up to 60 kg/m.sup.3. The bulk density then ranges from 950 to 1000 kg/m.sup.3. An example of the bulk density profile of a conventional HDF panel is shown in FIG. 7. FIGS. 8 and 9 depict examples of bulk density profiles of building panels used according to the invention.

[0042] The HDF panel can supplied press-finished, i.e. with the complete press skin. Preferably, however, the press skin is sanded down to a thickness of about 0.3 mm in order to deliberately “weaken” the top layer.

[0043] In order to emboss depressions 5, 6 into the upper side 2 of building panel 1, said panel is first heated to a temperature between 30 and 50° C. by applying 10 to 30 g/m.sup.2 of steam. 10 to 50 g/m.sup.2, preferably 30 g/m.sup.2, aqueous melamine resin is then applied as a tempering agent. This can be a standard impregnating resin with a solid content of 50 to 65% by weight, preferably 60% by weight. In addition to water a solvent, other additives such as curing agents, wetting agents and the like may be present in the formula. Alternatively, UF resin or, in mixtures, UF and melamine resin can be used as a tempering agent. It is either a postforming resin or a standard impregnating resin, which is rendered more elastic by adding flexibilizing agents (e.g. 1,4-butanediol, caprolactam, polyglycol etc.) A subsequent addition of the elasticizer should be in the range of about 3 to 7% by weight.

[0044] The building panel 1 pre-treated in this way is passed through one or more calender rolls 20 arranged one behind the other with embossing rings 21 arranged parallel to them. In a first embossing step, depressions 5, 6 with a depth T of up to 0.7 mm are embossed into the upper side 2 via the at least two embossing rings 21, wherein said depressions extend in longitudinal direction L and transverse direction Q. Here, the line pressure of the embossing rings 21 is up to 300 N/mm and the surface temperature is up to 220° C. In this first embossing step, the tempering agent on the upper side 2 is at least partially converted, i.e. it cures at least partially and thus increases the bulk density again. The depressions 5, 6 can be formed in steps, for example by using several calender rolls 20 with different embossing rings 21 and initially embossing, for example, 0.3 mm and then a further depth T of up to 0.7 mm.

[0045] If the diameter of the calendar roll 20 is large enough, webs running parallel to the axial direction can also be provided on its circumference, with which the depressions 6 can be embossed in the transverse direction Q. If necessary, a calender roll 20 with embossing rings 21 can be followed by a calender roll with parallel webs running only in the axial direction.

[0046] After the first embossing step, one or more layers of resin-impregnated paper can be applied to the upper side 2 as an underlay and a decorative paper 3 then applied on top; it is also possible to only apply such a decorative paper. The decorative paper 3 can be single-colored or multicolored and is applied in such a way that it is at least partially synchronised with the structure that has just been embossed. The decorative paper 3 may feature markings 7. The markings 7 can be circles 7.1, crosses 7.2, lines 7.3 and dashes 7.4 or other geometrical figures. Via these markings 7, the building panel 2 can be aligned by a camera system for carrying out further processing steps.

[0047] A backing layer 8 is subsequently placed on the lower side 9 of the building panel 1 and an overlay paper 4 on the decorative paper 3 as an abrasion-resistant layer. This structure is then fed to a short cycle press 30 with an upper press plate 31 and a lower press plate 33. The upper press plate 31 features strip-shaped elevations 32. Using the markings 7 and a camera system, the building panel 1 is aligned so that the elevations 32 dip again into the embossed depressions 5, 6 during the subsequent pressing of the structure and the side walls 5.1, 5.2 of the depressions 5, 6, which are rounded during the coating of the upper side 2, are embossed again in order to adjust parallel and flat side walls 5.1, 5.2 in a second embossing step without changing the depth T of the depressions 5, 6 or the position of the bottom wall 5.3. As FIG. 4 shows, the elevations 32 in the transition area from the side walls 5.1, 5.2 to the bottom wall 5.3 are designed to be larger than the width of the depressions 5, 6, in order to safely form the lower edges of the depressions 5, 6. Between the strip-shaped elevations 32, the press plate 31 can feature an engraving by means of which a structure is embossed into the upper side of the overlay during pressing, said structure being at least partially aligned synchronously with the decoration (embossed in register).

[0048] By corresponding processing of the press plate 11, geometric figures or lines can also be embossed on the floor walls 5.3, which appear as matt or shiny areas on the surface.

[0049] The press time in the second embossing step is between 10 and 30 seconds, preferably 12 to 15 seconds, during which time the resins melt and bond to the building panel 1. The temperature of the press plates 31, 33 is up to 200° C. The pressure curve changes from a pressure build-up phase to a holding phase and a pressure reduction phase. Here, the embossing depth T will occur in the manner of a path control. The pressure in the short cycle press is 40 to 100 kg/cm.sup.2. The temperature of the heating plate, via which the press plates 31, 33 are heated, is 180 to 220° C. Preferably, pressing is carried out at a heating plate temperature between 190 and 210° C.

[0050] To achieve a sensible design, at least two depressions 5, 6 must be embossed in the first embossing step in the longitudinal direction L and at least two in the transverse direction Q, so that the side edges of the divided panels are all lowered.